Question

A: Skull bones are investing in bones
R: they develop due to ossification of cartilage in dermis

(1) if both assertion and reason are true and the reason is the correct explanation of the assertion, then mark (1)

(2) if both assertion and reason are true but the reason is not correct explanation of the assertion, then mark (2)

(3) if assertion is true statement but reason is false, then mark (3)

(4) if assertion and reason are false statements, then mark (4)

Answer 1

A dermal bone or membrane bone is a bony structure derived from intramembranous ossification forming components of the vertebrateskeleton including much of the skull, jaws, gill covers, shoulder girdle and finspines rays (lepidotrichia), and the shell (of tortoises and turtles). In contrast to endochondral bone, dermal bone does not form from cartilage that then calcifies, and it is often ornamented.[1] Dermal bone is formed within the dermis and grows by accretion only – the outer portion of the bone is deposited by osteoblasts.

The function of some dermal bone is conserved throughout vertebrates, although there is variation in shape and in the number of bones in the skull roof and postcranial structures. In bony fish, dermal bone is found in the fin rays and scales. Special examples of dermal bones include the clavicle, patella, and os cordis.