Anterior Abdominal Wall

Boundaries of the Abdomen:
• Superior Boundary: The diaphragm. It extends to ICS-5 superiorly (at the median line; it is more inferior around the
edges).
o Hence the superior limit of the liver is also ICS5 since it push up into the diaphragm.
• Posterior Boundary: Lumbar Vertebrae, and Quadratus Lumborum and Transverse Abdominis muscles.
• Anterolateral Borders: The muscles of abdominal wall: transversus abdominis, and internal and external abdominal
oblique.
• Inferior Borders: The Pelvic Brim

PELVIC BRIM: Inferior border of the abdomen.
• It consists of the Right and Left Coxal Bones.
o Each coxal bone is made up of an ilium, ischium, and pubic bone.
• Iliac Crest: The superior portion of the iliac bone. The Iliac Tubercles are bony prominences on the iliac crest.
• Anterior Superior Iliac Spine (ASIS): The anterior most feature on the iliac crest.
• Pubic Tubercle: Lateral edge of pubic bone.
• Inguinal Ligament: Found between the ASIS and the pubic tubercle, running in the same direction as the ASIS.
o The femoral vessels and the inguinal canal are both related to the inguinal ligament.
o Formed from aponeurosis part of the external abdominal oblique.

UMBILICUS: Found between L3 and L4 in physically fit persons.
Grandparents Like Pediatric Doctors Preventing Kids Sickness: One Transpyloric Plane -- The Transpyloric plane passes
through L1 and contains the following structures:
• Gall-bladder
• Liver
• Pylorus of Stomach
• Duodenal Bulb (Duodenum I)
• Pancreas Body and Tail
• Kidneys
• Spleen

Processus Vaginalis: The portion of peritoneum that remains with the testes when they descend into the scrotum.
• Anything that pushes through the anterior abdominal wall will become invested with peritoneum.
• The testes push through the wall, but normally a piece of peritoneum is left behind as the processus vaginalis.
• When the testes descend, the peritoneum goes with it and then scales back. The portion of peritoneum that remains with
the testes is called the processus vaginalis.

7 Layers of the Abdominal Wall:
• Skin
o Epidermis -- the part we shed
o Dermis -- contains nerves, capillaries, sweat glands, hair follicles.

• Has collagen fibers that tend to be horizontal, forming the creasing of the skin. These are called Langer's Lines.

• In surgery, you should cut with Langer's Line, the direction of the collagen, so as to minimize surgical scars.

• Superficial Fascia -- Connective tissue that is not aponeurosis, tendon, or ligament. This is the same thing as the hypodermis.
o Camper's Fascia: Fatty layer, first of the two layers. It is found throughout.
o Scarpa's Fascia: Lower layer, found in the lower 1/3 of the anterior abdominal wall. It has a restrictive location,defined by the extent of damage occurring with a straddle injury.
Limits:
The area is restricted to the anterior abdominal wall.
Lateral Limit: Basically the inguinal ligament, where it intersects with fascia lata, so that fluid
does not pass into the thigh.
Inferior Limit = the base of the scrotum.
Posterior Limit = it goes back to the anus, and fills the pelvis in between.
The outlined region is called the superficial perineal space.
It is called different fascia at different places: Dartos Fascia in scrotum / labia majora, and Colles Fascia around perineum.

o Fundiform Ligament: The false suspensory ligament of the penis or clitoris. It is an extension of superficial
fascia.

• Deep Fascia
o A true suspensory ligament occurs in the deep fascia layer, which extends into the penis / clitoris. So, we have
both a true suspensory ligament (deep fascia) and a false one (fundiform ligament / superficial fascia).
o Deep fascia encompasses all muscles of the entire body.

• Muscles -- Three flat muscles plus the longitudinal rectus sheath muscle.
o External Abdominal Oblique -- muscle fiber direction is antero-inferior (like external intercostals -- hands in pocket).
 Originate at border of Thoracic ribs T5 - T12
 Extends to midline and attaches on linea alba. Also attaches to the iliac crest.
 Again, the aponeurosis portion of the externals form the inguinal ligaments.
 Also forms the superficial inguinal ring, which allows passage of the spermatic cord (male) or round
ligament (female).

 Superficial Inguinal Ring is made up of two components, lateral crus and medial crus.
Intercrural fibers separate the two.

o Internal Abdominal Oblique
 Also has fibers that attach along the inguinal ligament to the pubic crest.
 Direction of fibers tends to go outward, from medial to lateral and a little bit inferiorly (inferolaterally).
 Borders on ribs 7 - 12.
 The aponeurosis splits and goes both anteriorly (to merge with external aponeurosis) and posteriorly (to merge with transversus aponeurosis)

o Transversus Abdominis Deep most layer of flat muscles.
 Also borders on ribs 7 - 12. Extends down to the pubic crest and medially to the linea alba.
 It creates a diagonal pathway for the spermatic cord or round ligament to pass through.
 Fibers run transversely! -- horizontally from lateral to medial.

o Rectus Abdominis: Straight muscle.
 Passes from Xiphoid Process inferiorly to pubic symphysis (inferior center of pubic bone).
 Rectus Sheath holds this rectus muscle in place. It is directly shallow to it, formed by the aponeuroses
of the three flat muscles. It has a posterior and anterior layer, formed from the aponeuroses of the three
flat muscles.

 Upper 3/4 of Abdominal Wall: All three muscle layers converge on rectus sheath, and pass
both anteriorly (external aponeurosis) and posteriorly (transversus aponeurosis).
 This part of the wall is suturable in surgery.

 Lower 1/4 of abdominal wall is transversalis fascia. Here, all three muscle layers pass
anteriorly. Here it is called transversalis fascia.
 This part of the wall is not suturable in surgery.

 Arcuate Line: The line that divides the upper 3/4 of abdomen from lower 1/4, by the differences in the
aponeurotic layers.

 Transversalis Fascia -- Deep fascia on the interior (deep) surface of the transversus abdominis muscle.
 Esp. found in the lower 1/4 of the abdomen.
o It has several names, but it is one continuous plane of fascia, just outside the peritoneum.
o As a continuous plane, it is also an avenue for infection.
• Subserous Fascia
• Peritoneum: A serous membrane that secretes fluid, thus allowing internal organs frictionless movement.

Linea Alba: The best place to make a surgical cut and not hit any nerves is straight down the linea alba.

NERVOUS SUPPLY of Anterior Wall: Ventral Rami of T7 - T12, and L1.
• Dermatomes: How nerves innervate the anterior abdominal wall -- in sections.
• Referred Pain: Example
o T10 goes to umbilical region.
o Appendicitis pain will go to sympathetic nervous system ------> refers back to T10. When rupture occurs, toxins
are released and irritate the peritoneum, resulting in a localized effect.
• Ilioinguinal Nerve: Goes through the inguinal canal, with the spermatic cord (male) or round ligament (female).
o Supplies scrotum (or labia majora) and medial aspect of thigh.
• Iliohypogastric Nerve: Directly superior to ilioinguinal nerve.
o Innervates the suprapubic area.
• Both Ilioinguinal and Iliohypogastric may come off as a single nerve and branch later.

McBurney's Point: The point of surgical incision for an appendectomy.
• Is located on a line along the ASIS. The iliohypogastric nerve is right there, about 1cm superior to the ASIS, so that is the
nerve that ya gotta be weary of when doing an appendectomy.

ARTERIAL SUPPLY of Anterior Wall:
• Superior Epigastric Artery -- Runs directly over rectus abdominis muscle.
• Inferior Epigastric Artery
• Superficial Epigastric Artery

VENOUS SUPPLY of Anterior Wall: The same as the veins above.
• When using a needle to drain peritoneal fluid, do not hit the Superior or Inferior epigastric veins! The result would be massive bleeding.

Tags: nerves, arteries, veins, muscles, ligaments

Category: Anatomy Notes