Abdominal Cavity and the Digestive Tract

Comprehensive vocabulary flashcards covering the gross anatomy, histology, vascular supply, autonomic innervation, embryology, and clinical pathologies of the abdominal wall, peritoneal compartments, alimentary tract, hepatobiliary system, spleen, and retroperitoneal urinary and adrenal organs.

Linea Alba

The midline fibrous band where the aponeuroses of the left and right external abdominal oblique and other lateral abdominal wall muscles meet.

Rectus Sheath

The aponeurotic sheath formed by the lateral abdominal wall muscles (external oblique, internal oblique, and transversus abdominis) that surrounds the rectus abdominis and pyramidalis muscles anteriorly and posteriorly.

Cremaster Muscle

A muscle surrounding the spermatic cord formed by the caudal part of the internal abdominal oblique in biological males, innervated by the genital branch of the genitofemoral nerve.

Inguinal Canal

An oblique tunnel situated posterior to the inguinal ligament between layers of lateral abdominal muscle aponeuroses; transmits the spermatic cord in males and the round ligament of the uterus and lymphatics in females.

Direct Inguinal Hernia

An acquired protrusion occurring medial to the inferior epigastric vessels within Hesselbach's triangle; it parallels the spermatic cord without passing through the deep inguinal ring and carries a low risk of strangulation.

Indirect Inguinal Hernia

A congenital or acquired hernia that passes lateral to the inferior epigastric vessels, enters the deep inguinal ring, traverses the entire inguinal canal inside the spermatic cord, and carries a high risk of strangulation or infarction.

Hesselbach's Triangle

The anatomical region on the inner surface of the anterior lower abdominal wall medial to the inferior epigastric vessels where direct inguinal hernias occur.

Greater Sac

The main and largest part of the peritoneal cavity, lined by parietal peritoneum along the internal abdominal walls.

Mesentery

A double fold of peritoneum containing blood vessels, nerves, lymphatics, and fat that suspends intraperitoneal organs from the posterior abdominal wall.

Secondarily Retroperitoneal Organs

Organs that had a mesentery during early embryonic development but lost it later, including the descending, horizontal, and ascending parts of the duodenum, the pancreas, the ascending and descending colon, and the upper two-thirds of the rectum.

Epiploic Foramen (Omental Foramen)

The opening connecting the greater peritoneal sac to the lesser sac (omental bursa), located posterior to the free edge of the lesser omentum (hepatoduodenal ligament); a potential site of internal herniation.

Pouch of Morison

The right subhepatic space situated between the liver and right kidney where peritoneal fluid frequently collects in recumbent patients.

Rectouterine (Douglas) Pouch

The deep peritoneal recess between the rectum and the posterior wall of the uterus in females; a primary site for abnormal fluid accumulation in pelvic inflammatory disease.

Peritonitis

Inflammation of the peritoneum accompanied by sharp abdominal pain and increased serous fluid production, typically resulting from trauma, stab wounds, or a perforated appendix.

Ascites

Abnormal accumulation of serous fluid within the peritoneal cavity, commonly secondary to liver cirrhosis and portal hypertension.

Paracentesis

A clinical procedure involving the needle puncture of the peritoneal cavity for the aspiration and removal of accumulated ascitic fluid.

Foregut

The primitive digestive tract region extending from the esophagus through the stomach down to the major duodenal papilla in the second part of the duodenum; supplied by the celiac trunk and innervated parasympathetically by the vagus nerve ($\text{CN X}$).

Midgut

The developmental segment extending from the lower half of the second part of the duodenum through the jejunum, ileum, cecum, appendix, ascending colon, and proximal two-thirds of the transverse colon; supplied by the superior mesenteric artery and innervated by the vagus nerve.

Hindgut

The primitive gut segment giving rise to the distal one-third of the transverse colon, descending colon, sigmoid colon, rectum, and upper anal canal; supplied by the inferior mesenteric artery and innervated parasympathetically by pelvic splanchnic nerves ($S2\text{--}S4$).

Submucosal Plexus of Meissner

An intrinsic nerve network in the submucosa of the alimentary tract providing secretomotor regulation to mucosal glands for mucus secretion and fluid absorption.

Myenteric Plexus of Auerbach

The autonomic neural network located between the circular and longitudinal muscle layers of the muscularis externa, primarily controlling gut motility and peristalsis.

Achalasia

A neuromotor disorder of the lower esophageal sphincter (LES) characterized by retrosternal pain, dysphagia for solids and liquids, lack of peristalsis, and failure of LES relaxation due to a deficiency of ganglion cells in the myenteric plexus.

Barrett's Esophagus

Metaplastic transformation of the normal stratified non-keratinized squamous epithelium of the lower esophagus into simple columnar epithelium, induced by chronic acid exposure in GERD.

Hypertrophic Pyloric Stenosis

Progressive hypertrophy of circular smooth muscle in the pyloric sphincter causing gastric outlet obstruction; classically presents in male firstborn infants with projectile non-bilious vomiting and a palpable olive-sized mass at the right costal margin.

Parietal Cells

Epithelial cells located in the gastric glands of the stomach body and fundus that secrete hydrochloric acid ($\text{HCl}$) and intrinsic factor, which is essential for vitamin $B_{12}$ absorption in the ileum.

Chief Cells

Zymogenic cells situated in the basal regions of gastric glands that synthesize and release pepsinogen, a protein-splitting proenzyme activated into pepsin by gastric acid.

G Cells

Enteroendocrine cells situated predominantly in the pyloric antrum of the stomach that secrete gastrin to stimulate parietal cell growth and gastric acid secretion.

Sliding Hiatal Hernia

The most common form of diaphragmatic hernia in which the abdominal esophagus, cardia, and parts of the gastric fundus slide upward through the esophageal hiatus into the posterior mediastinum, often causing regurgitation and heartburn.

Para-esophageal Hiatal Hernia

A diaphragmatic hernia where the cardia remains in its normal position below the diaphragm, but a portion of the gastric fundus herniates alongside the esophagus through the esophageal hiatus; reflux is typically absent.

Fundoplication

A surgical antireflux procedure in which the gastric fundus is wrapped around the lower end of the esophagus and anchored below the diaphragm to reinforce the lower esophageal sphincter.

Major Duodenal Papilla

An elevation located in the descending (second) part of the duodenum that contains the common exit for the main pancreatic duct and common bile duct via the hepatopancreatic ampulla of Vater.

Sphincter of Oddi

A muscular valve surrounding the hepatopancreatic ampulla of Vater that controls the flow of bile and pancreatic juices into the descending duodenum.

Duodenal Atresia

Congenital failure of recanalization of the duodenal lumen, often associated with Trisomy 21 and polyhydramnios, presenting clinically with bile-stained vomitus and a radiographic 'double bubble' sign.

Paneth Cells

Specialized secretory cells situated at the base of the intestinal crypts of Lieberkühn that produce eosinophilic granules containing bactericidal enzymes.

Brunner's Glands

Compound branched mucus glands restricted to the submucosa of the duodenum that secrete an alkaline bicarbonate-rich fluid to protect the mucosa and optimize the pH for pancreatic enzymes.

Peyer's Patches

Aggregated lymphoid follicles concentrated within the lamina propria and submucosa of the ileum that monitor intestinal bacterial populations and initiate immune responses.

Vasa Recta (Intestinal)

Straight arterial branches arising from mesenteric vascular arcades; they are long and spaced apart in the jejunum, but short, closely packed, and numerous in the ileum.

Meckel's Diverticulum

A congenital ileal outpouching caused by persistent remnants of the embryonic vitelline (omphalomesenteric) duct, located approximately $50\text{--}75\text{ cm}$ ($2\text{ feet}$) proximal to the ileocecal valve; frequently contains ectopic gastric or pancreatic tissue.

Teniae Coli

Three distinct longitudinal ribbons of smooth muscle running along the external surface of the large intestine, whose contraction shortens the colon and forms sacculations called haustra.

McBurney's Point

An anatomical surface landmark located at the junction between the lateral one-third and medial two-thirds of an imaginary line drawn from the right anterior superior iliac spine to the umbilicus, used as the classic incision site for appendectomy.

Puborectalis Muscle

A U-shaped muscular sling derived from the levator ani muscle that loops around the anorectal junction to maintain an $80^\top\text{--}90^\top$ perineal flexure essential for fecal continence.

Pectinate Line (Dentate Line)

The horizontal serrated boundary in the anal canal formed by the inferior margins of the anal valves, separating the upper anal canal (endoderm, autonomic innervation, visceral pain insensitivity) from the lower anal canal (ectoderm, somatic pudendal innervation, sharp pain sensitivity).

Internal Hemorrhoids

Prolapses of mucosal vascular cushions containing varicosities of the superior rectal veins located above the pectinate line; typically painless because of visceral autonomic innervation.

External Hemorrhoids

Thrombosed veins of the external rectal venous plexus located below the pectinate line, covered by anal skin and highly painful due to somatic sensory innervation from the inferior rectal nerves.

Caput Medusae

Distended, engorged superficial periumbilical veins radiating outward from the umbilicus, resulting from portal hypertension diverting blood via paraumbilical veins into systemic abdominal wall veins.

Hirschsprung's Disease

Congenital megacolon caused by the failure of neural crest cells to migrate into the distal bowel wall, resulting in an absence of intramural ganglion cells in Meissner's and Auerbach's plexuses, distal aperistalsis, proximal dilation, and chronic obstipation.

Glisson's Capsule

A tense, fibrous connective tissue envelope enclosing the external surface of the liver and accompanying intrahepatic vessels and bile ducts.

Ligamentum Teres Hepatis

The fibrous cord found within the free inferior border of the falciform ligament, representing the obliterated umbilical vein that carried oxygenated blood from the placenta to the fetus.

Ligamentum Venosum

A fibrous remnant occupying a fissure on the visceral surface of the liver, representing the fetal ductus venosus that shunted placental blood directly from the umbilical vein to the inferior vena cava.

Space of Disse

The narrow perisinusoidal space situated between the fenestrated endothelial lining of liver sinusoids and hepatocytes; contains fat-storing hepatic stellate (Ito) cells.

Cholelithiasis

The formation of gallstones within the gallbladder or biliary tract due to an imbalance between cholesterol and bile salts; common risk factors are summarized by the '5 Fs' (Female, Fertile, Forty/fifty, Full-figured, Fair).

Islets of Langerhans

Endocrine cell clusters scattered throughout the pancreas consisting of alpha cells (producing glucagon), beta cells (producing insulin), and delta cells (producing somatostatin) that secrete hormones directly into the bloodstream.

Howell-Jolly Bodies

Basophilic nuclear remnants inside circulating red blood cells that are normally identified and removed during erythrocyte passage through the filtration meshwork of the spleen.

Horseshoe Kidney

A congenital malformation in which the lower poles of both kidneys fuse across the midline during embryonic development, causing ascent to be arrested by the inferior mesenteric artery.

Filtration Membrane (Renal)

The three-layer barrier in the renal corpuscle consisting of capillary fenestrated endothelium, the glomerular basement membrane, and podocyte filtration slits covered by slit diaphragms that retains blood cells and large proteins while permitting fluid and solute filtration.

Zona Glomerulosa

The outermost region of the adrenal cortex lying immediately beneath the capsule, responsible for synthesizing and secreting mineralocorticoid hormones (primarily aldosterone) to regulate electrolyte and fluid balance.

Zona Fasciculata

The thick middle layer of the adrenal cortex arranged in linear cords that secretes glucocorticoids (such as cortisol) to regulate carbohydrate, lipid, and protein metabolism under anterior pituitary ACTH stimulation.

Zona Reticularis

The innermost branching zone of the adrenal cortex adjacent to the medulla, responsible for producing small amounts of adrenal sex steroids (androgens).

Adrenal Medulla

The central neuroendocrine core of the suprarenal gland innervated directly by preganglionic sympathetic fibers, which stimulates the release of catecholamines (epinephrine and norepinephrine).

Iliopsoas Muscle

The powerful composite hip flexor formed by the junction of the psoas major and iliacus muscles, inserting onto the lesser trochanter of the femur to produce flexion and external rotation of the hip joint.