Understanding Of The Skeleton And Bone Matrix Biology Essay

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The stomach is the location in which food is stored and where pepsinogen and HCI is produced, these are secreted in order to initiate protein digestion Stevens, C.E. & Hume, I.D. 2004.

Gall Bladder

(Not located during dissection or shown in diagram) This can be found on the underside of the liver and its purpose is to store the bile produced by the liver, after eating the bile is secreted into the small intestines where it assists in food digestion (BBC Science. Date Unknown).

Large Intestines

Consisting of the caecum, colon, rectum and anal canal (The University of Waikato. 2011). Wider than the small intestines, the large intestine transports remaining food which could not be broken down any further, to the anus where it is secreted as faeces (Dallas, S. 2006).

Small Intestines

So named due to its narrow diameter, the small intestine is the location in which enzyme digestion is completed (Dallas, S. 2006). It consists of the duodenum, jejunum, and ileum (University of the Cumberlands. Date Unknown).


The initial section of the large intestines, this serves no purpose in carnivores, however in herbivores this is enlarged as it is the location of bacterial breakdown for vegetable food substance (Dallas, S. 2006).


The main section of the large intestine in which fluids are reabsorbed, reducing the faeces water content (IFFGD. 2013).


The location in which faeces is stored preceding defecation, a segment of the colon adjacent to the anus (Allaby, M 2009. A).


The pancreas plays a vital role in transforming food into fuel and has two main functions: Exocrine function which assists with digestion, and endocrine function which regulates blood sugar (Columbia University Medical Centre. 2011). It is made of glandular tissue and a structure of ducts, the main duct being the pancreatic duct which drains from the gland to the duodenum (Johns Hopkins University. 2012).


Found beneath the diaphragm and under the stomach, the spleen filters and cleans the blood, removing any old, damaged and dead cells using white blood cells known as macrophages (Children's Hospital of Pittsburgh of UPMC. Date Unknown).


Forming the start of the small intestines, the duodenum contains a large quantity of digestive enzymes which combine with bile from the gall bladder to break down food (Encyclopedia of Health. Date Unknown).


The second section of the small intestines, it continues to churn and mix food particles with the enzymes, reducing them down sufficiently enough for absorption (Dallas, S. 2006).


The last section of the small intestines where final absorption is completed (Dallas, S. 2006).


Located each side of the abdomen, the kidneys contain specialised cells which filter out materials from the body that need to be removed whilst containing materials that the body needs (Dallas, S. 2006). Any waste material removed is converted to urine and travels to the bladder via the ureter tubes (NIDDK. 2012).


The ribs form part of the axial skeleton alongside the head, vertebral column and the sternum (Kisia S.M. 2010).


A horizontal partition which separates the thoracic and abdominal cavities, lying arched into the thorax it allows for increased volume when relaxed thus allowing the lungs to enlarge (Allaby, M. 2009. C).


(Not shown in diagram) Located on both left and right sides of the thoracic cavity and protected by the ribcage, the lungs serve to bring oxygen into the body and expel carbon dioxide (American Thoracic Society. 2013).


Composed of cardiac muscle, the heart functions as a pump to transport and circulate blood around the body (Allaby, M 2009. B). In mammals and birds, the heart contains four chambers which prevent the mixing of oxygenated and deoxygenated blood, these are known as the atria (upper) and (lower) ventricles (The Encyclopedia of Science. Date Unknown).


The pharynx is the cavity found at the back of the mouth that is cone like in shape and lined with a mucus membrane, it controls and opens either the larynx or oesophagus canals (Biology Online. 2009).


Found at the top of the trachea, the larynx is a cartilaginous structure containing and protecting the vocal cords (Biology Online. 2007).


The oesophagus is found between the pharynx and the stomach (Allaby, M. 2009. D). Tubular in shape, the oesophagus produces mucus cells which lubricate food along the tract, this assists in the process of peristalsis where the oesophagus contracts in order to transport food through to the stomach (Dallas, S. 2006).


Also referred to as the windpipe, the trachea is a fibro-cartilaginous tube stretching from the larynx to the lungs (Biology Online. 2005).


The name given to the cap of a long bone (found at the joint) which is united to the main bone via the ossification process, it is initially separated by a layer of cartilage (Allaby, M. 2009).


The main part of a bone referred to as the shaft in a long bone (Allaby, M. 2009).

Epiphyseal Line

The part of a long bone that indicates where the epiphysis and the diaphysis meet and also marking the point in which the epiphyseal plate was located in early development (Wiser, M. 2013).

Spongy Bone

Also referred to as cancellous and trabecular bone, it is a light, porous bone that has a three dimensional honeycombed or spongy form, the spaces in which are usually filled with marrow (Encyclopedia Britannica Inc. 2013).

Medullary cavity

The hollow centre of the diaphysis which is lined with connective tissue known as the endosteum, in its early stages is used in blood cell production via red bone marrow in which it is filled, when fully developed its purpose is to store fat within yellow bone marrow (Kaufen, C. Date Unknown).

Compact Bone

This is the outer layer of most bones which provides the smooth white appearance, also known as cortical bone, the cells are tightly packed together, more so than that of the spongy bone however not completely solid, small canals allow for blood vessels to penetrate it (Blackburn, V. 2013).

The open space between the trabeculae is filled with blood cell producing red bone marrow and capillaries and this aids in the transfer of nutrients and other metabolic products from the blood to the bone.


A microscopic structure, rod-like in shape that provides support and serves as the main functional structure of the spongy bone, within spongy bone the trabeculae is made of bone whereas in other parts of the body it will usually be made of collagen (Foster, N. 2013).

The purpose of the experiment is to form an understanding of the skeleton and bone matrix and also understand how it contributes to animal management and welfare.

When working with animals it is of great importance to be able to identify any health and welfare issues in order to gain a precise diagnosis, this allows for an appropriate clinical course of action to be put in place including treatment options (Giger, U. 2008). This investigation focusses on issues affecting the bone, some of which may be hereditary and others which can be the cause of inadequate animal husbandry.

For the first investigation the following materials were used

• A Pre-cooked chicken bone

• Pestle and mortar

• Paper towels

A chicken bone is selected at random and attempts are made to bend and break it by hand whilst examining its structure and flexibility. The bone is then crushed using a pestle and mortar. Once crushed sufficiently the remains are examined once again.

*Please see results table below for findings.

Materials and Methods

For the second investigation the following materials were used:

• A Pre-cooked chicken bone soaked for 24 hours in;

• Hydrochloric acid (HCL)

• Forceps

• Water

• Paper towels

• Pestle and mortar

A second chicken bone is chosen and removed carefully from the Hydrochloric acid using forceps, it is then rinsed in water to remove any further trace of the HCL and to ensure it is safe to handle. Once dried with paper towels, the structure and flexibility of the bone is examined and attempts are again made in an attempt to bend and break it by hand. It is then placed it into the pestle and mortar and additional attempts made to crush it.

*Please see results table below for findings.

For the third investigation the following materials were used:

• A Pre-cooked chicken bone

• Forceps

• Bunsen Burner

• Paper towels

• Pestle and mortar

A final bone was chosen, using the forceps it was held over the flame of a Bunsen burner for two minutes. Once cooled the structure of the bone is examined whilst manual attempts are made to bend and break it. Again the bone is then placed into the pestle and mortar and further attempts made to crush it.

*Please see results table below for findings.

All investigations were simple to carry out however all bones were pre-cooked which I believe would have led to an inaccuracy within our results. Cooking the bones would have weakened them prior to our tests being carried out so if the investigations were to be conducted again, un-cooked bones would have provided us with slightly more accurate and realistic results. An uncooked chicken bone would be flexible to a certain extent however when cooked they become dry and brittle and tend to splinter (Roper, K. 2013).

The first investigation provided us with an understanding as to the texture and structure of a 'normal' bone when it is presumed healthy (without disease). The results of the second investigation closely mimic a metabolic bone disease known as "rubber jaw" (hyperparathyroidism). Metabolic Bone Disease's (MBD) are mostly caused due to the animal being fed an unsuitable and imbalanced diet which in turn can lead to severe crippling or even death (Opossum Society of the United States. 2011). Rubber jaw is caused by an over production of the parathyroid hormone (parathormone) which acts to regulate calcium and phosphate within the body (Gale Encyclopedia of Medicine. 2008), the results of which cause the jaw bone to become soft and flexible (Lane, D.R., et al. 2008).

The third investigation is closely representative of brittle bone disease (Osteogenesis imperfecta), a hereditary condition that causes weak bones that can break easily and sometimes for no known reason (National Institutes of Health. 2009). Osteoporosis displays similar effects; brittle and light bones which are easily broken, this disease is caused by more calcium being absorbed into the blood than the bone causing a thinning of the bone matrix (Kaplan, M. 2013).

Other bone conditions can occur these include Osteochondrosis (OC); a group of diseases which can affect numerous parts of the skeleton such as elbow dysplasia, in addition CHD or Hip dysplasia is another severe joint disease which can result in the incorrect development of a hip joint (Morgan, J.P. et al. 2003).

The investigations have allowed for us to understand further the effects that certain diseases have upon bones including how the function and structure of a bone can be altered so dramatically. It also allows for us to be able to notice and identify any signs and symptoms and therefore allow for appropriate treatment and husbandry adjustments.

Investigation 1 - Control Initially the bone felt slightly soft, however probably due to the fact it was pre-cooked.

When trying to manipulate by hand, smaller and thinner fragments at the edges did break away but with force.

It did take some effort to crush with the pestle and mortar, the bone tended to splinter and split along the grain which seemed to be as far broken down as it would go.

Investigation 2 - HCL Having been removed from the HCL it was clear that to the touch the bone was extremely soft and had a rubber like texture.

The bone was extremely easy to manipulate, bending it back upon itself and twisting it although it still appeared very tough. To break or split by hand was very difficult.

When crushing with the pestle and mortar it did again take some effort and the bone tended to split.

Investigation 3 - Heat The bone did burn down very quickly to a charcoal colour and texture.

To break by hand was very easy, the bone was extremely delicate and tended to 'snap' and fall apart unintentionally with basic, minimum handling.

Crushing took no time at all to reduce the bone down to a powder consistency.

Pericardium - The pericardium is a protective sac surrounding the heart and the major veins and arteries which lead to it, its purpose is to protect the heart, keep the heart lubricated so it can pump easily and efficiently and also to prevent the heart from expanding too much when it is filled with blood by limiting the available space (Pollick, M. 2013).

Aorta - Made of smooth muscle cells (Frank, E.D. & Warren, L. 1981), the aorta is the main artery that arises from the left ventricle and transports blood to the body (Allaby, M. 2009) and it consists of four sections; the ascending aorta, aortic arch, thoracic aorta, and abdominal aorta (Farlex Inc. 2003).

Right Atrium - The upper, right chamber of the heart that receives blood returning from body (Farlex Inc. 2013).

Right Ventricle - The apex of the heart, the right ventricle, forms the foremost section of the anterior surface of the heart, pumping deoxygenated blood to the lungs from the body (University of Minnesota. 2013. B).

Left Anterior Descending Artery (LAD) - A direct extension of the left coronary artery, the LAD and its branches provide the major blood supply to the majority of the interventricular septum, in addition it also delivers collateral circulation to the posterior section of the interventricular septum, anterior right ventricle and the posterior descending artery (University of Minnesota. 2013. A).

Left Ventricle - The left ventricle has a thick muscular wall, thinker that that of the right as it is required to pump blood throughout the entire body by means of powerful contractions (Parsons, R. 2008).

Cardiac Muscle

The four chambers of the heart are made up of cardiac muscle (Myocardium), the thickness of which depends on the chamber (Think Quest. 2013). Cardiac muscle resembles striped muscle as it is striated in appearance and contains a similar construction of actin and myosin, in addition it allows for involuntary and spontaneous contractions that occur synchronously (Jurd R.D. 2004.B).

Left Atrium - Blood returning from the lungs enter into the left atrium before passing through to the left ventricle (Jurd R.D. 2004.A).

Vena Cava - The largest vein in the body, the vena cava carries blood from the body into the heart (Allaby, M. 2009).

Endocardium - The endocardium is an endothelial lining of the heart which also plays a vital role in the hearts overall development, in particular, the formation of cardiac valves and the development of purkinje fibres, as an example (Harris, I.S. & Black, B.L. 2010).

Cardiac muscle controls the beating of the heart, this begins in the sino-atrial node (SAN) which lies within the wall of the right atrium, it sends out regular waves of electrical activity which is received by the purkinje tissues (bundle of His), these tissues carry the electrical waves to the muscular walls of the left and right ventricles which causes them to contract (systole) simultaneously, setting the heartbeat rhythm (Parsons, R. 2008).

Blood depleted of oxygen enters the vena cava where it is transported to the right atrium (Berger, S. 2013).

The right atrium rapidly transports a high volume of blood to the right ventricle, serving as a reservoir for when the tricuspid valve is closed and releasing stored blood from the systemic and coronary veins when the valve is open (Gaynor, S.L., et al. 2005). The tricuspid valve separates the right atrium from the ventricle (Jurd R.D. 2004.A).

The right ventricle drives blood through to the pulmonary artery where it is then passed onto the lungs for the blood to become oxygenated (Burgess, M.I., et al. 2002).

Having now been oxygenated by the lungs, the pulmonary veins transport blood back through and into the left atrium (National Cancer Institute. 2012).

The left atrium expands as it receives the newly oxygenated blood where it then contracts to push the flow of blood through open valves and into the left ventricle, this is done simultaneously with the right atrium (Jurd R.D. 2004.A).

The left ventricle receives the oxygenated blood from the left atrium where it is then pumped into the aortic valve, from here the blood flows into the aorta and is transported to the rest of the body (Ellis-Christiansen, T. 2013).

The right atrium and ventricle are separated by the tricuspid valve with three flaps and the left atrium from the left ventricle by the bicuspid / mitral valve with two flaps, these flaps are thin yet strong and as each ventricle contracts the opening between them is closed by the flaps coming together, this preventing a backflow of blood (Jurd R.D. 2004.A).

Sclera - a thick connective tissue that surrounds a large proportion of the eye, its strength allows for the shape of the eye to be maintained white also providing a location in which extraocular muscles can attach, in addition it assists in the maintenance of intraocular pressure and also protects from trauma (Sainze De La Maza, M., et al. 2012).

Cornea - Together with the sclera, the cornea forms the outer shell of the eyeball, made of a dense connective tissue, the cornea serves as a transparent window that allows for the entry of light into the eye whilst also providing protection from the surroundings (Krachmer, J.H., et al. 2011)

Vitreous Humour - The majority of the eye interior is made up of the vitreous humour, a substance that is gel like in texture which helps to maintain the round shape of the eye whilst millions of fibres within it attach it to the surface of the retina (National Eye Institute. 2009).

Aqueous Humour - it is found filling the anterior and posterior chambers of the eye which consequently assists in maintaining the eye's shape, the aqueous fluid is water based and discharged from ciliary tissues surrounding the eye, its function is not only to maintain the shape of the eye but also to deliver vital nutrients such as glucose (Ellis, J. 2012).

Lens - A transparent structure located directly behind the iris, the lens functions to focus light onto the retina, the curvature of the lens is controlled by a system of muscles surrounding it and by changing the curvature it allows for focus upon objects at different distances (Fight for Sight. 2013).

Choroid - A layer of connective tissue and blood vessels which lay between the retina and the sclera, supplying oxygen and nutrients to the inner parts of the eye (Dugdale, D.C. & Zieve, D. 2011.B).

Tapetum Lucidum - Found in the eye of various vertebrates and invertebrates, the tapetum lucidum is a device which increases the amount of light received by the photoreceptors (Schwab, I.R., et al. 2002) Reflecting light back to the retina, it increases the sensitivity of the eye to dim light, at night this causes 'night shine' if the animal suddenly turns to look at a bright light (Allaby, M 2009).

Retina - A thin, light-sensitive layer of tissue that lies at the back of the inner eye, the retina received images from the lens and converts them into electrical signals, these signals are then sent to the brain via the optic nerve, a rich blood supply provides its red colour (Dugdale, D.C. & Zieve, D. 2011.A).

The vertebrate eye has evolved through frequent subtle changes and many random mutations, a theory of which is supported by overwhelming evidence, however important advances of the vertebrate eye occurred over 500million years ago and therefore fossil records are either non-existent for certain species or inadequately represented in the fossil record (Lamb, T.D., et al. 2008).

There are certain mechanisms of the eye that appear to share a common ancestry although intricate, image forming eyes have evolved many times and therefore many different eye types have developed simultaneously in many different animals, the differences in the eye of the mollusc is often referred to as examples of parallel evolution to that of the human eye (Cox, B. & Cohen, A. 2013). The argument over the independent evolution of the eye has continued between scientists for many decades, evidence would suggest that all types of eye share a unity in the genes which are used to build them, by tracing the history of these shared genes, the evolutionary steps of the eye can be uncovered (Zimmer, C. 2009).

Evolutionary biologists have studied the origins of the eye and also the variety that is seen today, the human eye is similar to that of the octopus and squid in so much that it functions like a camera, however there are major differences such as the photoreceptors of the human eye are facing away from the pupil and back at the wall of the retina, the opposite to that of the octopus and squid (Zimmer, C. 2009). To hypothesise the evolutionary stages of the eye, scientists have used a selection of light sensitive structures that exist within species today; it is believed that a light sensitive area on the skin of an ancestral being may have given it a slight survival advantage, a deepening depression of the sensitive patch was produced which consequently provided a slightly sharper vision, simultaneously the depression, now a pit, also narrowed to create a small pinhole sized aperture of which light would now enter, the sensitive patch would eventually evolve into a retina (Nilsson, D.E. 2001).

A molecule known as opsin is located on the surface of photoreceptor cells which when light enters the eye, transmits electrical messages to the brain via a series of chemical reactions, it is known that all vertebrates have the same simple type of opsin within the eye known as c-opsin which are the same molecular shape regardless of the animal, due to the homologies it is proposed that c-opsins existed in the common ancestor of all vertebrates (Zimmer, C. 2009). Rhodopsin is a composition of opsin and retinol and is a pigment found in the rod cells of the retina (Allaby, M. 2009), it is found within the eye of every animal on the planet therefore suggesting that even though eyes have developed and evolved separately, a very ancient origin is shared (Cox, B. & Cohen, A. 2013).

The eye developed as a tool of species survival and has evolved accordingly, this being the reason for the different structures and types we see today. Although all eyes may have common ancestry, their specific development is due to species specific evolutions.