Lecture 20: Secretions from Salivary Glands and Stomach Flashcards
1
Q
What triggers the cephalic phase
A
Anticipation of food
2
Q
Cephalic phase is activated due to activation of ___efferents
A
PNS
3
Q
What does PNS activity during cephalic phase result in
A
Increased secretion of saliva, gastric acid, gastrin and pancreatic enzymes
4
Q
The cephalic reflex serves to ___ the GI tract
A
Prepare
5
Q
What are the 3 phases of salivary and gastric secretion
A
- Cephalic
- Gastric
- Intestinal phase
6
Q
What stimulates the gastric phase of salivary and gastric secretions
A
Mechanical stimulation of oral cavity and stomach
7
Q
What stimulates the intestinal phase of gastric secretion
A
Regulation of stomach emptying and digestion/absorption in small intestine
8
Q
What stimulates release of HCl in the cephalic phase
A
Vagus—> parietal
Vagus—> gastrin—> parietal
9
Q
What % of HCl secretion occurs in cephalic phase
A
20%
10
Q
What triggers HCl secretion in gastric phase
A
- Vagus—> parietal
- Vagus—> gastrin—> parietal
- Local reflex—> gastrin—> parietal
- Gastrin—> parietal
- Gastrin—> ECL—> histamine—> parietal
11
Q
What inhibits the release of HCl in the gastric phase
A
PH <2 in stomach will trigger release of somatostatin which will inhibit parietal cells and decrease gastric acid
12
Q
What % of HCl is secreted in gastric phase
A
70%
13
Q
What triggers HCl release in intestinal phase
A
- Intestinal G cells activated
14
Q
What inhibits HCl release in intestinal phase
A
- Low pH in duodenum activates somatostatin to inhibit parietal cells and decrease gastric acid
- Block G cells—> decrease gastrin
15
Q
What % of HCl is secreted in intestinal phase
A
10%
16
Q
What 4 glands produce saliva
A
Parotid, mandibular, lingual, and baccalaureate
17
Q
In cattle saliva is a major source of what
A
Water and bicarbonate to the rumen
18
Q
What is saliva composed of
A
Water, proteins, electrolytes and urea (ruminants)
19
Q
What are some functions of saliva
A
- Stimulate taste buds
- Food lubrication
- Keeps mouth clean
- Contains lysozymes, buffer and antitoxic proteins
20
Q
Salivary glands are ___glands
A
Acinar
21
Q
What is the secretory unit of salivary glands
A
Acini
22
Q
Fluid is secreted into the lumen of the acini and is modified through what
A
Intercalated and striated ducts
23
Q
All salivary glands are composed of multiple ___that drain into ___ before being secreted into ___cavity
A
Acini, collecting ducts, buccal cavity
24
Q
What is the salivary enzyme responsible for breaking down starch
A
Ptyalin (alpha-amylase)
25
What is the ideal pH in dogs, cats and pigs for ptyalin/alpha-amylase
6-7
26
What is mucin
Lubricant that facilitates swallowing and protects buccal surfaces
27
What ions are reabsorbed and secreted in salivary glands
Reabsorbed: Na+ and Cl-
Secreted: K+ and HCO3-
28
What is a salivary mucocele
Painless swelling in the neck or oral cavity that is a collection of saliva as a result of a damaged salivary gland or duct
29
__osmotic secretion by acini cells and selected reabsorption by duct cells creates a ___saliva
Iso-osmotic, hypotonic
30
What is the tonicity of normal saliva
Hypotonic
31
Acinar cells release ___ and ___ via exocytosis and secrete ___, ___ and ___
Proteins and mucous
Chloride, bicarbonate, and potassium
32
Salivary duct cells reabsorb __ and ___
Na+ and Cl-
33
What can not pass through tight junctions in salivary glands and what is the result
Tight junctions are impermeable to water, therefore creating the hypotonic saliva
34
What determines salivary osmolarity
Flow rate
35
Saliva is hypotonic at __salivary flow rates
Low
36
Saliva is isotonic at __salivary flow rates. And why?
High because there is not enough time to reabsorb Na+, Cl- and HCO3-
37
The pH ___ when salivary secretion rate increases
Increases
38
What salivary gland consists of just serous cells that provide proteins to saliva
Parotid gland
39
What salivary glands consist of a mixture of serous and mucous cells
Sublingual and submandibular
40
Ptyalin (alpha-amylase) hydrolyzes starch to what
Maltose
41
What enzyme is frequently present in young animals on a milk diet but less in mature animals
Lingual lipase
42
What does lingual lipase do
Hydrolysis of triglycerides into diacylglyceride and free fatty acids
43
In ruminants and other herbivores saliva contains ___ and ___
Lysozymes and antitoxic proteins
44
What is the purpose of lysozymes in ruminants and other herbivore saliva
Antibacterial effect- breaks beta 1-4 glycosidic bond between N-acetylmuramic acid and N-acetylglucosamine in peptidogylcan which is the major bacterial cell wall polymer
45
The loss of peptidoglycan via salivary lysozymes results in ___ in a ___environment
Rapid cell lysis in a hypo-osmotic environment
46
What are tannins
Plants defense mechanism as they provide a bitter taste
47
What are some negative effects of tannins
1. Decrease food intake
2. Reduce ruminal protein digestion
3. Inhibit digestive enzymes
4. Overall negative effect on nutrient absorption in SI
48
How do ruminants and other herbivores combat tannins that are present in their natural diet
Parotid gland produces proline-rich proteins which bind and neutralize tannins
49
Do deers or cattle have larger parotid glands and why
Deer as their diet consists of more tannins
50
How does saliva buffer rumen fluid
Bicarbonate
51
Why does the saliva need to buffer ruminal fluid
Microbial activity in the rumen is producing VFA therefore bicarbonate production will control pH
52
What are the 4 major components of gastric juce
1. HCl
2. Pepsinogen
3. Mucus
4. Intrinsic factor
53
What is the purpose of HCl
Decrease pH of stomach, activate pepsinogen, aids in protein digestion, kills bacteria
54
What is the purpose of pepsinogen and what is the active form
Pepsin is active form that digests proteins
55
What is the purpose of mucus secretion
Protect the gastric mucosa from acidic actions of HCl
56
What is the purpose of intrinsic factor
Necessary for absorption of Vitamin B12 in lieum
57
What activates pepsinogen
HCl
58
What species have a glandular stomach
Dogs and cats
59
What species have a non-glandular and glandular stomach
Horses
60
Which portion of the stomach contains chief cells, parietal cells, and enteroendocrine cells
Glandular
61
What do chief cells do
Pepsinogen—> pepsin
62
What do parietal cells do
Secrete HCl
63
What do surface mucous cells do
Protect against acid and mechanical damage
64
What do mucous neck cells do
Serve as stem/progenitor cells
65
What do D cells, G cells and ECL cells do
Produce hormones that regulate gastric secretion and motility
66
How do parietal cells form HCl
ATP dependent protein pump excretes H+ and Cl- enters lumen down electrical gradient
67
Cl- is exchanged for ___ on basolateral membrane producing an alkaline tide
Bicarbonate
68
What catalyzes bicarbonate from OH- and CO2
Carbonahydrase
69
When does an alkaline tide occur
After meal
70
During alkaline tide the ___ blood is more alkaline than ___ blood
Venous, arterial
71
What 3 receptors stimulate HCl production
M3, CCK, and H2
72
How does nervous system control HCl secretion
PNS and CNS activates parietal cells via M3 receptors
73
How does the endocrine system control HCl secretion
1. Gastrin is secreted from G cells and binds to CCK-B receptors
2. Gastrin stimulates histamine release which binds to H2 receptors
74
What receptor does gastrin bind to do secrete HCl
CCK-B
75
What cell secretes histamine that then binds to __receptors
ECL cells, H2 receptors
76
Gastrin is released in response to what 3 things
1. Small peptides and AA in stomach
2. Distention of stomach
3. Vagal stimulation
77
What two intracellular mechanisms mediate activation of H/K ATPase
1. PNS (ACh) and gastrin released onto M3 and CCK-B receptors stimulate IP3/DAG which increase CA2+
2. Histamine binds H2 receptors and increase cAMP
78
___ and ___ stimulate the proton pump
Ca2+ and cAMP
79
What are the 3 pathways and 2 intracellular mechanisms to secrete/increase HCl
3 pathways:
1. Gastrin binds CCK-B
2. ACh binds M3
3. Histamine binds H2
2 intracellular mechanisms:
1. Gastrin and ACh increase Ca2+
2. histamine increases cAMP
Ca2+ and cAMP stimulate proton pump, provides H+ for HCl
80
___ and ___ down regulate HCl production
Somatostatin and prostaglandins
81
How does somatostatin down regulate HCl
Inhibits cAMP
82
How do prostaglandins down regulate HCl
Inhibit G cells which secretes gastrin and ECL cell which secretes histamine
83
What 3 components make up the gastric mucosal barrier
1. Compact epithelial cell lining
2. Gastric mucus covering
3. Bicarbonate
84
What are some causes of gastric ulcers
1. Defect in mucosal barrier
2. Hyper secretion of HCl
3. Helicobacter pylori
85
What are some therapeutic approaches to treating gastric ulcers (broad approaches)
1. Reduce acid production (vagotomy or pharmacologically via proton pump inhibitors)
2. Stimulate re-epithelialzation
3. Antibiotics for Helicobacter
86
What specific treatments can be done to control ACh secretion to decrease HCl secretion
1. Vagotomy
2. Atropine
87
What specific treatment can be done to reduce histamine secretion to control HCl secretion
Cimetidine
88
What specific treatment can be done to reduce activity of proton pump to reduce HCl secretion
Omeprazole
89
Pepsinogen is produced and secreted by ___
Chief cells
90
Pepsinogen is stored in what
Zymogen granules
91
Why is pepsin released as proenezyme
To prevent auto digestion
92
What is the function of pepsin
Cleave proteins to peptides
93
How is pepsinogen stimulated
1. PNS (vagus)
2. Gastrin
3. Secretin from duodenum
