The Vertebral Column

The vertebral column, also known as the backbone or spinal column, is the central supporting structure of the skeleton. The vertebral column forms the backbone of vertebrate animals and protects the spinal cord. It is made up of five groups of bones called the vertebrae (singular: vertebra) in mammals. In rabbit it consists of 46 vertebrae. The vertebrae are held one to the others with strong ligaments having compressible cartilage pads called intervertebral discs between consecutive vertebrae.

In mammals, the five different vertebrae are: (i) Cervical Vertebrae It is found in the neck region

(ii) Thoracic Vertebrae It is found in the chest region

(iii) Lumber Vertebrae – It is found in the upper abdomen

(iv) Sacral Vertebrae – It is found in the lower abdomen

(v) Caudal Vertebrae – It is found in the tail region.

Features of a Typical Vertebra

All Vertebra even though they have different functions have certain features in common.

A typical Vertebra possess the following features:

i) Neural Spine: This projects upwards dorsally for the attachment of muscles.

(ii) Transverse Processes: They project from the sides of each vertebra for the attachment of muscles and ligaments.

(iii) Centrum: It is a solid piece of bone below the neural canal.

(iv) Facet: This is a small, smooth, flat or slight depressed area on a bone that is usually a point of contact with another bone. Zygapophysis: These are articular surfaces for the articulation of successive vertebrae. They are grouped into two parts – the pre- zygapophyses facing inwards and upwards and post zygapophyses facing outward and downward.

Cervical Vertebrae

The cervical vertebrae are found in the neck region. In rabbit, they are seven in number. The first cervical vertebra is called the atlas while the second is called the axis. The third to seventh bones are the normal cervical bones.

Characteristics of the Atlas

(i) The atlas vertebra has a large neural canal.

(Ii) It has a flat and broad transverse process.

(iii) The neural spine is very short or absent. (iv) The centrum is absent.

(v) It has a vertebrarterial canal for the passage of blood vessels.

Function of the Atlas

It allows the head to nod on it (i.e. it permits nodding of head) as it fits into the occipital condyles of the skull.

Characteristicss of the Axis

(i) The Axis has a broad and flat centrum

(Ii) It articulates with the atlas through the odontoid process.

(iii) It has a large, flattened neural spine.

(iv) The transverse process is reduced to a pin-like structure.

(v) It has a vertebraterial canal

Function of the Axis

It allows the head to be turned easily, i.e., twisting of the head.

Thoracic Vertebrae

Thoracic vertebrae are found in the chest region. In Rabbit, they are twelve in number.

Characteristics of Thoracic Vertebrae

(I)The thoracic vertebrae has a long and prominent neural spine which projects upwards and backwards.

(Ii) It has a pair of short transverse process.

(iii) There is presence of demifacets and articular surfaces for attachment of ribs.

(iv) There is a large neural canal and neural arch.

(v) A large cylindrical centrum is present.

Functions of the Thoracic Vertebrae

(i) It aids the attachment of the ribs.

(Ii) Muscles of the shoulder and back are attached to beural spines.

(iii) It asissts in breathing alongside with the ribs.

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