Question

In mammals, the number of cervical vertebrae is always -
(a) 7
(b) 9
(c) 1
(d) 12

Answer 1

Hint: All mammals, regardless of the animal, are vertebrates and have a specific number of cervical vertebrae. The vertebrae are the ones that are immediately below the skull and at the neck part of the spinal column.

Complete answer:
- Cervical vertebrae are present below the skull and are present in the neck. These vertebrae are the smallest of all the true vertebrae and are divided through the foramen (hole) from the thoracic or lumbar regions in each transverse process.
- The vertebrae are numbered as C1 to C7, with C1 the first below the skull and the rest six after it and along the spinal column.
- The number of cervical vertebrae remains constant in all mammals, which is 7.

Additional information:
- The two topmost vertebrae, the C1 and C2 are known as atlas and axis, respectively. They are named so as they are highly specialized. C1 connects the skull and the spine. C2 forms the pivot on which C1 rotates.
- C3 to C7 are characterized as classic vertebrae.
- The vertebral column, the spine, or the backbone, in human beings, has usually 33 vertebrae.
- It is divided into the following regions - cervical vertebrae, thoracic vertebrae, lumbar vertebrae, sacrum, and coccyx.
So, the correct answer is ‘(a) 7’.

Note:
- An injury to the cervical column is a cervical fracture and is commonly known as a broken neck.
- The development of the skeletal axis is dependent on the Hox genes among other factors.
- Various ligaments are involved in holding the vertebrae together in a column - the longitudinal, interspinous, supraspinous, and nuchal ligaments.