11th Class Biology Locomotion and Movement Characters, Adaptation, Types, Movement And Disorder Of Bones

Characters, Adaptation, Types, Movement And Disorder Of Bones

Category : 11th Class

(1) Characteristics of female's skeleton : In female's skeleton, (i) skull is lighter, (ii) shoulders are narrower (iii) sacrum is shorter but wider, (iv) pelvis in wider, has a broader front and larger bottom opening to facilitate child birth, and (v) coccyx is more movable than in male's skeleton.

(2) Adaptations in skeleton for upright posture : Human skeleton shows many adaptive features for upright posture –

(i) Foramen magnum is directed downward so that the head may rest vertically on the vertebral column.

(ii) Four curves in the backbone keep the centre of gravity near the heels. This helps to maintain balance and makes walking erect on two legs much easier.

(iii) Thorax is wider from side-to-side than from front-to-back. This helps to maintain equilibrium.

(iv) Bowel-like pelvis supports the lower abdominal viscera.

(v) Metacarpals form a wide palm and the pollex is opposable. This make the hand a grasping organ to work with it.

(vi) Leg bones are stronger than the arm bones as the femur carry the entire weight of the body in locomotion. 

(vii) Broad feet provide stability in the upright posture.

(viii) The arches of the feet enable the body to move with a degree of springiness.

(ix) Increased mobility of the neck to see all round.

(x) Increased skeletal height provides greater range of vision.

(3) Types of bones : Bones are divided into 4 categories regarding their size and shape –

(i) Long bones, e.g., humerus of upper arm, radius and ulna of forearm, femur of thigh, and tibia and fibula of leg.

(ii) Short bones, e.g., metacarpals of palm and metatarsals of foot, phalanges of fingers and toes.

(iii) Flat bones, e.g., scapula of shoulder girdle, sternum, cranial bones.

(iv) Irregular bones, e.g., vertebrae, carpals of wrist and tarsals of ankle.

(4) Bone movement : Movements of bones occur only at the joints. The movements are brought about by contractions of skeletal muscles inserted onto the articulating bones by firm cords of white fibrous tissue called tendons. Cords of yellow elastic tissue, termed ligaments, stabilise the joints by holding the articulating bones together.

(5) Disorder of skeleton and joints : Any violent movement, such as jump, fall or knock, may cause injury to the skeleton. The injury can be of 5 types - sprain, dislocation, fracture, arthritis and slipped disc.

(i) Sprain : Sprain refers to injury to a joint capsule, typically involving a stretching or tearing of tendons or ligaments. Unfortunately, both these structures have much poorer regenerative power than bone, and once stretched often remain weak. Sprain is often considered a minor disorder, but it may become chronic.

(ii) Arthritis or Aching Joints : Arthritis refers to inflammation of the joints. It is a common disease of the old age. Its common symptoms are pain and stiffness in the joints. It has many forms. Three more common forms are described here - osteoarthritis or degenerative arthritis, the rheumatoid arthritis and gout.

(a) Osteoarthritis : Secretion of the lubricating synovial fluid between the bones at the joint stops. The smooth cartilage covering the ends of the bones at the joint stops. The smooth cartilage covering the ends of the bones at the joint wears out due to years of use and is replaced by uneven bony spurs. The joint becomes inflamed, its movement becomes painful, and its function is diminished. Such a stiffness or fixation of a joint is also called ankylosis. The condition of osteoarthritis is more or less permanent. It is common in old persons, mainly affecting weight bearing joints.

(b) Rheumatoid arthritis : It is a chronic painful inflammation of the synovial membranes of many joints simultaneously. It usually starts in the small joints in the hand and progresses in centripetal and symmetrical manner. In severe cases, it eventually results in crippling deformities. There may be other manifestations such as fever, anaemia, loss of weight and morning stiffness. The rheumatoid arthritis involves erosion of joints. It usually starts at the age of 20 - 40 years, but may begin at any age. It affects the women more often than the men. Rest and exercise under medical advice may give relief.

(c) Gout : It is an inherited disorder of purine metabolism, occurring especially in men. Body forms excess amounts of uric acid and the crystals of sodium urate are deposited in the synovial joints, giving rise to a severe arthritis. It generally affects one or two joints only. It is very painful, particularly at night, and makes movement difficult. Redness and tenderness may be noticed in and about the affected joint. Gout generally affects the great toe. Occurrence of gout is related to diet. Persons suffering from gout should avoid meat. There is no cure for arthritis. However, pain relieving (analgesic) drugs are available to give comfort.

(iii) Osteoporosis

(a) Meaning : Osteoporosis is reduction in bone tissue mass causing weakness of skeletal strength (G.osteon = bone, poros = pore, osis = condition). It results from excessive resorption of calcium and phosphorous from the bone. There is relatively greater loss of trabecular bone than of compact bone. This leads to vertical compression, or crush fracture, of the vertebrae (which consist primarily of trabecular bone), and fracture of the neck of the femur (which has considerable trabecular bone).

(b)     Causes : Osteoporosis occurs in postmenopausal women and elderly men. It may result from defective intestinal calcium absorption and menopause. Possible environment factors include smoking, excessive drinking, and decreased exercise. Osteoporosis is more common in women than in men, and in older than in middle-aged persons.

(c) Symptoms : Symptoms of osteoporosis are pain in the bone, particularly the back, and vertebral crush, usually in weight bearing vertebrae (thoracic-8 and below).

(d) Prevention : Preventive measures in high-risk patients include supplementary calcium and exercise, and, in postmenopausal women, estrogen replacement therapy. Supplementary calcium and sex hormones decrease bone resorption and may arrest or reduce disease progression.

(iv) Dislocation : Dislocation is displacement of bones from their normal positions at a joint, for instance, slipping out of the ball of one bone from the socket of another bone into which it is fitted. Dislocation is accompanied by pulling or even tearing of the ligaments. Dislocation also tends to become chronic.

(v) Slipped disc : Slipped disc is a displacement of vertebrae and the intervertebral fibrocartilage disc from their normal position. It may result from mechanical injury or defects of ligaments holding the vertebrae together.

(vi) Fracture : Fracture is a break of a bone. Fracture occurs rarely in children. The bones of children have a large quantity of organic matter and are, therefore, very flexible and less likely to break. With advancing age, mineral matter (calcium phosphate) is deposited in the bones. This decreases the organic matter, making the bones hard and brittle. Thus, old people are more liable to fracture of bones. Bones fractures are of many types –

(a) Green-stick fracture or complete : It complete is mearly a crack. The bones remains partly intact, occurs only in children.

(b) Simple or complete fracture : Bone breaks completely into two parts which remain close to each other.

(c) Comminuted fracture : Bone breaks into more than two pieces (smaller fragments between two main fragment,

(d) Compound fracture : Bone breaks completely but a fragment pierces out through the skin.

(e) Evulsive fracture : A small piece breaks off fully from the bone but remains attached to the ligament. Fractures need surgical treatment for healing and should be promptly and properly attended to.

 

 

(f) Bursitis : Bursitis in inflammation of the bursae present in the joints. It is caused by physical injury or constant pressure on a single joint for a long time.

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