Vertebrae - Bones, Diagram and Features

Vertebrae (sing: Vertebra) are a series of bones that make up the vertebral column (or spine) in all vertebrate species. Our vertebral column is composed of 33 irregular sized bones that are connected to each other by intervertebral discs.

The vertebral column is divided into five regions – cervical (7), thoracic (12), lumbar (5), sacral (1-fused) and coccygeal (1-fused).

Anatomy of a Vertebra

A typical vertebra is made up of the vertebral body (or body) that has a large anterior centrum and a posterior neural arch (or vertebral arch). The surfaces of the body, both upper and lower are flattened and rough, allowing easy attachment with the intervertebral discs.

The vertebral arch is composed of pedicles and laminae. Two pedicles extend from either side of the body and join with the arch. From each pedicle arises the lamina that extends towards the back and the middle to complete the vertebral arch.

There are seven processes (projections from tissues) arising from the vertebra –

Four articular processes
One spinous process
Two transverse processes

Well-Labelled Diagram of all the Vertebrae in a Vertebral Column

Vertebrae Diagram

Cervical Vertebrae

Cervical vertebrae are the first region in the vertebral column and are located just below the skull.
The cervical vertebrae are denoted as C1 to C7, C1 being closest to the skull and C7 being farther away towards the spine.
It is a true rib that possesses vertebral foramen (hole) in each of the processes from where the spinal cord, vertebral arteries and veins go through.
Atlas (C1) and axis (C2) are the topmost vertebrae. Atlas is the first cervical vertebra that is a ring-like structure and does not have a vertebral body or spinous process. It forms a connection between the skull and the spine.
Axis is the second cervical vertebra which forms a pivot on which the atlas rotates.
C7, or the vertebra prominens has long and prominent spinous processes that are quite visible on the skin surface.
The C3 – C6 are small vertebrae with broad sides.
The cervical vertebrae are mainly responsible for the movement of head by the joint present between the atlas and axis.

Thoracic Vertebrae

The thoracic vertebrae form the second segment of the vertebral column present between the cervical and lumbar vertebrae.
There are 12 thoracic vertebrae that are denoted as T1 – T12.
The lumbar vertebrae are intermediate in size and keep on increasing towards the lumbar vertebrae.
The characteristic feature of the thoracic vertebrae is the presence of costal facets.
The vertebral body is heart-shaped and broad in the anteroposterior region.
The facets on these vertebrae are useful for articulation with the ribs.
The spinous processes are long and triangular in shape.

Lumbar Vertebrae

The lumbar vertebrae are the largest bones of the vertebral column. There are five bones in the lumbar region that are denoted as L1 – L5.
The vertebral body of the lumbar vertebra is kidney-shaped which is wide in the sides.
The spinous process is short and thick as compared to other two regions which extends in a perpendicular angle from the body.
The L5 is the largest bone across the vertebral column with the largest vertebral body and transverse processes.

Sacral Vertebrae

The sacral vertebrae are five in number and are denoted as S1 to S5.
These five bones fuse into one large triangular bone in humans between the age of 18 to 30.
The sacral bone is situated at the base of the vertebral column at the upper back portion of the pelvic cavity between the two pelvic wings.
The sacral vertebrae has four articulations, one with the last lumbar vertebrae, one with the coccygeal vertebrae and two on either side of the hip bones.

Coccygeal Vertebrae

The coccyx or the coccygeal vertebrae is commonly referred to as a tailbone.
It is composed of three to five segments that fuse to form one single structure.
It has a rudimentary vertebral body and transverse and articular processes.
It does not have a pedicle, laminae or spinous processes.
The coccyx has an important function as it is an important site of attachment for various pelvic ligaments and tendons.

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