Nerves, Blood Vessels, and Lymphatics
of the Abdomen
The skin, muscles, and other structures of the abdominal wall need nerve supply, blood, and lymphatic drainage. The abdominal wall surrounds the abdominal cavity. It covers the trunk from just below the diaphragm to the pubic symphysis and the pelvis. The main function of the abdominal wall is to surround and protect the vital abdominal organs inside as well as assist in posture, bending, twisting, and breathing.
A number of nerves run to the muscles and skin of the abdomen:
Thoracoabdominal nerves: Five pairs of thoracoabdominal nerves continue from the 7th through 11th intercostal nerves. They run between the layers of abdominal muscles to innervate the muscles of the anterolateral abdominal wall. Anterior and lateral and cutaneous branches provide nerve supply to the skin.
Subcostal nerves: These nerves stem from the anterior rami of the 12th thoracic spinal nerves. They run just inferior to the 12th ribs and down to below the umbilicus (the navel). Subcostal nerves innervate the abdominal wall muscles and the skin (via cutaneous branches) between the iliac crests and the umbilicus.
Iliohypogastric nerves: The iliohypogastric nerves stem from the anterior rami of the 1st lumbar spinal nerves and form branches that run below the subcostal nerves to the lower part of the abdominal wall. They innervate the skin over the iliac crests, upper iliac (inguinal) regions, and hypogastric (pubic) regions (the area below the navel). They also give nerve supply to the internal oblique and transversus abdominis muscles.
Ilioinguinal nerves: These nerves stem from the anterior rami of the 1st lumbar spinal nerves. They run between the layers of abdominal muscle and down to the inguinal canal. They innervate the scrotal skin in men and labia majora in women, the area over the pubic bone, and the medial portions of the thigh. They also innervate the internal oblique and transversus abdominis muscles.
Lateral cutaneous nerves of the thigh: These nerves run from the 2nd and 3rd lumbar spinal nerves inferiorly on the iliacus muscles to the thighs. They supply the skin on the anterolateral parts of the thighs.
Femoral nerves: These nerves come from the 2nd through 4th lumbar spinal nerves and run along the lateral part of the psoas major muscles to innervate the iliacus muscle before descending into the thigh to supply extensors of the knee.
Obturator nerves: These nerves come from the 2nd through 4th lumbar spinal nerves and run from the medial part of the psoas major muscle through the pelvis and into the thighs, where they supply the adductor muscles.
Lumbosacral trunk: These nerves come from the 4th and 5th lumbar nerve roots. They pass over the sacrum and descend into the pelvis to help form the sacral plexus.
The abdominal wall has quite a few blood vessels. It includes all the arteries covered:
Musculophrenic artery: Branches off the internal thoracic artery and runs along the costal margin to supply the hypochondriac region of the abdominal wall and the anterolateral muscles and the diaphragm.
Superior epigastric artery: Stems from the internal thoracic artery and runs down behind the rectus abdominis to supply blood to the rectus abdominis and the superior portion of the anterolateral abdominal wall
10th and 11th posterior intercostal arteries and subcostal arteries: Branch off the aorta and run past the ribs to the abdominal wall where they provide blood flow to the lateral part of the abdominal wall
Common iliac arteries: Form the terminal branches of the abdominal aorta; diverge and run inferiorly alongside the psoas muscles to the brim of the pelvis where they divide into the internal and external iliac arteries
Median sacral artery: Rises up from the abdominal aorta at its bifurcation and then descends into the lesser pelvis
Inferior epigastric artery: Branches from the external iliac artery and runs superiorly into the rectus sheath to supply blood to the rectus abdominis and part of the abdominal wall
Deep circumflex iliac artery: Starts at the external iliac artery and runs parallel to the inguinal ligament, supplying blood to the iliacus muscle and inferior part of the anterolateral abdominal wall
Superficial circumflex iliac artery: Branches off the femoral artery and runs along the inguinal ligament to supply blood to the superficial part of the abdominal wall of the inguinal region and anterior thigh
Superficial epigastric artery: Also branches off the femoral artery, running to the umbilicus in the superficial fascia to supply blood to the skin below the umbilicus and pubic area
Veins are in this area too, of course. They have the same names as the arteries and are located near them.
Superficial lymphatic vessels follow along with the superficial veins. The ones that run above the umbilicus drain into the axillary nodes of the armpits, whereas the vessels below the umbilicus drain into the superficial inguinal lymph nodes.
Deep lymphatic vessels follow the deep veins and drain into the external iliac, common iliac, and lumbar lymph nodes.