Very Complex Structure Of Bones Biology Essay

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The back is a very complex structure of bones, tissues and muscles that are made from the lower back to the neck. The spinal column which is known as the centipede is a protection for the spinal cord as well as holding the upper body weight. The vertebrate is made up of 30-33 bones which are stacked up to make the spine. The bones are stacked in a certain way that they create a hole that surrounds the spinal cord [1]. The spinal cord carries signals that control the body's movement and sensations; the spinal cord runs from the brains base to just under the rib cage. The small nerve routes enter the spinal cord through the Vertebrate, spaces between the vertebrate are made up of cartilage known as the inter vertebral discs these act as shock absorbers these run through the whole spinal column and to allow the body to move freely (as shown in fig 1). Ligaments and tendons are used to attach the muscle to the spinal column and to hold the muscles to the vertebrate, the spinal cord reaches its full lengthy at a very early age.

In the spine between each vertebrate there is a spinal disc which is made up of soft cushion, as age plays a contributing factor the disc becomes more prone to injury as it has loses its elasticity. Young individuals have a soft and elasticity this helps them to have a centre of gravity and keep the back up right. A herniated disc usually occurs with age but also has been found in younger population, the disc can crack and leaks the disc fluid pushing outside. This causes a bulge to appear between the vertebrates and can cause a pinched spinal nerve or cord, if the disc is pushed out further can cause the nerves to become compressed, having a compressed nerve can cause a variety of problems.

Sciatica is the name given to anything that irritates or causes discomfort to the Sciatica nerve. The Sciatica nerve is the widest and longest nerve in the body, the nerve starts from the nerve roots in the lumbar spinal cord, lower back in the pelvis and runs through the buttock and down the legs to the feet. (As shown in fig 2).

The exact cause of Sciatica is not known and fully understood but it is usually associated with a slipped disc or a damaged disc, a herniated disc is known as a damaged disc this is usually cracked and has allowed the inner disc material to come out which is causing a pressure and trapping the root nerve which is the Sciatica. The sciatica nerve is made up of 5 nerves, each nerve exists the spine via the vertebrate segments. The 5 nerves join up on the piriformis muscle and become a sciatica nerve, the nerve travels down the back of the leg to allow function in the foot.

Where there is irritation or discomfort to the Sciatica nerve it causes a pain to shoot from the lower back down to the calf muscle, there are two common types of Sciatica there is acute Sciatica this is when the pain lasts up to 6 weeks but the pain can pass without the need of treatment hot baths and pain killers will help relieve the pain. The second is persistent Sciatica this is where they symptoms last up to 6 weeks or greater. Surgery can be performed for several cases or a structured physio and exercise program can be undertaken. The exercise will help relieve the pressure of the Sciatica nerve. Sciatica has also the tendency to disappear and return when there is a sudden movement or when there is heavy weight being lifted.

Sciatica is when there is compression of the nerve root. A muscle strain can lead to Sciatica as inflammation will pressure the nerve. The main cause of Sciatica is a slipped disc also known as a herniated disc; the disc can cause discomfort and inflammation of the nerve. The spine is made up of vertebrate discs and nerves. The vertebrate is the structure of the spine and this helps protect the nerves and they are very delicate.

Spinal stenosis: - this is where there is narrowing of the spinal column the space is reduced. This occurs when the spine compresses the nerve the main cause of spinal stenosis is arthritis or ageing. The narrowing of the spinal stenosis leads to the compression of the nerve. Osteoarthritis is when the cartilage is broken and is left in the spinal joints this causing inflammation and irritation and could lead to pressure building up on the Sciatica nerve. Spondyloisthesis is not a major cause to Sciatica but in some cases occurs when one disc slips over another and the misaligned vertebrate causes Sciatica pain.


The sciatica nerve passes through the buttock the nerve travels through a muscle known as the piriformis muscle this is inside the gluteus maximums, the piriformis muscle has been associate with the rotation of the hip it also contributes in playing a role in walking and running. The pain of sciatica is very dependent on which nerve is trapped and by how much, the most common affected areas are in the last 5th Lumbar L5/S1. The 4th and 5th Lumbar vertebrate is also affected L4/5 sciatica.

Sciatica does not affect the back, but starts from the buttock a burning, numbness or muscle weakness sensation can be felt from the buttock shooting down to the calf or the feet, some cases have been proven that Sciatica can lead to hip pain or even cause equina syndrome this is when there is the compression of the nerve that can lead to them becoming damaged.

Sciatica pain is worsened when sitting or standing for long period of time. The pain can also be worsened by coughing sneezing this is because of the whole body tensing up and contracting the muscles, or a server movement. Simple tasks like going to the toilet can lead to discomfort. The nerve can become affected and stop function correctly the power, sensation and reflexes can also be tested using different exercises.

The diagnosis and of Sciatica is specific to each patient and they relevant medical history. Some common causes are numbness in the feet or legs, there can also be impaired reflexes or weakness. The diagnosis results are usually from the physician made up of practical examinations. The patient will be required to move in certain ways and adapt several positions consisting of squatting, walking, rotating hip backwards and forwards, the doctor may also check sensation, reflexes and power of the patient to ensure that these have not been affected as these can be affect easily by compression of a nerve. If no improvement occurs in 6 weeks and the continuous is then persistent Sciatica images of the back may be taken this will include an MRI or a CT scan. MR neurography is a modified and adapted from the MRI this is used to provide more detailed pictures of the spinal nerve and help rule out any nerve or tissue damage MR neurography has shown figures of helping up to 95% of persistent Sciatica patients.

The treatment of Sciatica has been traditionally proven that bed rest helps a research team led by Dr. Patrick Vroomen used 183 patients to bed rest and resolved that in a 12 week process under examination proved that there was a functional change in pain scores and determined that resting improved they scores.

The prognosis of sciatica. Studies show that individuals with back pain 75% suffer at least once a year of the back pain returning, in another study after 5 years around half of the individuals were pain free with no recurrences. There are some specific conditions that help the rate of improvement.

Registered NHS chiropractors will adjust the back and massage the affected areas reliving the pressure. The alignment of the spine is very important as the longer it stays in place the better chance it has of healing and staying in place. Exercise is very important as this will help allow the muscles to relax and not stiffen up light exercises should only be completed ensuring your doctor approves of them. Sciatica takes a long time to treat and requires a lot of patience. Non NHs methods such as acupuncture, herbal therapies have also helped but not in all cases as these believe that it involves types of energy good and they are not scientifically proven. Some of the home treatments your doctor may advise you to complete apply heat or ice to the painful area as this will help the muscle to relax and numb the pain. Taking pain killers such as ibuprofen which can be brought over the counter. Also by changing your sleeping position can help by placing a pillow under the knees this will help to reduce the pain and help relive the pressure on the nerve. The doctor may also provide you with anti inflammatory tablets such as naproxen which will help reduce the inflammation and release the pressure, the doctor will only provide these if there is a persistent sciatica pain.

The largest branch of the sacral plexus is the Sciatica nerve. There are two nerves the tibial and common fibular are wrapped in a common sheath, the Sciatica nerve exits the pelvis via the greater sciatica notch, and they diverge just proximal to the knee.

Pain is a complex, distressing experience involving sensory, emotional and cognitive components. The quality and intensity of pain vary with each person and are influenced by sociocultural and physiological factors. Pain also plays a very protective role everyone from a very early age learns to avoid situations that can cause pain.

Passive pain is pain that cannot be ignored. The pain that is caused has a signal and a warning function, which means pain, has a survival value. There are many ways in which pain is classified, the most common are; chronic pain which is caused by continuing pain even after the damaged tissue has healed (e.g. after surgery) this kind of pain can last from a few weeks to years. Acute pain is a temporary pain that is caused by tissue damage, such as a skin burn. This type of pain will disappear as the injury heals (Wall 1999). There are various types of pain that can be achieved with different kinds of pain FIG 1. It can be concluded that when the athlete grazes their knee he suffers from acute pain, it is known as initial pain and the pain gives a pinpricking, pinching sensation.




Deep pain

Superficial pain

Initial pain

Delayed pain

Connective tissue





There is s structure in which you realise how pain is the sensory components tell you were the site of the stimulus is; therefore there is an acknowledgment of pain. The second is the autonomic component which deals with the physical changes that occurs as in the eyes dilate and additional blood and nutrients are sent to the damaged tissue. The third component which offers a protective reflex and the final component is the affective component which handles the emotional aspect of pain.

The human bodies have pain receptors, which are waiting to become by and experience of tissue damage. All the tissues within the human body have a variety of sense receptors that are specialised by the nerve endings. The nerve endings are known as nociceptors and there are three different types known as a delta (1 &2) and C fibres (cambell 1964)

Pain receptors

Pain receptors can be found on free endings located throughout the body. As the body experiences a painful stimulus the pain receptors are activated, after activation the receptor releases neurotransmitters the information of the pain is sent along the nerves to the spinal cord and to the brain, the entire process is known as a nociceprion, nociceptors if the name given to the pain receptors that are found in the tissues.

A delta (1 &2) and C fibre information chart:



Pain perceived

A delta (1) fibre



A delta (2) fibre


Sharp, well focused pain

C fibre


Dull burning pain

In the chart above, each fibre is specific to a particular pain sensation. The Myelinated transmit the impulse very rapidly so the brain is notified sooner. This issue to the impulse is able to travel from one Node of rainvier to another, jumping over the myelin sheaths. A sudden, pain producing stimulus can cause two pain sensations. The impulses that are transmitted by the myelinated fibres produce the sharp, pricking, localised pain that is felt immediately when the injury occurs. The non-Myelinated fibres (c fibre) transmit the impulses very slowly and are responsible for the more throbbing, burning type of pain or ache that follows the immediate sharp pain.

The A delta 1&2 and C fibres release substance P which is a neurotransmitter, into the synaptic Cleft fig 2. The impulse then travels up to the thalamus located in the brain. Once the thalamus is signalled, it will send two messages. The first is sent to the cerebral cortex of the brain. The cerebral cortex assesses the damage and the origin of pain signal. The second message is then sent back to the original pain location, telling the nociceptors to stop sending more pain unnecessary pain impulses (wall 1999).

Once the cerebral cortex is alerted, it notifies the limbic centre (the limbric system is responsible for the perception of pain and can less in testify pain by controlling emotional responses) produces emotions that accompany pain such as anxiety and frustration. The cerebral cortex also alerts the autonomic nervous system to control breathing, blood flow, and pulse rate. This system also sends additional blo0dd and nutrients around the damaged tissue (Clancy 1995).

Fig 2:- shows the pathway of pain, How it travels from the nociceptors to the brain (Ross 1963)

If there was an individual who hurt grazed his arm the light enters the pupil of the eye. The cornea and the lens focus and invert the light signal that is entering the eye and project it to the back of the eye where the retina is located (diagram and details of the eye can be seen in minett 1989). The retina consists of several layers of alternating cells and process that convert the light signal into an action potential, which is known as signal transduction. In the retina of the human eye, there are two types of photoreceptors, rods and cones (see fig 3). Both of these receptors have different functions. For example, rods, located in the periphery of the eye are more sensitive towards light and have a wider range of wavelengths compared to cones. Where cones function bettering the light and provide high resolution (Eckert 1938). The action potentials that are produced from the light signal stimulate the ro9d and cone cells. (Ross 1963)

Fig 3:- the two types of photoreceptor cells that are present in the retina along their different arrangements of synapse in the retina give a visual system (fullick 1994)

It can be seen that each rod and cone cell has an outer segment with a stack of discs in which each of the visual pigments are embedded.

Another difference between rods and cones is that they contain different photosensitive receptors. The pigment in rods and rhodopsin, which contains opsin (protein) and retinal (the light sensitive part). Cones are also composed of a photosensitive pigment that is similar to rhodopsin. There are types of cones, which all contain different kinds of photo pigment, erthrolabe, chlorolabe or cyanolabe. Each of the three primary colours (red, yellow and blue) reflects the light at different wavelengths. Therefore, when the athlete is looking at his grazed arm it enables him to look at it in colour. The way in which the athlete is able to see in colour is by the cone cells (Vander 1933). The injury the rhodopsin absorbs the light entering the eye that reaches these cells, the retinal component alters its shape, leading to a signal- transduction pathway that reacts in a reactor potential in the rod cell membrane. Rhodopsin is then converted into metarhodopsin 11. The retinal's shape change causes a conformational change in the opsin. The altered opsin molecule then activates a g-protein called transduction which is also in the disc membrane. The protein then activates phosphodiesterase, which chemically alters the second messenger in the rod cell, a nucleotide called cyclic guanosine mono-phosphate (cGMP). When the light alters the retinal, the signal transduction pathway is triggered. This result in cGMP being converted to GMP causing a change in the membrane potential as the sodium channels have closed this is known as hyperpolarisation which causes a decrease in the release of neurotransmitters.

There are many cells in the retina Receptor cells, horizontal cells, bipolar cells, amacrine cells and ganglion cells. The horizontal cells join the rods and the cones from one region to another in the retina. Receptor cells play the role of transducer light signals into action potential. The bipolar cells connect one layer of the retina to the next requiring all information produced by the receptor cells to pass through the bipolar cells. Amacrine cells control signals from the bipolar to ganglion cells. The ganglion cells send action potentials along the optic nerve to the brain. There are two pathways, (vertical and lateral) in which signals from the cones and rods can follow.

Once the action potential have reached the brain via the optic nerve the activity from left side of the retina of each side passes to the right side of the brain and vice versa. This crossover occurs in the optic chiasma, which lies just anterior to the pituiriaty gland at the base of the brain. Once the crossover has occurred the bundles of nerve cells pass to the dorsal root. After going to the thalamus the neural pathway diverge so action potentials from the retina arrive at different parts of the brain. These areas are involved in putting a perception image of the object. (Eckert 1938).

Finally, it can be concluded that pain affects each and every one of us in different ways. There are multiple factors of which a few are listed below that can influence an individual's experience of pain and the level at which it is experienced. personality can also affect the level of pain experienced if an incident occurs to an individual more often than someone else they will get used to it and the body learns to handle the pain so u don't experience as much as pain as u did the first time. Emotionally and psychological factors can also play a big role in the level of pain that is experienced positive experiences such as joy, humour or love can sometimes lessen the pain. Experiencing pain is a survival value; individuals that do not experience pain have a shorter lifespan than an average individual. The experience of pain is also age dependant as a young child will not have experienced as much pain compared to an adult so the pain will be worse.

Inflammation is were the body protects us from infection and foreign bacteria and viruses. In some cases the body can activate an inflammatory response when there are no viruses to fight off. Inflammation is the most powerful defence in the body the immune system switches on and causes a chain of events the inflammatory cascade. Inflammation is the protective reaction of vascular arise tissue to injury. Acute inflammation is the immediate reaction to the tissue and is the first stepping stone in healing, acute inflammation is usually triggered by cell or tissue damage, or having dead cells or bacteria. Acute inflammation occurs before the immune response becomes established and works on remaining the injury causing agents and limiting the amount of tissue damage, acute inflammation is made up of two steps which overlap each other the vascular and cellular stages.

In the vascular stage arterial venulas near the site of injury constrict briefly and then are caused to dilate, the dilation process promotes the congestion, which leads to the movement of fluid into the affected tissue resulting in inflammation, the signs of inflammation are redness, swelling, heat and pain and also the loss of function. As the fluid leaves the capillaries the blood remains more thick which causes it to flow more slowly and causes clotting. The cellular stage of acute inflammation is initiated by the phagocyte white blood cells or leukocytes in the area of injury, the leukocytes begin to join into the vessel wall and then in a process known as emigration squeeze through the wall and travel through the tissue guided by the chemical signals which is known as chemo taxis, the cellular stage eats and degrading the bacteria which is called phagocytises products of the phagocytises plasma and blood cells form exudates these accumulate causing pain. Exudates are made up of white blood cells or tissue debre and the white blood cells are there to break down these products. parallel vascular and cellular stages release chemical mediator agents that act to mediate the inflammatory response, mediators are derived from the cell or plasma, the first mediator have an inflammatory response is called a derived mediator. Histamine is found in high concentrations in the mast cells connective tissues adjacent to blood vessels histamine also causes dilation. Seriotin which is another mediator performs very similar actions the three major plasma derived mediators are present in the plasma in pre-curser forms that must be activated usually by a sense of profeolitic enzyme.

The prognosis of sciatica. Studies show that individuals with back pain 75% suffer at least once a year of the back pain returning, in another study after 5 years around half of the individuals were pain free with no recurrences. There are some specific conditions that help the rate of improvement.

Statistics of back pain

In most counties up to 80% of the population experience back pain at some point in they life, a percentage between 20-30% suffer from back pain a any one point in the year, age plays a contributing factor to back pain, back pain is just as common for younger generation or the older generation.

The NHS have shown figures that show spending of an excess of 1 billion pounds per year, the private health care showing a figure of 565 million on back pain. The NHS distribute the 1 billion into 3 sectors 512 million is spent on hospitals and patients, 141 million goes to GP consultants for back pain and 150 million being spent on physiotheraphy. All in all the total cost of back pain including health and safety comes to a total of around 1-2% of the GDP. [1] [2]

Palmer KT, Walsh K, et al. Back pain in Britain: comparison of two prevalence surveys at an interval of 10 years BMJ 2000;320:1577-1578.

Maniadakis A, Gray A. The economic burden of back pain in the UK. Pain 2000;84:95-103

Burton AK, Balague F, et al. European guidelines for prevention in low back pain. Eur Spine J 2006:15(suppl 2):S136- S168

Nachemson AL, Waddell G, Norlund AI. Epidemiology of neck and low back pain. In: Nachemson AL & Jonsson E (eds). Neck and back pain: The scientific evidence of causes, diagnosis and treatment. Philadelphia: Lippencott Williams & Wilkins, 2000. Andersson GBJ. The epidemiology of spinal disorders. In: Frymoyer