subcostalis

Subcostalis refers to the subcostal muscles, a group of small, thin muscle slips located on the inner surface of the thoracic wall. The term comes from Latin, meaning beneath or under the ribs.

Anatomy and variation: Subcostal muscles originate on the inner surface of a rib near its angle and extend downward and outward to insert on the inner surface of a lower rib, typically two or more spaces below. They occur along the length of the thoracic cage but are most numerous in the lower thorax. The number and arrangement of subcostal slips are variable between individuals.

Innervation and blood supply: Subcostal muscles are innervated by the intercostal nerves, with segments corresponding to the ribs involved. Their arterial supply comes from branches of the intercostal arteries, mirroring the pattern seen in other thoracic wall muscles.

Function: These muscles function as accessory expiratory muscles, helping to depress the ribs and reduce the volume of the thoracic cavity during forced or labored expiration. They can also contribute to stabilizing the thoracic wall.

Clinical relevance: Subcostal muscles are usually of minor clinical importance but may be encountered or mobilized during thoracic surgery, trauma assessment, or detailed anatomical study of the chest wall.

See also: intercostal muscles, transversus thoracis, thoracic wall anatomy. Etymology: subcostalis is Latin for “under the ribs.”