Lecture 25: Secretion Flashcards
(95 cards)
1
Q
What are endocrine secretions produced by?
A
Epithelia
2
Q
What are the components of exocrine secretions?
3
A
- Mucus
- Electrolyte solution
- Digestive enzymes
3
Q
What are the roles of mucus?
3
A
- Protection
- Lubrication
- Aid in mechanical digestion
4
Q
What are the roles of an electrolyte solution?
2
A
- Dilute food
- Provide optimal pH for enzymes
5
Q
What are electrolyte solutions essential for?
A
Chemical digestion of food
6
Q
What do digestive enzymes aid in alongside chemical digestion?
A
Absorption
7
Q
What are digestive enzymes essential for?
A
Chemical digestion of food
8
Q
How many salivary glands are there?
A
3 pairs
9
Q
How much fluid do salivary glands produce a day?
A
1.5L
10
Q
What is the basal rate of secretion for the salivary glands?
A
0.3 ml/min
11
Q
What is the stimulated rate of secretion for the salivary glands?
A
1.5 ml/min
12
Q
What is the composition of salivary secretion?
A
- Mucus
- Dilute solution of NaHCO3/NaCl
- Digestive enzymes
13
Q
What is the role of mucus in salivary secretions?
A
Lubrication
14
Q
What is the role of a dilute solution of NaHCO3/NaCl in salivary secretions?
A
- Dilute food
- Provide optimal pH for digestive enzymes
15
Q
What digestive enzymes are present in salivary secretions?
2
A
- Lingual lipase
- Alpha-amylase
16
Q
What proportion of total salivary secretion is produced by the sublingual glands?
A
5%
17
Q
What proportion of total salivary secretion is produced by the submandibular glands?
A
70%
18
Q
What proportion of total salivary secretion is produced by the parotid glands?
A
25%
19
Q
Is salivary secretion essential?
A
No
20
Q
What does salivary secretion aid in?
3
A
- Talking
- Chewing
- Swallowing
21
Q
How does salivary secretion aid in hygiene?
2
A
- Irrigation
- Dry mouth (from reduced or absent saliva)
22
Q
What do lingual lipase help to begin digestion of?
A
Fats
23
Q
What do Alpha-amylase help to begin the digestion of?
A
Starch
24
Q
What are conscious nervous stimulations for salivary secretion?
(2)
A
- Thought/smell/sight of food
- Presence of food in the mouth
25
How does the parasympathetic nervous system influence salivary secretions?
It stimulates secretion of copious quantities of fluid
26
How does the sympathetic nervous system influence salivary secretions?
It stimulates small volumes of viscous fluid to be produced
27
What volume of gastric secretion is produced in a day?
2-3L
28
What is the rate of gastric secretion between meals?
15-30 ml/h
29
When eating what happens to gastric secretions from Mucous/Parietal/Chief cells?
They are superimposed on the basal rate
30
What is the function of mucus as a gastric secretion?
| 2
- Protection from abrasion
| - Protection from acid
31
What is the function of intrinsic factor as a gastric secretion?
The absorption of vitamin B12 in the small intestine
32
What is pepsinogen as a gastric secretion?
The inactive form of pepsin
33
What is pepsin?
A gastric proteolytic enzyme that starts the digestion of proteins
34
How is pepsinogen converted to its active form?
By acid
35
What are the functions of gastric acid as a gastric secretion?
(5)
- Dilute food
- Denature proteins
- Activate pepsinogen
- Create optimum pH for pepsin
- Protection
36
What do mucous cells contribute towards gastric secretion?
Mucus
37
What do parietal cells contribute towards gastric secretion?
| 2
- HCl
| - Intrinsic factor
38
What do chief cells contribute towards gastric secretion?
Pepsinogen
39
Where is the source of acid by parietal cells from?
The dissociation of of H2CO3, after H2O and CO2 react, giving HCO3- and H+
40
Where is the H-K ATPase found?
In the apical membrane of parietal cells
41
What does the H-K ATPase in the parietal cell do?
Pumps hydrogen ions into the lumen of the stomach in exchange for K ions
42
How does the anion counter transporter in the serosal membrane of the parietal cell work?
It ejects bicarbonate ions into the interstitial fluid in exchange for Cl- ions into the cell
43
Once in the parietal cell what do Cl- ions do?
Diffuse across the cell and enter the lumen of the stomach via a channel in the apical membrane
44
Gastric secretion is co-ordinated with what?
Eating and the arrival of food
45
What are the 3 phases of gastric secretion?
- Cephalic phase
- Gastric phase
- Intestinal phase
46
What controls the cephalic phase of secretion?
The head
47
What % of secretion from a meal is associated with the cephalic phase?
20%
48
What does the parasympathetic nervous system act through during the cephalic phase of secretion?
The enteric nervous system
49
What does the parasympathetic nervous system cause via the enteric nervous system during the cephalic phase of secretion?
- Parietal/chief/goblet cells to secret
| - Secretion of the hormone gastrin
50
What does gastrin stimulate?
| 2
- Parietal cells
| - Chief cells
51
What % of secretion from a meal is associated with the gastric phase?
70%
52
What controls the gastric phase of secretion?
The stomach
53
What does the gastric phase of secretion ensure?
There is sufficient secretion to handle ingested food
54
What are stimuli in the stomach during the gastric phase of secretion?
(3)
- Stretch/distension of the stomach wall
- Products of digestion are present
- Elevated pH
55
What is the local nervous reflex that controls gastric secretion?
The enteric nervous system
56
What is the external nervous reflex that controls gastric secretion?
Parasympathetic nervous system
57
What does nervous/hormonal regulation stimulate during gastric secretion?
- More secretion
| - Motility
58
What does gastrin do during the gastric phase of secretion?
Further stimulates secretion and motility
59
What % of secretion from a meal is associated with the intestinal phase?
10%
60
What regulates the intestinal phase of secretion?
The small intestine
61
The intestinal phase of secretion controls what?
Delivery of substance to the duodenum
62
What are stimuli for the intestinal phase of secretion?
| 2
- Distension of the duodenum
| - Arrival of acid chyme/lipids/carbohydrates
63
What hormones regulate gastric secretion?
| 3
- GIP
- CCK
- Secretin
64
What nerve regulates the intestinal phase of secretion?
The enterogastric reflex
65
What does the enterogastric reflex and GIP,CCK, Secretin hormones do during the intestinal phase of gastric secretion?
Both inhibit secretion and motility
66
What kind of organ is the liver?
An endocrine and exocrine organ
67
What is the volume of pancreatic secretion a day?
1-1.5L
68
What are the 2 main components of pancreatic secretion?
- Enzymes
| - Alkaline fluid
69
What cells in the pancreas produces enzymes?
Acinar cells
70
What are enzymes produced in the pancreas important for?
Chemical digestion
71
What produces alkaline fluid in the pancreas?
Duct cells
72
What is alkaline fluid produced in the pancreas important for?
(2)
- Neutralising acid
| - Providing the optimum pH for enzymes
73
The pancreas is the most important source of what?
Digestive enzymes
74
What stimulates the secretion of digestive enzymes by acinar cells?
Cholecystokinin (CCK)
75
What is the function of pancreatic enzymes?
Luminal chemical digestion of food
76
Proteolytic enzymes are secreted as what in the duodenum?
Inactive precursors
77
What is the precursor to trypsin?
Trypsinogen
78
What is the precursor to chymotrypsin?
Chymotrypsinogen
79
What is the precursor to carboxypeptidase?
Procarboxypeptidase
80
In the small intestine what does activation of enzymes involve?
Enterokinase
81
What is enterokinse bound to?
The duodenal membrane
82
What does enterokinase do?
Converts trypsinogen to trypsin
83
What does trypsin do?
Converts other enzymes to their active form
84
What is secretion of alkaline fluid stimulated by?
Secretin
85
What is the secretion of secretin stimulated by?
Arrival of acid chyme in the duodenum
86
What does alkaline fluid do?
Neutralises acid chyme that is delivered from the stomach
87
What is produced in Billary secretions?
| 2
- Bile salts
| - HCO3-
88
What is the role of bile salts?
Fat digestion
89
What is bile secreted constantly by?
The liver
89
Where is bile stored and concentrated?
In the gallbladder
89
When is bile delivered to the duodenum?
With the arrival of food
90
What % of bile is reabsorbed and where is it reabsorbed?
95% is reabsorbed in the ileum
91
What stimulates the release of bile?
CCK
92
What is bile transported back to the liver in?
Enterohepatic circulation
93
What does the small intestine secretion contain?
| 3
- Mucus
- Isosmotic fluid
- Digestive enzymes
