Anatomy: Viscera and Peritoneum

Parietal Peritoneum

The serous membrane lining the internal surface of the abdominopelvic wall, receiving somatic sensory innervation.

Visceral Peritoneum

The serous membrane invaginating to cover abdominal organs, sharing the same visceral neurovascular supply as the organ it covers.

Peritoneal Cavity

The potential space located between the parietal and visceral layers of peritoneum containing lubricating serous fluid.

Mesentery

A double layer of peritoneum that connects intraperitoneal organs to the posterior abdominal wall, providing a conduit for blood vessels, nerves, and lymphatics.

Omentum

A specialized double-layered fold of peritoneum extending from the stomach and proximal duodenum to adjacent abdominal organs.

Greater Omentum

A prominent four-layered peritoneal fold hanging down from the greater curvature of the stomach like an apron, capable of wrapping around inflamed organs to contain infection.

Lesser Omentum

A double-layered peritoneal fold extending from the lesser curvature of the stomach and proximal duodenum to the liver, subdivided into the hepatogastric and hepatoduodenal ligaments.

Peritoneal Ligament

A defined section or fold of peritoneum connecting an organ to another organ or to the abdominal wall.

Mesocolon

The specific peritoneal fold attaching sections of the colon—such as the transverse and sigmoid colon—to the posterior abdominal wall.

Intraperitoneal Viscera

Abdominal organs almost completely encased by visceral peritoneum and anchored by a mesentery, such as the stomach, jejunum, ileum, spleen, and transverse colon.

Retroperitoneal Viscera

Organs located posterior to the peritoneal cavity covered only anteriorly by parietal peritoneum, including the kidneys, pancreas (except tail), descending duodenum, and ascending/descending colon.

Greater Peritoneal Sac

The primary and largest compartment of the peritoneal cavity, extending from the diaphragm superiorly down into the pelvic cavity.

Lesser Peritoneal Sac (Omental Bursa)

A smaller peritoneal compartment positioned posterior to the stomach and lesser omentum that permits free movement of the stomach.

Omental (Epiploic) Foramen

The natural anatomical opening situated posterior to the free edge of the hepatoduodenal ligament that serves as the communication gateway between the greater and lesser peritoneal sacs.

Foregut

The embryonic digestive region comprising the abdominal esophagus, stomach, liver, gallbladder, spleen, proximal duodenum, and pancreas, supplied by branches of the celiac trunk.

Midgut

The embryonic digestive section spanning from the distal duodenum to the proximal two-thirds of the transverse colon, supplied by the superior mesenteric artery.

Hindgut

The embryonic digestive region encompassing the distal third of the transverse colon, descending colon, sigmoid colon, rectum, and upper anal canal, supplied by the inferior mesenteric artery.

Pylorus

The distal muscular sphincter region of the stomach regulating the passage of chyme into the duodenum, which can undergo smooth muscle hypertrophy in congenital pyloric stenosis.

Duodenum

The C-shaped first section of the small intestine divided into four parts (superior, descending, horizontal, ascending), mostly retroperitoneal except for its proximal portion.

Major Duodenal Papilla

An elevation located within the descending (2nd) part of the duodenum where the hepatopancreatic ampulla opens to release bile and pancreatic secretions.

Suspensory Muscle of Duodenum

A fibromuscular band arising from the right crus of the diaphragm that supports the duodenojejunal junction.

Jejunum

The proximal two-fifths of the intraperitoneal small intestine located primarily in the upper left quadrant, characterized by a thicker wall, prominent plicae circulares, long vasa recta, and few arterial arcades.

Ileum

The distal three-fifths of the small intestine situated mostly in the lower right quadrant, featuring thinner walls, short vasa recta, numerous complex arterial arcades, and encroaching mesenterial fat.

Cecum

The intraperitoneal blind pouch of the large intestine positioned in the right iliac fossa inferior to the ileocecal junction that lacks a dedicated mesentery.

Appendix

A narrow diverticulum projecting from the posteromedial wall of the cecum suspended by its own mesoappendix, which causes vague periumbilical pain (T10–T11) before localizing to the right lower quadrant when inflamed.

Teniae Coli

Three narrow, thick bands of longitudinal smooth muscle running along the exterior surface of the colon that contract to form haustra.

Haustra

Sacculated pouches along the length of the colon produced by the tonic contractions of the teniae coli.

Omental Appendices

Small, fat-filled peritoneal sacs attached along the outer surface of the colon.

Porta Hepatis

The transverse fissure on the visceral surface of the liver where the portal triad (hepatic portal vein, proper hepatic artery, bile duct) and nerves enter and exit.

Portal Triad

The neurovascular grouping composed of the hepatic portal vein, proper hepatic artery, and common bile duct enclosed within the hepatoduodenal ligament.

Bare Area of Liver

The region on the diaphragmatic surface of the liver devoid of visceral peritoneum where the liver lies in direct contact with the diaphragm.

Gallbladder

A pear-shaped organ situated on the visceral surface of the liver that stores and concentrates bile before releasing it into the cystic duct.

Hepatopancreatic Ampulla (Ampulla of Vater)

The dilated chamber formed by the union of the common bile duct and main pancreatic duct prior to entering the descending duodenum.

Uncinate Process

A hook-like projection from the lower posterior part of the head of the pancreas that extends posterior to the superior mesenteric vessels.

Spleen

The largest intraperitoneal lymphoid organ located in the left upper quadrant posterior to the stomach, highly susceptible to rupture from blunt abdominal trauma.

Renal Papilla

The apex at the tip of each renal pyramid that excretes urine into a minor calyx within the renal sinus.

Greater Splanchnic Nerve

Sympathetic preganglionic nerve fibers originating from T5–T9 spinal cord segments that synapse in the celiac ganglion to innervate foregut structures.

Pelvic Splanchnic Nerves

Parasympathetic preganglionic nerve fibers arising from S2–S4 spinal cord segments providing motor innervation to hindgut organs

Falciform Ligament

A sickle-shaped peritoneal fold connecting the liver to the anterior abdominal wall and diaphragm, separating the anatomical right and left lobes of the liver.

Round Ligament

The fibrous remnant of the obliterated fetal umbilical vein located within the free inferior border of the falciform ligament.

Coronary Ligament

Peritoneal reflections attaching the superior and diaphragmatic surfaces of the liver to the diaphragm, demarcating the borders of the bare area of the liver.

Hepatoduodenal Ligament

The thickened, free right margin of the lesser omentum connecting the liver to the proximal duodenum, enclosing the portal triad and forming the anterior border of the omental foramen.

Hepatogastric Ligament

The membranous, main portion of the lesser omentum extending from the visceral surface of the liver to the lesser curvature of the stomach.

Gastrosplenic Ligament

A double layer of peritoneum extending from the greater curvature of the stomach to the hilum of the spleen, forming part of the left boundary of the omental bursa.

Splenorenal Ligament

A peritoneal fold extending from the spleen to the left kidney that transmits the splenic vessels and tail of the pancreas, contributing to the left boundary of the omental bursa.

Gastrocolic Ligament

The prominent, upper portion of the greater omentum extending between the greater curvature of the stomach and the transverse colon.

Gastrophrenic Ligament

A peritoneal reflection extending from the superior portion of the greater curvature of the stomach to the inferior surface of the diaphragm.

Phrenicocolic Ligament

A peritoneal fold extending from the left colic (splenic) flexure to the diaphragm, acting as an anatomical shelf that supports the spleen.

Ligamentum Venosum

The fibrous remnant of the fetal ductus venosus located within a fissure on the visceral surface of the liver between the caudate and left lobes.

Phrenico-esophageal Ligament

A fascial fold anchoring the abdominal esophagus to the margins of the esophageal hiatus of the diaphragm