21. Locomotion and Movement (11)

Sight is not the function of endoskeleton

Hyaluronic acid lubricates ligaments and tendons, and is an important constituent of synovial fluid of bone joints, vitreous humour of eyes, etc.

Ca²⁺ions are essential of muscle contraction, neuro-muscular functions and nerve impulse transmission.

ATP is the source of energy for muscle contraction.

Running along the length and present in the wall of bone, there are a number of longitudinal canals called the Haversian canals, which are interconnected by a number of small transverse and oblique canals called Volkmann's canals.

Parasphenoid bone is a flattened and inverted T-shaped bone, which forms the floor of cranium.

The reduction in force of contraction of a muscle after prolonged stimulation is called muscle fatigue. The accumulation of lactic acid leads to muscle fatigue. Lactic acid is produced by glycolysis in the absence of O₂.

Nucleus pulposes is the central soft part of intervertebral disc representing remains of notochord (shock absorber).

During contraction and relaxation of muscles, both I-band and H-zone progressively shorten and disappears.Dark A-band (anisotropic) undergo no change during contraction and relaxation of muscle fibres.

When muscles contract, they have squeezing effect on veins running through them, this is called muscle pump.

In hinge joint, the convex surface of one bone fits into the concave surface of another bone, e.g. knee, elbow and interphalangeal joints.

A transverse ligament is found in atlas. It divides the neural foramen of atlas into a smaller anterior (front) odontoid fossa and a posterior, larger vertebral foramen.

Osteoporosis is a disease, in which bones loses minerals and fibres from its matrix. Imbalances of hormones like calcitonin, parathyroid and sex hormones, deficiencies of calcium and vitamin-D are the main causes of osteoporosis.

During anaerobic situation, lactic acid formation is started by the body cells. Later on, this lactic acid is delivered by the blood to the liver, where lactic acid dehydrogenase enzyme converts lactic acid to pyruvic acid.

 Each actin filament is made of two ‘F’ (filamentous) actins helically wound to each other. Each ‘F’ actin is a polymer of monomeric ‘G’ (Globular) actins. Two filaments of other proteins, tropomyosin also run close to the ‘F’ actins throughout its length. A complex protein troponin is distributed at regular intervals on the tropomyosin. In the resting state, a subunit of troponin marks the active binding sites for myosin on the actin filaments.

Each arm consists of 30 bones, one humerus, one radius, one ulna, eight carpal bones, five metacarpal bones and fourteen phalanges bones, i.e. 1 + 1 + 1 + 8 + 5 + 14 = 30.

  During muscle contraction, actin and myosin interact to form actomyosin. According to sliding filament theory, cross bridge is formed by myosin filament to slide act in filament. During muscle contraction, length of A-band remains constant.

Synovial fluid is present in perfectly movable joints. The synovial membrane secretes synovial fluid, which lubricates and provides nourishment to articular cartilage.

Axis is the second cervical vertebra, which is identified by a prominent odontoid process. The odontoid process of axis vertebra fits in the odontoid fossa of first cervical vertebra, forming the actual pivot joint at which the skull rotates around together with the atlas.

A fracture of the distal end of radius in which the distal fragment is displaced posteriorly is called Colles’ fracture.