Final answer:
The thoracic cage, or rib cage, is composed of ribs, sternum, thoracic vertebrae, and costal cartilages, and functions to protect vital organs, support the upper body, and facilitate breathing.
Step-by-step explanation:
The thoracic cage, also known as the rib cage, is a vital structure within the human body. It provides several crucial functions such as protecting vital organs, supporting the upper body, and aiding in respiration. The thoracic cage is composed of several parts:
- Ribs: There are 12 pairs of long curved bones that form the main structure of the thoracic cage.
- Sternum: Also known as the breastbone, it is divided into three parts—the manubrium, body, and xiphoid process. The manubrium and body are joined at the sternal angle, which is also the attachment site for the second rib.
- Thoracic vertebrae: Twelve vertebrae labeled T1-T12 to which the ribs are anchored posteriorly.
- Costal cartilages: They connect the anterior ends of most ribs to the sternum, allowing the rib cage to be flexible enough for breathing.
Functionally, the thoracic cage encloses and protects the organs of the thoracic cavity, including the heart and lungs, supports the shoulder girdles and upper limbs, and serves as an attachment point for the diaphragm, as well as muscles of the back, chest, neck, and shoulders. Breathing is aided by the ability of the thoracic cage to change in volume, a process that allows the lungs to expand and contract during respiration.