The chest, or thorax, is the region of the body situated between the neck and the abdomen, forming a protective cage for the heart and lungs. While the general public often uses simple descriptive terms like “upper chest,” anatomists divide this space into specific regions for precision in medical and scientific communication. Understanding these precise terms helps to accurately locate structures and discuss conditions affecting the superior, anterior torso.
Primary Surface Regions
The anatomical region encompassing the upper chest is referred to as the superior pectoral region. This area is divided into distinct surface landmarks, with the collarbone (clavicle) serving as a major dividing line. The region immediately above the clavicle is called the Supraclavicular Region. This area is characterized by a slight depression, known as the supraclavicular fossa.
The area directly below the collarbone is the Infraclavicular Region, which extends downward to the level of the second rib. Both the supraclavicular and infraclavicular regions are clinically significant for examination. For example, listening to lung sounds (auscultation) often involves placing a stethoscope over these specific surface regions to assess the apex of the lung.
The Bony Framework
The superior aspect of the chest is defined and supported by a specific set of skeletal structures. The most prominent bone in this area is the Clavicle, or collarbone, which acts as a strut connecting the shoulder to the trunk. Medially, the clavicle articulates with the Manubrium, which is the broad, uppermost section of the sternum, or breastbone. This junction is the sternoclavicular joint, a flexible joint that allows for movement of the shoulder girdle.
The manubrium itself is easily palpable and features a shallow depression at its superior border called the suprasternal notch. The manubrium also provides an attachment point for the cartilages of the first pair of ribs. Just below this, the manubrium joins the body of the sternum at a noticeable ridge known as the sternal angle. This angle is the landmark used to locate the second rib and is a starting point for counting the ribs on the anterior chest.
Underlying Musculature and Reference Points
Beneath the skin and surface fascia of the upper chest lie several layers of muscle that contribute to the shape and function of the area. A major muscle in this region is the Pectoralis Major, a large, fan-shaped muscle divided into two heads. The most superior portion is the clavicular head, which originates directly from the medial half of the clavicle. This specific muscle segment is a focus for exercise and resistance training, as it is largely responsible for the upper curve of the chest muscle.
The infraclavicular region also contains the Deltopectoral Triangle, a small, triangular space bordered by the clavicle, the pectoralis major, and the deltoid muscle of the shoulder. This triangle is a reference point for the cephalic vein, which runs through it as it passes toward the shoulder. Furthermore, the supraclavicular fossa is an important clinical reference point because the apex of the lung extends slightly above the level of the clavicle and into the neck base in this location.