L44&45 - GI Physiology - 3/3/15 Flashcards
1
Q
The 4 physiological processes of GI include:
A
SMAD.
Secretion
Motility
Absorption
Digestion
2
Q
What is the largest immune organ of the body?
A
GI tract
3
Q
Into which segment of the GI tract are major enzymes secreted?
A
Duodenum
4
Q
Which sphincter protects the airways?
A
UES: upper esophageal sphincter
5
Q
Which sphincter protects against gastric reflux?
A
LES: lower esophageal sphincter
6
Q
What sphincter controls the release of bile and pancreatic contents into the duodenum?
A
Sphincter of Oddi
7
Q
What sphincter controls the release of stomach contents into the duodenum?
A
Pyloric sphincter
8
Q
What sphincter controls the release of small intestinal contents, into the caecum?
A
Ileocecal sphincter
9
Q
What sphincter(s) control the release of fecal matter?
A
Internal and external anal sphincters
10
Q
The splanchnic circulation receives what % of cardiac output?
A
25%
11
Q
What are the 3 major arteries that supply the abdominal organs?
A
Celiac artery
SMA
IMA
12
Q
Where do hepatic veins drain?
A
Inferior vena cava
13
Q
Where does the portal vein drain?
A
Liver
14
Q
Do lipid soluble substances travel to the liver?
A
No, they don’t use the portal vein and go to liver. Instead they’re absorbed by lymphatics.
15
Q
Where do lymphatics drain into systemic circulation?
A
Thoracic duct
16
Q
Where is the thoracic duct?
A
L. subclavian vein
17
Q
What are the 4 layers of the gut wall?
A
- Mucosa
- Submucosa
- Muscularis EXTERNA
- Serosa
18
Q
What 3 layers compose the mucosa?
A
- Epithelium
- Lamina propria
- Muscularis mucosae
19
Q
Gut epithelial cells are tied together via
A
tight junctions
20
Q
What is the most abundant form of epithelial cells, that plays a role in digestion and absorption?
A
Absorptive ENTEROcytes
21
Q
What cells release regulatory peptides and amines?
A
Enteroendocrine cells (EEC’s)
22
Q
What specialized mucosal cells produce H+ protons?
A
Gastric mucosal cells
23
Q
What cells produce mucin?
A
Mucin-producing cells. DUH!
24
Q
What type of epithelial cells line the esophagus?
A
Squamous
25
What type of epithelial cells line the intestine, and specialize in absorption?
Columnar
26
What theory explains the short lifespan of villi epithelial cells?
Since there is an increased risk of mutation, better to get rid of them
27
Where are proliferative cells located in the intestinal villi?
Cryptes - zone of intestinal stem cells
28
What is considered the "unit of absorption"?
A. Vilus
B. Microvillus
A. Villus
29
What composes the "brush border"?
A. Villi
B. Microvilli
B. Microvilli
30
Mucosal folds, villi, and microvilli increase SA of intestine by
600 fold
31
Name a disease that decreases SA of absorptive intestinal surface
Celiac's disease
32
Microvillar membrane (MM) has a high % of
Cholesterol and sphingolipids
33
What mucosal layer is between the epithelium and the muscularis mucosae?
Lamina propria
34
What mucosal layer contains lymph vessels, nerves, nodes, and capillaries?
Lamina propria
35
Meissner's plexus is also known as
The submucosal plexus
36
What 2 layers sandwich the submucosal (Meissner's) plexus?
Submucosa & Circular smooth muscle
37
What 2 layers sandwich the Myenteric plexus?
Circular smooth muscle & longitudinal smooth muscle
38
What 2 plexi compose the little brain of gut?
Submucosal (Meissner's) and the myenteric plexus
39
Which muscle layer adjusts the diameter of the tract?
Circular smooth muscle
40
What layers compose the muscular externa
Circular and longitudinal muscle layer
41
Ever hear of Auerbach's plexus?
aka myenteric plexus
42
What secretes viscous fluids to reduce friction of the GI tract?
Serosa
43
Name the 3 principle regulatory systems of GI
1. Neural
2. Endocrine
3. Paracrine
44
What's the post-prandial period?
Intense GI activity after meal
45
What are the sensor cells of the GI system?
Entero-Endocrine cells (EEC)
46
What 2 types of EEC's are there?
Open (for SENSING) and closed.
The apex of OPEN EEC's are in contact with the lumen, and the base secrete hormones into the blood stream.
47
Are ECL cells open or closed type EEC?
Closed
48
G cells are EEC's that secrete
gastrin
49
gastrin from G-cells stimulates secretion by
ECL and parietal cells
50
T/F: a signal that travels from gut to CNS brain is PARACRINE.
False. Endocrine. Paracrine is not transported via circulation
51
What's an ECL?
enterochromaffine-like cell. It's a specialized EEC (closed) that regulates contractile activity of smooth muscle in GI.
52
Name a paracrine signal secreted by ECL
histamine
53
5-HT (seratonin) is paracrine or endocrine, in today's lecture?
Paracrine
54
Cholecystokinin is both
Paracrine - acts on local nerves
| Autocrine - acts on pancreas
55
Dietary protein and lipid enters DUODENUM, promoting secretion of
Cholecystokinin
56
What receptor binds cholecystokinin?
CCK1
57
Allergen in gluten
gliadin
58
Secretin is para or endo
BOTH
59
I-cells of duodenum secrete
CCK
60
S-cells of duodenum secrete
secretin
61
K-cells of duodenum and jejunum secrete
GIP (gluco-insulinotropic peptide)
62
K-cells secrete GIP in response to
fatty acid and glucose
63
S-cells secrete secretin in response to
H+ in duodenum
64
I-cells secrete CCK in response to
FA and hydrolyze protein
65
G-cells secrete gastrin in response to
small peptides and AA's
66
Gastrin ultimately promotes 3 things:
H+ secretion from parietal cells
Histamine secretion from ECL cells
Growth of gastric mucosa
67
CCK promotes
DECREASED gastric emptying and H+ secretion.
DECREASED food intake.
INCREASED pancreatic enzyme secretion
INCREASED contraction of gallbladder
("HOLD ON! Let me process all this food!"
68
Secretin promotes
Secretion of H20 and HCO3- from pancreatic duct
69
GIP promotes
insulin secretion from pancreas
70
PYY is para or endo?
Both
71
GLP1/2 is para or endo?
Both
72
Name 4 hormones that are both para and endo:
1. CCK
2. Secretin
3. PYY
4. GLP1/2
73
L-cells from intestine secrete
PYY and GLP-1/2
74
PYY secretion is stimulated by
FA, gluc, hydrolyzed protein
75
GLP-1/2 secretion is stimulated by
same as PYY
FA, gluc, hydrolyzed protein
76
PYY promotes
DECREASED (ALL):
1. gastric emptying and H+ secretion
2. pancreatic secretion
3. intestinal motility
4. food intake
77
GLP-1/2 promotes
glc homeostasis
| Increased epithelial cell proliferation
78
The gut brain is extrinsic or intrinsic NS?
intrinsic ns
79
T/F: salivary gland secretion is controlled by CNX
False
80
What are the 2 divisions of the EXTRINSIC neural regulation of GI
Parasympathetic and sympathetic
81
What innervates the esophagus, stomach, 1st part of the intestine, cecum, and proximal colon?
CN X (extrinsic parasymp. innervation)
82
What innervates distal colon and anorectal region?
Pelvic nerves (extrinsic parasymp. innervation)
83
What % of CNX is afferent? Efferent?
75% afferent. 25% efferent.
84
What type of reflexes in CNX use both afferents and efferents at once?
"Vagovagal" reflexes
85
Sympathetics generally _______ GI smooth muscle function?
inhibit
86
EXCEPTION: sympathetics _______ sphincter muscles
constrict
87
Parasympathetic ________ fibers are longer and synapse ________ the GI tract
preganglionic, outside
88
Name 3 sympathetic ganglia that serve the GI tract
1. Celiac
2. Superior mesenteric
3. Inferior mesenteric
89
```
Post-ganglionic nerves that contract GI sphincters release:
A. ACh
B. Substance P
C. VIP
D. Norepinephrine
```
D. Norepinephrine (adrenergic)
We're talking sympathetics here.
90
50% of these fibers are afferent, while 50% are efferent.
Sympathetic
91
Challenge: what ganglion relays sympathetic innervation to the esophagus?
Superior cervical ganglion
92
Which plexus lies between longitudinal and circular muscle layers?
Myenteric plexus
93
T/F: ENS needs external innervation to react.
False. It can act autonomously. Thus little brain of gut.
94
ENS can release:
Neurotransmitters, neuromodulators
95
Two types of GI contraction
Phasic (periodic) or tonic (sustained tone)
96
Esophagus, gastric antrum, and small intestine display what kind of contraction?
Phasic
97
upper (orad) stomach, lower esophageal, ileocecal, and internal anal sphincters display what kind of contraction?
Tonic
98
Slow waves are characterized by
Oscillating depol and repol
Don't typically hit threshold
AP may occur on top of slow wave
99
Slow wave frequency is 3/min in
stomach
100
Slow wave frequency is 12/min in
duodenum
101
Where do slow waves originate?
Interstitial cells of Cajal (ICC) - pacemaker cells of GI between longitudinal and circular muscle layers of muscular externa
102
T/F: sub threshold slow waves produce contraction
TRUE, though weak. Tonic contractions are composed of sub-threshold waves
103
What kind of contractions rely on AP that occur on top of slow waves?
Phasic contractions
104
Are individual AP's followed by separate muscular twitches in GI smooth muscle?
No! They summate into one long contraction.
105
No forward movement of bolus for mixing.
Segmental contraction
106
Orad to caudad contractions to propel chyme
Peristaltic contraction
107
What NT is required for orad contraction
ACh and sP
108
What NT is required for caudad relaxation
VIP and NO
