 |
| The Thoracic Cage |
|
| The skeleton of the thorax is made up of bone and cartilage. The thorax is a cone-shaped cavity, broader below than above, and longer behind than in front. |
| |
| It is formed by the twelve thoracic vertebrae at the back, the sternum in front, and the twelve pairs of ribs at the sides, which encircle the trunk from the vertebral column behind and to the sternum in front. |
| |
| The Sternum |
| |
| The sternum or the breast-bone is a flat bone divided into three parts. It is a long, narrow, flat vertical bone in the middle of the front wall of the chest. It is about 15 cm long and is shaped like a dagger with a handle called manubrium. It articulates with the the clavicles at its upper and outer aspect on each side by means of the clavicular notches. These are seperated by suprasternal or jugular notch. The first pair of ribs articulates with the sides of the manubrium, and the second pair, at the junction of the manubrium and the body of the sternum. The body of the sternum is long and narrow and notched on each for the attachment of 3rd 4th 5th 6th and 7th costal cartilage. The xiphod bone is the lowest part of the sternum. The true ribs are attached to the sides of the sternum. |
| |
 |
| |
| Sternum |
| |
| Functions |
| |
| i. It takes part in the formation of the protective thoracic basket. |
| |
| ii. It has a significant role in respiratory mechanism. |
| |
| Ribs |
| |
| The ribs are curved bars, which movably articulate with the thoracic vertebrae at the back and unite with the sternum in front, all collectively forming a bony cage, the thoracic basket. There are twelve pairs of ribs. The upper seven is directly attached to the sternum in front. These are called true ribs. The next three pairs of ribs are joined to the rib above each. They are termed as false ribs. The lower two pairs of ribs are free in front. They are known as floating ribs. |
| |
 |
| |
| Ribs and Rib Cage |
| |
| A rib consists of 2 parts- vertebral and sternal. The vertebral part is long and bony. It articulates with the thoracic vertebrae by 2 facets the capitulum and tuberculum. The sternal part is short and cartilagenous. It articulates with the sternum or sternal part of its upper rib. |
| |
 |
| |
| Functions |
| |
| i. They protect the heart, large blood vessels and lungs. |
| |
| ii. They bear respiratory muscles, and play an important role in respiration. |
| |
| iii. The last two pairs of ribs protect the kidneys. |
| |
