Refers to the chest. Thorax is a bony cage formed by sternum (breast bone), costal cartilage, ribs and bodies of the thoracic vertebra.
Sternum (breast bone)
- Sternum is flat, narrow bone measuring about 15 c.m. (6 inch) located in the median line of anterior thoracic wall.
- It consists 3 basic portions: the manubrium (superior portion), the body (middle & largest portion) and the xiphoid process (inferior & smallest portion).
- The junction of the manubrium and the body forms the sternal angle.
- The manubrium on its superior portion has a depression called jugular (supra sternal) notch.
- On each side of the jugular notch are clavicular notch that articulates with medial end of clavicle.
- The manubrium also articulates with the 1st and 2nd rib.
- The body of the sternum articulates directly or indirectly with 2nd to 10th rib.
- The xiphoid process consists hyaline cartilage during infancy and child hood and do not ossify completely up to the age of 40.
- Human being contains 12 Pair of ribs that make up the side of thoracic cavity.
- Ribs increase in length from 1st through 7th and they decrease in length through 12th.
- Each ribs posteriorly articulates with the body of its corresponding thoracic vertebra.
- Anteriorly the 1st seven ribs have direct attachment to sternum by costal cartilage hence they are called true ribs.
- The remaining 5 ribs are called false ribs.
- The 11th & 12th ribs are designated as floating ribs because their anterior part even doesn’t attach indirectly to sternum.
Figure 9- Sternum Figure 10- Thorax