Define:

(a) Skeleton system

(b) Bone marrow

(c) Gristle

(d) Pivot joint

(e) Antagonistic muscles

Do the muscles pull the structures, or push them? Explain briefly.

What are antagonistic muscles? Give one example.

Give reason:

(a) Decalcified bones become soft and flexible.

(b) People in old age complain of stiff joints.

(c) In the female skeleton, the pelvis or hip bone is wider and trough-shaped.

(d) Bones are considered to be a living tissue.

(e) Vertebral column is curved.