Sternocostal joints

Sternocostal Joints are the articulations connecting the sternum and the costal cartilages of the true ribs. These joints are part of the thoracic cage, which protects vital organs such as the heart and lungs.

Anatomy

The sternocostal joints are classified into two types: primary and secondary. The primary sternocostal joint is the articulation between the first rib and the sternum, which is a synchondrosis joint. The secondary sternocostal joints are the articulations between the costal cartilages of the second to seventh ribs and the sternum, which are synovial joints.

Primary Sternocostal Joint

The primary sternocostal joint is a cartilaginous joint, specifically a synchondrosis. This means it is a rigid joint that allows little to no movement. The costal cartilage of the first rib is directly connected to the manubrium of the sternum.

Secondary Sternocostal Joints

The secondary sternocostal joints are synovial joints, which allow for more movement than the primary joint. These joints are formed by the articulation of the costal cartilages of the second to seventh ribs with the sternum. The second rib articulates with the sternal angle, where the manubrium and the body of the sternum meet, while the third to seventh ribs articulate with the body of the sternum.

Function

The sternocostal joints play a crucial role in respiration. During inhalation, the intercostal muscles contract, elevating the ribs and expanding the thoracic cavity. This expansion decreases the pressure inside the cavity, allowing air to flow into the lungs. During exhalation, the intercostal muscles relax, lowering the ribs and reducing the size of the thoracic cavity. This increases the pressure inside the cavity, forcing air out of the lungs.

Clinical Significance

Injuries or diseases affecting the sternocostal joints can lead to pain and difficulty in breathing. Conditions such as costochondritis, Tietze syndrome, and sternocostal joint sprain can cause inflammation and pain in the sternocostal joints.