LOCOMOTION AND MOVEMENT

 

  • Appendicular skeleton: 126 bones
    • Fore limb – 60 ( 30 in each)
      • Humerus – 1 bone
      • Radius and ulna – 2 bones
      • Carpals (wrist bones) – 8 in numbers.
      • Metacarpals (palm bones) – 5 in numbers
      • Phalanges (digits) – 14 in number.

    • Hind limb – 60 (30 in each)
      • Femur (thigh bone- the longest and heaviest bone) – 1 number.
      • Tibia and fibula – 2 bones.
      • Tarsals (ankle bone) – 7 bones.
      • Metatarsals – 5 in numbers.
      • Phalanges (digits) – 14 in numbers.
      • Patella (knee cap) – 1 bone.

    • Pectoral girdles: consists of 2 bones each = 4 bones.
      • Helps in articulation of fore limb with the axial skeleton.
      • Each pectoral girdle made of two half.
      • Each half made of two bone the clavicle and scapula.
      • Scapula is a large triangular flat bone situated in the dorsal part of the thorax between the second and the seventh ribs.
      • Scapula is characterized by spine with acromion process.
      • Below acromion, is glenoid cavity to which head of humerus fits.
      • Clavicle is commonly called collar bone.

    • Pelvic girdle: 2 bones.
      • Pelvic girdle consists of two coxal bones.
      • Each coxal bone is formed of fusion of three bones
        • Ilium
        • Ischium
        • Pubis.

      • At the point of fusion of the three bones is a cavity called acetabulum to which the femur articulates.
      • Two halves of the pelvic girdle meets ventrally to form the pubic symphysis containing fibrous cartilage.

JOINTS :

  • Joints are the points of contact between bones, or between bones and cartilages.
  • Force generated by the muscles is used to carry out movement through joints, where joint acts as a fulcrum.
  • Joints are classified into three types:
    • Fibrous joint
    • Cartilaginous joint
    • Synovial joint

Fibrous joints :

  • Do not allow any movements.
  • Found in flat bones which fuse end-to-end with the help of dense fibrous connective tissues in the form of sutures.
  • These types of joints are found in the bones of cranium.

Cartilaginous joints :

  • The bones involved are joined together with the help of cartilages.
  • Permits very little movements.
  • Joint between the vertebral column are the example of such joints.

Synovial joints :

  • Characterized by the presence of a fluid filled synovial cavity between the articulating surfaces of the two bones.
  • Allow free movement between two bones.
  • The fluid inside it called synovial fluid covered by synovial membrane.
    • Ball and socket joint - between humerus and pectoral girdle
    • Hinge joint – knee joint
    • Pivot joint – between atlas and axis.
    • Gliding joint – between carpals.
    • Saddle joint – between carpals and metacarpals of thumb.

DISORDERS OF MUSCULAR AND SKELETAL SYSTEM :

Myasthenia gravis :

  • It is an auto-immuno disorder.
  • Affects the neuromuscular junction leads to fatigue.
  • Caused weakening and paralysis of skeletal muscle.

Muscular dystrophy : Progressive degeneration of skeletal muscle mostly due to genetic disorder.

Tetany: rapid spasms (wild contractions) in muscle due to low Ca++ in body fluid.

Arthritis : inflammation of joints.

Osteoporosis : age related disorder characterized by decreased bone mass and increased chances of fractures. Decrease levels of oestrogen are a common cause.

Gout : inflammation of joints due to accumulation of uric acid crystals.

 

CBSE Biology (Chapter Wise) Class XI ( By Mr. Hare Krushna Giri ) 
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