Anatomy of Midgut and Hindgut

Question 1

What is in the midgut

Answer 1

Lower part of the duodenum (after the hepatopancreatic ampulla)
Jejunum and Ileum
Cecum
Appendix
Ascending colon
First 2/3 of the transverse colon

Question 2

What is the 
1. Blood supply
2. Sympathetic innervation
3. Parasympathetic innervation
of the midgut?

Answer 2

1. Superior mesenteric artery
2. Lesser splanchnic nerves (T10, T11)
3. Vagus nerve

Question 3

What is the 
1. Blood supply
2. Sympathetic innervation
3. Parasympathetic innervation
of the hindgut?

Answer 3

1. Inferior mesenteric artery
2. Least splanchnic nerves (T12, L1)
3. S2,3,4

Question 4

What is in the hindgut?

Answer 4

Last 1/3 of transverse colon
Descending colon
Sigmoid colon
Rectum
Upper 2/3 of anal canal (bottom 1/3 from ectoderm)

Question 5

Intra vs retroperitoneal

Answer 5

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

Question 6

What does primary vs secondary retroperitoneal organ mean?

Answer 6

Primary: Organs that are formed behind the peritoneum from the beginning
Secondary: organs that are suspended in early embryonic life, but later become retroperitoneal

Question 7

What are examples of primary and secondary retroperitoneal organs?

Answer 7

Of the organs that ARE retroperitoneal:
Primary: not the GI tract (kidneys, IVC, aorta, some muscles and nerves)
Secondary: GI tract (duodenum, pancreas)

Question 8

What regions of the abdomen do the
1. Jejunum
2. Ileum
occupy?

Answer 8

1. Umbilical

2. Hypogastric

Question 9

4 main differences between the jejunum and ileum

Answer 9

1. Walls: jejunum is thicker and more vascular
2. Lumen: jejunum is wider
3. Mucosal folds: large, tall, and closely packed in the jejunum
4. Peyer’s pathces: found in the lamina propria of the ileum and lower jejunum

Question 10

Meckel’s diverticulum

Answer 10

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

Question 11

Where is Meckel’s diverticulum?

Answer 11

2 feet away from the ileocecal junction

Usually 2 inches long

Question 12

Differences between the large and small intestine

Answer 12

Shorter and wider
No mesentery (except for appendix, transverse colon, and sigmoid colon)
Taenia coli and haustra coli

Question 13

Taenia coli

Answer 13

3 ribbon like bands formed by the longitudinal muscular coat

Question 14

Where do we not have taenia coli?

Answer 14

Appendix

Rectum

Question 15

Epiploic (omental) appendices

Answer 15

Small bags of peritoneum filled with fat

Scattered over the surface of the large intestine

Question 16

Where are there no epiploic appendices

Answer 16

Appendix
Cecum
Rectum

Question 17

McBurnery’s point

Answer 17

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

Question 18

Rectal ampulla

Answer 18

Most dilated part of the rectum just before the anal canal

Question 19

2 kinds of anal sphincters and their innervation

Answer 19

Internal (sympathetic fibers from the superior rectal and hypogastric plexuses)
External (pudendal nerve)

Question 20

The superior mesenteric artery arises from the abdominal aorta at the level of which vertebrae?

Answer 20

L1

Question 21

The inferior mesenteric artery arises from the abdominal aorta at the level of which vertebrae?

Answer 21

L3

Question 22

The celiac trunk arises from the abdominal aorta at the level of which vertebrae?

Answer 22

T12

Question 23

Portal vein

Answer 23

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

Question 24

4 porto-systemic communications

Answer 24

Umbilicus
Lower end of esophagus
Anal canal
Posterior abdominal wall and bare area of liver

Question 25

Caput medusa

Answer 25

Obstruction of the veins around the umbilicus causing enlargement
Can see them on the abdomen
Sign of cirrhosis

Question 26

Where is referred pain of the
1. Midgut
2. Hindgut
felt?

Answer 26

1. Umbilical
2. Hypogastric
   Referred pain is dull
   Once the peritoneum is involved it is sharp