Lecture 17 - Midgut and Hindgut Flashcards
(93 cards)
1
Q
Where does the midgut begin?
A
Duodenum
2
Q
Where does the midgut end?
A
2/3 of the way along the transverse colon
3
Q
Where does the hindgut begin?
A
2/3 of the way along the transverse colon
4
Q
Where does the hindgut end?
A
Partway through the anal canal
5
Q
What branch of the abdominal aorta goes to the midgut?
A
Superior mesenteric artery (L1)
6
Q
What branch of the abdominal aorta goes to the hindgut?
A
Inferior mesenteric artery (L3)
7
Q
What are the parts of the midgut?
A
- Duodenum (distal 1/2)
- Jejunum
- Ileum
- Cecum + appendix
- Ascending colon
- Transverse colon (proximal 2/3)
8
Q
What are the parts of the hindgut?
A
- Transverse colon (distal 1/3)
- Descending colon
- Sigmoid colon
- Rectum
- Anal canal (proximal)
9
Q
What is the duodenum?
A
Proximal portion of the small intestine
10
Q
What is the distal end of the duodenum?
A
Duodenojejunal flexure
11
Q
What supports the duodenojejunal flexure?
A
Suspensory muscle of the duodenum
12
Q
What is the proximal end of the duodenum?
A
Pylorus
13
Q
What divisions of the duodenum are part of the midgut?
A
- Inferior (D3)
- Ascending (D4)
14
Q
What is the jejunum?
A
Middle portion of the small intestine
15
Q
What quadrant is the jejunum in?
A
Left upper quadrant
16
Q
What is the proximal end of the jejunum?
A
Duodenojejunal flexure
17
Q
What is the distal end of the jejunum?
A
N/A
18
Q
What are the characteristic features of the jejunum?
A
- Numerous, deep plicae circulares
- Arterial supply within mesenteric:
- Thicker walls
19
Q
What is distinct about the arterial supply in the mesenteric of the jejunum?
A
a) Long vasa recta
b) Few arterial arcades
20
Q
What are the plicae circulares?
A
- Circular mucosal folds inside the lumen
- Increase surface area for nutrient absorption
21
Q
What shape are the vasa recta?
A
Straight arteries
22
Q
What shape are the arterial arcades?
A
Loops/arches
23
Q
What is the ileum?
A
Distal portion of the small intestine
24
Q
What quadrant is the ileum in?
A
Right lower quadrant
25
What is the proximal end of the ileum?
N/A
26
What is the distal end of the ileum?
Ileocecal junction
27
What are the characteristic features of the ileum?
1. Sparse, small plicae circulares
2. Numerous lymphoid nodules
3. Arterial supply within mesentery
28
What is distinct about the arterial supply in the mesenteric of the ileum?
a) Short vasa recta
b) Numerous arterial arcades
29
What are the lymphoid nodules in the ileum?
- Peyer's patches
- Role in intestinal immune response
30
What is the mesentery of the small intestine?
- A double layer of peritoneum
- Suspends the jejunum and ileum from the posterior abdominal wall
- Carries blood vessels, lymphatic vessels and nerves
31
What structures contribute to the blood supply in the mesentery?
Arterial branches of the superior mesenteric artery and vein
32
What is the function of the large intestine?
1. Some absorption of fluids, electrolytes, etc
2. Conversion of liquid waste into semisolid fecal matter
33
Which is shorter, the large or the small intestine?
The large intestine
34
How long is the large intestine?
1.5 m
35
How long is the small intestine?
6-7 m
36
What are the divisions of the large intestine?
1. Appendix
2. Cecum
3. Ascending colon
4. Transverse colon
5. Descending colon
6. Sigmoid colon
7. Rectum
8. Anal canal
37
What are some characteristics of the colon wall?
1. Haustra
2. Epiploic appendages
3. Teniae coli
38
What are the haustra on the colon wall?
Pouches/sacculations
39
What are the teniae coli on the colon wall?
3 longitudinal bands of smooth muscle
40
What is the cecum?
Blind intestinal pouch
41
What is the function of the cecum?
1. Absorption of fluids and electrolytes
2. Secretion of mucus to lubricate food waste
42
What type of organ is the cecum?
Intraperitoneal (no mesentery)
43
Where is the cecum located?
Right lower quadrant
44
What is the appendix?
Blind intestinal diverticulum (outpouching)
45
What is the function of the appendix?
1. Contains lymphoid tissue
2. Possible reservoir for healthy gut bacteria
46
What type of organ is the appendix?
Intraperitoneal
47
Where is the appendix located?
Right lower quadrant
48
What are the most common positions of the appendix?
1. Retrocecal (43%)
2. Pelvic (32%)
49
What are the less common positions of the appendix?
3. Subcecal (2%)
4. Pre/post ileal (<2%)
50
What is McBurney's point?
- AKA appendicitis
- 1/3 of the way from ASIS to umbilicus
51
What are the structures on the appendix?
1. Ileocecal valve
2. Orifice of the appendix
52
What action does the cecum have on the sphincter?
Closes it
53
What action does the ileum have on the sphincter?
Opens it
54
What is the function of the ascending colon?
Connects and allows fluids to move freely between abdominal compartments
55
What is the proximal end of the ascending colon?
Cecum
56
What is the distal end of the ascending colon?
Hepatic flexure
57
What type of organ is the ascending colon?
Retroperitoneal
58
What are the structures of the ascending colon?
1. Hepatic flexure
2. Right/left lateral paracolic gutters
59
What impression does the hepatic flexure create?
The colic impression on the underside of the liver
60
What are the right/left lateral paracolic gutters?
- Folding of the peritoneum forming gutters
- Between the colon and the posterolateral abdominal wall
61
What is unique of the transverse colon?
Longest and most mobile region
62
What is the proximal end of the transverse colon?
Hepatic flexure
63
What is the distal end of the transverse colon?
Splenic flexure
64
What type of organ is the transverse colon?
Intraperitoneal
65
What are the structures of the transverse colon?
1. Transverse mesocolon
2. Greater omentum
66
What is the transverse mesocolon?
Mesentery associated with the transverse colon
67
What is the greater omentum?
Connected to the transverse colon and adheres to the transverse mesocolon
68
What is the proximal end of the descending colon?
Splenic flexure
69
What is the distal end of the descending colon?
Sigmoid colon
70
What is the blood supply of the midgut?
Branches of the superior mesenteric artery (L1)
71
What are the branches of the superior mesenteric artery?
1. Inferior pancreaticoduodenal
2. Jejunal arteries
3. Ileal arteries
4. Ileocolic artery
5. Right colic artery
6. Middle colic artery
72
What type of organ is the descending colon?
Retroperitoneal
73
What impression does the splenic flexure create?
Colic impression on the spleen
74
What connects the splenic flexure to the diaphragm?
The phrenicocolic ligament
75
What is characteristic of the sigmoid colon?
S-shaped portion of the distal large intestine
76
What type of organ is the sigmoid colon?
Intraperitoneal
77
What does the sigmoid colon run?
Crosses the left iliac fossa and enters pelvis
78
What is the distal end of the sigmoid colon?
Rectum
79
What is the function of the rectum?
Stores fecal matter before it is released through the anal canal
80
What type of organ is the rectum?
Retroperitoneal
81
What is the proximal end of the rectum?
Rectosigmoid junction (@ S3)
82
What is the distal end of the rectum?
Anorectal junction
83
What is the anal canal?
Terminal part of the GI tract
84
Where is the anal canal located?
Located within the pelvic floor
85
What is the proximal end of the anal canal?
Anorectal junction
86
What is the distal end of the anal canal?
Pectinate line (ends at anus)
87
What is the pectinate line?
Point at which the anal canal surface transitions from endoderm to ectoderm
88
What is the difference between endoderm and ectoderm?
Endoderm: Like rest of anal canal
Ectoderm: Like skin
89
What are the structures of the anal canal?
1. Internal anal sphincter
2. External anal sphincter
90
Which sphincter is involuntary?
Internal sphincter
91
Which sphincter is voluntary?
External sphincter
92
What is the blood supply of the hindgut?
Branches of the inferior mesenteric artery (L3)
93
What are the branches of the inferior mesenteric artery?
1. Left colic artery
2. Sigmoid arteries
3. Superior rectal artery
