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NEET Biology Notes Movement and Locomotion Joints

NEET Biology Notes Movement and Locomotion Joints

Joints

A joint is the point of contact between bones. Arthrology is the study of joints. Joints can be classified into three types:

NEET Biology Notes Movement and Locomotion Joints 1

  • Immovable Joints(Fibrous or Synarthrose)

In these, the adjoining bones are joined by strong bundles of collagen fibres so that the bones cannot move freely.

  1. The bones of the skull articulate with one another with a type of immovable joint called suture.
  2.  Articulation of teeth with mandible and maxillae. Here, peg-shaped roots fit into cone-shaped sockets in the jawbones.
  3. Articulation between the first pair of ribs and the breast bone.
  •  Slightly Movable Joint (Cartilaginous)

In these joints, there is a pad of fibro-cartilage between two adjoining bones, which allows very slight movements

  •  Freely Movable Joints (Synovial)

In these joints, the movement is possible in one or other directions. The ends of articulating bones are covered by smooth articular cartilages. A synovial cavity is present between two bones, which is filled with a gelatinous synovial fluid.
These joints are further classified according to the types of movements:

  1.  Ball and Socketjoint
    The ball-like head of one bone fits into the socket or the concavity of the other. In this, movements are possible in all directions, e.g.
    (a) Shoulder joint between head of humerus and glenoid cavity of pectoral girdle.
    (b) Hip joint between head of femur and acetabulum of pelvic girdle.
    Disorders of Muscular and Skeletal System
    The muscular and skeletal system are prone to injury, wear and tear, inflammations and other metabolic dysfunctions. Listed below are some common disorders of These are also called symphysis, e.g. joints between pubic bones of pelvic girdles and the joints between the vertebrae (intervertebral disc).
  2. Hinge Joint
    In these joints, a protuberance (condyle) at the end of one bone fits into corresponding depression of the other. A hinge joint allows movement in one plane only. Similar to how a door opens and close by means of its hinges, e.g. ankle, knee and elbow joints and joints between phalanges of digits.
  3.  Pivot or Rotatory or Trochoid Joint
    Here, one bone is fixed and bears a peg-like projection of pivot.
    The other bone fits over the pivot by a concavity and freely rotates around, e.g. head of the radius and capitulum of humerus, between atlas and axis of mammals.
  4.  Saddlejoint
    One bone of the joint shaped like a saddle and the other like the back of a horse. These are like ball and socket joints but both ball and socket are poorly developed, i.e. movements take place in many directions, e.g. joint between metacarpal and carpal of thumb.
  5. Gliding Joint
    The articulating bones can slide upon one another at this joint, e.g.- the joint between zygapophysis of successive vertebrae and between radio-ulna and carpals.
  6.  Ellipsoid or Condyloid or Angular Joint
    Here, one bone is movable on another bone in two planes, back and forth and side to side, e.g: joint between radius and carpals and between skull and first vertebra.

 

Disorders of Muscular and Skeletal System

The muscular and skeletal system are prone to injury, wear and tear, inflammations and other metabolic dysfunctions. Listed below are some common disorders of muscular and skeletal system.

  1.  Muscular Dystrophy It is the progressive degeneration of muscle fibres due to some genetic disorder leading to weakness and loss of mobility.
  2. Myasthenia Gravis It is the chronic autoimmune disorder which affect the neuromuscular junction, in which the body produces antibodies that block the muscle from receiving messages from nerve cells. It leads to fatigue, weakening and paralysis of skeletal muscle.
  3.  Tetany It is the rhythmic cramping of the muscle due to lowCa2+ (hypocalcemia) in body fluid.
  4.  Arthritis It is the inflammation of joints leading to stiffness, swelling and pain in joint. Its various types are:
  5.  Osteoarthritis The wearing away of the cartilage which covers the bones in the joints leads to osteoarthritis. It can affect middle aged and older people.
  6.  Rheumatoid Arthritis The inflammation of synovial membrane that protects and lubricated the joint leads to rheumatoid arthritis. It affects individual of all age groups.
  7. Still’s Disease Juvenile rheumatoid arthritis is another kind of rheumatoid arthritis that occurs in younger people. There is no cure for arthritis. However, pain releiving (analgesic) drugs are available to give comfort.
  8. Gout It is the inflammation of joints due to the accumulation of uric acid. It is an inherited disorder of purine metabolism.
  9. Spondylitis It is a chronic inflammatory disorder that affects vertebrae causing pain and stiffness.
  10.  Sprain It is the twisting of joint without dislocation.
  11. Dislocation It occurs when bones are forced out of a joint, often accompanied by sprains, inflammation and joint immobilisation.
  12. Cartilage Tears Cartilage may tear when joints are twisted or when pressure is applied to them.
  13.  Osteoporosis In this, a reduction in bone tissue mass occurs, causing weakness of skeletal strength. It results from excessive resorption of calcium and phosphorus from the bone. Decreased level of oestrogen is a common cause for this.

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