AP: Anterior Abdminal Wall

10/2/25, 10/7/25

abdominal region

found between the thorax/diaphragm superiorly and the pelvic region inferiorly

pelvis

pubic symphysis to sacral promontory

composition

skeletal muscle

peritoneal lining

visceral

skeletal muscle

lines the abdominal wall and serves function of protection, assistance in respiration, and increasing abdominal pressure (important for urination/defacation/childbirth)

peritoneal lining

retroperitoneal region located behind and outside the peritoneal cavity but anterior to the posterior abdominal wall muscles

lines the pelvic region and is a continuous layer

viscera (organs)

includes GI tract (stomach/large intestines), small organs (liver/gallbladder/pancreas), spleen and urinary system

retroperitoneal

the area behind or outside the peritoneum 

• kidney and ureters

linea alba

mostly avascular band of tissue where aponeurosis of rectus sheath meet

semilunar line

lateral border of rectus abdominis muscle in rectus sheath

umbilicus

t10 dermatome. L3-4 level. former umbilical cord attachment

iliac crest

rim of ilium. L4 level

inguinal ligament

marks division of lower abdominal wall and upper thigh of leg

RUQ

• ascending colon (superior portion)

• duodenum (superior, descending, inferior)

• gallbladder

• liver (r lobe)

• r. colic (Hepatic) flexure

• r kidney

• r suprarenal gland

• pancreas (head)

• stomach (pylorus)

• transverse colon (r portion)

RLQ

• appendix

• ascending colon (inferior portion)

• cecum

• ileum (majority)

• r. ovary

• r. spermatic cord (abdominal ortion)

• r. uterine tube

• uterus (when enlarged)

  • urinary bladder when full

LUQ

• descending colon (superior portion)

• ileum (proximal portion)

• jejunum (majority)

• L colic (splenic) flexure

• L. kidney

• L. suprarenal gland

• liver (L lobe)

• pancreas (body + tail)

• spleen

• stomach (majority)

• transverse colon (L. portion)

LLQ

• descending colon (inferior portion)

• ileum

• L. ovary

• L. spermatic cord

• L. ureter

• L. uterine tube

• sigmoid colon

• uterus

• urinary bladder

iliac crest

most superior curved border of ilium

anterior superior iliac spine

anterior end of iliac crest. inguinal ligament attachment point

pubic tubercle

landmarks just lateral to pubic symphysis bilaterally. attachment point of inguinal ligament

pubic symphysis

smallest and most anterior component of pubic bone

bony landmarks

xiphoid process, costal margin, pubic bone

crus

on each side of the esophageal and aortic openings are a thickening (plra is crura)

diaphragm apertures

inferior vena cava T8

esophageal T10

Aortic T12

action of central tendon for IVC

widens with inspiration

action for crura for esophagus

contract to active LES (Lower Esophageal Sphincter) preventing gastric reflux

The LES contracts (closes) to stop stomach acid from flowing back into the esophagus, which causes acid reflux or GERD symptoms.

action of crura for aorta

stabilization

parietal peritoneum*

lines abdominal and pelvic walls*

visceral peritoneum

wraps around your organs

the peritoneal cavity is the space in between the visceral and parietal peritoneum

peritoneum

smooth tissue lining abdominopelvic cavity and surrounds abdominal organs, pads and insulates your organs, secretes a lubricating fluid to reduce friction

peritonitis

inflammation of the peritoneal cavity often associated with perforation of visceral organs, infection or collections of fluid such as blood, medication, or gastric/pancreatic fluids

ascites

pathologic accumulations of fluid. normally abdomen contains 100 cc serous fluid

peritoneal dialysis

infusion of hypertonic solution in the peritoneal cavity, this fluid helps absorb waste and then drained out in a cyclic methodmal

malignancy

pleura lining can be the site of metastatis, treatment is surgical

hydrocephalus

patients with hydrocephaly can have VP shunt placed that allows drainage of excess cerebrospinal fluid in the brain is shunted to the abdominal cavity. here it is absorbed into the body

aponeuroses

elastic, thin connective tissue sheaths that extend from muscles to form termination attachments to bone or fascia

rectus sheath

facial sheath that contains rectus abdominis and pyramidalis muscles. extends from xiphoid process pubic symphysis. formed by the aponeuroses of the external oblique, internal oblique, and transversus abdominis muscles

• encapsulates the rectus abdominis

• attaches to linea alba

• contains S. and I. epigastrics, lymphatics, and nerves

anterior abdominal wall

3 flat muscles create the rectus sheath that encapsulates the rectus abdominis muscles (they make a stomach)

• external oblique muscles

• internal oblique m.

• transversus abdominis m.

transveralis fascia

membrane between the peritoneum of the anterior abdominal wall and the transversus abdominis muscle

arcuate line

below this, you have less strength because of the contribution of the aponeuroses

seen on the peritoneal surface and is found halfway between the umbilicus and pubic crest. runs along the inferior margin of the posterior wall of the rectus sheath

site of entry for the inferior epigastric artery into rectus sheath

anterolateral abdominal wall*

• external oblique

• internal oblique

• transverse abdominis

• rectus abdominins*

above arcuate line and anterior

aponeurosis of external oblique and internal oblique

above arcuate line and posterior

aponeurosis of internal oblique, transversus abdominis and transversalis fascia

below arcuate line and anterior

aponeurosis of external oblique, internal oblique, and transversus abdominis

below arcuate line and posterior

no extension of aponeurosis from EO/IO/TA. rectus abdominis rests on trasversalis fascia

transverse fascia

never goes away posteriorly!

rectus abdominis

• runs within the rectus sheath vertically

• parallel to linea alba

• arises from pubic symphysis and crest to attach at 5-7th costal cartilage and xiphoid

• have tendinous intersections

• flex and compress trunk

linea alba

• midline fibrous sheath that is a connection point for the 3 main muscles that contribute to the anterior abdominal wall

diastasis recti

expansion of linea alba (often seen in pregnancy or other intra-abdominal pressure, which can ewaken te linea alba))

separation of the 2 parallel rectus abdominis muscles along the midline of the linea alba, resulting in a widened gap in the anterior abdominal wall

diastasis recti anatomic structures affected

• rectus abdominis muscles

• linea alba

• integrity of rectus sheath formed by the aponeuroses of the external oblique, internal oblique, and transversus abdominis muscles

external oblique muscles

• most superficial of the anterolateral muscles

• arise from rib 5-12

• aponeuroses extend to become part of rectus sheath

• flexes and rotates trunk

internal oblique muscles

• immediately deep to the external

• originate from lumbar fascia, iliac crest, and lateral inguinal ligament

• wrap and extend aponeuroses to become part of rectus sheath

• arcuate line defines upper and lower fibers

• upper fibers enclose rectus sheath anteriorly and posteriorly

• lower fibers run anteriorly 

• flex and rotate trun

transverse abdominis

• deepest of the anterolateral muscles of the rectus sheath

• arises from 7-12 costal cartilages, lumbar fascia, iliac crest, and inguinal ligament

• aponeuroses contribute to rectus sheath

• contributes to the posterior rectus sheath above the arcuate line

• below the arcuate line, aponeuroses contributes to the anterior sheath

• provides compression and support for viscera

blood supply of GI

bifurcation of the aorta occurs at L4. for reference your umbilicus is at the level of L3-4 and the iliac crest is at the level of L4

external iliac artery

blood supply to the leg

internal iliac artery

gives blood to the pelvic region

superior blood supply

subclavian A+V → internal thoracic A+V → splits into

• musculophrenic A+V: supplies blood to muscles of diaphragm

• superior epigastric A+V: blood flow to rectus abdominis

inferior blood supply

common iliac A+V → external iliac A+V → inferior epigastric A+V
- inferior epigastrics anastomose with superior epigastrics

inferior epigastric branch off above inguinal ligament

principle muscles of anterolateral abdominal wall

1. external oblique

2. internal oblique

3. transversus abdominis

4. rectus abdominis

hematoma

if you try to needle compression below arcuate line anteriorly and you end up hitting the epigastric artery, this will happen (and the rectus sheath is stretchy which contributes to this as well)

inferior epigastric

turns superficial above the arcuate line (epigastric DOES NOT THROUGH THE ARCUATE LINE)