Skeletal Specimens for Scientific Studies

This report is about the proper techniques for preparing, cleaning, whitening and articulation of skeletal specimens for osteological, biological, veterinary or zoological study. It will explain the three usual techniques used to clean the bones of soft tissue and a few of the more uncommon ways to do so. It will go slightly in depth in each category and then move onto the proper ways and improper ways that the bones themselves are whitened and all lipids are removed from the bones, than it will discuss how to seal the bones to protect them from the elements. Then it will discuss actual articulation and go into detail on the types of articulation commonly used. Lastly it will go over common uses for prepared articulated skeletons.

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Skeletal articulations have been going on since museums first started displaying taxidermied animals. Many times the animals bones didn’t want to be wasted so either the skulls or entire skeletons would be saved in archives to help accurately catalog specimens kept in the museum. Eventually the idea was had to reconstruct these skeletons into lifelike poses and display them in the museum as well, this is where skeletal articulation found its roots. In the picture below is an example of an articulated skeleton of a Potto, a species of primate
There are multiple ways to clean the specimens that are used for articulations. There are three common ways that it is done with satisfactory results, the first and most common method is with the use of the beetle Dermestes maculatus, otherwise known as the dermestid, or skin, beetle. These beetles start their life as a small microscopic egg typically laid near dried animal material, which than hatch out as small furry larvae which are black to brown in color. The eggs typically take a day to hatch and the larvae go through multiple stages, or instars, before finally pupating and emerging as an adult. Post, L (n.d) Bone Builders notebook. Pg. 21 Homer, AK, Author published. The male beetle attracts the female with pheromones, which is a common method in the insect world. There is no intermale aggression or territorial aggression.
These beetles are useful not only in skeletal articulation but also in the field of human forensics. The main way these beetles assist in the cleaning of bones for articulation is they eat the flesh fairly quickly, the larger the colony the faster the job gets done. With a colony of one thousand beetles an animal the size of a weasel could be cleaned overnight, as opposed to some of the other methods which take considerably longer. An example of a small colony cleaning a deer skull can be seen in the below picture
The beetles are also extremely delicate and thorough in the job that they do, being able to clean even the skeletons of young animals without fully formed bones while doing little to no damage. B. Shaver & P.E Kaufman (2009). They also allow articulators to perform ligamentary articulations. A drawback to using beetles for cleaning is they often leave a lot of fat in the bones, making for a longer whitening and degreasing process. Beetles usually live for around 6 months in their adult form, however they breed very quickly. I have personally raised a colony of these beetles from just eighteen beetles to well over five thousand in a little over a year.
A second common method for cleaning bones for use is maceration, which requires less maintenance than a beetle colony but also takes a lot more time to fully clean the bones. Maceration is the submersion of the specimen in water to decompose fully. This is further broken down into two categories, cold water maceration and warm water maceration. Cold water maceration typically takes a longer period of time to completely decompose the specimen, however it is easier maintenance and is typically used in warmer climates. Warm water maceration usually uses some form of heating element in the water to speed up the process of decomposition. It also has the added benefit of helping to melt some of the lipids left in the bones, helping to degrease the bones while cleaning them at the same time. Maceration when used properly results in much cleaner bones than the other methods of cleaning, however it takes a considerable amount of time to complete. Times can vary from a week or two for a small animal like a mouse to a few years for larger animals such as horses and cattle. Generally the water temperature is kept at or above 80 degrees for warm water maceration. This dramatically lowers the degreasing time by melting and liquefying the lipids in the bones, making it easier for the bacteria to consume and for physical removal of the fat. This techniques major drawback is mostly the smell it produces, which if never smelled before has been known to produce ill responses.
Most of the time maceration is done in small containers with separate bone groups separated from each other, for example the arm bones separated, the leg bones separated, and the ribs and spine separated. This makes it much easier to rearrange the bones after the cleaning process is done. These sections are often placed in mesh bags made of some form of plastic, as if it were a form of cloth it could potentially also be digested and consumed by the bacteria in the water. Other times specimens may be placed in wire cages and placed in streams, rivers, or ponds to macerate, which also allows natural scavengers to help do the work, however there is a far greater potential to lose bones this way, or have it tampered with.
A third common technique for cleaning bones is “boiling”. This technique involves actually cooking the specimen for multiple hours until the soft tissues become soft enough to come away from the bones. There are several problems with this method and the main one being that people tend to actually boil the bones, damaging them with the heat and making them soft and flaky. It is best to simmer the bones on low heat for a long period of time to help avoid from damaging the bones. Often times the heat tends to leech the fat directly into the bones, making for a terribly long degreasing process. This technique is commonly employed by taxidermists for “European mounts”, which is keeping the skull and horns of game animals such as deer or antelope. A European mount may be seen in the below picture
Some people will also add baking powder to help strip the soft tissue from the bones, this is highly damaging to the bones and though initial results may look alright, without proper sealing the bones will soon turn dusty and deteriorate overtime, until you are left with nothing more than dust. This process is also usually done in pieces so as to make organization of the skeleton a simpler process. Times can vary from a few hours for smaller sections of bone to well over twenty four hours for larger animals or sections of bones. Often times the spine of the animal will present a problem as there is much cartilage, nervous tissue and muscle tissue holding them together. Manuel removal of flesh is required for this technique, often involving fine scalpel blades and knives, as well as stiff wire brushes.
Overall this technique is the least efficient of the three common techniques and has the most potential for damaging the specimen, therefore it is often not recommended to be tried by those first starting skeletal articulations, as they are more prone to make careless errors and mistakes. The most efficient and time efficient method of the three common methods is using dermested beetles.
There are many more ways to clean the bones of specimens for display however now I will discuss just two of the more uncommon ways of doing this. The first less uncommon way of cleaning bones is simply burying the specimen in the ground and allowing nature to do the work. Often times the specimen is placed in a cloth bag and buried so as to not lose bones, however the cloth bag can also be effected by decay, and be eaten away in the soil by invertebrates and bacteria naturally present there.
Bones are commonly lost using this method and it may take several years for the soft tissue to effectively be decomposed even in small specimens. A large problem with using this method is the fact that minerals are naturally found in the soil and often will leave orange or rusty red stains on the bones due to the presence of iron in the soil. These stains can be removed but not always thoroughly using strong chemicals which also damage the bone; this is not an optimal situation.
Sometimes after removing the bones from the ground it will be discovered that the soft tissues have “mummified” to the bones, making it very hard to remove. This happens frequently in warmer dryer climates. The dried tissue than has to be removed manually with tools and than most of the time needs to be “boiled” or put into a dermested colony, defeating the purpose of putting the specimen in the ground to begin with.
A second uncommon technique used for cleaning is using chemicals to remove the soft tissues. L. Post (n.d) Bone Builders notebook. Pg 24. Homer, AK, self published. Commonly household drain cleaner is used for this process, as it eats away at the soft tissue by either being strongly acidic or basic. Other times fifteen percent or higher hydrogen peroxide is used as it oxidizes the flesh. A drawback to this technique is the obvious danger of using strong chemicals which may severely burn the user. These chemicals if not used in proper percentages can completely eat away a small specimen in just a few hours, so a close eye has to be kept on the entire process. Often times the ligaments are the last parts to be dissolved and with proper timing can be used to make a ligamentary articulation.
The benefit of these techniques are they are fairly hands off, however there are often multiple things that can go wrong and ruin a specimen or possibly even harm the articulator. Some of these techniques are still new to practice and must be tuned a bit more to get proper results. Often times it is best just to use those techniques which are proven safe and effective as they are the ones that have most likely been around the longest. Those who wish to start skeletal articulations are often suggested to ask the area museum of natural history what their opinion is or which technique they employ for their own skeletal displays, they will often be more than happy to help you.
After proper cleaning of the specimen has been achieved it is necessary to remove all fat from the bones and make them as white as possible for a clean looking display. By removing the fat not only are you making the skeleton look better but also you are removing a possible source of bacterial growth and unsanitary conditions. This also helps to lessen the risk of possibly having the skeleton have any off odors of decay, not what is wanted for proper display of specimens.
Often the first step to degreasing is doing a preliminary soak in hydrogen peroxide, three percent for smaller skeletons or up to thirty percent for larger bones or skeletons, though thirty percent hydrogen peroxide can be an extremely dangerous chemical, and all proper precautions must be taken. Hydrogen peroxide works on the principal of oxidization, which is the removal of one or more electrons from a chemical composition. Basically oxidization is what causes rust to occur on certain metals. By removing an electron, the chemical composition of the substance is changed. In this instance it makes bones turn from a natural color to a brighter white.
This first preliminary soak in hydrogen peroxide whitens the bone in areas where less natural fat deposits are occurring, typically at the ends of the bones away from the marrow in the center of most long bones. By whitening these areas first it reveals the areas with the most fat present, thus making an area to target for the actual degreasing process. Without doing this first preliminary soak it would make the process of degreasing longer and require more water changes than what might truly be necessary.
There are a few different ways to go about degreasing the bones of specimens used for articulation. The two most common methods are using ammonia and using some form of detergent in warm water, both being an effective means of degreasing bones, however the detergent method is a bit more complicated. When using ammonia to remove lipids from bones it is usually done using uncut household ammonia, though this is not the strongest form of ammonia that can be used, it does the job and is the safest to use. It does not need to be warmed to be effective, however the warmer it is the faster it acts on the fat molecules in the bone.
When using the detergent method for degreasing it is common to use one cup of detergent per five to ten gallons of water. Using straight detergent has been done before but often leaves less than desirable effects, such as discoloration of bone. An aquarium heater or other form of water heater can be used to warm the water in the container, making the detergent act upon removing the fat a bit faster. With small skeletons this method may take a few weeks to a month, but with larger bones and skeletons it may take several months and several water changes to reach the desired effects. With the ammonia method it usually takes a shorter period of time than if you were using the detergent method, from a few days for small bones to a month or two for larger skeletons.
It is very important to protect the bones and skeletons that are being worked on from the elements and the natural passage of time. There is more than one way to do this and most are effective. The first and most common way to seal bones is using a dipping technique using a mixture of Elmer’s glue and water. The glue tends to be soluble in water and it is a very natural and non-harsh way to treat bones. The whole skeleton or bone is dipped into the mixture and allowed to dry, the glue naturally forms a clear protective layer over the skeleton however if it needs to be removed all that need be done is for it to be re-dipped in hot water and the glue will melt off.
Reasons why the glue, or any sealant, might need to be removed range from grease coming to the surface of the bone or skeleton after it was thought it was all removed, which can be a frustrating and disheartening occurrence, to the skeletons position needing to be changed, for any number of reasons. Sometimes the sealant might need to be removed because a new, more reliable sealant has been found, with the first being used temporarily to protect the bone from harm.
Sometimes damaged skeletons can be salvaged if using the correct sealant. If the bone was compromised during cleaning, often from harsh chemicals or too much heat being applied, the sealant will keep the bones from coming apart or further cracking. The teeth of large carnivorous mammals have a tendency to crack over time due to moisture in the teeth slowly evaporating, and when a liquid evaporates into a solid it takes up more room, cracking the tooth. This can be avoided by placing the tooth in a drying material such as rice or cotton, and letting it sit for a few weeks to a few months. The tooth is than covered in a clear strong sealant, clear nail polish being a good example of this. Several coats are applied to make the tooth very strong and stable. The same procedure can be applied to the keratin sheath on the claws of animals.
Another method of sealing bones or skeletons involves buying a clear spray paint from a reputable brand that is known to not yellow over time. The skeleton or bone is laid out in a ventilated area and sprayed in several coats of the spray paint and allowed to dry. Depending on the type of paint used the sealant will either appear dull and non-reflective, keeping the natural properties of the bone, or it will appear to be shiny and reflective, which often times may be applied to teeth and claws for those who keep private collections of skeletons for their own research. Typically in a museum quality specimen a flat coat is used to keep the bones looking as natural as possible. Other times no sealant is used at all on bones which have been professionally cleaned, and the bones or skeletons are simply kept under glass or in a display case, to protect them from dust and the oils found on human fingers and skin.
Several types of articulations exist and are used in different manners for different institutions or research. Articulations and collections can be broken down into personal collections, museum or educational collections, or veterinary models, though often times in recent year’s replicas and reproductions are used for this purpose as they are often cheaper and far less fragile. Articulations and collections for personal use can be found in the homes of hunters, taxidermists, medical and veterinary students or just those people who are interested in natural history, anatomy or biology.
Skull collections are often a simple and less complicated means of having an inventory of collections for certain species without having to do full skeletal articulations, these are fairly common in the homes of hunters and taxidermists. Those who keep full skeletal articulations often times have them on bases or in a natural habitat type setup. Often, those who are more interested in the general anatomy of the skeletons themselves have free standing skeletal articulations or those without bases, These are simpler to complete and may sometimes require bars to keep the articulation stable and from falling and possibly becoming damaged.
Free standing articulations of smaller animals may be done through the use of ligament articulations. This involves letting a dermested beetle colony clean the skeleton, and watching the process very carefully so as to know the precise time to take the skeleton out of the colony. This takes practice to do, but when done right can make articulations much easier to complete. Essentially the beetles eat away all soft tissues except those ligaments which are holding the skeleton together. Often one or two bones may break away from the main skeleton but can easily be reattached at the time of the actual articulation. Than the entire skeleton goes through the degreasing process and during this time the ligaments are kept hydrated, making the skeleton very flexible and easy to manipulate.
A stand may be built and pins used to put the skeleton into the position that you want it to dry in, though as ligaments dry they begin to contract and become hard, and on small enough animals such as mice, may not be visible at all. It is often necessary to re-align bones that shift during the drying process, as contraction of the ligaments causes them to move around, but if it dries in a position not right, all that need be done is for the skeleton to be re-hydrated and posed again. Once the skeleton is dried in an acceptable pose the pins and remove the support frame and often times the skeleton may be free standing.
With larger skeletons, more tools and work may be involved. Common tools used for articulation of larger skeletons include drills, pins, eye screws, and metal pars or wiring. Where ligaments would normally hold bone to bone, metal pins sunk into the joints may be necessary, and these are often siliconed into place so as not to come apart again. An example of a cougar skeleton on a base may be found below
A bar is often ran up the neural canal of the spine and reshaped to form the natural arch and support found in the spinal column of most vertebrates. The rod terminates after entering the foramen magnum of the skull, and may then be epoxied into place to keep from coming apart. There is naturally cartilage which attaches from the ventral end of the ribs to the sternum, to be as accurate as possible this cartilage must be rebuilt. The cartilage is often rebuilt be using thin wires which come from the sterna end of the ribs and attach to each other and to the sternum, and are than covered in layers of clear silicone to replicate cartilage.
Another interesting articulation which is rarely seen is known as the Beauchene skull, which was first developed for human skeletal articulations by a French anatomist named Claude Beauchene in the mid eighteen hundreds. Cult of weird staff (n.d) Beauchene skull, retrieved from Cult Of Weird website This type of articulation is where the individual bones of the skull on one side of the skull are removed from each other in an “exploded” manner, so that the internal anatomy and the individual bones may be studied. This is a very infrequently seen articulation in animal skeleton articulations.
Young animals may also be used in skeletal articulations, and though it may be sad to think that a young animal lost its life before it could grow into an adult, they are also an important research for the continuation of Osteological study. The bones of young animals are often much softer and not fully connected which makes for a more difficult articulation. Young animals also usually contain more bones than adults, as the individual bones grow they form together to make larger bones. These skeletons may be used in comparative anatomy with the skeleton of an adult of the same species of the animal. Young animals require a much finer touch and can usually only be cleaned through the use of beetles, as other cleaning techniques that were previously discussed will most likely be too harsh on the young bones, resulting in damage or complete disintegration of the bones.
Skeletal articulations may also be used in area nature centers in parks, to help demonstrate the local wildlife in that particular area. They are found in taxidermist shops to help promote business and show the skill of the taxidermist who owns the company. Often time’s larger universities have a colony of dermested beetles to help demonstrate to students the natural life cycle of the beetle for entomology students while also having an inventory of bones or skeletons for other majors of the college, such as anatomy biology or zoology.
Skeletal articulations are a necessary component of anatomical and other fields of study. Without the use of skeletons for research we would never know how bones connect to each other, how different teeth of animals are used for different food that the animals ingest and how certain animals from certain families have unique evolutionary adaptations, such as the cat family, with their retractable claws, or the pinniped family, who’s limbs have evolved into flippers, but are still able to haul out on land to escape predators from the ocean. Skeletal anatomy is important to most if not all biological sciences, and without skeletal articulators there would be far less to look at in your favorite natural history museum, and we may never have known what dinosaurs skeletons may have looked like properly articulated. The next time you take a look at a skeleton in a museum, think about the hard work and patience that went into putting that skeleton together.

Compare and Contrast Cardiac and Skeletal Muscle

Something that differentiates animals from other organisms is their ability to voluntarily carry out actions using their muscles. They do this by muscle cells changing length, which is known as contracting. There are three types of muscle, which are distinguished by their structures and functions. These are cardiac, skeletal and smooth muscle. Here I shall be comparing the structures of cardiac and skeletal muscle and looking at how their histological, structural and functional differences allow them to carry out their specific roles more effectively.

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Cardiac muscle is found only in the heart and causes contractions, in the heart called systole, which pump the blood out of the heart and around the body supplying the oxygen and other vital substances to cells. Skeletal muscle is attached to tendons, which in turn attach to bones. The contractions of skeletal muscles cause the tendons to pull on the bones, which results in movement of, for example, an arm.
There is only one similarity between the structures of cardiac and skeletal muscles. Both their structures are striated (striped), formed by actin and myosin myofilaments. They are tightly organised into repeating patterns so that actin can slide over the myosin during contraction.
Figure 1 shows one of those repeating units in cardiac and skeletal muscle, called a sarcomere. For contraction to occur in cardiac and skeletal muscle, the actin filaments slide over the myosin filaments in a process known as the sliding-filament theory. So in figure 1 the thin pink filaments would slide over the dark blue filaments (not true colours). Myosin heads are attached to the actin. Adenosine triphosphate (ATP) induces the dissociation of the myosin head, the myosin head then attaches again to the actin and eventually inorganic phosphate (Pi ) is released changing the angle of the myosin head, causing the actin filaments to slide over the myosin filament.  This causes a decrease in length of the I band but the A band always stays the same length.
One of the main differences between the two types of muscle is in the way that their contractions are brought about. If one wanted to raise their arm, their brain would produce an action potential via the somatic nervous system (SNS). The action potential will lead to a muscle action potential and the T-tubules will depolarize and open calcium ion (Ca2+) channels, leading to cross-bridge cycling, where the actin and myosin slide past each other and cause the skeletal muscle to contract, lifting the bone with it. So the muscle will not contract without the input of the nervous system.
Cardiac muscle is also connected to the nervous system. But as contractions are involuntary, cardiac muscle is connected to the autonomic nervous system (ANS). However, unlike in skeletal muscle, the actual action potentials that stimulate muscle contraction are created by myogenic cells in the heart. Myogenic means that it is the cells themselves that create the electrical action potentials, without the need for any external input. The cells are located in the Sino Atrial Node (SAN), which itself is located by the right atrium; the cells in the SAN are known as the pacemaker. They produce a pacemaker potential “which sets the frequency of action potentials and thus the intrinsic rhythm of the normal heart.”  The ANS, connected to the SAN, only modulates the heart rate, with the sympathetic nervous system speeding up the heart rate ready for the fight or flight reaction and the parasympathetic nervous system slowing the heart rate down.
It is important that the heart is controlled automatically so that we are not conscious of the heart beating, because it would be almost impossible and probably exhausting for us to have to consciously think about making every single heart beat, especially when we are asleep. Moreover, because the heart is myogenic, there are benefits for transplants because the heart muscle can continue beating while the heart is being taken to the new body.
Skeletal muscle must be under voluntary control so that every action can be carried out consciously, such as picking up a cup. If it were automatic there would be no conscious control of when the muscles should contract and our limbs would not be under our control. Nevertheless in reflex reactions, the skeletal muscle does come under the control of the ANS. For example, if one’s hand was to touch a hot object, the ANS would react following a reflex arc of stimulus, receptor, sensory neuron, relay neuron, motor neuron, effector, response; the arm would automatically move away from the heat source. Generally, compared to the beating of the heart, there is no such pattern in our voluntary skeletal muscle contractions thus an automatic myogenic rhythm of action potentials are not required in skeletal muscles.
Looking at a fasciculus from both a cardiac and skeletal muscle shows that they are structured slightly differently. Figure 2.1 and Figure 2.2 (see below) show simplified versions of the structure of both muscles. Figure 2.1 shows an example of skeletal muscle. It is made of long thin cylindrical fibres, each being innervated by a single somatic alpha motoneuron. The axon enters the muscle and branches, connecting to single muscle fibres.
In cardiac muscle the fibres are linked together by a type of intercalated disc called a gap junction. Also the fibres are held together by adherens junctions. These strengthen the overall structure of the cardiac muscle so the forceful contractions in the heart don’t tear the fibres. The gap junctions are vital for the functioning of the heart. They allow the electrical signals produced from the SAN to pass between muscle cells so they all contract in a synchronised way and the atria followed by the ventricles undergo systole.  The heart has Purkinje fibres that conduct the action potential so that they go from the SAN in the right atrium all the way to the left ventricle. Damage to cardiac muscle fibres may cause unsynchronised contractions. This irregular and fast contraction of the heart is called fibrillation. If this occurs in somebody, without treatment they are likely to die. It can be treated by a large electric shock delivered across the chest by the use of a defibrillator. This aims to stop and then restart the APs from the SAN and thus for the heart to beat regularly again.
Cardiac and skeletal muscle will both react to a single action potential by producing a single twitch response. When the frequency of signals increase, skeletal muscles show summation, where two APs, which occur very close together, will result in one stronger response rather than two normal responses. Eventually a tetanus can occur and instead of simply undergoing a series of single twitches for each action potential, the muscle remains in a contracted state for brief periods, which is far more efficient. This tetanus occurs because the refractory period is a lot shorter than the time it takes for a single cycle of contraction and relaxation.
In cardiac muscle cells however, the duration of the action potential is a lot longer, due to slowly activating calcium channels and the T-tubules being relatively longer. Because another action potential cannot occur until the response of the previous action potential has been completed, cardiac muscle cannot undergo a tetanus. This is extremely important for cardiac muscle because time is needed for the heart to sufficiently fill up with blood before the next action potential arrives. A tetanus would prevent this happening and the heart would undergo systole and relaxation (diastole) at times when there is very little or no blood in the heart. Again, fibrillation is likely to occur. Due to the fact that cardiac muscle relaxes fully between contractions, it doesn’t tire like skeletal muscle does. This is a benefit for cardiac muscle because if one’s heart started to tire one would get angina and some areas of cardiac muscle may start to die.
Due to the heart being constantly active, a lot more ATP is needed in cardiac muscle cells than in skeletal muscle cells, which only contract when required to. Therefore cardiac muscle has a larger number of mitochondria than skeletal muscle. Cardiac muscle undergoes constant oxidative phosphorylation to provide the ATP required for the actin to slide over myosin and thus for the muscle to contract. This means the cardiac muscle also requires its own supply of oxygen and respiratory substrates to respire aerobically. These are supplied via coronary arteries, which branch off from the ascending aorta. Having this supply and consequently producing a lot more ATP, is very effective for contractions. Skeletal muscle though, does not have as many mitochondria because it contracts relatively less frequently and does not need the constant supply of ATP.
Relatively there is a huge difference in the length of a cardiac muscle fibre and a skeletal muscle fibre. Each cardiac fibre is up to 100µm whereas each skeletal fibre is between a few mm to a 10cm . A muscle fibre is also known as a muscle cell. Most cells, including cardiac muscle fibres (cells), have one nucleus. Skeletal muscle fibres have many nuclei along the fibre (figure 2.1).
This can be explained by looking again at the lengths of each type of fibre. Each skeletal muscle fibre is at least ten times the length of a cardiac muscle fibre. It would not be very effective for skeletal muscle to have just one nucleus to supply the whole length of the cell. The rough endoplasmic reticulum, which is positioned in the cell near the nucleus, has ribosomes on its surface where polypeptides are compiled. Therefore even if the nucleus was positioned in the middle of the cell, any polypeptides or proteins will be synthesised near there and would require ATP to transport it to where it is needed along the length of the cell. As a result, it is far more effective to have many nuclei scattered along the muscle fibre. Cardiac myocytes (muscle cells) are relatively a lot shorter, thus one nucleus is enough to provide for the whole fibre (see figure 2.2).
Aerobic respiration is vital in cardiac muscle. It is the main source of ATP in cardiac muscle and is as a result of oxidative phosphorylation. The main respiratory substrates in cardiac muscle are fatty acids  , and also carbohydrates. Approximately 1 – 2% of the ATP in the heart originates from anaerobic respiration in basal metabolic conditions. This can go up to around 9% in hypoxic conditions, but in any more extreme hypoxic circumstances not enough oxidative phosphorylation occurs so there’s not enough ATP produced for cardiac contractions, and the cardiac muscle will begin to die.
Skeletal muscles have three sources of phosphate to make ATP as and when it is required: creatine phosphate, glycogen and cellular respiration. The creatine phosphate gives its phosphate to an ADP to leave ATP and creatine. There is about 10 times the amount of creatine phosphate than there is of ATP, so this is provides a good source of ATP. Skeletal muscle only contains about 1% glycogen. It can though undergo glycogenolysis to convert glycogen to glucose-1-phosphate. This goes on to yield just two molecules of ATP, so evidently this is a limited source. Cellular respiration is the main source of ATP during lengthy exercise and when converting lactic acid to glycogen.  
There are many differences between cardiac and skeletal muscle. Both have striations but beyond that, they have special unique features that make their functions more effective. The heart is myogenic making it self-sufficient whereas skeletal muscle is controlled by the nervous system. It is also vital that the heart’s cardiac muscle works without any problems, as even the slightest of problems in the heart can lead to death. Both types of muscle are important to not only humans but all animals. Cardiac muscle, as previously mentioned, is vital to our existence; without it we could not survive as it is needed to circulate oxygen and nutrients around the body. Skeletal muscle allows us to interact with our environment with ease and for humans this is most important as it lets us drive a car, use a computer or walk to university for example. For other animals it allows them to chase prey or run from a predator. And if the muscles weren’t as effective, there may be less ease when carrying out such activities.
Literature cited
Gillian Pocock, Christopher D. Richards (2006). Human Physiology – The Basis of Medicine. Oxford Core texts. Pages 84 & 85, Page 87 figure 7.6
José Marín-García & Michael J Goldenthal (2002) – ‘The Mitochondrial Organelle and the Heart’, Rev Esp Cardiol, Volume 55, Issue 12, pp. 1293 – 1310, ISSN: 1579-2242

Understanding Skeletal Muscle Contraction Physiology Essay

Muscle contractions are a result of the buildup of tension within the muscle, and for muscles to contract, they must have a continuous supply of energy in the form of a molecule called adenosine triphosphate or ATP (Silverthorn, D.U., 2010). Through muscle contractions, we are able to run, walk, lift, push, sit, and even chew our food (Stabler,, 2009). In addition to an energy requirement, skeletal muscles must be stimulated to contract (Stabler,, 2009). Skeletal muscles are stimulated from an action potential that originates from within motor neurons (Stabler,, 2009). Motor neurons are those that send electrical signals to skeletal muscle cells (Stabler,, 2009). An action potential is the electrical signal that occurs when positively charged ions flood into the motor neuron as a result of a chemical, electrical, or other type of stimulus (Stabler,, 2009). This signal, an area of intracellular positivity, self propagates down the length of the neuron towards the muscle cell (Silverthorn, D.U., 2010). Once this signal reaches the muscle cell, it is converted into a muscle contraction through a process called excitation-contraction coupling (Stabler,, 2009). The interior of muscle cells also becomes very positive resulting in a muscle contraction.

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Muscle contractions have 3 different phases which include the latent period, contraction phase, and the relaxation phase (Silverthorn, D.U., 2010). The latent period occurs between the start of an action potential and the beginning of a muscle contraction (Stabler,, 2009). This is the phase that will be studied later. The contraction period begins at the end of the latent period and ends when muscle tension ends (Stabler,, 2009). The relaxation period occurs begins at the end of the contraction period until the muscle becomes free of tension (Stabler,, 2009). To initiate a muscle contraction, the stimulus must reach its threshold. This is the minimal stimulus required to generate the action potential within a muscle cell causing the internal cellular environment to become positive (Stabler,, 2009). In addition, the change in stimulus intensity can play a role in how strongly the muscle generates force when it contracts which is referred to as the active force (Stabler,, 2009). As a stimulus is repeatedly applied to a muscle, fatigue will eventually occur. Fatigue can refer to a deficit in muscle functioning or a gradual decline in the force sustained by a muscle (Enoka and Duchateau, 2008). Other research has shown that fatigue could be the result of metabolic changes that occur within the contractile mechanisms within the muscle fibers such as changes in ion concentrations (Allen and Westerbland, 2001).
If the latent period length is dependent upon the strength of the stimulus, increasing the electrical stimulus intensity should also increase the latent period, and since a threshold stimulus needs to be reached for a contraction to occur, then there will be a minimal amount of electrical stimulation required to generate a muscle contraction. In addition, if the active force strength is dependent upon the strength of the stimulus intensity, an increase in stimulus intensity should increase the active force. If muscle fatigue is occurring due to repeated stimuli over a period of time, then applying a stimulus at a constant rate should result in a decrease of sustainable force within the muscle. These experiments will be carried out using an electrical stimulus by passing a known amount of voltage through an isolated skeletal muscle attached to a metal holder that will transmit the data to a recorder and an oscilloscope screen for analyses (Stabler,, 2009)
Materials and Methods
In order to understand muscle contraction physiology, I evaluated 4 different experiments. The first 3 experiments were designed to use a single stimulus to evaluate the latent period of a muscle contraction, to evaluate the threshold stimulus of a muscle contraction, and to evaluate the effects of increased stimulus intensity on a muscle contraction. The fourth experiment was designed to demonstrate the effects of muscle fatigue. The following materials were used for these experiments: an isolated skeletal muscle (75mm in length), a metal holder to measure force generated by the skeletal muscle, an oscilloscope, an electrical stimulator (single and multiple stimulus), and a data collection box. The first experiment was designed to determine the latent period of a muscle contraction. First, the muscle was attached to the metal holder. The electrode from the electrical stimulator was rested on the surface of the muscle. The electrical stimulator was set to 6.0 volts. A muscle contraction was induced by applying a single electrical stimulus using the electrical stimulator. The data generated a tracing on the oscilloscope screen which was used to determine the latent period by selecting the point where the flat line began to rise. The data were recorded using the data collection box. I repeated this experiment using the following voltages: 1.0 volts, 3.0 volts, and 10.0 volts. These voltages were used to see if changes occurred within the latent periods. For the second experiment, the data generated was used to determine the threshold voltage. The threshold voltage occurred when the active force measured in grams was greater than 0. The equipment setup was the same as the last experiment, and the electrical stimulator was set to 0.0 volts. At 0.0 volts, the muscle was stimulated and the results observed and recorded using the oscilloscope and data recorder respectively. This experiment was repeated multiple times by increasing the voltage by 0.1 volts until the minimal threshold voltage was determined. For the third experiment, the effects on muscle contractions due to an increase in the electrical stimulus intensity were explored. Again the same equipment setup was used. The initial voltage was set to 0.5 volts followed by stimulation of the skeletal muscle. The data were observed and then recorded. This experiment was repeated multiple times by increasing each subsequent voltage by 0.5 volts. This continued until the data showed there was no change in the increase in active force. For the final experiment, fatigue was induced in the skeletal muscle. The equipment setup for this experiment was similar to the first three experiments. However, a different electrical stimulator was used which incorporated a multiple stimulus option as well as a single stimulus option. The multiple stimulus option added the ability to start and stop the stimulus activity. This experiment was designed so that several stimuli per second were being applied to the skeletal muscle if so desired. The electrical stimulator voltage was set to 7.0 volts, and the number of stimuli per second was set to 100. The muscle was then stimulated for approximately 400 seconds by selecting the multiple stimulus option, and the graphical data were recorded from the oscilloscope.
For experiment one, the latent period was recorded in milliseconds and was compared to its corresponding stimulus voltage. The time measurement (latent period) reflected the start of the flat line until it began to rise. Below is a summary of the recorded data.
Latent Period Determination
Stimulus Voltage (V)
Latent Period (msec)
For experiment two, the threshold stimulus determination data was collected by measuring the electrical stimulus voltage and its corresponding active force generated. Once the active force became greater than 0, the experiment was stopped. Below is a table with the collected data.
Threshold Determination
Stimulus Voltage (V)
Active Force Generated (gms)
For experiment three, the data were collected in order to determine the effects of increased stimulus voltage on muscle contractions. The data reflected 0.5 volt interval increases in the electrical stimulus until 10 volts were reached. Below is the summary of the data.
Muscle Contractions – Increased Stimulus Effects
Muscle Contractions – Increased Stimulus Effects
Stimulus Voltage (V)
Active Force Generated (gms)
Stimulus Voltage (V)
Active Force Generated (gms)
For experiment four, data was graphed in order to demonstrate the effects of fatigue. The rate of the multiple stimulus was 100 stimuli/second at a constant setting of 7.0 volts. The data were recorded over a 400 second interval. Below is a graphical representation of the collected data.
Muscle Fatigue – Effects of Prolonged Stimuli Over Time (Stabler,, 2009)
C:Shea’s StuffHuman PhysiologyFatigue.jpg
Allen, D.G. and H. Westerbland. (2001). Topical Review: Role of phosphate and calcium stores in
muscle fatigue. Journal of Physiology 536.3: 657-665.
Enoka, R. and J. Duchateau. (2008). Muscle Fatigue: what, why and how it influences muscle function.
Journal of Physiology 586.1: 11-23.
Silverthorne, D.U. 2010. Human Physiology: An Integrated Approach. 5th Edition. Pearson
Benjamin Cummings, pp. 408-422.
Stabler, T., Smith, L., Peterson, G., and Lokuta, G. 2009. PhysioEx 8.0 for Human Physiology —
Laboratory Simulations in Physiology. pp. 17-22.

Histological Features of Skeletal Muscle

The aim of this report is to describe the basic histological features of a skeletal muscle and the differences between type I and type II skeletal muscle fibres. I will also describe the motor neuron unit and explain Henneman’s size principle of recruiting motor units.
The basic features of skeletal muscle
General Structure   
The main function of skeletal muscle is to provide support, maintain posture and provide movement. Skeletal muscles comprise of densely packed groups of elongated cells which are known as muscle fibres, which are held together by fibrous connective tissue. Many capillaries penetrate this tissue to enable muscles to be supplied with oxygen and glucose needed for muscle contraction. Skeletal muscle is comprised of bundles of long striated fibres; the striated appearance is caused by the repeated structure of the fibres inside the muscle cell (Page, 2001). Individual muscle cells are called myocytes and muscles are made up of bundles of individual muscle cells. These bundles are called fascicles. Each muscle cell is surrounded by a connective tissue cover called the endomysium, and each bundle is surrounded by a connective tissue covering called the perimysium. Fascicles form muscle which is surrounded by a connective tissue called the epimysium.

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Skeletal muscles are made up of three types of fibres. Type I (red/ slow fibres), type IIa (red/ fast fibres) and type IIb (white/ fast fibres). Type I fibres are slow-contracting muscle fibres and they have a very dense capillary network, because these fibres have a high capacity for ATP production and a low myosin ATPase activity compared to type II fibres; the main pathway for ATP production is aerobic cellular respiration. Type IIa fibres have a higher myosin ATPase activity than type I fibres, a high capacity for ATP production and a dense capillary network; because of this the main pathway for ATP production is aerobic cellular respiration. Type IIa also has high levels of intracellular myoglobin. Type IIb fibres have a higher myosin ATPase activity than type I fibres but a lower capacity for ATP production and a lighter capillary network; this means that the main pathway for ATP production is anaerobic glycosis, which is fast but not sustainable for as long as aerobic respiration which means muscle fatigue happens sooner. There is no intracellular myoglobin unlike type I and IIa, which means that it is white in colour (Types of skeletal muscle Fibres, 2016).
The structure of the sarcomere
The plasma membrane of the skeletal muscle fibre is the sarcolemma and contains cylindrical structures called myofibrils. The myofibrils practically fill the cells and push the nuclei to the edges of the cell. Each myofibril have light and dark bands and are aligned with each other so that the light and dark bands are next to each other; this gives the cells their striated appearance. The light bands are called I bandsand the dark bands are called A bands. In the middle of the I bands there is a line which is called the Z line and in the middle of the A bands there is a light zone called the H zone. In the middle of the H zone there is another line called the M line. The sarcomere consists of several individual protein elements and some of these proteins are thread-like proteins called myofilaments.
There are two main types of myofilaments. The thick myofilaments which are made up of proteins molecules called myosin. The myosin molecules are shaped like golf clubs with long shafts. Myosin forms the thick myofilaments by forming bundles in which the heads of the “golf clubs” stick out at either end of the filament and the shafts form a “bare” zone in the middle of the filaments. The heads of the thick myofilaments form attachments with the other type of myofilaments, the thin actin myofilaments and these attachments are called cross bridges.The heads are the areas on the thick myofilaments that use the energy in the ATP molecule to power the muscle contraction. The second type are the thin myofilaments, which are made of the protein actin. They have binding sites to which the heads of the thick myofilaments attach (Hwang, 2015).
The triad
A triad is a structure that is formed from a T-tubule with a sarcoplasmic reticulum known as the terminal cisternae on either side. Each skeletal muscle fibre has many thousands of triads, visible in muscle fibres that have been sectioned longitudinally (Al-Qusairi & Laporte, 2011).
Table 1; Comparison of the different types of skeletal muscle fibres

(Bushell, 2013)
The structure of a motor unit
A motor unit is made from a motor neuron and the skeletal muscle fibres innervated by that motor neuron’s axonal terminals (Purves, et al., 2001). A group of motor units is called a motor pool and the number of fibres in each unit can differ within muscles. This impacts precision and force generation. Differential initiation of single or multiple motor units with a motor pool can therefore control precision and force of movement.
Henneman’s size principle of motor unit recruitment
Henneman’s size principle states that; motor units are recruited from smallest to largest and as more force is needed, motor units are recruited in a certain order per the extent of their force output. This means that the smaller units are recruited first which means that it reduces the amount of fatigue an organism experiences by only using fatigue resistant muscle fibres, unless a higher force is needed and then fatigable fibres are used. This means that slow twitch, low-force, and fatigue resistance muscle fibres are activated before fast twitch, high-force, less fatigue resistant muscle fibres (Bawa, Jones, & Stein, 2014).
The motor unit and the Henneman’s size principle of motor unit recruitment
The structure of the motor unit
A motor unit is constructed from a motor neuron and skeletal muscle fibres, they innervated by the axonal terminals (Purves, et al., 2001). The motor neuron and its muscle unit are inseparable in function, this is because the action potetial in the neurons activates the fibres of the muscle unit (Karpati, 2010). A group of motor unit are gathered in columnar, spinal nuclei and this is called motor neuron pools. The number of fibres in each unit can differ from another and this then affects the force generation and the precision of the movement (Present, 1997).
The Henneman’s size principle of recruiting motor unit
The Henneman’s size principle expresses that motor units that are recruited from the smallest to the largest, this is because if more force is needed, then are recruited in a certain order due to the extent of their force output. Therefore, this means that the smallest motor units are employed first and this reduces the amount of fatigue that an organism experiences, by only using fatigue resistant muscle fibres, unless a higher force is needed, then fatigable fibres are used (Bawa, Jones, & Stein, 2014).
Al-Qusairi, L., & Laporte, J. (2011). T-tubule biogenesis and triad formation in skeletal muscle and implication in human diseases. Skeletal Muscle, 1(1). doi:10.1186/2044-5040-1-26
Bawa, P., Jones, K., & Stein, R. (2014). Assessment of size ordered recruitment. 8. Retrieved from
Bushell, D. (2013). Muscle-specific hypertrophy: Chest, Triceps and shoulders. Retrieved from TheGymLifestyle:
Hwang, P. (2015). Targeting the sarcomere to correct muscle function. Nature Reviews Drug Discovery, 14(5). doi:10.1038/nrd4554
Page, M. (2001). Human body: An illustrated guide to every part of the human body and how it works. (A. Baggaley, Ed.) London: Dorling Kindersley Publishers.
Purves, D., Augustine, G., Fitzpatrick, D., Katz, L., LaMantia, A.-S., McNamara, J., & Williams, M. (2001). The Motor Unit. Sinauer Associates. Retrieved from
Types of skeletal muscle Fibres. (2016). Retrieved from Ivy Roses:

Forces in Skeletal Structure of the Arm

2); hence if it is far away then it is smaller (d2> d1). Therefore the mechanical advantage may increase or decrease depending on the distances from the fulcrum.
We can also measure torque (any point of the fulcrum), which refers to the force applied over a distance (lever arm) that causes rotations of the fulcrum. The torque is dependent on three variables: amount of force, angle of application of force and the length of the moment arm/ R. As mentioned above in figure 1, the total torque is equal to zero;. The following formula is used to calculate Torque τ:

Where F is the force (0.71Nm),
R is the distance from the location force is applied to the joint (moment arm) (35cm)
Ï´ is the angle between the force and the radial line
I will now find out the torque for the same question, if the angle is 20°;

This links in with the above statement of the total torque being equal to zero.
I am now going to discuss about the elbow and the forces applied to it. There are many properties which can be used to calculate the forces of the biceps: the angle of the elbow; the length of the upper and lower arm bone; and the distance from the bone to the location the muscle is attached to.
I will now use this formula to find out the force exerted by the biceps (equilibrium) in holding the object, which is the sum of the clockwise moments about any points, equals the sum of the anticlockwise moments about the same point:

Taking 5cm from bone to the biceps attachment;

The force exerted by the biceps holding the object is 891.8N.
Similarly, we can also measure the tension of the bicep/arm holding the object. The image below shows an arm being held out and elevated from the shoulder by the deltoid muscle. The forces can be measured the taking the sum of the torques (of the shoulder joint, the tension (T) can be calculated:

Where W1 is the weight of the arm,
W 2 is the weight of the object
Using the above question; if = 20; the weight of the arm (W1) is 68.6N and the weight of the object (W2) is 49N, then calculate T:

= 113.96N
Therefore the force needed to hold up the bicep/arm at 20, is 113.96N.
Task 2. A) You must complete the energy changes/momentum worksheet. Assessment criteria 2.3,2.4
See attachments
b) You must produce a report that describes the equations of motion needed to calculate the range and maximum height that a projectile thrown by a human can achieve. This report must include examples of both the range equation and maximum height equation. You could use a sports person throwing a ball as an example.
A projectile is any object that has been thrown or shot by a human (measures projectile motion). Projectiles are affected by two factors: gravity (Horizontal motion) and air resistance (vertical motion which is the force of gravity pulling down the object).
As part of this task I am going to carry out various calculations to find out the range and maximum height that a golf ball can achieve when a golf player hits the ball.

A golfer hits a ball so that it moves off with a speed of 37m/s at an angle of 45. I am going to calculate how far the ball goes; the maximum height it will reach; and how long it takes for the ball to get there.
Firstly, I am going to use the following formula to calculate how far the ball travels;

Where R is the range/resultant (how far the ball goes),
V0 is the initial velocity of the ball speed (37m/s)
g is the gravity (9.8m/s) also can be used as (a) since it is constant
Ï´ is angle of the ball (45°)

Hence, when a ball is hit with a speed of 37m/s at 45°, the ball will go far as 139.7m.
Secondly, I will calculate the maximum projectile height (how high a ball will go) by using the following method;

Where Ymax is the maximum projectile height that the ball will go

The maximum projectile height that a ball will reach is 34.9m.
The final calculation that I am going to carry out is the flight time so that I can find out how long it takes for the ball to get there. I will use the following method;

Where Tflight is the time flight of how long it takes for the ball to reach there.

The flight time for the ball to get there is 5.3s.
Using the same question, I now want to find out how far the ball travels horizontally from A to C and the time that the ball is in the air, ignoring any air resistance and taking g = 10ms-2.

Firstly, I will calculate the time that the ball is in the air for, by using the following formula;
I need to find out the vertical motion from A to B first = 90° – 45° = 45°
Where v is the final velocity (0 since it is moving horizontally),
u is the initial velocity (37m/s x cos 45) is 26.16m/s
a is the acceleration (10m/s)
t is the time

, so the time it takes from A to C is twice this
I will now look at the horizontal motion from A to C.
Horizontal component of velocity. This is constant during motion.
Horizontal distance = horizontal velocity X time of flight

Therefore the horizontal distance the ball travels from A to C is 136.8m.
Task 3. You must produce a report showing how the variation of blood pressure affects the human body. Your report must include calculations to determine pressure based on area or density values. Assessment criteria 3.1,3.2
Bernoulli’s Principles explains that flowing blood has different speeds and therefore different kinetic energies (KE) at different parts of the arteries. It determines the relationships between the pressure, density and velocity at every point in a fluid. Bernoulli’s Principle was discovered by a Swiss physicist called Daniel Bernoulli in 1738. He has demonstrated that as the velocity of fluid flow increases, its pressure decreases.

Flowing blood has mass and velocity. The mean velocity squared (V2) is equal to the kinetic energy. The image below demonstrates the variance of kinetic energy at different parts of the vessels and also shows the theory of Bernoulli’s Principle:
Therefore KE = ½ mV2. As we know from above that blood flows inside arteries, were pressure is applied laterally against the walls of the vessel which is known as the potential or pressure energy (PE). The total energy (E) of the blood pressure within the artery is the sum of the kinetic and potential energies (presuming there are no gravitational effects):
E = KE + PE(where KE ∝ V2)  Therefore,E ∝ V2 + PE
Similarly, Bernoulli’s Principle states that the sum of the Pressure (P), the kinetic energy per unit volume (1/2 pv2), and the gravitational potential energy per unit volume (pgy) has the same value at all points along a streamline. The equation below shows this:

There are two vital theories that follow from this relationship, which includes:

Blood flow driven by the variation in total energy between two points. Normally, pressure is considered as the driving force for blood flow but in fact it is the total energy that moves flow between two areas (i.e. longitudinally along a blood vessel or across a heart valve). KE is relatively low in most of the cardiovascular system; hence PE difference is the energy that drives flow. Similarly, is KE is high then the total energy increases which explains the flow across the aortic valve during cardiac ejection. This is because, as KE drives blood across the valve at a very high velocity, it ensures that the total energy (E) in the blood crossing the valve is higher than the total energy of the blood more distal in the aorta.

KE and PE can be converted to maintain the total energy unchanged, which is the basis of Bernoulli’s Principle. This principle is basically about the blood vessel that is suddenly narrowed then returned to its normal diameter. The velocity increases as the diameter decreases in narrowed region (stenosis). Blood flow (F) is the mean velocity (V) and the vessel cross-sectional area (A) is directly related to diameter (D) (or radius, r2); hence V ∝ 1/D2. If the diameter is reduced by half in the region of the stenosis, the velocity increases 4-fold, due to KE ∝ V2, hence KE increases 16-fold. The image below demonstrates this:

The image above shows the total energy being conserved within the stenosis (E actually decreases because of resistance), then the 16-fold increase in KE will decrease in PE. Once past the narrowed segment, KE will go back to its pre-stenosis value as the post-stenosis diameter is the equal to the pre-stenosis diameter, hence flow is conserved. Due to the resistance of the stenosis and turbulence, the port stenosis PE and E will both fall. Therefore, blood flowing at greater velocities has greater ratio of KE to PE.

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As we know, blood pressure is the force of fluid against the walls of the arteries, similar to how water exerts the pressure inside aplastic pipe. It is made up of systolic and diastolic pressure. Systolic pressure is the top figure and relates to when the heart is contracting (beating) and forcing blood through the arteries and transporting it to the rest of the body i.e. brain, kidneys etc. The normal values for systolic pressure is from 120-139mmHg. Diastolic pressure is the bottom figure and is linked to when the heart is relaxing. The normal value for diastolic pressure is between 80-89mmHg. Hence, if the values exceed these numbers, then it is considered to be hypertension.
Hypertension is high blood pressure which is caused by the increased force of blood flowing through the arteries. Healthy arteries are flexible, strong and elastic. Inner lining of the arteries are smooth allowing the blood to flow freely, supplying important organs and tissues with adequate nutrients andoxygen. Hypertension can gradually lead to wide range of problems such as damaging the cell’s inner lining of the arteries; hence releasing a cascade of events that causes the artery wallsthick and stiff (called arteriosclerosis), or hardening of the arteries. Similarly, the fats from the diet enter the bloodstream and passes through the damaged cells. However, plaques are prone to building up in the arteries leading to atherosclerosis. These changes lead to blocking blood flow to the heart, kidneys, brain, arms and leg.

Heart: it causes coronary artery disease, which is narrowing of the arteries that doesn’t allow blood to flow freely through the arteries. Leading to chest pain, heart attack (myocardial infarction)or irregular heart rhythms (arrhythmias). Hypertension can also cause enlarged left heart as the pressure forces the heart to work harder than necessary. Similarly, overtime the strain on the heart leads to the heart muscles to weaken and work less effectively causing the heart to wear out and fail.
Brain: – hypertension can cause mini-strokes (Transient ischemic attack (TIA)), which a temporary disruption of blood supply to the brain caused by blood clot or atherosclerosis. Similarly, it can lead to the full-blown stroke which happens when part of the brain is deprived of oxygen and nutrients leading brain cells to die. Uncontrolled hypertension damages and weakens the brain’s blood vessels, causing to narrow, rupture or leak. Narrowing and blockage of the brain’s blood vessels can also lead to Dementia and mild cognitive impairment.
Kidneys: – filters excess fluid and waste from the blood via a process that depends on healthy blood vessels. Hypertension can damage both the blood vessels and leading to the kidneys. This leads to various kidney diseases, failure and scarring of the kidney.
Eyes:- Blood vessels supplies blood to the eyes; hence high blood pressure can damage the blood vessel (retinopathy)

Reference 22nd October 2013 22nd October 2013 24th October 2013 24th October 2013 25th October 2013 26th October 2013 26th October 2013 27th October 2013 27th October 2013 29th October 2013 29th October 2013 30th October 2013 1st November 2013 25th November 2013 25th November 2013 27th November 2013,d.ZGU 28TH November 2013
Dobson et al. (2002). ‘ Collin advanced – Physics’. Collins eduction : London
Rounce, J.F and Lowe, T.L. (1992). ‘Calculations for A level Physic’. Second edition. Stanley Thornes: Britain
Boutal et al. (2008). ‘AS-Level physics – exam board’. Coordination group publications CGP: Newcastle
Tsokos, KA. (2008). ‘Physics for the IB Diploma’. Fifth edition. Cambridge university press: united kingdom
Johnson et al. (2000). ‘Advanced physics for you’. Nelson Thornes: united kingdom

Structure And Functions Of The Skeletal System

HUMAN SKELETON – is the internal structure that holds the human body up and with the help of the muscular system allows us to move, also works to protect the delicate and vital organs found inside it from being damaged.
At birth the human skeleton is made up of 275 different bones and as the body matures some of these bones start to fuse together leaving only 206 bones in an adult human.
A skeleton has got five different job roles which are:
Blood production.
There are two major systems of bones in the human body which are Axial & Appendicular skeleton.
AXIAL SKELETON – it is essentially suited for protection.
It forms the main axis/core of a human skeletal system.
It consists of:
Cranium – protects the brain.
Made up of hard sheets of bones with fixed joints.
Sort of a ball shape at the back.
It is comprised of eight cranial and fourteen facial bones.
The cranial bones make up the protective frame of bone around the brain.
The facial bones make up the shape of a human face.
Thorax – takes part in both protecting the heart and lungs, and also helps in shape of the body.
Made up of a sternum and 12 pairs of ribs.
Forms a concave shape.
Ribs are flat bones that are close together and make a concave shape that goes around the internal organs that are vital such as heart and lungs.
DIAGRAM: fully labeled on next page.
Vertebral column (spine or backbone) – consists of a series of 33 irregularly shaped bones that are called vertebrae.
Extends from the base of the cranium to the pelvis, providing a central axis for the body
Accounts for around 40% of a human overall weight.
The vertebrae of a human spine are held together strongly by powerful ligaments that allow little movement between your adjacent vertebrae but afford a considerable degree flexibility along the spine as a whole.
Its main job role is to protect the spinal cord even though it also helps by supporting the ribcage by maintaining the balance between it and the abdominal cavity.
The bones of a vertebral column have got cartilage joints.
It is divided into parts which are:
Cervical vertebrae (seven) – these are the vertebrae in the neck. The first two are known as the atlas (C1) and the axis (C2). These two form a pivot joint that allows the head and neck to move freely. It is the smallest and most vulnerable vertebrae of the vertebrae column but it is the most important because it sends signal to the thoracic from the head.
Thoracic vertebrae (twelve) – these are the vertebrae of the mid spine, which articulate with the ribs and are also found in the thorax. The thoracic vertebrae are larger than the cervical ad increase in size from top to bottom.
Lumbar vertebrae (five focused) – these are situated at the lower back and are the largest of the movable vertebrae. They are required to support more weight than other vertebrae and provide attachment for many of the muscles of the back. The discs that lie between these vertebrae produce a concave curve in the back.
Sacral vertebrae (five) – these are fused to form the sacrum. This is a triangular bone located below the lumbar and it forms the back wall of the pelvic griddle sitting between the two hip bones.
Coccygeal vertebrae (four focused) – this is the last part of the vertebral column which has got four fused bones that form a coccyx or a tail bone.
APPENDICULAR SKELETON – it is for movement/leverage, shape, and blood production.
It can also sometimes take part in protection
Consists of 126 bones
makes body movement possible and protects the organs of digestion, excretion, and reproduction.
The word appendicular means referring to an appendage or anything attached to a major part of the body, such as the upper and lower extremities.
The appendicular skeleton is the part of the skeleton that includes the pectoral girdle, the upper limbs, the pelvic girdle, and the lower limbs. The appendicular skeleton and the axial skeleton together form the complete skeleton
Pectoral griddle – consists of two shoulder blades (scapulae) and two collar bones (clavicles). These bones articulate with one another, allowing some degree of movement.
Shoulder blades (scapulae) – is a flat triangular bone which stretches from the shoulder to the vertebral column at the back.
On the back side it has a bony ridge for the attachment of the muscles.
The bony ridge forms a major projection, the acromion, above the shoulder joint.
Beneath the collar bone and just on the inside of the shoulder joint, is another bony projection of the shoulder blade, the coracoid process, which also serves for the attachment of muscles.
The upper outer corner of the shoulder blade ends in the glenoid cavity into which fit the head of upper arm bone forming a ball and socket joint.
collar bones (clavicle) – has got a rod-shaped and forms a roughly S-shape
It lies horizontally and articulates with the upper end of the breastbone, right in the middle and front, just above the first rib
The lateral end articulates with the acromium.
Collar bones serve as a support for the shoulder blades in front and keep the shoulder blades back so that the arms can hang freely at the sides of the body.
They prevent the pectoral girdles from getting out of joint easily and sufficient movement of the shoulders.
Pelvic girdle – is composed of two coxal (hip) bones that are located at the base of the spine. It is also known as the hip girdle. It is the bony structures to which the last limbs of a vertebrate are attached to.
1. Ilium – is the upper part of the bony pelvic which is also the largest. It has a prominent ridge running along its upper surface called the iliac crest. (@biology)
2. Iliac crest – is for the attachment of body wall muscles.
3. Symphysis pubis – is the midline cartilaginous joint uniting the left and right pubic bones.
Upper limb – can be divided into five main regions which are:
The Upper Arm (Humerus) – is a single bone.
The upper end consists of a hemi-spherical ball which fits into the socket of the shoulder blade to form the shoulder joint.
The lower end of the humerus forms a shallow ball and socket joint with the radius and a hinge joint with the ulna in the elbow.
Forearm (Radius & Ulna) – the ulna is the larger of two bones situated in the inner side of the forearm.
The upper end of the ulna articulates with the lower end of the humerus forming a strong hinge joint in the elbow region.
The lower end of the ulna is slender and plays a minor role in the formation of the wrist joint.
The radius is situated on the thumb side of the forearm and its upper end articulate with both the humerus and the ulna.
The broad, lower end of the radius forms a major part of the wrist joint, where it articulates with the wrist bones (carpals). The radius also allows the forearm to be rotated. The radio-ulnar joints are pivot joints in which the moving bone is the radius. As the head of the radius pivots at these joints, the lower end of the radius moves round the lower head of the ulna.
The Wrist
The wrist consists of eight carpal bones. These are small, short bones that are arranged in two rows of four. They have articulating facets which allow them to slide over one another.
The Palm of the Hand
The palm is supported by five long metacarpals. The metacarpals articulate with carpals at one end and with the phalanges at the other end.
The Fingers
The fingers are made up of fourteen phalanges. There are three phalanges in each finger but only two in the thumb.
Task 1b
The bones in the skeleton are classified according to their shape and size. They are divided into different categories such as:
Long bones – they are found in the limbs. These have a shaft known as the diaphysis and they consist of two rounded ends known as the epiphysis. They act as levers.
Short bones – these are small, light, strong and cube-shaped bones. They are like sweet with a hard shell and a soft centre.
Flat bones – these are thin, flattened and slightly curved. They have a large surface area.
Sesamoid bones – these are bones found in the tendons, such as the patella in the knee.
Irregular bones – these are bones with complex shapes and cannot be classified under any of the other categories.
The cranium is a box-like cavity that consists of interlinking segments of bone that gradually fuse together during first few years of life. It contains and protects the brain.
They are long and slim bones. They provide a strong and mobile attachment for the arms and are designated for the performance of complex movements.
The ribs are long, thin, curved, flat bones. They form a protective cage around the organs in the upper body.
This is a long and flat bone that lies at the centre of the chest. It is commonly referred to as the breast bone and it divided into three sections: the top, the mid and the lower section. It forms the rib cage that protects the heart, lungs and major blood vessels.
The humerous is the largest bone in the upper limbs. It’s a long bone and its head joins with the scapula to make the shoulder joint. The end of this bone joins with radius and ulna to make the elbow joint.
Radius and ulna
The ulna and radius articulate distally with the wrist. The radius contributes more to the movement of the wrist than the ulna and is also the longer bone. The convex shape of the radius allows it to move around the ulna to make the hand turn.
The scapulae are large, triangular, flat bones that form the posterior part of the shoulder girdle. It serves as an attachment for several muscles. Movements of the scapula are brought about by scapular muscles.
The Ilium is the wide flat upper portion of the pelvis that is connected to the base of the vertebral column. It supports the lower abdominal organs. The ilium is the largest part of the innominate bone.
The pubis is also known as the pubic bone. It makes the lowest part of the innominate bone.
The Ischium is located below the ilium and makes the middle of the innominate bone.
These are the bones that make up the wrist. They are made of regular and small bones which are fit closely together and kept on place by ligaments.
On the palm of the hand metacarpals are padded by a thick layer of fibrous, connective tissue on the back of the hand and they can be seen and felt through the skin. The heads of the metacarpal bones form the knuckles. Metacarpals join the carpals with the phalanges and help support movement of the fingers.
These are small bones that make up the skeleton of the thumbs, fingers and toes. The phalanges at the top of the fingers are and toes are called distal phalanges, the ones that join the bones of the hands and feet are known as the proximal phalanges.
The patella (knee cap) is the triangular shaped bone in front of knee joint. It protects the knee joint.
Tibia and fibula
The tibia is the inner and thicker of the two long bones in the lower leg. It is also called the shin bone and is the supporting bone of the lower leg. The fibula is the outer and thinner bone of the lower leg. The fibula provides attachment for the muscles.
These are short and irregular bones. They help to support the weight of the body and provide attachment for the calves.
The metatarsal is one of the five long, cylindrical bones in the forefoot the forefoot is responsible for supporting body weight and balance pressure through the balls of the feet.
This is the longest bone in the body. The top of it fits into the sockets of the pelvis to make the hip joint, and the lower ends joins with the tibia to make the knee joint. The femur supports the weight of the upper body and enables movement of the legs.
Joints provide the link between bones. A joint is formed wherever two or more bones meet. There are three types of joint, each classified according to the degree of movement they allow.
A fixed joint occurs where the margins of two bones meet and interlock. Bands of tough, fibrous tissue hold the bones together. They are also known as fibrous or immovable joints. An example of a fixed joint is between the plates in the cranium.
Slightly movable
These allow some slight movement as the name suggests. The ends of bone are covered in hyaline cartilage which is separated by pads of white fibro cartilage. Slight movement is made possible because the pads of cartilage compress. Between most of vertebrae is an example of this type of joint.
They offer the highest level of mobility at a joint and they consist of two or more bones, the ends of which are covered with articular cartilage, which allows the bones to move over each other with minimum friction. Synovial fluid lubricates and nourishes the joint. The joint capsule is held together by ligaments. This provides the strength to avoid dislocation, while being flexible enough to allow movement.
Synovial joints can be divided into groups according to the type of movement they allow.
These allow movement in one direction only. Elbow and knee are typical examples of hinge joints. The types of movement allowed are flexion and extension.
Ball and socket
It allows movement in all directions. The types movement allowed are flexion, extension, abduction, adduction, circumductiom, rotation, pronation, supination, dorsiflexion, plantar flexion, inversion, evasion and hyper – extension. Examples include the hip and shoulder joints.
These are a modified version of ball and socket. Movement is backward and forwards and from side to side. They are also known as condyloid joints and the wrist joint is an example. Ellipsoid joints allow circumductiom, inversion and eversion.
These allow movement over a flat surface in all directions, but this is restricted by ligaments or bony prominence, for example carpals and tarsal. Gliding joints allow inversion, dorsiflexion, plantar flexion and eversion.
These allow rotation only about a single axis. An example is in the neck, where the atlas and axis join.
These are similar to ellipsoid joints but the surfaces are concave and convex. Movement occurs backwards and forward and from side to side, as at the base thumb.
Synovial Fluid – movement at joints stimulates the secretion of Synovial fluid. Becomes less thick & range of movement at joints increases.
Mineral Content – increased by physical activity on bones e.g. increase of calcium & collagen to keep up with the demand pressed on your bones.
Cartilage- becomes thicker becoming better at shock absorption, with regular exercise & it also connects the ribs to the sternum.
Tendons – they become thicker and are able to withstand greater forces applied when we take part in a physical activity.
Ligaments – these will stretch causing an increase in flexibility so that the person taking part in the physical activity is able to twist and turn without getting any injuries. (it helps increase agility)
Bones – becomes stronger & denser as a result of the demands you place on them through physical activity & exercise. So it becomes hard for the bones taking part in an activity to break compared to that of a person who is not taking part in any activity.
The main function of the muscles is to move the bones of the skeleton. There are three different types of muscle tissue which are:
Is an involuntary muscle that forms the wall of the heart and works continuously. It is highly resistant to fatigue. Each contraction and relaxation of the heart muscle as a whole represents one heart beat.
It is also known as striped or striated muscle. They are attached to the bones of the skeleton by tendons and they usually work in pairs. These muscles are voluntary i.e. works under conscious control.
It is an involuntary muscle that functions under the control of the nervous system. it is located in the walls of the digestive system and blood vessels and helps to regulate digestion and blood pressure.
All skeletal muscles contain a mixture of fast and slow twitch fibres.
Type 1 muscle fibres – slow-twitch
This type of muscles contract slowly with less force. They are slow to fatigue and suited to long duration aerobic activities. They are recruited for low intensity activities likes’ long-distance running.
Type 2a muscle fibres – fast-oxidative
They contract very quickly, are able to produce a great force as well as resistant to fatigue. These muscle types are suited for middle-distance evens like 800m and 1500m running.
Type 2b – fast-glycoltic
This type of muscle fibre contracts rapidly and can produce large amounts of force; they are better suited to activities that require sudden bursts of power such as high jump. They also tire easily.
Origin – muscles origin is attached to the immovable bone.
Insertion – muscles insertion is attached to the movable bone.
Function – flexes the lowers arm.
Location – inside of arm.
Movement – the origin is the scapula, which is movable, and the radius is the insertion that moves with contraction.
Sporting/exercise – when taking a jump shot in basketball the insertion moves back as the biceps contracts to pull the arm.
Agonist when making the shot.
Concentric contraction.
Function – extends the lower arm.
Location – outside of upper arm.
Structure –
Movement –
Sporting/exercise – when
Agonist when lowering then arm.
Antagonist when working against biceps.
Functions – abducts, flexes and extends upper arm.
Location – forms cap of shoulder.
Origin – clavicle, scapula and acromion.
Insertion – humerus.
Sport/exercise – forward, later and back-arm raises, overhead.
Functions – flexes and abducts upper arm.
Location – large chest muscle.
Origin – sternum, clavicle and ribcage.
Insertion – humerus.
Sports/exercise – all pressing movements.
Functions – flexion and rotation of lumbar region of vertebral column.
Location – six pack muscle running down abdomen.
Origin – pubic crest and symphysis
Insertion – Xiphoid process.
Sports/exercise – sit-ups.
Rectus femoris
Vastus lateralis
Vastus medialis
Vastus intermedius
Functions – extends lower leg and flexes thigh.
Location – front of thigh.
Origin – Ilium and femur
Insertion – tibia and fibula
Sports/exercise – knee bends, squats
Biceps femoris
Functions – flexes lower leg and extends thigh.
Location – back of thigh.
Origin – ischium and femur.
Insertion – tibia and fibula.
Sports/exercise – e.g. running (extending leg and flexing knee)
Function – plantar flexion flexes knee.
Location – large calf muscle.
Origin – femur
Insertion – calcaneus.
Sports/exercise – running, jumping and standing on tiptoe.
Function – plantar flexion.
Location – deep to gastrocnemius.
Origin – fibula and tibia.
Insertion – calcaneus.
Sports/exercise – running and jumping.
Functions – dorsiflexion of foot.
Location – front of tibia on lower leg.
Origin – lateral condyle.
Insertion – by tendon to surface of medial cuneiform.
Sports/exercise – all running and jumping exercise.
Function – extension of spine.
Location – long muscle running either side of spine.
Origin – cervical, thoracic and lumbar vertebrae.
Insertion – cervical, thoracic and lumbar vertebrae.
Sporting/exercise – prime mover of back extension.
Function – rotates and abducts the humerus.
Location – it is found between the scapula and humerus.
Origin – posterior surface of the scapula.
Insertion – intertubercular sulcus of humerus.
Sporting/exercise – all rowing and pulling movements.
Function – elevates and depresses scapula.
Location – large triangular muscle at top of back.
Origin – continues insertion along acromion.
Insertion – occipital bone and all thoracic vertebrae.
Sporting/exercise – shrugging and overhead lifting.
Functions – extends and abducts the lower arm.
Location – large muscle covering back of lower ribs.
origin – vertebrae and iliac crest
Insertion – humerus.
sporting/exercise – rowing movements
Function – lateral flexion of trunk.
Location – found on the waist.
origin – pubic crest and iliac crest
insertion -fleshly strips to lower eight ribs
Sporting/exercise – oblique curls.
Function -0 extends the thigh.
Location – large muscle on the buttocks.
Origin – ilium, sacrum and coccyx.
insertion – femur
Sporting/exercise – knee-bending movements, cycling.
Short-term responses – these are the responses that happens immediately and do not continue to be like that after the physical activity.
An increase in muscular temperature and metabolic activity.
Muscles become more pliable which increases their flexibility and reduce the risk of injuries.
Long-term responses – this is sort of an outcome that is achieved after a long time of training
Muscle bulk and size will increase.
Tendons become thicker and stronger.
Articular cartilage becomes thicker.
There is an increase in muscle tone and possibly reduction in body fat.
Cardiovascular System – Structure
The cardiovascular system consists of heart, blood vessels and blood. It is also referred to as the circulatory system. This system is the major transport system in the body by which food, oxygen and all other essential products are carried to the tissue cells.
The heart is the centre of the cardiovascular system. It is a muscular pump which pumps blood to the working muscles. It is situated in the left side of the chest beneath the sternum. An adult heart is about the size of a closed fist. The heart wall is made up of three layers: the epicardium (the outer layer), myocardium (the strong middle layer that forms most of the heart wall), and the endocardium (the inner layer). The septum separates the right and left side of the heart. Each side has two chambers which function separately from one another.

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The atria are the upper chambers of the heart. They receive blood returning to the heart from either the body or the lungs. The right atrium receives deoxygenated blood from the superior and inferior vena cava. The left atrium receives oxygenated blood from the left and right pulmonary veins. The ventricles are the pumping chambers of the heart. They have thicker walls than the atria. The right ventricle pumps blood to the pulmonary circulation for the lungs and the left ventricle pumps blood to the systematic circulation for the body.
Valves prevent backflow of blood. The bicuspid valve allows blood to flow in one direction only, from the left atrium to the right ventricle. The tricuspid valve allows blood to flow the right atrium to the right ventricle. The pulmonary valve prevents backflow from the pulmonary artery. The aortic valve prevents backflow from the aorta into the left ventricle. Chordae tendineae are cord-like tendons that connect to the bicuspid and tricuspid valves. They prevent the valves from turning inside out.
The aorta is the main artery in the body and it originates in the left ventricle and carries oxygenated blood to body tissues except the lungs. The superior vena cava receives deoxygenated blood from the upper body to empty into the right atrium of the heart. The inferior vena cava receives deoxygenated blood from the lower body to empty into right atrium of the heart. The pulmonary vein carries oxygenated blood from the lungs to the left atrium of the heart. The pulmonary artery carries deoxygenated blood from the heart back to the lungs. It is the only the artery in the body that carries deoxygenated blood.
As the heart contracts, blood flows around the body in a complex network of vessels. The structure of the different vessels within the cardiovascular system is determined by their different functions and the pressure of blood exerted within in them. Arteries carry blood away from the heart and with exception of the pulmonary artery they carry oxygenated blood. They have thick muscular walls to carry blood at high speeds under high pressure. The contractility of the arteries helps to maintain blood pressure in relation to changes in blood flow. Arterioles have thinner walls than arteries. These vessels control blood distribution by changing their diameter. Capillaries form an extensive network that connects arteries and veins. They are the smallest of all blood vessels, narrow and their walls are just one cell thick. Veins facilitate venous return – the return of deoxygenated blood to the heart. They branch into smaller vessels called venules, these collect blood leaving the capillaries and transport it to the veins.
Delivery of Oxygen and Nutrients – the key function of the circulatory system is to supply oxygen and nutrients to the tissues of the body. Blood carries nutrients absorbed from the intestine to the of the body, along with oxygen and water.
Removal of waste products – the circulatory system is responsible for the removal of waste products from the tissues to the kidneys and liver returns carbon dioxide from the tissues to the lungs.
Thermoregulation – the cardiovascular system is also responsible for the distribution and redistribution of heat within the body to maintain thermal balance.
CARDIO VASCULAR – Responses to Exercise
During exercise, the heart beats faster and harder in order to meet the demands of the energy by the working muscles. If these demands are repeated frequently, the heart eventually becomes stronger. The heart and blood vessels of the circulatory system adapt to these repeated demands.
Short-term responses
Anticipatory heart rate – before starting exercise the heart rate usually increases above resting levels to meet the demands of an exercise.
Heart rate at onset of exercise – this is the heat rate as exercise begins.
Redirection of blood flow – at the start of exercise, nerve centres in the brain detect an activity resulting in the rate and pumping strength of heart to increase. Regional blood flow is changed in proportion to the intensity of the activity to be undertaken.
Vasodilatation – this is the widening of blood vessels in order to increase blood flow when it is getting pumped out in high amounts.
Vasoconstriction – this is the narrowing of blood vessels to reduce blood flow.
Long-term Responses
Cardiac hypertrophy – this is when the heart increases in size and blood volume. The wall of the ventricle thickens, increasing the strength potential of its contractions delivering more oxygenated blood to the working muscle so that they do not fatigue easily.
Increased stroke volume – the volume of blood pumped out each beat increases.
Increased cardiac output – the volume of blood pumped in one minute increases as a result the of increased heart rate, stroke volume or both.
Decreased resting heart rate – the heart rate returns to normal after exercise quickly. This reduces the work load on the heart.
Nasal cavity – this is the passage above and behind the nose.
Air enters the body through the nostrils. Small hairs within the nostrils filter out dust and all sorts of foreign particles before the air passes into the two nasal passages of the nasal cavity.
The air is then further warmed and moistened before it passes into the nasopharynx. A mucous layer within this structure traps smaller foreign particles, which the cilia transport to the pharynx to be either swallowed or spit out.
This is a funnel shaped that connects the nasal cavity and the mouth to the larynx and oesophagus.
Commonly known as the throat, the pharynx is a small length of tubing that measures approximately 10-13cm from the base of the skull to the level of the sixth cervical vertebrae. The muscular pharynx wall is composed of skeletal muscle throughout its length.
It is a passage way for food as well as air. This outlines that it has to have special adaptations to prevent choking when swallowing food or drink.
Larynx – it has got rigid walls made up of muscles and cartilage and it contains the vocal cords and connects the pharynx to the trachea.
Trachea – It is also known as windpipe and it is approximately 12cm long and 2cm in diameter in size, containing rings of cartilage to prevent it from collapsing. It travels down the neck in front of the oesophagus and branches into two bronchi.
Bronchus – the main aim for the bronchi is to conduct air into the lungs. The right bronchus is shorter and wider than the left. When air is inhaled and reaches the bronchi, it is warm, clear of most impurities and saturated with water vapour.