Chest

The chest, or thorax, is the region of the body between the neck and abdomen. It houses the thoracic organs, notably the heart and lungs, within the mediastinum and pleural sacs. The thoracic cage, formed by the sternum anteriorly, 12 pairs of ribs with their costal cartilages, thoracic vertebrae, and the diaphragmatic floor, protects these organs and supports breathing and upper-limb movement.

The chest wall is composed of bone, cartilage, and muscle. Major muscles include the pectoralis major and minor anteriorly, the intercostal muscles between the ribs, the serratus anterior laterally, and the diaphragm forming the floor of the cavity. The pleural cavities enclose the lungs, while the mediastinum houses the heart, great vessels, trachea, esophagus, and thymus.

Development and variation: The chest develops from somatic mesoderm and related structures during fetal growth. Anatomical variations include spinal curvature disorders such as scoliosis and kyphosis, and congenital deformities such as pectus excavatum (sunken sternum) or pectus carinatum (protruding sternum), which can affect respiratory mechanics or imaging interpretation.

Function and clinical relevance: The chest protects thoracic organs, enables ventilation by changing thoracic volume through rib movement and diaphragmatic contraction, and provides attachment for many muscles of the upper body. Clinical concerns include chest injuries, rib fractures, cardiopulmonary diseases, chest pain, and findings on imaging such as chest radiographs and CT scans.