Ribs

There are usually twelve ribs on each side of the thorax, for a total of twenty-four in adults. The number of ribs is variable,but this number may be increased by the development of a cervical or lumbar rib so there may be eleven or thirteen on a side. The upper ribs (1 - 7) atriculate directly with the sides of the sternum via cartilage.They are connected behind with the vertebral column. Ribs 8,9 and 10 are interconnected medially by common cartilages that attach to the sternum. The last two ribs, 11 and 12, have free floating ventral ends. all ribs articaulte via their proximal ends with thoracic vertebrae. The ribs usually increase in length from rib 1 to rib 7 and decrease from rib 7 to rib 12.
For studing ribs there are several sidings like:

1. Head : the swollwn proximal part of the rib
2. Neck : The short segment between the head and the rib's articulation with the transverse of the thoracic vertebrae
3. Tubercle : located on the posteroinferior corner of each ribs.
4. Angle : sharve curve in the bone lsteral to tubercle.
5. Shaft : the curved, tapering segment between the tubercle and the rib's distal (ventral)end.
6. Costal Groove : the grrove along the medial side of the inferior edge of the rib shaft.
7. Sternal End : the anterior (ventral) end of the shaft. Its surface change substantially with increasing the age.
8. Cranial (upper) Edge: for most of the ribs is blunt, smooth and convex.
9. Caudal (lower) Edge : for most of the ribs is sharp, with a costal groove on the medial surface.

The first seven ribs with the sternum are called true or vertebro-sternal ribs, the remaining five are false ribs.

Special ribs are : 1,2,10,11 and 12th.

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