Anatomy of the Pubis and Abdominal Wall

Pubis (Arcuate Line)

• Arcuate line is a curved line on the inside of the pelvis that marks the transition between the abdominal wall and the pelvic floor
• The aponeurosis of the transversus abdominis muscle passes behind the rectus abdominis muscle above the arcuate line
• The aponeurosis of the transversus abdominis muscle passes in front of the rectus abdominis muscle below the arcuate line

Formation of Arcuate Line

• The arcuate line is formed by the aponeurosis of the transversus abdominis, internal oblique, and external oblique muscles

Posterior Side of the Anterior Abdominal Wall: Folds (and Ligaments)

• The falciform ligament connects the anterior abdominal wall to the liver
• The median umbilical fold contains the urachus (remnant of the allantoic duct)
• The medial umbilical fold contains the remnant of the umbilical artery
• The lateral umbilical fold overlies the inferior epigastric vessels

Cutaneous Innervation of the Abdominal Wall

• T7-T9 nerve roots innervate the skin from the xiphoid process to just above the umbilicus
• T10 nerve root innervates the skin around the umbilicus
• T11, T12, and L1 nerve roots innervate the skin just below the umbilicus to the pubic area
• The ilioinguinal nerve (L1) supplies the anterior surface of the scrotum or labia majora

Boundaries of Inguinal Canal and Inguinal Hernia

• Indirect inguinal hernia: occurs when a peritoneal sac protrudes through the deep inguinal ring, passing through the inguinal canal lateral to the inferior epigastric vessels
• Direct inguinal hernia: occurs when a peritoneal sac protrudes through the abdominal wall medial to the inferior epigastric vessels, in an area known as the inguinal triangle (Hesselbach's triangle)
• Inguinal triangle boundaries:
  • Lateral: inferior epigastric vessels
  • Medial: rectus abdominis muscle
  • Inferior: inguinal ligament

Lesser Omentum

• The lesser omentum is a fold of peritoneum connecting the lesser curvature of the stomach and the first 2 cm of the duodenum to the liver
• It consists of two parts: the hepatogastric ligament and the hepatoduodenal ligament
• The hepatoduodenal ligament contains the hepatic artery proper, portal vein, bile duct, lymph nodes, lymphatics, and hepatic plexus of nerves
• The hepatogastric ligament contains the right and left gastric vessels, gastric group of lymph nodes, and gastric nerves

Omental (Epiploic) Foramen

• This opening connects the greater sac and lesser sac of the peritoneal cavity
• Boundaries:
  • Anterior: portal vein, hepatic artery proper, and bile duct
  • Posterior: inferior vena cava
  • Superior: caudate lobe of the liver

Arteries of the Stomach

• Right gastro-omental artery: branches off the gastroduodenal artery
• Left gastro-omental artery: branches off the splenic artery
• Short gastric arteries: branches off the splenic artery

Posterior Relations of the Stomach

• Left kidney
• Splenic artery
• Spleen
• Transverse mesocolon
• Pancreas
• Transverse colon

Gastric Ulcers

• Gastric ulcers occur in the alkaline-producing mucosa of the stomach usually on or near the lesser curvature
• Chronic ulcers can invade the muscular coats and involve the peritoneum, causing adhesions to neighboring structures
• Ulcers on the posterior wall of the stomach can perforate into the lesser sac or adhere to the pancreas
• Erosions of the pancreas can cause pain referred to the back
• Erosion of the splenic artery can lead to fatal hemorrhage

Cholecystitis (Inflammation of the Gallbladder)

• Common in female, fatty, fertile patients in their forties
• Pain can be felt in the right hypochondrium, tip of right shoulder, below the scapula, and epigastric region

Superior Mesenteric Artery

• Supplies the midgut
• Branches off the aorta anteriorly about 1 cm inferior to the celiac trunk (L1 vertebral level)
• Crossed anteriorly by the splenic vein and neck of the pancreas
• Posterior to the superior mesenteric artery are the left renal vein, uncinate process of the pancreas, and the third part of the duodenum

Superior Mesenteric Artery Distribution

• Branches
  • Inferior pancreaticoduodenal artery
  • Jejunal and ileal arteries (intestinal arteries)
  • Middle colic artery
  • Right colic artery
  • Ileocolic artery

Inferior Pancreaticoduodenal Artery

• First branch of the superior mesenteric artery
• Divides into anterior and posterior branches
• These branches ascend on the corresponding sides of the pancreas
• They anastomose with the anterior and posterior superior pancreaticoduodenal arteries
• Supplies the head and uncinate process of the pancreas and the duodenum

Marginal Artery (of the Colon)

• Forms an anastomosis between the superior and inferior mesenteric arteries
• Important clinically because it provides collateral supply to the colon, maintaining blood supply in case of occlusion or stenosis of one of the major arteries

Superior Mesenteric Artery Syndrome

• Occurs when the angle between the superior mesenteric artery and aorta is too acute
• Compresses the third part of the duodenum resulting in obstruction

Parts of the Duodenum

• Superior (first) part
• Descending (second) part
• Horizontal (third) part
• Ascending (fourth) part

Duodenal Ulcers

• Most inflammatory erosions of the duodenal wall are located in the posterior wall of the superior part of the duodenum, within 3 cm of the pylorus
• Ulcers can perforate the duodenal wall, causing peritonitis
• The superior part of the duodenum is in close relation to the liver and gallbladder, which can be ulcerated by a duodenal ulcer
• Erosion of the gastroduodenal artery can result in severe hemorrhage into the peritoneal cavity

Meckel’s Diverticulum

• A remnant of the proximal part of the embryonic omphaloenteric duct
• Usually appears as a finger-like pouch

Epidemiology of Meckel’s Diverticulum

• Most common congenital anomaly of the GI tract
• Affects around 2% of the population, with a 2:1 male predominance
• Usually located 2 feet proximal to the ileocecal valve in adults
• 50% of cases are symptomatic under the age of 2
• May contain heterotopic tissue, such as gastric mucosa or pancreatic acini

Clinical Presentation of Meckel's Diverticulum

• Often asymptomatic
• Bleeding is the most common presentation in children, due to acid production by heterotopic gastric mucosa
• Other possible presentations include intestinal obstruction and diverticulitis

General Characteristics of Large Intestine

• Larger internal diameter compared to the small intestine
• Peritoneal-covered accumulations of fat (omental appendices)
• Longitudinal muscle segregated into three narrow bands called taeniae coli
• Sacculations (haustra) of the colon

Inferior Mesenteric Artery

• Artery of the hindgut
• Arises from the anterior aspect of the aorta at the level of the third lumbar vertebra (L3), 3-4 cm above the aortic bifurcation
• Supplies the left one-third of the transverse colon, descending colon, sigmoid colon, rectum, and part of the anal canal above the anal valves
• Branches include:
  • Left colic artery
  • Sigmoid arteries
  • Superior rectal artery

McBurney's Point

• Located at the junction of the lateral and middle 1/3 of a line from the anterior superior iliac spine to the umbilicus
• People with appendicular problems may experience pain near this point
• The iliohypogastric nerve is often injured during appendectomy due to its location near McBurney's point

Appendicitis

• Acute inflammation of the appendix
• Causes severe abdominal pain
• Pain usually begins as vague pain in the peri-umbilical region due to afferent pain fibers in the spinal cord at the T10 level
• Later, pain in the right lower quadrant develops because of irritation of the parietal peritoneum lining the posterior abdominal wall

Diverticulosis

• Disorder in which multiple false diverticula (outpocketings of the mucosa of the colon) develop along the intestine
• Primarily affects middle-aged and elderly individuals
• Commonly found in the sigmoid colon
• Diverticula can become infected or rupture, leading to diverticulitis

Hepatic Portal System

• Refers to the venous blood from the viscera passing through a second vascular bed in the liver before entering the systemic venous system (inferior vena cava)
• Drains blood from the gastrointestinal tract (except the lower part of the anal canal), spleen, pancreas, and gallbladder
• Conveys absorbed products of digested food to the liver
• Blood passes through the liver until it reaches the hepatic veins

This quiz covers important aspects of the arcuate line and the posterior side of the anterior abdominal wall. It includes details about the formation of the arcuate line and the various folds and ligaments associated with the abdominal wall. Test your understanding of these anatomical features and their innervation.