Musculosketal Systems and Physiology of Exercise

The growth of the skeleton determines the growth and proportion of the body, the skeleton begins to form 6 weeks after fertilisation, bone growth goes through rapid growth through adolescents however genrally the skeleton does not stop growing up to the age of 25.

Ossification is the formation of bone. The process of calcification – the deposition of calcium salts-occurs during ossification, but it can also occur in other tissues. When calcification occurs in tissues other than bone, the result is a calcified tissue (calcified cartilage) that does not resemble bone. Two major forms of ossification exist: endochondral and intramembranous. In endochondral ossification, bone replaces existing cartilage. In intramembranous ossification, bone develops directly from mesenchyme or fibrous connective tissue. (fundamentals of A and P)

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The human skeleton consists of 206 bone. When together the skeletal system provides the framework which all other tissues and organs attach giving the body shape. The skeletal system is divided into two parts the axial which is made up of the spine, skull, ribs and sternum. The appendicularskeleton which is made up of the pelvis, arm and leg bones. The skeleton has 5 main functions.

Shape- The shape of the bone structure changes as the body grows. The skeletal system determines the height and width of a person, body shape is heredity. The three main body shapes are ectomorphs (tall and thin), mesomorphs (short and muscular), endomorphs (apple shape)
Support- the skeleton provides support to the body and keeps the internal organs in place. The vertebral column allows someone to stand erect. The pelvis and leg bones are strong enough to carry the weight of the whole body.
Movement- The bones are held together by ligaments. Tendons attach the muscles to the bones. Combined the muscular and skeletal system carry out movement, when muscles contract bones move.
Protection- The skeleton protects vital organs from damage. The skull houses the brain, while the vertebral column protects the spinal cord which controls all bodily functions through communication with the brain. The thorax and sternum protect the heart and lungs.


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The Pivot joint- In a pivot joint, the rounded or pointed surface of one bone articulates with a ring formed partly by another bone and partly by a ligament. A pivot joint is monoaxial because it allows rotation around its own longitudinal axis only.

Ball and socket- Consists of a bonelike surface of one bone fitting into a cuplike depression of another bone. Examples of functional ball and socket are the shoulders.

Hinge Joint- The convex surface of one bone fits into the concave surface of another bone. Hinge joints are in the knee, elbow, ankle and interphalangeal joints.

Ellipsoid Joint- The convex oval-shaped projection of one bone fits into the oval shaped depression of another bone. Examples are the wrist and metacarpophalangeal joints.

Saddle Joint- The articular surface of one bone is saddle shaped and the articular surface of the other bone fits into the saddle as a rider would sit. The most common saddle joint is the trapezius

Gliding Joint- The articulating surfaces of bones in a planar joint are flat or slightly curved. Some examples are the intertarsal joints between tarsal bones at the ankle joints. Sternocostal joints sternum ends of the costal cartilages at the tips of the second through seventh pairs of ribs. Gliding joints primarly permit side to side and back to back movements. (words 220)

The bones at a synovial joint are covered by articular cartilage, which is typically hyaline cartilage and occasionally fibrocartilage. The cartilage covers the surface of the bones with a smooth surface but does not bind them together. Articular cartilage reduces friction between bones in the joint during movement and helps to absorb shock.

Articular capsule- A sleeve like capsule l surrounds a synovial joint, encloses the synovial cavity, and unites the articulating bones. This is composed of two layers, an outer fibrous capsule and an inner synovial membrane. The FC, usually consists of dense, irregular connective tissue that attaches to the periosteal of the articulating bones. The flexibility of the FC permits considerable movement at a joints while tensile strength helps prevent bones from dislocating. The fibres of some FC’s are arranged in parrelel bundles that adapted for resisting strains (ligaments). The mechanical structure of ligaments helps to hold bones together in a SJ. The SM, is composed of areolar connective tissue.
Synovail Fluid- The SM secretes SF, which forms a thin film over the surfaces within the articular capsule. This clear/yellow fluid consists of hydrochloric acid and interstitial fluid filtered from blood plasma. The functions of this fluid are reducing friction by lubricating the joint and supplying nutrients to and removing metabolic wastes within articular cartilage.

(Grabowski and tortora 2003)

(220 words)


Three layers of connective tissue are part of each muscle; epimysium, perimysium and endomysium. The entire muscle is surrounded by epimysium a dense layer of collagen fibres. The epimysium separates the muscle from surrounding tissues and organs. It is connected to the deep fascia, a dense connective tissue layer. The connective tissue fibres of the perimysium divide the skeletal muscle into a series of compartments, each containing a bundle of fibres called a fascicle. Possessing collagen and elastic fibres, the perimysium contains blood vessels and nerves that maintain blood flow and innervate the muscle fibres within the fascicles. Each fascicle receives branches of these blood vessels and nerves. At each end of the muscle, the collagen fibres of the perimysium, perimysium and endomysium come together to form a bundle known as the tendon or aponeurosis. Tendons and aponeurosis usually attach skeletal muscles to bones. Where they contact the bone, the collagen fibres extend into the bone matrix, providing a firm attachment. Any contraction of the muscle will exert a pull on the attached bone. Muscle contraction huge quantities of energy. An extensive vascular network delivers the necessary oxygen and nutrients and carries away metabolic wastes generated by active skeletal muscles. (Martini2006) words 200

The primary cell types of tendons are the tenoblasts and tenocytes. Tenocytes are mature tendon cells that are found throughout the tendon structure, connected to collagen fibres. Tenocytes are mature tendon cells that are found throughout the tendon structure.

Tendon tissue is the tissue which connects muscles to bones. Tendons are the connective tissues that transmit the mechanical force of muscle contraction to the bones; the tendon is firmly connected to muscle fibres at one end and components of the one at its other end. The tendons are the strongest amongst the soft tissues. They require great strength is necessary for withstanding the stresses generating muscular contraction. A tendon is composed of dense fibrous connective tissue made up primary fibres are bunched together into subfasicles. Multiple secondary fibre bundles form tertiary fibre bundles, groups of which in turn form the tendon unit. Primary, secondary and tertiary bundles are surrounded by a sheath of connective tissue (endotenon) which facilitates the gliding of bundles against one another during movement. ( (words 160)

Skeletal muscle adaptations to extend to underwater time despite selective vasoconstriction include elevated myoglobin concentration, high acid buffering ability and high aerobic and anaerobic enzyme activities. Because cardiac muscle is perfused during dives, it will rely less heavily on MB and anaerobic pathways to support contractile activity even before birth, it may be more physiolically mature at birth and develop faster than skeletal muscles. ( The energy for muscle contraction comes from ATP, which in turn comes from the metabolism of glucose and fatty acids. But not much ATP is stored in the muscles that just a few twitches could quickly exhaust the supply. Creatine phosphate cannot be used directly to power muscle contraction but phosphate can transfer its phosphate group to ADP to form ATP: Creatine phosphate + ADP += creatine + ATP.

Two types of skeletal muscle Red (Slow twitch) White (Fast twitch).

Red has a rich blood supply, numerous mitochondria and myglobin, that forms a loose combination with oxygen and stores it in the muscle. Although it contracts rather slowly it is capable of long term activity without fatigue. White Muscle has a limited blood supply, few mitochondria and a low myoglobin content. It depends entirely on anaerobic breakdown of glycogen for its energy supply is capable of very strong rapid contractions for a short period of time. Because these fibres have fewer mitochondria and capillaries than red fibres, their ability to resynthesize ATP through oxidative phosphorylation is limited and they fatigue rapidly. Muscle fibre types also differ between the sexes. Women tend to have more red fibres and less white fibres so a female will have less strength than a male but has more endurance. Men with more white fibre depend more on storing carbohydrate for fuel, therefore they have less endurance. Smooth muscle has some differences to skeletal muscles they are applied slowly and smoothly- contractions of the digestive system can occasionally rapid. In smooth muscle Ca ions activate the myosin, through two intermediate enzymes before the ATP becomes involved. Although smooth muscle contraction is slow it is efficient it uses 10% of the ATP required by skeletal muscle to produce the same strength contraction.

Cardiac muscle is unique to the heart. It is able to beat incessantly because it never maintains a contraction. It contracts and promptly relaxes and the relaxation period is twice as long as its contraction period. The relaxation periods and contraction periods are strictly programmed; the muscle rests, then it must contract before it can rest again. Cardiac muscle is unlike smooth or skeletal muscle, it cannot rely on anaerobic metabolic pathways to provide its energy; it must never fail to get all the oxygen it needs. Cardiac muscle is the muscle in our bodies that is unable, except in disease states, to achieve a state of sustained contraction. (

(Martini 2006)

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The Impact of exercise on the Cardiovascular system:

At rest the average cardiac output is 5.8 litres per minute, this changes significantly during exercise, the pattern of blood distribution changes.

Light exercise: before you begin to exercise, the heart rate will increases slightly because of the rise in sympathetic activity.

Extensive vasodilation occurs as the rate of oxygen consumption in skeletal muscles increases. Peripheral resistance drops, the blood flow through the capillaries increases and blood enters the venous system at a fast rate.
The venus return increases as skeletal muscle contractions squeeze blood along the peripheral veins and increased breathing rate pulls blood into the venae cavae via respiratory pump.
Cardiac output rises, primarily in response to the rise

Respiratory System

As the cardiac output rises the blood flow to the lungs ( pulmonary perfusion) increases. The oxygen diffusing capacity a measurement of the rate the avelor air into the blood increases during maximal exercise because more pulmonary capillaries become perfused. There becomes a greater surface area available for diffusion of oxygen into the pulmonary blood capillaries. During vigorous exercise, oxygen consumption and pulmonary ventilation both increase dramatically. With moderate exercise the increase is due to an increase in the depth of ventilation rather than the increased breathing rate.

The abrupt increase in ventilation at the beginning of exercise is due to neural changes that send impulses to inspiratory area. The gradual increase in ventilation is due to chemical and physical changes in the blood stream

Decreased hypophosphite due to increased oxygen
Slightly increased Pc02 due to CO2 production contracting muscle fibres
Increased temperature, due to the release of more heat as more oxygen is utilized.

Smoking lowers respiratory effiency during exercise even with moderate exercise because several factors effect the respiratory system

Nicotine constricts terminal bronchioles
Carbon monoxide binds to haemoglobin reducing oxygen carrying capability
Irritants in smoke cause muscus secretion to increase


People with a higher proportion of fast glycolytic fibres often participate in activities which require periods of intense activity such as weight lifting. People with higher percentages of slow oxidative fibres are better at activities that require endurance ( long distance running). The total number of skeletal muscle fibres do not increase, the characteristics can alter to some extent. Aerobic exercises cause gradual transformation of FG fibres into FOG fibres. The transformed muscle fibres show slight increases in diameter. Exercise require great strengths for short periods of time to produce an increase in the size and strength of FG fibres. The increase is due to increased synthesis of thick and thin filaments. The result of muscle enlargement is evidence by the buldging muslces of body builders. Anabolic steroids are hormones similar to testosterone which increase muscles and strength during exercise. The large doses required have damging effects such as aggression, heart disease, kidney damage and stunted growth.


Bones have the ability to alter their strength in response to changes in mechanical stress. When placed under stress the bone tissue adapts by becoming stronger through increased deposition of mineral salts and production of collagen fibres. Another effect of stress is to increase the production of calcitonin. Without mechanical stress, the bones are unable to remodel normally because bone resorption outstrips bone formation. Removal mechanical stress weakens the bones through demineralisation and decreased collagen fibres.

The most common of mechanical stress on the bones is from the the pull of skeletal muscles and the pull of gravity. The bones of an athletic person become thicker and stronger, weight bearing activities help build and retain bone mass. Astronauts and people which have fractured bones can lose up to 1% of bone mass per week.

Words 560 (tortora grabowski 2003)



This is a degenerative non- inflammatory disease where over a period of time the cartilage is gradually lost. This will result in painful and restricted movement of the affected joints. This disease is a result of aging, irritation of the joints. This disease is the cause of disability in the elderly. The articular cartilage becomes thinner because its renewal does not keep in unison with its repair. Eventually the bony articular surfaces come in contact and the bones beings to degenerate. Some abnormal bone repair does take place and the articular surfaces become misshapen. Chronic inflammation develops with the effusion into the joints, due to the irritation caused by the tissue debris not removed by phagocytes. In some cases there is abnormal outgrowth of the cartilage at the edges of the bones which becomes ossified.

Primary Osteoarthritis- Is the most common type, the cause of this disease is unknown. The changes may be due to acceleration of the normal aging process within the joints which have had excessive use over the years due to plenty of physical activity. This usually begins to develop in the late stage of middle age and affects large weight bearing joints; the hips, knees, cervical and lumbar spine. In most cases of primary osteoarthritis only affects one joint.

Secondary osteoarthritis- This tends to occur in the joints where the cartilage has already been damaged due to

Congential deformity of bones such as dislocation
Trauma, intracapsular fracture of the bone and injury to intracapsuel structures.
Other conditions, inflammatory diseases, haemophilia following repeated haemorrhages into the joints, peripheral nerve lesions, gout, acromegaly, diabetic neuropathy.

Osteoarthritis of the spine

This condition is more common within the elderly. Degenerative changes cause narrowing of intervertebral discs and osteophytes may develop around the margins of joints of the vertebral column, commonly in the cervical region. This may cause damage to the nervous system, varying from compression of the individual spinal nerves to spinal cord injury ( the main cause of paralysis). (340) (Grabowski and tortora 2003)

Cruciate Knee

This is where the ligament in the knee is torn which may result in reconstructive surgery. The anterior cruciate ligament is a tough band of tissue joining the thigh bone to the shin bone at the knee joint. ( This condition tends to affect people which are more athletic. The cruciate ligaments are found inside the knee joint. They cross each other to form an x with the anterior cruciate ligament in front and the posterior cruciate ligament in the back and forth motion of the knee. The anterior cruciate ligament runs diagonally in the middle of the knee, it prevents the tibia from sliding out in front of the femur and this provides rotational stability for the knee.

There are 3 different grades of sprains which occur to the knee

Grade 1 sprain is where the ligament has been slightly stretched and the knee is still stable. This will result in discomfort whilst walking and inability to participate in strenuous activity.

Grade 2 This stretches the ligament to the point where it becomes loose. This is often referred to as a partial tear.

Grade 3 This is referred to as a complete tear of the ligament. The ligament has been split in two pieces and the knee joint is unstable.

The cruciate anterior is often injured by stopping suddenly, changing direction instantly, slowing down whilst running, landing from jumping incorrectly, direct collision’s in contacts sports such as football and rugby.

When the anterior cruciate is injured often the patient will hear a popping sound and will feel their knee giving way underneath them. The most common symptoms are;

The knee will swell within 24 hours. The pain and swelling may resolve naturally. However if the patient choses to attempt returning back to sports they may cause further damage to the meniscus of the knee.
Loss of a range of movement in the knee
Tenderness along the joint line

When a person does not have the adequate muscles strength coordination or balance to quickly react to the demands of sports there is an increased risk for a serious knee injury. Glute weakness and instability lead to excessive strain being placed on the ALC. (

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Martini F.H, 2006, Fundamentals of Anatomy and Physiology, seventh edition, San Fracisco, Pearson

Grabowski Sandra.Tortora Gerard, 2003, Principles of Anatomy and Physiology, tenth edition, Hoboken, John Wiley and sons,inc

Waugh.A,Grant. A.2001, Ross and Wilson Anatomy and Physiology in health and illness, ninth edition,London, Harcourt Publishers

Tortora Gerard, Grabowski Sandra, principle of Anotomy and physiology. New York. Harper Collins college. (9/10/2014) (15/05/2015) (26/05/2015) (1/06/2015) (1/06/2015) (2/06/2015)

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