GI Tract Anatomy

Question 1

Esophagus

Answer 1

o Starts at C6 vetebrae and ends at T12; traveling through esophageal hiatus at T10
o Initially most posterior structure but moves anterior to descending aorta at sterna angle
o Moves lateral and anteriorly at its distal end

Question 2

Esophagus Narrowings

Answer 2

 Junction of esophagus to pharynx
 At arch of aorta
 At left main bronchus
 At esophageal hiatus of diaphragm

Question 3

Esophagus Blood Supply

Answer 3

 Arteries
• Cervical segments – inferior thyroid artery
• Thoracic segments – bronchial arteries, aorta, and right posterior intercostals
• Abdominal segments – left gastric artery with contribution from short gastric and left inferior phrenic arteries
 Venous Drainage
• Cervical segments – inferior thyroid vein
• Thoracic segments – azygous and hemiazygous system
• Abdominal segments – portal system through left gastric and short gastric veins

Question 4

Esophagus Lymphatics

Answer 4

 Lower internal jagular, posterior mediastinal, tracheal, tracheobroncheal, retrocardiac, infracardiac, diaphragmatic, and left gastric lymph nodes

Question 5

Esophagus Relations

Answer 5

 Posterior – thoracic duct, thoracic aorta, hemiazygous v., right posterior intercostals a.
 Anterior – trachea, right pulmonary artery, left main bronchus, left atrium

Question 6

Stomach

Answer 6

 Food storage (1/2 gallon), digestive organ, churn
 When stomach is empty, the lining forms folds called rugae
 Synthesizes gastric juices
• HCl – softens connective tissue in meat and destroys foreign organisms
• Pepsin – enzyme
 Chyme – partially digested food that leaves the stomach and enters the duodenum

Question 7

Stomach Anatomy - cardiac, cardiac notch, fundus, body, angular notch, pyloric antrum, greater/lesser curvature

Answer 7

 Cardiac/cardia – tumpet shaped opening of esophagus into stomach
 Cardiac/cardial notch – between esophagus and fundus
 Fundus – dilated superior portion just below the diaphragm and above cardiac
 Body – between fundus and pyloric antrum
 Angular notch/incisure – where body and pyloric antrum meet
 Pyloric antrum – dilated portion before the pyloric canal
 Greater curvature – longer, convex border
 Lesser curvature – shorter, concave border

Question 8

Stomach Blood Supply - left/right gastric; left/right gastroepiploic;short gastric

Answer 8

• Right gastric – usually branch off hepatic artery
• Left gastric – branch of celiac trunk
• Right gastroepiploic/gastro-omental - 1 of 2 terminal branches of gastroduodenal artery
• Left gastroepiploic/gastro-omental – arises from splenic artery
• Short gastric arteries (4-5) – arise from splenic artery

Question 9

Stomach Lymphatics

Answer 9

drain to celiac nodes following path of arteries

Question 10

Stomach Relations

Answer 10

 Anterior – left lob of liver, anterior body wall, diaphragm
 Posterior – pancreas, spleen

Question 11

Duodenum and Blood Supply

Answer 11

 First and shortest portion of small intestine
 Runs from pylorus to the duodenojejunal junction (L1 – L3)
 Retroperitoneal organ
 Secretes large amounds of mucous to protect the small intestine from strong acidic chyme
o Blood Supply – derivatives of gastroduodenal and superior mesenteric arteries

Question 12

Duodenum Anatomy

Answer 12

 Superior (1st) – L1; mostly horizontal; receives stomach juices
 Descending (2nd) – L2/L3; curves around head of pancreases; receives bile and pancreatic duct
 Horizontal (3rd) – L3; crosses anterior to IVC & aorta, posterior to superior mesentery a/v
 Ascending (4th) – L2/L3; joins duodenojejunal junction (an acute angle supported by ligament of Treitz)

Question 13

Jejunum & Ileum

Answer 13

 Part of small intestines that is 10-30 feet long
 Where most digestion and absorption occurs
 Villi and microvilli to increase surface area
o Jejunum looks patchy due to plicae circularis
 Jejunum located in umbilical region
 Thicker wall than ileum
 long vasa recta; fewer arterial arcades
o Ileum – looks smooth
 Located in pelvic region
 Thinner wall
 Shorter vasa recta; more arterial arcades
 More lymphatics (Peyer’s patches)

Question 14

Jejunum & Ileum BLood Supply

Answer 14

 Superior mesenteric artery – named arteries arise from right side of main trunk whereas 20 jejunal-ileal branches emerge from its left side
• vasa recta – longer in jejunum but arcades are more prominent in ileum

Question 15

Large Intestine

Answer 15

 Secretes large quantities of mucus, NO enzymes
 Water is reabsorbed
 Undigested food is stored, formed into solid waste
 Bacteria work on feces to produce vitamin K and some B complex vitamins
 Systemic antibiotic therapy may destroy these symbiotic bacteria

Question 16

Large Intestine Anatomy - parts and flexures

Answer 16

 4 parts – ascending, transverse, descending, sigmoid

 2 flexures – right (hepatic) and left (colic) flexures

Question 17

Large Intestine Features

Answer 17

 Taeniae coli – three thick bands of longitudinal muscle fibers that run along the length of the colon; shorter than the colon itself, creating sacculations/pouches/haustra
 Omental appendices are fat pads located on the colon

Question 18

Large Intestine Blood Supply

Answer 18

 Ascending colon – ileocolic and right colic arteries (branches of superior mesenteric)
 Transverse colon – middle colic artery (branch of superior mesenteric); may also be right and left colic arteries
 Descending colon – left colic and sigmoid arteries (branches of inferior mesenteric)
 Sigmoid colon – left colic and sigmoid arteries (branches of inferior mesenteric)

Question 19

Appendix and Blood Supply

Answer 19

 Located where 3 taeniae coli meet at posteromedial aspect of the cecum, inferior to ileocecal junction
 Generally lies deep to point 1/3 of way along line joining right ASIS to umbilicus (spinoumbilical or McBurney’s point)
o Blood Supply - Appendicular artery (branch of ileocolic artery)

Question 20

Rectum and Blood Supply

Answer 20

 Joins sigmoid colon at the S3 level
 5 inches long and spans from S3 to the coccyx
o Blood Supply
 Superior rectal artery (continuation of inferior mesenteric)
 2 middle rectal arteries (from inferior vesical artery in men; from uterine artery in girls)
 Inferior rectal arteries (from internal pudendal artery)

Question 21

Abdominal Blood Vessel Locations

Answer 21

o Celiac trunk, superior/inferior mesenteric arteries branch of anterior portion of aorta
 Celiac trunk – T12/L1; 3 branches
• Left gastric -
• Splenic artery – travels behind stomach
• Common hepatic
o Right gastric (varies) – lesser curvature
o Gastroduodenal -
 Superior mesenteric – L1
 Inferior mesenteric – L3

Question 22

Abdominal Nervous System

Answer 22

o Parasympathetics stimulate – vagus (CN X), pelvic splanchnic (S2-S4)
o Sympathetics inhibit – greater Splanchnic (T5-T9), lesser T10-T11, least T12 (foregut & midgut); lumbar Splanchnic L1-L2 (Hindgut)

Question 23

Meckel’s Diverticulum

Answer 23

– remnant of vitelline duct (proximal part of yolk stalk); found in 2% of people
o 2x more common in males
o 2 inches long and located 2 feet from ileocecal junction
o Most commonly diagnosed in first 2 years of life