Abdominal Wall Muscles Overview

Abdominal Wall Muscles

• The external oblique muscle fibers run in a similar direction as the external intercostal muscles.
• The external oblique muscle is the most superficial muscle on the anterolateral abdominal wall.
• You must reflect the external oblique muscle to see the deeper internal oblique and transversus abdominis muscles.
• The tendons of the oblique muscles form the rectus sheath.
• The rectus sheath is a robust, opaque structure in the anterior portion of the abdominal wall.
• The linea alba is a more opaque structure than the rest of the rectus sheath.
• The linea alba is the medial attachment point of the three anterolateral abdominal muscles.
• The rectus abdominis muscle extends from the xiphoid process to the pubic symphysis.
• The anterior portion of the rectus sheath must be reflected to see the rectus abdominis.
• The rectus abdominis muscle has tendonous intersections interspersed throughout the muscle.
• The posterior portion of the rectus sheath ends about three-fourths of the way down the abdominal wall.
• The inferior most portion of the rectus sheath is comprised of transversalis fascia.
• The arcuate line is the line of demarcation between the posterior rectus sheath and transversalis fascia.

Inguinal Canal

• The inguinal canal extends from the deep inguinal ring to the superficial inguinal ring.
• The superficial inguinal ring is visible on superficial dissection.
• The superficial inguinal ring is the exit of the inguinal canal and is formed by the external oblique aponeurosis.
• The round ligament of the uterus exits the inguinal canal through the superficial inguinal ring.
• The round ligament of the uterus often appears as a tubular collection of adipose tissue.
• The ilioinguinal nerve runs superficial to the round ligament of the uterus.
• The round ligament of the uterus connects the uterus to the labia majus.
• The round ligament is a remnant of the gubernaculum.
• The spermatic cord also exits the inguinal canal through the superficial inguinal ring.
• The spermatic cord contains many structures, which will be discussed in the reproductive anatomy session.
• The inguinal ligament is the floor of the inguinal canal.
• The inguinal ligament extends from the anterior superior iliac spine to the pubic tubercle.
• The inguinal ligament is composed of the external oblique aponeurosis.

Deep Surface of the Anterior Abdominal Wall

• The inferior epigastric vessels run on the deep surface of the anterior abdominal wall (medial to the deep inguinal ring).
• The deep inguinal ring is the entrance to the inguinal canal.
• The deep inguinal ring is formed by the invagination of the transversalis fascia.
• The round ligament is more robust (larger) around the deep inguinal ring than the superficial inguinal ring.

Diaphragm

• The diaphragm is a major subdivision between the thoracic and abdominal cavities.
• The diaphragm has three openings for structures to traverse: the esophagus, vagal trunks, inferior vena cava, and aorta.