Anatomy of Midgut and Hindgut Flashcards
What is in the midgut
Lower part of the duodenum (after the hepatopancreatic ampulla) Jejunum and Ileum Cecum Appendix Ascending colon First 2/3 of the transverse colon
What is the 1. Blood supply 2. Sympathetic innervation 3. Parasympathetic innervation of the midgut?
- Superior mesenteric artery
- Lesser splanchnic nerves (T10, T11)
- Vagus nerve
What is the 1. Blood supply 2. Sympathetic innervation 3. Parasympathetic innervation of the hindgut?
- Inferior mesenteric artery
- Least splanchnic nerves (T12, L1)
- S2,3,4
What is in the hindgut?
Last 1/3 of transverse colon Descending colon Sigmoid colon Rectum Upper 2/3 of anal canal (bottom 1/3 from ectoderm)
Intra vs retroperitoneal
Intra: organs in the abdomen that are suspended by folds of peritoneum and are mobile
Retro: organs that are fixed and rest directly on the posterior abdominal wall, and are covered by peritoneum on one side
What does primary vs secondary retroperitoneal organ mean?
Primary: Organs that are formed behind the peritoneum from the beginning
Secondary: organs that are suspended in early embryonic life, but later become retroperitoneal
What are examples of primary and secondary retroperitoneal organs?
Of the organs that ARE retroperitoneal:
Primary: not the GI tract (kidneys, IVC, aorta, some muscles and nerves)
Secondary: GI tract (duodenum, pancreas)
What regions of the abdomen do the
1. Jejunum
2. Ileum
occupy?
- Umbilical
2. Hypogastric
4 main differences between the jejunum and ileum
- Walls: jejunum is thicker and more vascular
- Lumen: jejunum is wider
- Mucosal folds: large, tall, and closely packed in the jejunum
- Peyer’s pathces: found in the lamina propria of the ileum and lower jejunum
Meckel’s diverticulum
Also called diverticulum ilei
The persistent proximal part of the vitellointestinal duct (yolk sac) in embryo
Acute inflammation of the diverticulum can product symptoms that resemble appendicitis
Where is Meckel’s diverticulum?
2 feet away from the ileocecal junction
Usually 2 inches long
Differences between the large and small intestine
Shorter and wider
No mesentery (except for appendix, transverse colon, and sigmoid colon)
Taenia coli and haustra coli
Taenia coli
3 ribbon like bands formed by the longitudinal muscular coat
Where do we not have taenia coli?
Appendix
Rectum
Epiploic (omental) appendices
Small bags of peritoneum filled with fat
Scattered over the surface of the large intestine
Where are there no epiploic appendices
Appendix
Cecum
Rectum
McBurnery’s point
Base of the appendix lies deep to a point that is 1/3 of the way along the oblique line that joins the right ASIS to the umbilicus
Site of maximum tenderness in acute appendicitis
Rectal ampulla
Most dilated part of the rectum just before the anal canal
2 kinds of anal sphincters and their innervation
Internal (sympathetic fibers from the superior rectal and hypogastric plexuses)
External (pudendal nerve)
The superior mesenteric artery arises from the abdominal aorta at the level of which vertebrae?
L1
The inferior mesenteric artery arises from the abdominal aorta at the level of which vertebrae?
L3
The celiac trunk arises from the abdominal aorta at the level of which vertebrae?
T12
Portal vein
Collects blood from the GI tract and associated glands and spleen and carries it to the liver
Formed by the union of the splenic vein and superior mesenteric vein
Inferior mesenteric vein empties into the splenic vein
Portal vein ends in the porta hepatis by dividing into the R and L branches
4 porto-systemic communications
Umbilicus
Lower end of esophagus
Anal canal
Posterior abdominal wall and bare area of liver
