Sternocostale

The sternocostale muscle is a small, thin, and flat muscle located in the upper part of the chest, between the sternum and the costal cartilage of the ribs. It is one of the accessory muscles of respiration, along with the scalene muscles and the serratus anterior. The sternocostale muscle is innervated by the long thoracic nerve, which arises from the brachial plexus, and it plays a crucial role in the elevation of the ribs during inspiration.

The sternocostale muscle originates from the sternal end of the costal cartilage of the second to the sixth ribs and inserts onto the sternum. It is supplied by the internal thoracic artery, a branch of the subclavian artery. The sternocostale muscle is often referred to as the "little muscle of the chest" due to its small size and relatively minor role in respiration compared to other muscles in the region.

The sternocostale muscle is particularly important in conditions where the scalene muscles are paralyzed or weakened, such as in certain neurological disorders or after surgery. In these cases, the sternocostale muscle can compensate for the loss of function of the scalene muscles, helping to elevate the ribs and facilitate breathing. However, if the sternocostale muscle is paralyzed or weakened, it can lead to a condition known as "winging of the scapula," where the scapula is elevated and rotated outward, causing a visible deformity of the shoulder.

In summary, the sternocostale muscle is a small, thin, and flat muscle located in the upper part of the chest, between the sternum and the costal cartilage of the ribs. It is an accessory muscle of respiration, innervated by the long thoracic nerve, and plays a crucial role in the elevation of the ribs during inspiration. It is particularly important in conditions where the scalene muscles are paralyzed or weakened, and its paralysis or weakness can lead to a condition known as "winging of the scapula."