Question

Number of bones present in forelimb of human is
A) 30
B) 32
C) 35
D) 40

Answer 1

Hint: Limbs of mammals are plain, that of the pentadactyl limb (i.e. each limb ends in five digits). The limb bones support the arms (upper limbs) and legs (lower limbs).

Complete answer
Each arm contains 30 bones, namely humerus in the upper arm, radius and ulna in the forearm, 8 carpals in the wrist, 5 metacarpals in the palm and 14 phalanges. Arrangement of bones:
Humerus – 1, Radius – 1, Ulna – 1, Carpals – 8, Metacarpals – 5, Phalanges - 14.
(i) Radius and ulna are so arranged in the forelimbs as to allow the radius to rotate around the ulna.
(ii) The distal phalanges support broad, arched, horny nails.
(iii) Many small bones in the wrist and hand allow us to hold objects, to write, paint etc.
(iv) Phalanges formula for human hand is $2,3,3,3,3.$
(v) In the human arm, the joints are more movable than in the forelimbs of animals.
(vi) Animals use forelimbs mainly for locomotion whereas humans use the arms for grasping, writing, sewing, painting back and forth and side to side movements e.g. Joints found between the carpal bones and tarsal bones (in lower limb).
(vii) Saddle joints – They allow movement in two planes, back and forth and side to side e.g. joints between the metacarpals and phalanges.

Hence the correct answer is option (A).

Additional information:
(i) Different types of joints are present in forelimbs.
(ii) Gliding joint – permits only

Note:The lower limbs (legs) are considered to be stronger than forelimbs (arms).Humerus is the long bone of the forelimbs of land vertebrates. It forms the shoulder joint above, where it articulates with a lateral depression of the shoulder blade i.e. glenoid cavity of scapula, and the elbow joint below, where it articulates with projection of the ulna and the radius.