18. The Midgut & The Hindgut

Question 1

What structures are found in the midgut? Hindgut? What provides blood supply to each?

Answer 1

Midgut: (superior mesenteric a)

1/2 duodenum, jejunum, ileum, appendix, cecum, ascending colon, first 2/3 transverse colon

Hindgut (inferior mesenteric a):

last 1/3 transverse colon, descending colon, sigmoid colon, rectum

Question 2

Identify which structures in the midgut are intraperitoneal or retroperitoneal.

Answer 2

• 2nd half of duodenum: mostly retroperitoneal (at the end becomes intraperiotoneal)
• jejunum: intraperitoneal
• ileum: intraperitoneal
• appendix: intraperitoneal
• cecum: intra
• ascending colon: retro
• first 2/3 transverse colon: intraperitoneal

Question 3

In which quadrant is the jejunum and ileum found?

Answer 3

jejunum: upper left quadrant
ileum: bottom right quadrant

Question 4

How do you test to determine whether you have appendicitis or not?

Answer 4

the appendix is situatied at the first 1/3 between the ASIS and the umbilicus: if you palpate and feel pain there then you might have appendicitis

Question 5

What is the SMA view? What can be seen in this view?

Answer 5

SMA view: greater omentum is flipped up and the SI is pushed down to the bottom left

You can see the root of the mesentary when the SMA provides blood supply to the SI (where neurovasculature acceses the SI)

Question 6

Compare the jejunum and the ileum interm of arteries and structures.

Answer 6

1. Jejunum has thicker walls than the ileum.
2. The walls of the jejunum have many plicae circulares and are redder and darker. This allows for more absorption to occur. The ileum is whiter in color. The proximal ileum has a few plicae circulares and the distal ileum has no plicae circulares because water absorption occurs there (and water slides easily).
3. From the jejunal branches of the SMA: there are few small arcades (anastomoses) that give off long vasa recta. From the ileum branches of SMA: there are many arcades and shorter vasa recta (=straight arteries_

Question 7

What structure of the large intestine are intraperitoneal or peritoneal?

Answer 7

• appendix: intraperitoneal
• cecum: intraperitoneal
• ascending colon: retroperitoneal
• transverse colon: intraperitoneal
• descending colon: retroperitoneal
• sigmoid colon: intraperitoneal
• retrum: retroperioneal

Question 8

Identify the structure in purple and green.

Answer 8

Purple: at the ileocecal junction where ileum dumps into the cecum: ileocecal valve that protrudes out of the ileum (food in the cecum that pushes against valve closes it thus food cant return into the ileum)

green: orifice of the appendix: where enzymes (for plant digestion) produced by the appendix leave

Question 9

What causes appendicitis?

Answer 9

stool getting stuck in the orifice of the appendix: the appendix gets inflamed and may lose blood supply

Question 10

Identify the structures A, B. Why is B higher than A?

Answer 10

A. hepatic flexure

B. splenic flexure

B is higher bc liver is bigger

Question 11

What is the structure in blue?

Answer 11

TENIA COLI = 3 muscular bands that help with peristalsis: they form haustras from pinching together

Question 12

What is the structure indicated by C?E

Answer 12

epiploic appendages: floating fat

Question 13

What are mesocolons?

Answer 13

if parts of the colon is intraperitoneal it has mesocolon (same thing as a mesotenry execpt it inserts onto that part of the colon)

1. transverse mesocolon: anchors tranv colon onto posterior wall
2. sigmoid mesocolong: anchors sigmoid colon to psoterior wall

Question 14

What is the IMA view?

Answer 14

flop SI upward (upper right corner) w greater omentum

Question 15

Draw out the SMA and IMA and where they provide blood supply.

Answer 15

Question 16

Answer 16

b

cant be a: right goes to ascending colon

cant b c: bc goes to rectum