Abdominal wall muscles, fasciae, Rectus sheath, hernia site, cross section

Abdominal wall = sum of fibromuscular structure from thoracic bottom to top of pelvis

Abdominal wall fuction : Protection, Movements (Rotation, Bending, ), Abdominal press (Urination, Defecation, Coughing, Sneezing)

Anterior abdominal wall :

Below the Arcuate line, the structure of retus sheath is completely rearranged
  • Rectus abdominis muscle is totally encapsulated by aponeuroses of oblique and transversus abdominis muscles. (apparently shown the pic below)
  • Below the arcuate line of Douglas, the rectus abdominis muscle only have aponeurosis anteriorly (Douglas didn't like to wear the inner-wear)
  • Internal surface of abdominal wall has three folds
  1. Median umbilical fold is remnant of urachus, which was made in constriction of allantois and became a thick fibrous cord. (apex of the bladder ~ the umbilicus; Moore 297pg)
  2. Medial umbilical fold is a fibrous remnant of umbilical arteries (Moore 336pg), whose proximal part become internal iliac arteries and superior vesical arteries and distal part obliterate after birth and become medial umbilical fold.
  3. Lateral umbilical fold has inferior epigastric artery which is branch of the external iliac artery. (internal and external iliac arteries are all related to the umilical folds)
Cross section of three levels

Hernias :

Hernia locations

Inguinal hernia : Inguinal canal is used by the testicles to descend from the sides of lumbar vertebrae column to the scortum and later it encapsulates Vas Deferens, Testicular neurovasclature with lymph (in female, round ligament of the uterus occupies the inguinal canal). However, loop of small intestines and part of greater omentum might bulge out through this natural connection. In detail, it's a protrusion of parietal peritoneum with the small intestine.

  • Direct inguinal hernia : hernial sac is parallel to the spermatic cord (vestige of processus vaginalis) and occurs by weakness of anterior abdominal wall in inguinal triangle. Peritoneum and transversalis fascia exit from abdominal cavity.
  • Indirect inguinal hernia : hernial sac is within the spermatic cord through traversing inguinal canal within processus vaginalis and more frequency as 2/3~3/4 usually to males. (Moore 213pg)
  • During the inguinal hernia surgery, inferior epigastric artery, which is encapsulated by the lateral umbilical fold, should be payed attention because of its proximity to the inguinal canal.

Epigastric hernia : It usually occurs by birth defect due to weakness or tear of the rectus abdominis. It usually gets better as the babies are growing up as their muscles get stronger. It is much similar to the umbilical hernia

Process of epigastric hernia
Inferior Lumbar ('Petit') trigone location

Herniation occasionally occurs here 'Lumbar (Petit) trigone'

  • Lateral border : External oblique abdominis
  • Medial border : Latissimus dorsi
  • Bottom : Iliac crest
  • Floor : Internal oblique abdominis

Lateral abdominal wall :

  • Superficial fascia : 'Camper needs fat for bearing coldness and they cut the deer's abs. with scarpa at the center superficially'
  • Transversalis fascia is soundly and naturally lies down the transversus abdominis
  • Extraperitoneal fascia was named 'extra' because of the existence of parietal peritoneum. (inner peritoneum is visceral peritoneum)
  1. External oblique abdominis : origin- 5~12 rib, insertion- iliac crest, Inguinal ligament
  2. Internal oblique abdominis : origin-Iliac crest, Thoracolumbar fascia, Insertion- 10~12 rib, aponeurosis
  3. Transversus abdominis : origin- lateral part of inguinal ligament, iliac crest, thoracolumbar fascia, 7-12 ribs, insertion- aponeurosis

* As lateral abdominis going deeper, internal and transversus abdominis share their origin.

Posterior abdominal wall :

Posterior abdominal wall (Iliocostalis attaches from iliac crest to costal part of the rib)

Extraperitoneal fascia is divided into two by its location. (That's why it is called 'extra' not by its exact location name). It is mainly loose areolar tissue between peritoneum and 1) iliopsoas, 2) Thoracolumbar fascia covering Quadratus Lumbarum, 3) Transversalis layer which is very thick and fatty posteriorly around kideny but thin and fibrous anteriorly deep to the linea alba.

Two types of extraperitoneal fascia
Areolar tissue connected tightly by elastic, collagen and reticular fibers

Role of abdominal muscles :

  • Anterior bending uses rectus abdominis and rotation, lateral bending use internal, external oblique abdominis.

Innervation, Blood supply :

There are two big branches for the upward and downward innervation. Lateral and anterior senosory and motor nerve is from T7~12 spinal nerves. and lower abdominal area is innervated by hypogastric nerve and ilio-inguinal nerve from the lumbar plexus

Two big branches of nerves cover anterior and posterior sides

Like the innervation, there are two area but arteriole supply is anterior and posterior. For the simpler posterior area, only lumbar artery directly from the abdominal aorta. There are two different branches covering from up and down for the anterior side. Upper anterior is covered by superior epigastric and musculophrenic arteries from internal thoracic artery. Lower anterior is covered by inferior epigastric and deep circumflex arteries from the external iliac artery.

Two big branches cover abs. from upper and lower level

Anatomy cartoon :

Abdominal cavity (horizontal section; lowest level)

Abdominal cavity (horizontal section made at lower level of the omental bursa)

Created By
AN Chyyoung

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