Digestion 3: Secretion Flashcards
1
Q
secretion
A
release of materials from cells that line the lumen of the GI
2
Q
Where do secretion products end up?
A
- ISF: paracine action
- blood stream
- lumen of GI
3
Q
where can goblet cells be found?
A
small & large intestines
4
Q
which cells secrete mucus in the stomach?
A
Foveolar cells
5
Q
largest endocrine system in the body is…
A
enteroendocrine cells (EEC) - cells that secrete hormones in the GI
6
Q
there are ___ types of EECs, and ___ types of GI hormones
A
18-20;
18-20
7
Q
EEC function is influenced by…
A
- GI contents
- ANS
8
Q
describe EECs
A
single cells scattered throughout the length of the GI; secrete hormones
9
Q
Goblet cells refer to…
A
mucus secreting cells that is shaped like a goblet (more like a comma “,”)
10
Q
we take in about __ L of fluid a day, but there is __ L of fluid entering the GI tract in total due to…
A
2L;
7L;
secretions from the liver, pancreas, etc.
11
Q
how much is secreted & absorbed in toe GI tract per day?
A
9 L total input
12
Q
secretions into the GI include…
A
- saliva
- bile
- gastric secretions
- pancreatic secretions
- intestinal secretions
13
Q
secretions into the GI = ___x the volume of ____
A
2x;
plasma
14
Q
how are fluids removed from the GI?
A
- absorption: small (main effect) & large intestines
- excretion: feces (small effect)
15
Q
How is SA in the GI increased?
A
1) folds (3x)
2) hills & valleys (10x)
3) microscopic protrusions (20x)
16
Q
SA increase method that can be found in the stomach
A
folds & valleys (no hills!)
17
Q
rugae
A
folds on the inside of your stomach to allow expansion
18
Q
valleys in the stomach =
A
gastric pits
19
Q
gastric pits = opening to…
A
gastric gland
20
Q
entrance to gastric glands are within the ___
A
rugae
21
Q
anatomy: upper curve of the stomach
A
fundus
22
Q
anatomy: antrum
A
nearly closed cavity located immediately before the stomach outlet. It is lined by mucosa and it does not produce acid
23
Q
hills & valleys =
A
hills = villi valleys = crypts
24
Q
SA increase methods that can be found in the small intestines
A
- folds (plica or valvulae conniventes)
- hills (villi)
- valleys (crypts of Lieberkuhn)
- microscopic protrusions (microvilli)
25
differences between rugae and plica
plica is in small intestines, and is permanent
26
Crypts of Lieberkuhn extend to...
into the mucosa of the small & large intestines
27
SA increase in large intestines
1) folds (haustra)
| 2) valleys (crypts of Lieberkuhn) - no hills!
28
haustration
when food pushes the haustra outwards, creating bulges & increased SA
29
what causes haustra in the large intestines?
lack of resistance underlying the circular muscle in the large intestine during segmentation
30
what can haustration be classified as?
motility pattern
31
microvilli is supported by...
| why?
microfilaments;
| allow microvilli to waves around to increase flow in small intestines
32
celiac disease
- immune disease where patients allergic to gluten
| - microvilli are shorter → less SA → less absorption of nutrients → malnutrition
33
where are goblet cells found in the small intestines?
between the epithelial cells making up the villi
34
salivary gland is made up of...
1) parotid gland
2) sublingual gland
3) submandibular gland
35
saliva contains....
- water
- electrolytes
- bicarb
- mucus
- IgA antibody
- lysozyme
- defensins
- enzymes (salivary amylase & lingual lipase)
36
function of saliva
- protection
- lubrication (try to prevent secondary peristalsis)
- taste
- digestion
37
defensins
antimicrobial proteins that break bac't cell walls
38
salivation is controlled by...
CNS (salivary center in medulla)
39
conditioned response to salivation vs. unconditioned response
unconditioned: mechanoreceptors & chemoreceptors sense food in the mouth
conditioned response: see, smell, etc. becomes associated with taste of food
40
conditioned response to salivation
sight/smell of food → cerebral cortex → salivary center (medulla) → salivation
41
salivary center is at...
pons / medulla
42
effect on salivation: PNS vs. SNS
PNS: lots of watery saliva
SNS: small amount of thick saliva
43
PNS control on salivation (process)
salivary center → CN VII, IX → salivary glands → watery saliva
44
SNS control on salivation (proess)
thoracic spinal cord → pelvic nerves → superior cervical ganglion → post-ganglion fibres → salivary glands → thick saliva
45
what secretory cells are found in the stomach (order from lumen → gastric pit → gastric gland)?
- mucous cells
- parietal cells
- chief cells
- enterochromaffin-like cells
- D cells
- G cells
46
mucous cells secrete...
- mucus
| - bicarb
47
parietal cells secrete...
- HCl
| - intrinsic factor
48
chief cells secrete...
- pepsinogen
| - gastric lipase
49
enterochromaffin-like cells secrete...
histamine
50
D cells secrete...
somatostatin
51
G cells secrete...
gastrin
52
physical layer of production in the stomach is ___, while chemical layer of production is ___
mucus;
| bicarb
53
Zollinger-Ellison syndrome
hyperacidic stomach that breaks down protective barriers and damages cells of the stomach
54
pH of stomach lumen
2
55
symptoms of ZE syndrome
- GERD
- nausea
- pain
- malnutrition
- heartburn
56
GERD
reflux of acidic chyme up the esophagus → dull chest pain
57
function of HCl in stomach
- kill bacteria
- denature protein
- activate pepsinogen
58
function of intrinsic factor
binds to vit B12 → proper absorption in ileum
59
vit B12 is also known as...
cobalamin
60
How does parietal cells secrete HCl?
1) water dissociates to H+ and OH-
2) H+ is pumped into lumen by H/K-ATPase
3) OH- + CO2 → bicarb (catalyzed by CA)
4) bicarb leave on basolateral side using Cl/bicarb-exchanger
5) Cl- is pumped into lumen by Cl-transporter
6) Cl joins with H in lumen to form HCl
61
Alkaline tide
build up of bicarb in ISF of stomach (parietal cells), so blood leaving the stomach is very basic
62
how to activate pepsinogen?
- Acid in stomach
| - Pepsin (activates itself)
63
function of gastrin
- stimulates secretion of acid, histamine, pepsinogen, mucus
| - increase stomach motility & mass movements (gastrocolic reflex)
64
what stimulates release of gastrin?
peptides in the lumen of the stomach
65
G cells are mostly found in ___ region of the stomac
pyloric
66
2 ways in which gastrin can stimulate the release of HCl (and describe)
1) directly: gastrin → bloodstream → parietal cells → secrete HCl
2) indirectly: gastrin → bloodstream → enterochromaffin-like cells (ECL) → histamine → parietal cells → secrete HCl
67
gastrin is responsible for ___ reflex
gastrocolic
68
cause of ZE syndrome
hypersecretion of gastrin
| - gastrin secreting tumour in pancreas
69
which cells in the pancreas secrete things? where are they secreted into?
- acinar cells
- duct cells
secreted into pancreatic duct
70
what do acinar cells secrete?
- pancreatic amylase, lipase, nuclease, inactive protease
71
proteases secreted by acinar cells
- trypsinogen
- chymotrypsinogen
- procarboxypeptidase
- proelastase
72
duct cells secrete...
- bicarb
| - water
73
pancreatic secretions into the small intestines is controlled by...
sphincter of Oddi
74
How are pancreatic enzymes activated in the small intestines?
by enterokinase / enteropeptidase
75
enterokinase
enzymes embedded in brush border that is required for the activation of proteases secreted by the pancreas
76
how is bicarb secreted in the GI tract? (slide 20)
1) water + CO2 dissociate → bicarb + H (catalyzed by CA)
2) bicarb goes into lumen via bicarb/Cl-exchanger
3) H leaves the cell via NHE
4) NKCC transporter pumps stuff into lumen
5) Cl leaves cell via CFTR to lumen
6) Na leaves the cell to ISF via Na/K-ATPase
77
Why is the blood leaving the pancreas / small intestines acidic?
bicarb is secreted in lumen while H is secreted into ISF
| - this balances alkaline tide from stomach
78
CFTR
cystic fibrosis transmembrane regulator
79
how is water secreted in the GI tract?
- Na attracted to lumen because it's very negative from bicarb and Cl-
- water is attracted to solutes in lumen
- both transported to lumen via paracellular pathway
80
only way for Cl to exit in the lumen is...
CFTR
81
Why do people with cystic fibrosis have to ingest ____? Why?
pancreatic enzymes;
- defective CFTR channels
- no watery bicarb (only thick mucus from duct cells)
- mucus blocks pancreatic duct
- no enzymes can reach small intestines
- no digestion
82
bile is made up of...
- bile salts
- lecithin
- cholesterol
- bilirubin
- bicarb
83
where does bile come from?
- synthesized by liver
- diet
- secretions from duct cells
- remainders from body (e.g. bilirubin, cholesterol)
84
bile salt recycling =
enterohepatic circulation
85
bile salt recycling happens ___ x per day
5 - 15
86
define: enterohepatic circulation
cycling between the liver and small intestines
| - connected by hepatic portal vein
87
primary bile acids are synthesized by...
liver
88
secondary bile acids are syntheiszed by...
bacterial conversion in intestines
89
bile acid → bile salt
conjugation with glycine or taurine (amino acids)
90
difference between bile acid vs. bile salt
bile acid is lipophilic, so it wants to leave the lumen;
| bile salt is conjugated, so can be soluble in the lumen
91
process of bile salt recycling
1) liver makes primary bile acids
2) gets conjugated and enters small intestines
3) return to hepatic portal vein by...
- passive transport
- active transport
- bacteria mediated absorption (→ bile acids or continue → secondary bile acids)
4) goes back to liver
92
bacteria mediated absorption
convert bile salt → bile acids so it can easily cross epithelial membrane
convert the bile salt → bile acid → secondary bile acid → reabsorbed or lost in feces
93
fate of secondary bile acids
reabsorbed or lost in feces
94
secondary bile acids (specific names and fate)
| [MAYBE NOT ACCURATE]
- deoxycholic acid (reabsorbed)
| - lithocholic acid (lost)
95
what hormone is released by the stomach?
gastrin
96
what hormones are released from small intestines?
- secretin
- CCK
- GIP
- Motilin
- GLP-1
97
glucose-dependent insulintropic protein is secreted from...
K cells (mostly jejunum, some duodenum)
98
why is GIP secreted?
in response to mixed meal (glucose, fat, protein)
99
effect of GIP
- increase insulin
| - decrease acid
100
motilin is secreted by...
M cells
101
when is motilin secreted?
during fasting
102
function of motilin
regulates migrating motor complex (MMC)
103
secretin is secreted by...
S cells in duodenum
104
function of secretin
decrease acid in small intestines
- more pancreatic bicarb
- less gastric acid secretion
- less gastric emptying
105
CCK is secreted by...
I cells in duodenum and jejunum
106
CCK is secreted in response to...
fatty acids & AA in small intestines
107
CCK causes...
- contraction of gall bladder (more bile)
- increased release of pancreatic enzymes (increase small intestines)
- decreased gastric acid secretion & gastric emptying (slow stomach)
108
GLP-1 (glucagon-like peptide-1) is secreted by...
L cells of the ileum
109
GLP-1 is secreted in response to...
fatty acids & cabs in the small intestines
110
effects of GLP-1
- decreased gastric acid secretion & emptying (slows stomach)
- increased insulin & B-cell growth; decreased glucagon
111
GLP-1 causes feeling of...
satiation
