Abdominis

Abdominis is a Latin term meaning “of the abdomen,” used in anatomical names to indicate a relationship to the abdominal region. It is not a single muscle, but a genitive form appearing in several muscle names that together form the abdominal wall and contribute to core function.

Rectus abdominis is a paired, vertically oriented muscle along the front of the abdomen. It flexes the trunk and assists with forced expiration and postural support. It is segmented by tendinous intersections and runs from the pubic region to the lower ribs and sternum.

External oblique abdominis is the superficial lateral muscle whose fibers run inferomedially. It aids trunk flexion, lateral bending, and rotation, and works to increase abdominal pressure when needed.

Internal oblique abdominis lies beneath the external oblique and has fibers that run superomedially. It assists in flexion, rotation, and lateral bending of the trunk and reinforces the abdominal wall in concert with other core muscles.

Transversus abdominis is the deepest of the abdominal muscles, with horizontal fibers that primarily compress the abdominal contents and increase intra-abdominal pressure. It plays a key role in spinal stabilization and posture.

In combination, these muscles support movement, protect internal organs, regulate intra-abdominal pressure, and contribute to breathing and core stability. The term abdominis is derived from the Latin genitive of abdomen, used in naming to denote relation to the abdomen.