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.

Movement

Shape

Protection

DIAGRAM:

BACK

FRONT

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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.

DIAGRAM:

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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.

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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.

DIAGRAM:

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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.

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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.

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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.

Cranium

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.

Clavicle

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.

Ribs

The ribs are long, thin, curved, flat bones. They form a protective cage around the organs in the upper body.

Sternum

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.

Humerous

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.

Scapula

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.

Ilium

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.

Pubis

The pubis is also known as the pubic bone. It makes the lowest part of the innominate bone.

Ischium

The Ischium is located below the ilium and makes the middle of the innominate bone.

Carpals

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.

Metacarpals

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.

Phalanges

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.

Patella

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.

Tarsals

These are short and irregular bones. They help to support the weight of the body and provide attachment for the calves.

Metatarsals

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.

Femur

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

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.

Fixed

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.

Synovial

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.

Hinge

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.

Ellipsoid

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.

Gliding

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.

Pivot

These allow rotation only about a single axis. An example is in the neck, where the atlas and axis join.

Saddle

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.

SKELETAL RESPONSE TO EXERCISE

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.

MUSCLES

The main function of the muscles is to move the bones of the skeleton. There are three different types of muscle tissue which are:

Cardiac

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.

Skeletal

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.

Smooth

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.

MAJOR MUSCLES

Origin – muscles origin is attached to the immovable bone.

Insertion – muscles insertion is attached to the movable bone.

BICEP

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.

TRICEP

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.

DELTOIDS

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.

PECTORALS

Functions – flexes and abducts upper arm.

Location – large chest muscle.

Origin – sternum, clavicle and ribcage.

Insertion – humerus.

Sports/exercise – all pressing movements.

RECTUS ABDOMINIS

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.

QUADRICEPS

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

HAMSTRINGS

Semimembranosus

Semitendinosus

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)

GASTROCNEMIUS

Function – plantar flexion flexes knee.

Location – large calf muscle.

Origin – femur

Insertion – calcaneus.

Sports/exercise – running, jumping and standing on tiptoe.

SOLEUS

Function – plantar flexion.

Location – deep to gastrocnemius.

Origin – fibula and tibia.

Insertion – calcaneus.

Sports/exercise – running and jumping.

TIBIALIS ANTERIOR

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.

ERECTOR SPINAE

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.

TERES MAJOR

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.

TRAPEZIUS

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.

LATISSIMUS DORSI

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

OBLIQUES

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.

GLUTEUS MAXIMUS

Function -0 extends the thigh.

Location – large muscle on the buttocks.

Origin – ilium, sacrum and coccyx.

insertion – femur

Sporting/exercise – knee-bending movements, cycling.

RESPONSE TO EXERCISE

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.

CARDIO VASCULAR (CV) – Functions

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.

RESPIRATORY SYSTEM

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.

Pharynx

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.

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