Question

Out of 'X' pairs of ribs in humans only 'Y' pairs are true ribs. Select the option that correctly represents values of X and Y and provides their explanation

(a) X = 12, Y = 7	True ribs are attached dorsally to vertebral column and ventrally to the sternum.
(b) X = 12, Y = 5	True ribs are attached dorsally to vertebral column and sternum on the two ends.
(c) X = 24, Y = 7	True ribs are dorsally attached to vertebral column, but are free on ventral side.
(d) X = 24, Y = 12	True ribs are dorsally attached to vertebral column, but are free on ventral side,

Answer 1

Correct Option (a)
Explanation:

In the rib cage, the true ribs are those which are attached to the sternum in the front and vertebral column at back. These are 7 in numbers. Although there are total 12 ribs in the rib cage. The 11th and 12th ribs are attached to the vertebral column and keep floating in the thoracic cavity, so are called floating ribs.