Anatomy of Intraabdominal Hollow GIT

Esophagus: Passes through esophageal hiatus where diaphragm fibers split apart to allow entry into abdominal cavity.

Is anchored to the diaphragm firmly by phrenicoesophageal ligaments.
The inferior esophageal sphincter has circular muscle bands and is controlled by part of the diaphgram.
In interior of esophagus where mucosal epithelium changes over to gastric epithelium = esophagogastric junction = Z-line.

Anterior / posterior vagal trunks also pass through hiatus to give branches to stomach.

Hiatal hernia:

Protrusion of a portion of the stomach through the esophageal hiatus
Due to loose phrenicoesophageal ligaments.

Pyrosis (heartburn):

Regurgitation of food and acid above the Z line of the esophagus damaging the esophageal mucosa
Often associated with hiatal hernia.

Stomach:

Where esophagus enters stomach, have sharp angle = cardiac notch, right under the heart.
Another sharp angle is at base of lesser curvature (which is below junction of esophagus) = angular incisure.
Greater curvature is on opposite side

4 Portions:

Just after esophageal junction = Cardia.
Superior portion above cardiac notch = Fundus. Usually only have gas present here.
Below the fundus, the majority of the stomach = Body. Ends inferiorly at line drawn from angular incisure
Antrum = below body after angular incisure line. Remains open in empty stomach.
Canal = between Antrum and Pyloris. More of a narrow hallway toward pyloric sphincter.
Pyloris = location of pyloric sphincter (smooth muscle ring) – usually is closed. Will open for brief periods of time to allow chyme to enter the small intestine. Lumen of stomach is very narrow here = pyloric orifice.

On interior of stomach, have Rugae = gastric folds in the inner side of the lumen. Gastric canals are the spaces the gastric folds. These direct food toward the pyloric region.

On other side of pyloric sphincter, sudden increase in diameter of lumen = duodenal cap. This is the first portion of the small intestine (specifically the duodenum).

Blood supply to stomach: has many sources of blood through collateral circulaton.

All 3 branches of celiac trunk supply it.
Left gastric = supplies lesser curvature (in lesser omentum)
Splenic artery = behind stomach to supply the spleen and also branches to fundus of stomach via short gastric arteries.
Another branch of splenic = left gastro-omental artery→ lies within greater omentum, supplies greater curvature.
Common hepatic artery = Gives off gastroduodenal artery→ gives off right gastro-omental which supplies greater curvature→ anastomoses with left gastro-omental.
Right gastric aftery = Comes off of proper hepatic artery (may vary) = supplies lesser curvature (is within lesser omentum).

Small intestine: Duodenum

A C shaped tube. Most is retroperitoneal. The pancreas sits in the “pocket of the C” shape.
Superior duodenum portion = Connects to stomach. = intraperitoneal / retroperitonealà
Descending duodenum→ horizontal duodenum→ ascending duodenum.
Has mix of longitudinal and circular muscle in wall. Lumen is in folds that run circularly = Plicae circularis, increase surface area to allow greater absorption.
Does some absorption, but mostly for more processing.
- Pancreatic duct – brings in digestive enzymes from exocrine pancrease
- Common bile duct – brings bile from liver / gall bladder, contains bile salts to break down fats into micelles.
- These two fluids mix in the hepatopancreatic ampulla where it can enter the lumen.
Minor duodenal papilla = more superior to major. Receives only pancreatic duct.
Major duodenal papilla = Where both ducts will empty contents into lumen.
Superior mesentery vein passes over the duodenum
Terminal end of the duodenum (top of ascending portion) has connective tissue fibers that attach ascending part of duodenum to diaphgram and L1-2 vertebrae.
- This is the suspensory ligament of the duodenum (Treitz). – has both muscle and CT fibers, contracts to elevate duodenum in order to reduce flow into jejunum. These fibers are part of the Right Cruz of diaphragm.

Blood supply to Duodenum:

Small supraduodenal artery – Superior portion.
Superior pancreaticoduodenal artery – From gastroduodenal artery
Inferior pancreaticoduodenal artery – From superior mesenteric artery

Arteriomesenteric occlusion of the duodenum = Superior mesenteric artery compresses duodenum against aorta.

Typical patient is tall, frail, weak, slender (asthenic habitus) with flaccid abdominal musclesà can’t support intestinesà put tension on superior mesenteric artery.
Nausea and vomiting 1-2 hours after eating. Can relieve it by lying down after meal to reduce tension on intestines.

Small intestine: Jejunum and Ileum

Have gradual transition between jejunum and ileum. No sharp separation.
Jejunum: has thicker wall, larger diameter, has small number of arcades, longer vasa recta, poorer anastomoses. Also has less fat→ fat in mesentery ends at wall of jejunum. In ileum, have greater fat→ encroaches onto wall of ileum.
Jejunum: Also has more numerous Plicae (folds)
And fewer peyer’s patches than ileum.

Blood supply:

Arcades = Anastomotic connections between arteries. More arcades in the ileum→ causes shorter vasa recta.
Vasa recta = Straight vessels that go to intestine. Longer in the jejunum.
Also see fewer vessels running around the wall of the ileum, thus giving it a paler appearance.

Intussusception:

Telescoping of one part of intestine into adjacent section→ causes narrow lumen, and thus a blockage in the flow of contents. This occurs spontaneously, esp. in children.
Corrected surgically.

Volvulus:

Twisting of a loop to such an extend that blood flow through the mesentery is obstructed
Leads to ischemia and infarction of a portion of the intestine. Corrected surgically.

Large intestine:

Ileum flows into large portion of large intestine = cecum.
Has teniae coli = bands of longitudinal smooth muscle. Usually have 3 bands present that run along length. These bands converge at the appendix.
Haustra: bulges in the wall, correspond to compartments in the lumen of the large intestine. These are separated by ridges = semilunar folds. These two structures act with smooth muscle to regulate movement of materials.
Main function is absorption of water
Omental appendices = little lobules of fat that project along exterior wall, associated with teniae coli.
Has larger diameter than small intestine.

Portions:

Cecum = 8×8 cm square region.
Ascending colonà ends at Right colic flexure→ transverse colon→ turns at left colic flexureà descending colon→ sigmoid colon (shape allows movement into pelvis)
Rectum lacks teniae coli / haustra.

Ileocecal junction:

At ileocecal orifice.
Below, find the orifice of the appendix. The appendix is most often found behind the cecum = retrocecal orientation. 1/3 of time, it has Pelvic orientation.