M. transversus abdominis, digitatio costalis II
The second costal digitation of the transversus abdominis, originating from the medial surface of the costal cartilage near the 8th rib. These costal digitations interdigitate with those of the diaphragm.
Origin: Medial surface of costal cartilage of rib 8
Insertion: Linea alba via aponeurosis (contributing to internal lamina of rectus sheath)
Action: Compresses abdominal viscera; supports visceral weight; assists forced expiration
Innervation: Ventral branches of thoracic (T10–T18) and lumbar (L1–L3) spinal nerves
Strain or tearing of the transversus abdominis fibers, often from sudden exertion, rolling, or trauma. Being the deepest layer, injuries here can compromise the entire abdominal wall integrity.
Strain or tearing of the transversus abdominis fibers, often from sudden exertion, rolling, or trauma. Being the deepest layer, injuries here can compromise the entire abdominal wall integrity. Signs include: Focal pain on deep palpation of the flank; guarding during lateral flexion; ventral edema; ultrasonographic evidence of fiber disruption or hematoma between muscle layers.
See the Transversus Abdominis - Costal Digitation II on our interactive 3D horse model. Open 3D Model