Costal arch
Arcus costalis
Definition
The costal arch corresponds to the ventral and lateral portion of the thorax formed by the joining of the costal cartilages of the last ribs, which converge toward the sternum or unite with one another to form the costal margin. It delineates the cranial part of the abdomen and forms the inferior boundary of the thoracic cage.
Anatomically, the costal arch is composed of the costal cartilages, the insertions of the intercostal muscles, and the ventral portions of the abdominal oblique muscles. It overlies several cranial abdominal organs, including the liver, the stomach, and the cranial pole of the kidneys depending on the species.
The shape and width of the costal arch vary among species: in dogs and cats, it is relatively narrow and slender; in ruminants, it is broad and rounded; in horses, it is long and extends caudally; in humans, it forms the subcostal angle, characteristic of human thoracoabdominal anatomy.
References
Dyce KM, Sack WO, Wensing CJG. Textbook of Veterinary Anatomy. 5th ed. St. Louis: Elsevier; 2017.
König HE, Liebich HG, editors. Veterinary Anatomy of Domestic Mammals: Textbook and Colour Atlas. 6th ed. Stuttgart: Thieme; 2020.
Evans HE, de Lahunta A. Miller’s Anatomy of the Dog. 4th ed. St. Louis: Elsevier; 2013.
