Corpus: Subcostal muscles

The subcostal muscles are skeletal muscles that are part of the intercostal musculature.

The subcostal muscles are derivatives of the internal intercostal muscles, with their muscle fibers running in the same direction. They originate in the caudal-dorsal area of the thorax, near the costal angle, and typically skip one rib as they course upward to attach to the next but one higher rib.

The subcostal muscles are innervated segmentally by the intercostal nerves. Although these muscles may span several ribs, they are innervated by nerve fibers from a single spinal cord segment.

The subcostal muscles serve the same function in the caudal thorax as the internal intercostal muscles. They lower the ribs, thereby aiding in expiration.