10.1 Intestines

Vocabulary flashcards covering the gross anatomy, blood supply, venous drainage, enteric and autonomic nervous innervation, and clinical conditions of the small and large intestine based on Lecture 28.

Duodenum

The first, C-shaped portion of the small intestine extending from vertebral levels $L1$ to $L3$. It is divided into four parts: the superior part (its proximal $2.5\,\text{cm}$ is peritoneal/intraperitoneal), and the descending, horizontal, and ascending parts (which are all retroperitoneal).

Duodenojejunal Flexure

The junction that marks the transition between the end of the ascending duodenum and the beginning of the jejunum, supported by the suspensory ligament of the duodenum (ligament of Treitz).

Major Duodenal Papilla

An opening located in the descending part of the duodenum where the common bile duct and main pancreatic duct empty pancreatic enzymes and bile into the intestinal lumen via the hepatopancreatic ampulla.

Plicae Circulares (Circular Folds)

Large transverse mucosal folds found in the small intestine that are tall and closely packed in the jejunum, lower and sparser in the proximal ileum, and entirely absent in the terminal ileum.

Vasa Recta (Jejunum vs. Ileum)

Straight arterial branches arising from the arterial arcades of the superior mesenteric artery; they are long and arise from simple, single-layered arcades in the jejunum, but short and arise from complex, multi-tiered arcades in the ileum.

Ileocecal Junction (Valve)

The anatomical connection and functional sphincter mechanism situated between the terminal ileum and the cecum of the large intestine.

Caecum

The first part of the large intestine, measuring as a blind intestinal pouch situated in the right lower quadrant, continuous superiorly with the ascending colon and giving origin to the vermiform appendix.

Taeniae Coli

Three distinct longitudinal ribbons of smooth muscle running along the exterior surface of the large intestine that are shorter than the colon itself, causing the wall to pucker into pouches.

Haustra

Characteristic sacculations or pouches of the colon wall formed by the tonic shortening and contraction of the taeniae coli.

Right Colic Flexure (Hepatic Flexure)

The sharp bend marking the transition between the ascending colon and the transverse colon, located adjacent to the liver.

Left Colic Flexure (Splenic Flexure)

The acute bend marking the junction between the transverse colon and the descending colon, located adjacent to the spleen.

Celiac Trunk

The unpaired visceral branch of the abdominal aorta that provides arterial blood to foregut derivatives, including the stomach, liver, spleen, gallbladder, and proximal duodenum.

Superior Mesenteric Artery (SMA)

The major unpaired visceral branch of the abdominal aorta that supplies midgut derivatives, extending from the distal duodenum to the mid-transverse colon (including the jejunum, ileum, cecum, appendix, and ascending colon).

Inferior Mesenteric Artery (IMA)

The unpaired visceral branch of the abdominal aorta that supplies hindgut derivatives, extending from the distal transverse colon through the descending colon, sigmoid colon, and down to the upper rectum.

Marginal Artery

A continuous anastomotic arterial channel running along the inner border of the large intestine that connects branches of the superior mesenteric artery and inferior mesenteric artery.

Hepatic Portal Vein

The large venous channel formed by the union of the superior mesenteric vein and splenic vein (with drainage from the inferior mesenteric vein) that transports nutrient-rich blood from the GIT directly to the liver.

Sympathetic GIT Innervation

Thoracic and lumbar outflow ($T5-L2$) synapsing at the celiac ($T5-T11$), superior mesenteric ($T10-T11$), and inferior mesenteric ($T12-L2$) prevertebral ganglia; it decreases motility, secretion, and muscle contraction while inducing contraction of sphincters.

Parasympathetic GIT Innervation

Cranial outflow via the vagus nerve (dorsal motor nucleus) and sacral outflow ($S2-S4$ pelvic splanchnic nerves); it stimulates peristalsis, increases motility and glandular secretions, and relaxes gastrointestinal sphincters.

Submucosal Plexus (Meissner's Plexus)

An intrinsic network of the enteric nervous system restricted to the submucosal layer of the small and large intestines that primarily regulates local secretomotor function and mucosal blood flow.

Myenteric Plexus (Auerbach's Plexus)

An intrinsic network of the enteric nervous system positioned between the circular and longitudinal smooth muscle layers along the entire GIT from esophagus to rectum that primarily coordinates muscular motility and peristalsis.

Puborectalis

A muscular sling of the levator ani muscle that loops around the anorectal junction, providing a continuous sphincter action essential for fecal continence.

Celiac Disease (Histopathology)

An autoimmune enteropathy affecting the small intestine that microscopically presents with blunting or complete flattening of intestinal villi and loss of circular folds, resulting in malabsorption.