Question

Which one of the following is the correct description of a certain part of a normal human skeleton?
A. The glenoid cavity is a depression to which the thigh bone articulates
B. Parietal bone and the temporal bone of the skull are joined by fibrous joint
C. The first vertebra is the axis, which articulates with the occipital condyles
D. The 9th and 10th pairs of ribs are called the floating ribs

Answer 1

The cavity of the Pelvic girdle is known as the acetabulum. Sutures are the fibrous joints that are found in the skull. The first cervical vertebra is the atlas. There are twelve pairs of ribs. Moreover, the last two pairs are known as the floating ribs.

Complete answer: Let us look at all the statements that are given to us one by one.
Statement A: The Glenoid cavity is a depression to which the thigh bone articulates: The glenoid cavity is a part of the pectoral or the shoulder girdle. The pectoral girdle or the shoulder girdle consists of the clavicle and the scapula. The scapula has a shallow articular surface that is called the glenoid cavity. The glenoid cavity articulates with the head of the humerus and forms the shoulder joint. Therefore, this statement is incorrect.
Statement B: Parietal bone and the temporal bone of the skull are joined by fibrous joint: The bones of the skull are joined by the joints known as the sutures. The sutures are fibrous joints. These joints do not allow any movement. This is because the bones are firmly fixed together by the strong collagenous fibrous tissues. Therefore, this statement is correct.
Statement C: The first vertebra is the axis, which articulates with the occipital condyles: The first vertebrae in the vertebral column are the cervical vertebrae. These vertebrae are present in the neck region. The first vertebra is known as the atlas and the second vertebra is known as the axis. The atlas supports the head. It consists of a complete ring of the bone. The upper surface of the atlas vertebra has the articulations to articulate with the condyles of the occipital bones. It articulates with the axis vertebra. Therefore, this statement is incorrect.
Statement D: The 9th and 10th pairs of ribs are called the floating ribs: The ribs are the bones found in the thoracic region and which form the thoracic cage. There are three kinds of ribs namely, True ribs, False ribs, and Floating ribs. The 11th and the 12th pairs of the ribs are known as the floating ribs. This is because one end of these ribs is attached to the vertebral column but the other end is free. They protect the kidneys. Therefore, this statement is incorrect.
Thus, based on the above information we can conclude that the statement that the Parietal bone and the temporal bone of the skull are joined by fibrous joints is the correct statement regarding the description of a certain part of a normal human skeleton.
Hence, the correct answer is option (B).

Note: The second vertebra is known as the axis. The axis acts as a pivot for the rotatory motion of the atlas. From the axis vertebra, the process of bone known as odontoid peg arises. It articulates with the atlas on the back of the anterior arch. Together they form a pivot joint which makes the head move.