The thorax, or chest, is a complex anatomical structure that houses vital organs such as the heart and lungs. It is primarily composed of the rib cage, sternum, and clavicles, along with the muscles, tendons, ligaments, nerves, and blood vessels that support these structures and facilitate their function.
The rib cage is a bony structure that provides protection for the thoracic organs. It is composed of 12 pairs of ribs, each of which is attached to the vertebral column at the back and terminates at the front. The first seven pairs of ribs, known as the true ribs, connect directly to the sternum via costal cartilages. The next three pairs, the false ribs, connect to the sternum indirectly through the costal cartilage of the rib above. The last two pairs, the floating ribs, do not connect to the sternum at all.
Each rib is a curved, flat bone that consists of a head, neck, tubercle, and body. The head articulates with the vertebral bodies, the tubercle with the transverse process of the vertebrae, and the body extends anteriorly.
The sternum, or breastbone, is a flat bone located in the center of the chest. It is composed of three parts: the manubrium, the body, and the xiphoid process. The manubrium is the uppermost part, which articulates with the clavicles and the first pair of ribs. The body is the longest part of the sternum and articulates with the costal cartilages of the second to seventh ribs. The xiphoid process is the inferior, pointed part of the sternum.
The clavicles, or collarbones, are a pair of long bones that serve as a strut between the shoulder blade and the sternum. Each clavicle has a medial end that articulates with the manubrium of the sternum, and a lateral end that articulates with the acromion of the scapula. The clavicle supports the shoulder in a functional position with the axial skeleton and protects the neurovascular structures supplying the upper limbs.
The thorax is surrounded by several muscles that assist in respiration and upper body movement. These include the intercostal muscles (external, internal, and innermost), which lie between the ribs and help with breathing; the diaphragm, a dome-shaped muscle at the base of the thorax that plays a key role in respiration; and the pectoral muscles, which are involved in movements of the shoulder and arm.
Tendons, Ligaments, and Nerves:
Tendons are fibrous tissues that connect muscle to bone, while ligaments connect bone to bone. In the thorax, the costoclavicular ligament connects the first rib to the clavicle, providing stability for the shoulder girdle.
The thoracic region is innervated by the thoracic spinal nerves (T1-T12). Each of these nerves gives off a dorsal branch to the muscles and skin of the back, and a ventral branch that forms the intercostal nerves, supplying the muscles, skin, and parietal pleura of the thoracic wall.
The thoracic wall is primarily supplied by the thoracic aorta and its branches. The posterior intercostal arteries supply the intercostal spaces, while the internal thoracic arteries, which branch off the subclavian arteries, supply the anterior thoracic wall. Venous drainage is via the azygos system and the internal thoracic veins.
The thorax is a complex structure with a rich network of blood vessels, nerves, and muscles working together to protect vital organs and facilitate essential functions such as respiration and upper body movement. Understanding its anatomy is fundamental to many fields of medicine, from cardiology and pulmonology to trauma surgery.