Abdominal muscles

The abdominal muscles form a multilayer wall that protects the internal organs, maintains intra-abdominal pressure, and ensures flexion and rotation of the torso. This is not just a “press” - it is a functional corset, the condition of which determines the health of the spine.

Four muscle layers

Rectus abdominis (m. rectus abdominis) is a paired muscle that runs vertically from the pubic symphysis to the costal arch. It is she who forms the visible “cubes”. The muscle is divided by 3–4 tendon bridges, which create a segmented relief. In the middle there is a white line (linea alba) - a dense tendon suture connecting the right and left halves.

External oblique is the most superficial layer. The fibers run from top to bottom and front to back (like hands in pockets). Participates in flexion and rotation of the torso.

Internal oblique muscle - lies under the external oblique, the fibers are directed perpendicular to it. Together they create a crossover system that effectively resists torsional loads.

Transversus abdominis is the deepest layer. Its fibers run horizontally and it works like a natural corset, compressing the abdominal cavity. It is the transverse muscle that stabilizes the lumbar spine when lifting heavy objects.

Inguinal canal

In the lower part of the anterior abdominal wall, between the muscle layers, the inguinal canal is formed - a slit-like space 4–5 cm long. In men, the spermatic cord passes through it, in women, the round ligament of the uterus. The inguinal canal is the “weak spot” of the abdominal wall, where inguinal hernias most often form.

Functions of the abdominal muscles

• Bending the spine - twisting and lifting the torso
• Rotation - body rotations
• Abdominal press - increased intra-abdominal pressure during coughing, straining, childbirth
• Stabilization - protection of the lumbar region during any movements
• Breathing - participation in forced exhalation

Clinical aspects

Diastasis recti (separation along the linea alba) is a common occurrence after pregnancy. Weakness of the muscle wall can lead to hernias. Understanding the layered anatomy is critical for surgeons when performing laparotomy and laparoscopic approaches.

You can view all four layers of the abdominal muscles and the inguinal canal in detail in 3D atlas Humio - turn layers on and off to understand their relative position.