Human Skeleton And Locomotion 3qk6i

Institute Of Science Std-XI Biology paper II - Zoology

Chapter no - 14. HUMAN SKELETON AND LOCOMOTION Skeleton :- The external or internal framework of the body which s and protects the soft tissues of the body is called skeleton There are two types of skeleton i.e. exoskeleton and endoskeleton

Hyoid bone (Tongue bone) – It is a horse shoe shaped or U-shaped bone situated just above the larynx and below the tongue. It is the only bone of the body which is not articulated with any other bone of the body.

Exoskeleton :- The skeleton present on outer surface of the body is called exoskeleton Example – Scales in fishes, Scutes in reptiles, Feathers in birds, Fur, Hair, Nails in mammals

Vertebral column – 1] It is also known as backbone which forms the central axis of the body 2] It consist of 33 small ring like bones called vertebrae 3] It is about 70cms in length in an average adult 4] It is divided into five regions i.e. cervical (7), thoracic (12), lumbar (5), sacral (5), coccygeal (4) 5] The 5 sacral vertebrae fuse to form sacrum and 4 coccygeal vertebrae fuse to form coccyx 5] It shows four curvatures i.e. two outward and two inward 6] The cervical and lumbar region shows outward curvature and thoracic and sacral region shows inward curvature 7] The curvatures primarily help to balance the erect posture of the body

Endoskeleton :- The skeleton which remains inside the body forming internal hard framework is called endoskeleton Example – Cartilage and Bones in mammals Functions of skeleton ( Endoskeleton ) – 1] It provides to the whole body 2] It gives definite shape to the body 3] It prevents the internal organs like heart, lungs, brain, etc 4] It helps in locomotion 5] It provides the surface for attachment of muscles 6] It forms the blood cells so also called as haemopoietic organ 7] It helps in breathing 8] The long bones are store house of minerals i.e. calcium and phosphorus 9] The marrow cavity of long bones secrete fat due to presence of adipose tissue The adult human skeleton is mainly bony with some cartilage which is formed of 206 bones and makes upto 20% of body weight. About 35% of bones are rich in organic matter (protein and collagen) which provides flexibility to the bones and 65% of bones are rich in calcium and phosphorus which provides rigidity to the bones. Human endoskeleton is divided into two parts i.e. Axial skeleton and Appendicular skeleton. A] Axial skeleton – It runs along the median axis of the body. It consists of skull, hyoid bone, vertebral column and thoracic cage. It is formed of 80 bones. Skull – 1] It is formed of 28 bones 2] It is dicondylar (presence of two occipital condyles at the base of skull) 2] It shows main parts like cranium, face and ear ossicles 3] It protects the brain and provides sockets for ear, nasal chamber and eyes 5] It gives a proper shape to head and face 6] All the bones of skull are immovable except mandible (Lower jaw) 7] The mandible helps in opening and closing of mouth Ear ossicles – The bones of middle ear are called as ear ossicles. Each middle ear consist of three ear ossicles, they are malleus, incus and stapes. The stapes is also the smallest bone of the body. The ear ossicles help to carry the sound waves from the surrounding to the internal ear.

Thoracic cage – A bony protective cage present around the thorax is called thoracic cage or chest cage. It is formed by 12 thoracic vertebrae dorsally, 12 pairs of ribs laterally and the sternum and coastal cartilage’s ventrally 1] Thoracic vertebrae – There are 12 thoracic vertebrae present on the dorsal side. Each thoracic vertebra is articulated with the pair of rib. 2] Sternum – It is located in the chest region hence also called as chest bone. It is long, flat bone about 15cms in length. It consist of three regions i.e. manubrium, body and xiphoid process. a] Manubrium – It is the anterior triangular part of sternum which appears like a knot of tie. It articulates with the clavicles laterally and 1 st two pair of ribs. b] Body – It is long, flat middle part of sternum. It provides surface for the attachment of 3-7 pairs of ribs c] Xiphoid process – It is the inferior end of sternum. It is cartilaginous in youth but usually ossified in adults. It provides surface for attachment for diaphragm and anterior abdominal muscles. 3] Ribs – 1] Ribs are curved, slightly elastic rods which forms the greater part of the skeleton of thorax 2] There are 12 pairs of ribs present laterally 3] Ribs consist of head, neck, tubercule and coastal cartilage 4] The first 7 pairs of ribs are directly attached to the sternum through coastal cartilage hence called as true ribs 5] 8th to 10th pair of ribs are attached to the sternum indirectly through the 7th pair of rib hence called as false ribs 6] Last two pairs of ribs (11 th and 12th) are short, free in front hence called as floating ribs 7] In some person an extra rib is present like gorilla and chimpanzee hence such rib is called as gorilla rib 1

Functions of thoracic cage – 1] It forms a protective cage around vital organs such as heart, lungs and important blood vessels of thoracic cavity 2] It provides surface for attachment of back, chest and shoulder muscles 3] It provides articulation to clavicle or collar bone 4] Sternum and ribs help in breathing B] Appendicular skeleton – It is formed of 126 bones which mainly consist of girdles and bones of limbs Pectoral girdle – The girdle which consist of bones of forelimbs is known as pectoral girdle. It is also called as shoulder girdle. It consist of two bones, the anterior clavicle and the posterior scapula Bones of forelimbs – Each forelimb consist of three parts – upper arm, forearm and hand which consist of 30 bones A] Humerus – Upper arm B] Radius-ulna – Fore arm C] Bones of hand – Carpals – Wrist, Metacarpals – Palm and Phalanges - Digits Pelvic girdle – It consists of two large hip bones which are articulated anteriorly in mid line by cartilaginous t called pubic symphysis. Each hip bone is formed by ossification of ilium, pubis and ischium Bones of hind limbs – Each hind limb is formed of 30 bones. The hind limb is divisible into three parts – thigh, shank and foot A] Femur – Thigh B] Tibia-fibula – Shank C] Bones of the foot – Tarsal – Ankle, Metatarsal – Sole and Phalanges – Toes (digits)

There are four basic types of locomotions found throughout the animal kingdom, such as 1] Amoeboid movement – It is performed by pseudopodia e.g. Leucocytes, Amoeba, etc 2] Ciliary movements – It is performed by cilia e.g. Ciliated epithelium, Paramecium, etc 3] Whorling movements – It is performed by flagella e.g. Sperms, Bacteria, etc 4] Muscular movements – It is performed by muscles e.g. Limb movements Importance/Significance of locomotion – 1] It helps the organisms to search food, water and shelter 2] It helps the organisms to escape from enemy or predators 3] It prevents the organism from danger 4] It helps the organism to find mate for reproduction 5] It helps the organism to move from one place to another ts – The place where two or more bones articulate is called t Types of ts – The ts are of three different types a] Fibrous / immovable / synarthrosis ts b] Cartilaginous / slightly movable / amphiarthrosis ts c] Synovial / freely movable / diarthrosis / perfect ts a] Fibrous / immovable / synarthrosis ts – 1] This t does not provides any movement 2] The articulating bones are held together by tough fibrous connective tissue Ex – Sutures or skull t, peg and socket t, syndesmoses, etc

Locomotion – All living organisms exhibit movements. These movements take place with the help of some internal force. In human beings, there are two kinds of movements i.e. internal movements and locomotion 1] Internal movements – It includes the movements which may be voluntary or involuntary, these movements are brought about by three different types of muscles a] Peristaltic movements in the alimentary canal, constriction and dilation of blood vessels, etc are controlled by smooth muscles b] Contraction and relaxation of heart is controlled by cardiac muscles c] Movements of limbs, head, trunk, eyeballs, etc are controlled by striated muscles Significance of movements – 1] The body movements help to maintain equilibrium against gravity 2] It helps in food intake, speech, etc 3] Movements of diaphragm and rib cage help in the breathing process 4] Rhythmic movement of the heart helps in the circulation of blood 2] Locomotion - A willful act of displacing the whole body from one place to another is called locomotion

1] Sutures or skull t –

Skull t 1] It is present in skull bones 2] The bones of skull are flat with little gap in-between them 3] The margins of bones are serrate and interlocked with each other 4] The ts are held together by tough fibrous connective tissue 5] They are completely immobile and protective in function 2] Peg and Socket t (Gomphosis) –

Peg and socket t 1] It is an immobile t 2] It is present between the jaw bones and teeth 2

3] The jaw bones consist of a cavity called socket 4] The peg like root of teeth is fixed in the socket of jaw and held together by tough fibrous connective tissue 3] Syndesmoses –

4] The movement is brought by relaxin hormone secreted by placenta c] Synovial / freely movable / diarthrosis / perfect ts – The ts which provide maximum mobility to the articulating bones are called synovial or freely movable ts. Characteristic of synovial t –

Syndesmoses 1] 2] 3] 4]

It is an immobile t It is present at the distal end of tibia-fibula It is present along the length of radius-ulna The articulating material is dense fibrous connective tissue

b] Cartilaginous / slightly movable / amphiarthrosis ts – 1] This t provides slight movement 2] The articulating material is in the form of disc of fibro cartilage Ex – Intervertebral t, synchondroses, symphysis (pubic t), etc

A typical synovial t 1] Presence of hyaline cartilage on the surface of articulating bones 2] Presence of synovial cavity between articulating bones 3] Presence of yellow viscous fluid in synovial cavity 4] The articulating bones are held together by ligament 5] The synovial fluid prevents the t from friction

1] Intervertebral t – Types of synovial ts – On the basis of degree of mobility the synovial ts are of following types – 1] Ball and socket t – Intervertebral t 1] It is present between vertebra of vertebral column 2] The vertebra are articulated with intervertebral cartilaginous disc 3] Any mechanical injury causes slipped disc which leads to severe pain 2] Synchondroses –

Ball and socket t

Synchondroses 1] It is found in chest bone 2] It is present between I-rib and manubrium of sternum 3] It is found in epiphyseal plates in long bones of children 4] It is later on ossified called as synostosis

1] It is a maximum mobile synovial t 2] The ball like head of one bone fixes into the cavity of other bone 3] This t shows the movement of flexion, extension, abduction and adduction Example – 1] The t between head of humerus and glenoid cavity of pectoral girdle 2] The t between head of femur and acetabulum of pelvic girdle 2] Hinge t (Elbow t) –

3] Symphysis (Pubic t) –

Pubic t 1] It is present between the pubic bones of pelvic girdle 2] The gap present between the pubic bones is filled with fibro-cartilage 3] It provides a slight movement during parturition (child birth) in females

1] This t shows movement only in one direction 2] It shows the movement of flexion and extension 3] The head of one bone fixes in the cavity or notch of other bone 3

Example – 1] The t between lower head of humerus and olecranon process of ulna bone of forearm 2] The t between lower head of femur and proximal end of tibia-fibula 3] Pivot t –

Pivot t In this type of t the peg like projection of one bone fixes into the cavity of other bone Example – 1] The t between atlas and axis vertebra 2] The t between radius and ulna at proximal end 4] Condyloid t –

Condyloid t In this t, one articular end of the bone is oval and convex while the other end is elliptical and concave allowing biaxial or biplanar movement Example – 1] Wrist or radio-carpal t 2] Palm and finger t 3] Toes and sole t 5] Saddle t –

convex part of one bone fits into the concave part of the other bone and vice-versa Example –Thumb t 6] Gliding or plane t – In this t, articular ends of two bones are either flat or slightly curved to allow sliding or gliding movements Example – Intercarpal and Intertarsal ts Muscular movements – The muscular tissue is characterized by its property of contractility. It also shows the properties of extensibility, elasticity, flexibility, conductivity, etc. The muscular tissue consist of highly elongated modified cells called muscle fibers. There are three different types of muscular tissue in the body of vertebrates i.e. striated, unstriated and cardiac muscles. The striated muscles perform voluntary movements while the unstriated and cardiac muscles perform involuntary movements 1] Voluntary movements The movements of body parts carried under the control of our will are called voluntary movements. All types of voluntary movements are performed by striated muscles e.g. movements of limbs, head, etc The striated muscles are found attached to the skeleton by means of tendons. Tendons are inelastic thick bands of white fibrous connective tissue which give firm attachment to muscle with bone Location and structure of striated muscle – The muscle which moves a body part usually do not lie in that part but located in the upper part e.g. biceps and triceps that move forearm are located in the upper are. At any t two types of bones are present i.e. stationary and movable. The end of muscle attached to stationary bone is called origin while the opposite end attached to movable bone is called insertion. The part of muscle between origin and insertion is called belly Types of striated muscles – On the basis of movements striated muscles are of three types – 1] Prime movers (agonist) – Bring initial movement of part e.g. Biceps 2] Antagonists – Brin g the action opposite to that of prime movers e.g. Triceps 3] Synergists – Assist prime movers e.g. Brachialis assists Bies Working of striated muscles – Generally the muscles work in pair and produce opposite action e.g. biceps bring flexion and triceps bring extension of the elbow t. The muscles which bring opposite action are called antagonistic In antagonistic pair of muscles one member is much stronger than the other e.g. the biceps which flex the arm are stronger than the triceps which extend the arm. The fundamental characteristic of muscle is contraction therefore, muscle can only pull and not push the bone

Saddle t In this t, the bone ends are saddle shaped with both the concave and convex parts. The

Some important antagonistic muscles – 1] Flexor – On contraction results in bending or flexion of a t e.g. Bies Extensor – On contraction results in straightening or extension of a t e.g. Triceps 4

2] Abductor – It moves body part away from the body axis e.g. deltoid muscle of shoulder moves the arm away from the body Adductor – It moves body part towards the body axis e.g. latissimus dorsi of shoulder moves the arm near to the body 3] Pronator – To turn the palm downward backward Supinator – To turn the palm upward forward 4] Levator – Raises a body part Depressor – Lowers the body part 5] Protractor – To move forward Retractor – To move backward 6] Sphincters – Circular muscles present at the inner side wall of anus, stomach, etc for closure and opening

Flexor

beating of heart (working). These muscles are short, striated, branched, uninucleate. They show intercalated discs. The cardiac muscles form the thick part of the heart wall Skeletal disorders 1] Muscular dystrophy – It is inherited muscle destroying disease characterized by degeneration of individual muscle fibre which leads to progressive atrophy of the skeletal muscle. Usually the voluntary skeletal muscles are weakened equally on both sides of the body. The most common type of muscular dystrophy is Duchenne type 2] Osteoporosis – It is an age dependent disease caused by deficiency of vitamin-D, sex hormones and thyrocalcitonin. In women, after menopause the estrogen secretion becomes less causing loss of calcium and the bones become porous due to low bone mass and the skeleton fails to withstand the stress of the body 3] Arthritis – It is characterized by inflammation of ts. Inflammation, pain and stiffness may also be present in adjacent parts of the body such as the muscles near the t The arthritis is of three different types – A] Gouty arthritis (Gout) – It is caused due to excessive accumulation of uric acid in the body due to its excessive production or inability to excrete which gets deposited in the ts and leads to severe pain B] Osteoarthritis – It is characterized by degeneration of cartilage pad. ts of knees, hands and spine are usually affected by this disease C] Rheumatoid arthritis – It is characterized by the inflammation of synovial membrane. The membrane thickens and synovial fluid increases exerting pressure that causes severe pain. The membrane than starts secreting abnormal granules called pannus which cause erosion of cartilage

By - Prof. Santosh M Pandey M.Sc, B.Ed

Extensor

Mobile no – 9970706070 / 9967717896

2] Involuntary movements These movements are not under the control of our will but they are under the control of Autonomic Nervous System (ANS) A] Movement of visceral muscles – The visceral muscles are present in the walls of visceral organs such as alimentary canal, urinary bladder, blood vessels, etc. These muscles are neurogenic and on receiving motor impulse from ANS they show alternate contraction and relaxation. The visceral muscles do not undergo fatigue because their contractions are slow and for longer duration so they are able to do continuous work E.g. – Contraction of urinary bladder, Constriction and dilation of blood vessels, Peristaltic movement of alimentary canal, Gastric movements of stomach, etc B] Movements of cardiac muscles – These are present in the wall of the heart. They are involuntary in nature and bring about 5