The Thorax

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 1^st and 2^nd rib.
• The body of the sternum articulates directly or indirectly with 2^nd to 10^th rib.
• The xiphoid process consists hyaline cartilage during infancy and child hood and do not ossify completely up to the age of 40.

Ribs

• Human being contains 12 Pair of ribs that make up the side of thoracic cavity.
• Ribs increase in length from 1^st through 7^th and they decrease in length through 12^th.
• Each ribs posteriorly articulates with the body of its corresponding thoracic vertebra.
• Anteriorly the 1^st 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 11^th & 12^th ribs are designated as floating ribs because their anterior part even doesn’t attach indirectly to sternum.

Figure 9- Sternum Figure 10- Thorax