Skeletal System

By Dr. Shamanthakamani By Dr. Shamanthakamani NarendranNarendran

INTRODUCTIONINTRODUCTION

The skeletal system refers to the jointed The skeletal system refers to the jointed framework of rigid bones which supports framework of rigid bones which supports the soft tissues of the body.the soft tissues of the body.

There are 206 bones in the adult skeletal There are 206 bones in the adult skeletal system.system.

Importance of this system: Importance of this system: The bones form a complex lever system The bones form a complex lever system

which permits body movements.which permits body movements. They form cages and boxes which protest They form cages and boxes which protest

fragile organs. e.g. the rib cage, breastbone fragile organs. e.g. the rib cage, breastbone (sternum) and backbone (vertebral column) (sternum) and backbone (vertebral column) protect the heart and lungs.protect the heart and lungs.

The bones given the body its shape.The bones given the body its shape. As a prelude to the description of the As a prelude to the description of the

skeletal system, the skeletal system, the body cavitiesbody cavities will be will be discussed briefly, below.discussed briefly, below.

BODY CAVITIESBODY CAVITIES

The trunk of the human being is made up of The trunk of the human being is made up of threethree main cavities main cavities

ThoraxThorax

AbdomenAbdomen

PelvisPelvis

THORACIC CAVITYTHORACIC CAVITY

Thorax or chest extends from the bottom of Thorax or chest extends from the bottom of the neck, above, to the diaphragm, below.the neck, above, to the diaphragm, below.

The diaphragm is a muscular dome which The diaphragm is a muscular dome which separates the thoracic and abdominal separates the thoracic and abdominal cavities, and plays an important part in cavities, and plays an important part in respiration.respiration.

The thorax contains three cavities.The thorax contains three cavities. There cavities are all lined with a There cavities are all lined with a

membrane which also covers the organs membrane which also covers the organs inside them.inside them.

The central cavity is the The central cavity is the pericardial pericardial cavitycavity..

This contains the heart, covered by the This contains the heart, covered by the pericardiumpericardium..

On both sides of the pericardial cavity, On both sides of the pericardial cavity, there are two there are two pleural cavities, pleural cavities, which contains which contains the lungs, the lungs, covered by covered by pleurapleura..

ABDOMINAL CAVITYABDOMINAL CAVITY The region of the body located below the The region of the body located below the

chest and above the pelvis.chest and above the pelvis. The chest and abdomen are separated by a The chest and abdomen are separated by a

muscular dome, the diaphragm.muscular dome, the diaphragm. Inside this cavity are the vital organs which Inside this cavity are the vital organs which

play an important part in digestion play an important part in digestion (stomach, intestines, liver, pancreas, and (stomach, intestines, liver, pancreas, and others) and in excretion (kidneys).others) and in excretion (kidneys).

These organs are covered by the These organs are covered by the membrane which lines the abdominal cavity membrane which lines the abdominal cavity – the – the peritoneumperitoneum..

The muscles which form the anterior wall or The muscles which form the anterior wall or the front of the abdomen, hold the organs in the front of the abdomen, hold the organs in place and give support to them.place and give support to them.

PELVIC CAVITYPELVIC CAVITY The pelvic cavity lies within the bony which The pelvic cavity lies within the bony which

is made up of the lower part of the vertebral is made up of the lower part of the vertebral column (the sacral and coccygeal parts) column (the sacral and coccygeal parts) and the hip bones on either side.and the hip bones on either side.

The peritoneum lines the pelvic cavity and The peritoneum lines the pelvic cavity and also covers the organs inside it.also covers the organs inside it.

CARTILAGECARTILAGE Cartilage is flexible white tissue around the Cartilage is flexible white tissue around the

joints and in other parts of the body.joints and in other parts of the body. For example, cartilage is present in the For example, cartilage is present in the

windpipe (windpipe (tracheatrachea), the sound box ), the sound box ((larynxlarynx), the ears, and the tip of the nose.), the ears, and the tip of the nose.

It also makes up the discs between the It also makes up the discs between the vertebrae of the column vertebrae of the column

((backbonebackbone) and the ) and the

surfaces of certain joints.surfaces of certain joints.

In general – Cartilage In general – Cartilage improves flexibilityimproves flexibility, , Serves as paddingServes as padding, & , & Prevents frictionPrevents friction..

During early fetal life the human skeleton is During early fetal life the human skeleton is composed mainly of cartilage, which is later composed mainly of cartilage, which is later replaced by bone.replaced by bone.

Cartilage is subject to a number of Cartilage is subject to a number of disorders.disorders.

ArthritisArthritis produces degeneration of the produces degeneration of the cartilage as well as the bones of the joints.cartilage as well as the bones of the joints.

A A vertebral discvertebral disc may slip out of place and may slip out of place and cause severe back pain.cause severe back pain.

BONEBONE

Is a rigid structure of connective tissue Is a rigid structure of connective tissue interlaced with nerves and blood vessels.interlaced with nerves and blood vessels.

It is hardened by deposits of (mainly) It is hardened by deposits of (mainly) calcium phosphate.calcium phosphate.

The entire bone is sheathed in a tough The entire bone is sheathed in a tough tissue called the tissue called the periosteumperiosteum..

Babies’ bones are pliable and contain a Babies’ bones are pliable and contain a high proportion of cartilage, which is high proportion of cartilage, which is gradually replaced by more rigid bone gradually replaced by more rigid bone tissue.tissue.

In adults, each bone has a very dense In adults, each bone has a very dense outer layer with a high content of calcium.outer layer with a high content of calcium.

It is this dense layer which makes bones It is this dense layer which makes bones opaque and hence visible on X-rays.opaque and hence visible on X-rays.

Under this layer, the Under this layer, the

structure is spongy structure is spongy

with pores and with pores and

cavities of various cavities of various

sizes.sizes.

Bones are hinged and held together by Bones are hinged and held together by ligaments to form the skeletal system.ligaments to form the skeletal system.

This system provides support, mechanical This system provides support, mechanical leverage for movement, and protection for leverage for movement, and protection for the vital organs.the vital organs.

Also, the red blood cells, suppliers of Also, the red blood cells, suppliers of oxygen to the body, are produced in the red oxygen to the body, are produced in the red marrow of certain bones – such as the marrow of certain bones – such as the vertebrae and ribs.vertebrae and ribs.

Generally, bone is as strong as cast iron, Generally, bone is as strong as cast iron, but infinitely lighter and more flexible.but infinitely lighter and more flexible.

Its rigidity enables us to bear our own Its rigidity enables us to bear our own weight, plus the stress of lifting and weight, plus the stress of lifting and carrying.carrying.

Since bones are hinged together with Since bones are hinged together with ingenious joints – some working as levers, ingenious joints – some working as levers, others as hinges – this system also permits others as hinges – this system also permits us to be amazingly agile.us to be amazingly agile.

Bones also store minerals such as calcium.Bones also store minerals such as calcium.

DEVELOPMENT OF BONES

CLASSIFICATIONCLASSIFICATION

Since bones vary in shape their gross Since bones vary in shape their gross appearances have led to a classification appearances have led to a classification into – into – long boneslong bones, e.g. the bones of the , e.g. the bones of the limbs & limbs & short bonesshort bones, e.g. bones of the , e.g. bones of the fingers and toes.fingers and toes.

Based on whether the bones make up the Based on whether the bones make up the central frame or the limbs, they have been central frame or the limbs, they have been classified as the classified as the axial skeletalaxial skeletal – vertebral – vertebral column, skull, and rib cage & column, skull, and rib cage & appendicular appendicular skeletonskeleton – bones of the arms, hands, legs, – bones of the arms, hands, legs, feet, shoulder, and pelvic bones.feet, shoulder, and pelvic bones.

CLASSIFICATION OF BONES

JOINTSJOINTS The point where 2 bones comes into The point where 2 bones comes into

contact is called a contact is called a jointjoint.. There are three main types of joints based There are three main types of joints based

on the type of material which is present on the type of material which is present between the bones.between the bones.

Fibrous joints Fibrous joints – do not permit any – do not permit any movement, e.g. the structures between the movement, e.g. the structures between the skull bones.skull bones.

Cartilaginous jointsCartilaginous joints – permit slight – permit slight movement, e.g. is the type of joint which movement, e.g. is the type of joint which exists between the upper and lower parts of exists between the upper and lower parts of the breast bone (the breast bone (sternumsternum), before these ), before these parts fuse.parts fuse.

Synovial jointsSynovial joints – have maximum – have maximum movement.movement.

The parts of the bones which are in contact The parts of the bones which are in contact are enclosed within a are enclosed within a joint capsulejoint capsule..

There is There is nono continuitycontinuity between the two (or between the two (or more) bones.more) bones.

The bone surface are The bone surface are covered with a special covered with a special type of cartilage – type of cartilage – articular cartilagearticular cartilage..

It has a very low coefficient of friction.It has a very low coefficient of friction. The sliding contact (‘ice on ice’) is further The sliding contact (‘ice on ice’) is further

enhanced by the presence of a viscous enhanced by the presence of a viscous fluid – the fluid – the synovial fluidsynovial fluid..

This fluid is partially secreted by a This fluid is partially secreted by a membrane, the membrane, the synovial membranesynovial membrane..

It lines the joint capsule, and covers the It lines the joint capsule, and covers the exposed surfaces of the bones, ligaments, exposed surfaces of the bones, ligaments, and tendons within the capsule.and tendons within the capsule.

It It does notdoes not cover the articular cartilage and cover the articular cartilage and two other structures – articular discs and two other structures – articular discs and menisci. menisci.

(These are cartilaginous structures which (These are cartilaginous structures which improve the congruity of the joint surfaces.)improve the congruity of the joint surfaces.)

The membrane has two main functions – it The membrane has two main functions – it is one of the contributors to the production is one of the contributors to the production of synovial fluid, it also has cells which are of synovial fluid, it also has cells which are capable of ingesting debris and particulate capable of ingesting debris and particulate matter.matter.

The synovial fluid is a viscous, pale yellow The synovial fluid is a viscous, pale yellow fluid.fluid.

In human joints it is present in small In human joints it is present in small amounts.amounts.

Usually not more than 0.5ml can be Usually not more than 0.5ml can be aspirated (withdrawn by suction), even from aspirated (withdrawn by suction), even from the large joints (e.g. knee).the large joints (e.g. knee).

Functions include lubrication, reduction of Functions include lubrication, reduction of erosion, and provision of nutrition for erosion, and provision of nutrition for articular cartilages, articular discs, and articular cartilages, articular discs, and meniscusmeniscus

TYPES OF SYNOVIAL JOINTSTYPES OF SYNOVIAL JOINTS HingeHinge joint resemble hinges, and are joint resemble hinges, and are

designed to restrict movement to one plane, designed to restrict movement to one plane, e.g. are the elbow and knee joints (to be e.g. are the elbow and knee joints (to be precise the latter is described as a bicondylar precise the latter is described as a bicondylar joint).joint).

Sliding/PlaneSliding/Plane joints are appositions of almost joints are appositions of almost flat surfaces, e.g. wrist joint.flat surfaces, e.g. wrist joint.

PivotPivot joints are those in which rotation occurs joints are those in which rotation occurs around a around a pivotpivot. This type of movement . This type of movement occurs between the first and second vertebrae occurs between the first and second vertebrae (pivot = pin or shaft on which a wheel or body (pivot = pin or shaft on which a wheel or body turns)turns)

Ball-and-socketBall-and-socket joints are formed between joints are formed between a sphere like ‘head’ and an opposing ‘cup, a sphere like ‘head’ and an opposing ‘cup, e.g. hip and shoulder joints. These joints e.g. hip and shoulder joints. These joints allow maximum movement.allow maximum movement.

TYPES OF JOINTS

TENDONSTENDONS A tendon is a strong elastic tissue which A tendon is a strong elastic tissue which

connects muscles to bones.connects muscles to bones. Tendons may be short and thick, like those Tendons may be short and thick, like those

which attach the biceps to the shoulder.which attach the biceps to the shoulder. Others are long and slender, like those Others are long and slender, like those

which run from the muscles in the forearm which run from the muscles in the forearm across the back of the wrist to the bones of across the back of the wrist to the bones of the fingers.the fingers.

A tendons acts as an ‘anchor’ for the A tendons acts as an ‘anchor’ for the muscles.muscles.

They do not stretch.They do not stretch.

LIGAMENTSLIGAMENTS

A ligament is band of tough, elastic tissue A ligament is band of tough, elastic tissue which binds together the bones as a joint.which binds together the bones as a joint.

A major joint, such as the elbow has a set A major joint, such as the elbow has a set of overlapping ligaments to support the of overlapping ligaments to support the three bones.three bones.

A ligament can stretch.A ligament can stretch. Forcing a joint beyond its normal range of Forcing a joint beyond its normal range of

movement overstretches or tears the movement overstretches or tears the ligaments and causes a ligaments and causes a sprainsprain which which generally heals if the joint is rested.generally heals if the joint is rested.

BURSAE / BURSABURSAE / BURSA

A bursa is a fibrous sac lined with synovial A bursa is a fibrous sac lined with synovial membrane, bursae facilitate movement membrane, bursae facilitate movement without friction, and may be present without friction, and may be present between tendon and bone, skin and bone, between tendon and bone, skin and bone, and between two muscles.and between two muscles.

SPECIFIC BONES … SPECIFIC BONES … some salient featuressome salient features

The skullThe skull Protects the brain.Protects the brain. The bones of the skull are held together by The bones of the skull are held together by

fibrous joints.fibrous joints. These joints are not fused at birth, thus These joints are not fused at birth, thus

allowing for growth of the infant’s skull, and allowing for growth of the infant’s skull, and the area between the bones is soft – the the area between the bones is soft – the fontanellesfontanelles..

These fontanelles are all fused by eighteen These fontanelles are all fused by eighteen months.months.

The skull bones contain large hallow The skull bones contain large hallow spaces or air cavities inside them.spaces or air cavities inside them.

There are four sets of hallows in the skull, There are four sets of hallows in the skull, around the nose.around the nose.

These are called paranasal sinuses.These are called paranasal sinuses. They are situated in the forehead, behind They are situated in the forehead, behind

and below the forehead, in the cheekbones, and below the forehead, in the cheekbones, and at the back of the nasal passages.and at the back of the nasal passages.

These sinuses have passages leading into These sinuses have passages leading into the nose.the nose.

Their function is uncertain.Their function is uncertain.

They lighten the skull and add resonance to They lighten the skull and add resonance to the voice.the voice.

Within the skull there are three tiny bones, Within the skull there are three tiny bones, which help in the transmission of sound.which help in the transmission of sound.

They are located in the middle ear.They are located in the middle ear. The jaw bone or mandible comprises the The jaw bone or mandible comprises the

lower jaw and contains the lower row of lower jaw and contains the lower row of teeth.teeth.

TeethTeeth The teeth are embedded in the upper and The teeth are embedded in the upper and

lower jaws.lower jaws. They contain a hard bony substance.They contain a hard bony substance. Above the gum this is covered with tooth Above the gum this is covered with tooth

enamel – the ivory colored part which we enamel – the ivory colored part which we can see.can see.

This is the hardest material in the body.This is the hardest material in the body. It cannot be replaced.It cannot be replaced. If it gets worn away the inner core – the If it gets worn away the inner core – the

pulp – is exposed.pulp – is exposed.

The pulp has both blood vessels and The pulp has both blood vessels and nerves.nerves.

The presence of the latter is responsible for The presence of the latter is responsible for toothache.toothache.

There are 20 ‘milk’ or There are 20 ‘milk’ or

temporary teeth.temporary teeth. Permanent teeth are Permanent teeth are

32 in number.32 in number.

Teeth of a childTeeth of a childThe face of a six-year-old child showing the milk teeth in position and the developing permanent teeth (in red)The face of a six-year-old child showing the milk teeth in position and the developing permanent teeth (in red)

Vertebral columnVertebral column

Three important functions:Three important functions: To support the human body in the upright To support the human body in the upright

position.position. To protect the spinal cordTo protect the spinal cord To allow movement and locomotion.To allow movement and locomotion. The vertebral column consists of 24 The vertebral column consists of 24

separate bony vertebrae, together with 5 separate bony vertebrae, together with 5 fused vertebrae which form the sacrum, fused vertebrae which form the sacrum, and usually 4 fused vertebrae which form and usually 4 fused vertebrae which form the coccyx.the coccyx.

The 24 separate vertebrae include – the top The 24 separate vertebrae include – the top sevenseven in the in the neckneck, the , the cervical vertebraecervical vertebrae..

The first of these, the atlas, supports the The first of these, the atlas, supports the skull.skull.

Below the Below the twelvetwelve chest or chest or thoracicthoracic vertebrae, to which the ribs are attached.vertebrae, to which the ribs are attached.

Below are the Below are the fivefive lumbarlumbar vertebrae, which vertebrae, which lie in the abdomen.lie in the abdomen.

The The sacrumsacrum and then the and then the coccyxcoccyx (tail (tail bone) are fused, and lie below.bone) are fused, and lie below.

The entire vertebral column is made up of The entire vertebral column is made up of sets of vertebrae resting on each other.sets of vertebrae resting on each other.

The vertebrae consist of a The vertebrae consist of a vertebral bodyvertebral body, , which faces forwards.which faces forwards.

An arch projects backwards, and the bony An arch projects backwards, and the bony processes at the end of it can be felt in the processes at the end of it can be felt in the back.back.

The arch encloses a hallow area which is The arch encloses a hallow area which is called the called the spinal canalspinal canal, as the , as the spinal cordspinal cord passes through it.passes through it.

Nerves arising from the spinal cord pass Nerves arising from the spinal cord pass out through special spaces.out through special spaces.

There are specific parts where the ribs are There are specific parts where the ribs are attached, and where the vertebrae attached, and where the vertebrae articulate with those above and below articulate with those above and below them.them.

Between adjacent vertebral bodies, with the Between adjacent vertebral bodies, with the exception of the first and second cervical exception of the first and second cervical vertebrae, there is an intervertebral disc.vertebrae, there is an intervertebral disc.

There are also strong ligaments along the There are also strong ligaments along the anterior and posterior surfaces of the anterior and posterior surfaces of the vertebrae, keeping them in place.vertebrae, keeping them in place.

The muscles of the vertebral column and The muscles of the vertebral column and their ligaments are also essential for its their ligaments are also essential for its stability.stability.

The The intervertebral discsintervertebral discs play a vital role in play a vital role in the functioning of the spine.the functioning of the spine.

These discs have two important functionsThese discs have two important functions * they play an important part in the * they play an important part in the

transmission of loads from one vertebral transmission of loads from one vertebral body to the next.body to the next.

* they allow, and restrain movements at the * they allow, and restrain movements at the inter (vertebral) body joints.inter (vertebral) body joints.

The discs have a central part made up of The discs have a central part made up of semifluid gel – the semifluid gel – the nucleus pulposusnucleus pulposus, and , and surrounding this, concentric layers of surrounding this, concentric layers of fibrous tissue, called the fibrous tissue, called the annulus fibrosusannulus fibrosus..

It is important that the nucleus pulposus is It is important that the nucleus pulposus is fluid, as it can be deformed under pressure fluid, as it can be deformed under pressure without a change in volume.without a change in volume.

This enables it to accommodate to This enables it to accommodate to movement and to transmit some of the movement and to transmit some of the compressive load from one vertebra to the compressive load from one vertebra to the next.next.

The discs are thickest in the The discs are thickest in the lumbarlumbar region region where they are required to bear a greater where they are required to bear a greater proportion of the body weight.proportion of the body weight.

The discs tend to deteriorate with age.The discs tend to deteriorate with age. With age, or due to excessive strain a With age, or due to excessive strain a

condition called ‘slipped disc’ may occur.condition called ‘slipped disc’ may occur. In this condition, the nucleus pulposus In this condition, the nucleus pulposus

bulges through the annulus fibrosus and bulges through the annulus fibrosus and protrudes.protrudes.

This may compress the nerve arising from This may compress the nerve arising from the spinal cord, thus causing pain.the spinal cord, thus causing pain.

Certain postures increase the risk of a Certain postures increase the risk of a slipped disc.slipped disc.

Postures to be avoided are those in Postures to be avoided are those in which the spine is bent and which the spine is bent and compressedcompressed..

For e.g. if one bends to pick up a heavy For e.g. if one bends to pick up a heavy weight, it is always weight, it is always best to bend ones best to bend ones knees and hips, and minimize spine knees and hips, and minimize spine flexionflexion..

Spinal curvesSpinal curves When viewed from the side, the When viewed from the side, the

vertebral column shows four main vertebral column shows four main curves.curves.

The lower The lower cervicalcervical spine is spine is convexconvex forwards, the forwards, the thoracicthoracic part is part is concaveconcave forwards, the forwards, the lumbarlumbar curve is curve is convexconvex forwards, forwards, and the and the sacrumsacrum is is concaveconcave forwards.forwards.

The shape varies in normal spines.The shape varies in normal spines. Lateral curves or scoliosis are also Lateral curves or scoliosis are also

seen in some normal individuals.seen in some normal individuals.

Rib cage SternumRib cage Sternum

Rib cageRib cage The rib cage is made up of twelve pairs of The rib cage is made up of twelve pairs of

ribs, which articulate with the vertebrae at ribs, which articulate with the vertebrae at the back, and the breastbone or sternum, in the back, and the breastbone or sternum, in front.front.

The appendicular skeletonThe appendicular skeleton This includes the bones of the upper and This includes the bones of the upper and

lower limbs, and the bones which articulate lower limbs, and the bones which articulate with the axial skeleton.with the axial skeleton.

The upper limb consists of the The upper limb consists of the humerushumerus in in the arm.the arm.

The humerus articulates with two bones at The humerus articulates with two bones at the elbow.the elbow.

These are the These are the radiusradius and the and the ulnaulna.. They lie in the forearm.They lie in the forearm.

At its upper end, the humerus forms the At its upper end, the humerus forms the shoulder jointshoulder joint, where it articulates with the , where it articulates with the collar bone (collar bone (clavicleclavicle) and the shoulder ) and the shoulder blade (blade (scapulascapula).).

The radius and ulna form the wrist joint The radius and ulna form the wrist joint along with the along with the carpal bonescarpal bones..

The The metacarpal bonesmetacarpal bones make up the hand, make up the hand, and in the fingers there are tiny bones with and in the fingers there are tiny bones with joints in between (the joints in between (the phalangesphalanges).).

The lower limb has the long, heavy ‘thigh The lower limb has the long, heavy ‘thigh bone’ – the bone’ – the femurfemur..

At its upper end it articulates with the At its upper end it articulates with the hip hip bonebone to form the hip joint. to form the hip joint.

At its lower end it articulates with the bones At its lower end it articulates with the bones of the lower leg – the of the lower leg – the tibiatibia and and fibulafibula..

The ankle joint is formed by these two The ankle joint is formed by these two bones, and the bones, and the tarsaltarsal or ankle bones. or ankle bones.

Metatarsal bonesMetatarsal bones make up the feet, while make up the feet, while (as for the hand) in the digits there are the (as for the hand) in the digits there are the phalangesphalanges..

MUSCULOSKELETAL SYSTEMMUSCULOSKELETAL SYSTEM

In man, as in other animals, movement is In man, as in other animals, movement is carried out by muscles.carried out by muscles.

Muscle tissue is made up of elastic cells Muscle tissue is made up of elastic cells which can repeatedly contract and relax.which can repeatedly contract and relax.

These cells often very long, hence they are These cells often very long, hence they are called called fibersfibers..

Based on their structure and function Based on their structure and function muscles are classified as muscles are classified as threethree groups - groups - Voluntary muscle, Cardiac muscle, and Voluntary muscle, Cardiac muscle, and Smooth muscleSmooth muscle

Voluntary muscleVoluntary muscle is so called because it is so called because it responds to our conscious control.responds to our conscious control.

Voluntary muscles are concerned with Voluntary muscles are concerned with movement of the arms and legs.movement of the arms and legs.

For this reason it is also called skeletal For this reason it is also called skeletal muscle.muscle.

These fibers appear striped or striated These fibers appear striped or striated under the microscope.under the microscope.

Cardiac muscleCardiac muscle forms the heart. forms the heart. Like voluntary muscle, it is striated.Like voluntary muscle, it is striated. The beating of the heart, however is not The beating of the heart, however is not

under voluntary control.under voluntary control. The rhythmic contractions are maintained The rhythmic contractions are maintained

by the by the cardiac pacemakercardiac pacemaker..

Smooth muscleSmooth muscle is also called involuntary is also called involuntary or visceral muscle.or visceral muscle.

It functions entirely without our conscious It functions entirely without our conscious control.control.

Smooth muscle forms part of the wall of all Smooth muscle forms part of the wall of all the tubes and ducts, including the blood the tubes and ducts, including the blood vessels, digestive tract, and genitourinary vessels, digestive tract, and genitourinary system.system.

The contractions of smooth muscle help to The contractions of smooth muscle help to keep the contents of any duct moving keep the contents of any duct moving forward (in the digestive tract called forward (in the digestive tract called peristalsisperistalsis))

Approximately 40 percent of the body is Approximately 40 percent of the body is skeletal muscle, and almost another 10 skeletal muscle, and almost another 10 percent is smooth and cardiac muscle.percent is smooth and cardiac muscle.

Types of skeletal muscle contractionTypes of skeletal muscle contraction Isometric contractionIsometric contraction does not cause any does not cause any

appreciable change in muscle length, appreciable change in muscle length, though tension variesthough tension varies

Isotonic contractionIsotonic contraction is a ‘free’ contraction, is a ‘free’ contraction, in which the tension remains the same, in which the tension remains the same, while the length shortens.while the length shortens.

Isometric contractionIsometric contraction

Isotonic contraction Isotonic contraction

EFFECTS OF MUSCULAR CONTRACTIONEFFECTS OF MUSCULAR CONTRACTION

During muscular contraction chemical During muscular contraction chemical changes occur, and waste products result.changes occur, and waste products result.

These must be removed by the blood stream.These must be removed by the blood stream. Sometimes, if a person over exerts himself, Sometimes, if a person over exerts himself,

these waste products are not removed quickly these waste products are not removed quickly enough, so that their accumulation contributes enough, so that their accumulation contributes to experiencing fatigue.to experiencing fatigue.

Repeated use has a stimulating effect on the Repeated use has a stimulating effect on the muscles, resulting in muscles, resulting in hypertrophyhypertrophy..

In contrast, muscles which are less used are In contrast, muscles which are less used are said to be said to be atrophiedatrophied..

STRUCTURE OF BONES

JOINTS:  WHERE TWO BONES MEET

Joint capsule consists of two layers

SKELETAL ORGANIZATION

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