Question

Out of 'X’ pairs of ribs in humans only 'Y' pairs are true ribs. Select the option that correctly repeats the values of X and Y and provides their explanation:
(a) X = 12, Y = 5 True ribs are attached dorsally to the vertebral column and sternum on the two ends.
(b) X = 24, Y = 7 True ribs and dorsally attached to the vertebral column but are free on the ventral side.
(c) X = 24, Y = 12 True ribs are dorsally attached to the vertebral column but are free on the ventral side.
(d) X = 12, Y = 7 True ribs are attached dorsally to the vertebral column and ventrally to the sternum.

Answer 1

Hint: As we know that there are 12 pairs of ribs that are found in our bodies. In these pairs y. In these pairs some are of false ribs, some are floating and the major pairs of ribs are of true ribs as they are attached at both the ends.

Complete answer:
In human beings, 12 pairs of ribs are present. Out of these 12 pairs of ribs, the first 7 pairs ( from 1st pair to 7th pair) of ribs are said to be true ribs because these 7 pairs of ribs are dorsally (from the back) attached to the vertebral column and ventrally (from the front) attached to the sternum.

Therefore, ‘X’ pairs of ribs = 12 pairs of ribs are found in the human body.
‘Y’ pairs of ribs = 7 pairs of true ribs.

Additional Information:
- The 12 pairs of ribs along with the sternum, costal cartilage, and the thoracic portion of the vertebral column at the back together constitute a cage- like structure called the rib cage.
- The next 3 pairs of ribs ( from the 8th pair to 10th pair) or just after true ribs are false ribs because dorsally they are attached to the vertebral column but ventrally they are fused with the last pair or 7th pair of true ribs.
- The last two pairs ( the 11th and the 12th pair) of ribs are called floating ribs because only at one end are attached to the vertebral column and the other end is free or remains unattached.
- The rib cage is also known as the thoracic cage and includes ribs along with costal cartilage, sternum, and thoracic vertebrae.
- Its main function is to provide protection to the organs(the heart and lungs) in the thoracic cavity, also support the upper extremities and it assists in the process of respiration.
So, the correct answer is, ’(d) X = 12, Y = 7 True ribs are attached dorsally to the vertebral column and ventrally to the sternum’.

Note:
- Thoracic cage is another name for the rib cage.
- The rib cage contains 12 pairs of ribs.
- The 12 pairs of ribs includes 7 pairs of true ribs, 3 pairs of false ribs, and 2 pairs of floating ribs.
- The rib cage mainly provides protection to the heart and lungs.