Ribs their Structure and Types

In humans, there are 12 pairs of ribs, all of which are attached posteriorly to the lateral border of the sternum, giving rise to the cage like structure. This structure protects covers and protects most of the body organs situated in the chest cavity. Ribs are of three types, depending on the ways by which they articulate with the sternum.

1. True ribs: which articulate with sternum directly.
2. False ribs: which articulate with sternum indirectly.
3. Floating ribs: neither directly nor indirectly articulate with the sternum.

The ribs ranging from 1st to 7th are true ribs, while the 8th, 9th and 10th are false ribs. The last two ribs are floating ribs.

Structure of the Typical Rib

A typical rib is a flat, twisted and long bone, having round superior border and sharp, thin inferior border. Its main parts are head, neck, tubercle, shaft and angle. First and the last three ribs have single facet, while the ribs ranging from 2nd to 9th have two facets, by means of which they articulate with the thoracic part of the vertebral column. The neck of the rib is constricted portion between head and tubercle of the rib. A typical rib has two tubercles, articulated and non-articulated. Articulated tubercle articulates with the transverse process of the corresponding thoracic vertebral column. The shaft is the thin, twisted and long portion of the rib, which at its inferior side bends to form the costal groove. Costal groove accommodates intercostal arteries, veins, and nerves. The angle is where the shaft of the rib bends sharply forward.

Cervical Rib

It is an extra rib, which arises from the anterior tubercle of the transverse process of the 7th cervical vertebra. It occurs only in 0.5 % of humans. It may have a free anterior end, may be connected to the first rib by a fibrous band, or may articulate with the first rib.

The thoracic Outlet Syndrome

It is a condition in which an extra rib arises from the 7th cervical vertebra and compresses brachial plexus of nerves and the subclavian artery and the vein, which are closely related to the upper surface of the first rib and the clavicles, causing severe pain medially downward the forearm and the hand. Most of the symptoms are caused by pressure on the plexus nerves.

Rib Excision

It is mostly performed by the rib surgeons, wishing to gain an easy access to the thoracic cavity.

During which two incisions are made to remove large surface, A longitudinal incision is made through the periosteum on the outer surface of the rib and a segment of the rib is removed. A second longitudinal incision is then made through the bed of the rib, which is the inner covering of the periosteum. After the operation, the rib regenerates from the osteogenetic layer of the rib.