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PHYSL 210 Part 3 > Gastrointestinal Lecture 3 Part 2 Physiology of GI secretions > Flashcards

Gastrointestinal Lecture 3 Part 2 Physiology of GI secretions Flashcards

1
Q

In order to maximize absorption the digestive system has to _______?

A

secrete

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2
Q

Approximately how much do we consume?

A
  • Daily fluid intake = ~1.2 L
  • daily solids intake = ~500-800 g
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3
Q

Daily volume of secretions

A

~7 L

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4
Q

What happens to the majority of fluids, solids and secretions?

A

Majority absorbed back into the body, only small volume lost in the feces

  • ~ 100 mL fluid and 50-100 g solids leave through feces
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5
Q

Origins of gastrointestinal secretions>

A

most come from the accessory glands

  • Salivary glands
  • Liver
  • Gallbladder
  • Pancreas (exocrine)

and small intestine

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6
Q

Daily saliva production approx.

A

approx. 1500 mL

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7
Q

saliva components

A
  • water (98%)
  • electrolytes
  • mucus
  • enzymes
  • immune modulators
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8
Q

What saliva components provide lubrication?

A
  • water (98%)
  • electrolytes
  • mucus
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9
Q

Purpose of saliva lubrication

A

protects oral cavity and makes food easier to swallow

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10
Q

immune modulators of saliva

A

antibacterial antibodies, WBCs, etc.

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11
Q

Which phase of GI regulation does saliva secretion play a role in?

A

Primarily cephalic phase responses

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12
Q

Which nervous system does saliva secretion usually occur?

A

autonomic nervous system

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13
Q

saliva secretion of PNS and SNS

A
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14
Q

saliva secretion when anxious

A

Anxiety → increased sympathetic drive → decreased salivation/thickening

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15
Q

Saliva secretion with appetizing food

A

Appetizing food

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16
Q

Daily production of gastric secretions?

A

approx. 2000 mL

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17
Q

Gastric secretions components

A
  • mucus
  • HCl
  • enzymes
  • hormones
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18
Q

mucus from gastric secretions

A

Lubricates and protects stomach lining

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19
Q

HCl from gastric secretions

A
  • Solubilizes some food
  • kills ingested microbes
  • cleaves pepsinogen*
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20
Q

enzymes from gastric secretions

A

Pepsinogen → pepsin, cleaves proteins OTHERS

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21
Q

hormones from gastric secretions

A

Not secreted into stomach, but are secreted from stomach into bloodstream in response to stomach contents

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22
Q

Origins of gastric secretions

A

cells of the gastric glands → Exocrine glands within the wall of the stomach lining

  • mucus → surface mucous cells
  • HCl → parietal cells
  • enzymes → chief cells (pepsinogen)
  • hormones → ECL cell (Enterochromaffin-like cell) (histamine)
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23
Q

What GI regulation phase egulates HCl production from gastric secretion?

A

Mediated by cephalic and gastric phase responses

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24
Q

what part of gastric secretes HCl?

A

Parietal cells (also known as oxyntic cells) are epithelial cells in the stomach that secrete hydrochloric acid (HCl) and intrinsic factor. These cells are located in the gastric glands found in the lining of the fundus and body regions of the stomach.

25
How do parietal cells release HCl?
Signal received and second message may increase secretion by having vesicles with the H+/K+ ATPase pump dock with the membrane and so pumps gets expressed on the cell surface and pumps acid into lumen of the stomach.
26
What detects aa to be present for release of HCl?
G-cells (antrum) Detect the aa in lumen suggesting presence of a protein rick meal, and produce gastric which will enter circulation and signal to ECL cells which in turn will secrete histamine which will signal parietal cells to increase HCl production. Gastric can also work directly on parietal cells
27
What stimulates and inhibits HCl production?
* Stimulated by Gastrin, histamine, and ACh * Inhibited by somatostatin
28
WHat happened that was opposite of fletcherism?
29
Daily production of pancreatic secretions
approx. 1500 mL
30
Pancreatic secretions sometimes referred to as \_\_\_\_\_?
“pancreatic juice”
31
Pancreatic secretion components
* Bicarbonate (HC03-) * enzymes
32
Bicarbonate (HC03-) from pancreatic secretions
buffer acts to neutralize the acidity of chyme
33
anatomic considerations for pancreatic secretions
* exocrine cells & duct cells → produce juice and then travel down to duodenum * sphincter to help control secretions * pancreas and gallbladder secretion are mixed and secreted at the same time
34
GI regulation phase for pancreatic secretions
*Primarily intestinal phase control, but also cephalic and gastric phase inputs*
35
*Regulation of HCO3- pancreatic secretion*
36
Regulation of enzyme pancreatic secretion
37
Daily production of bile
approx. 500 mL
38
Where is biliary secretion produced?
Continuously produced by the liver (dilute bile)
39
Where is biliary secretions stored and concentrated?
stored and concentrated in the gallbladder
40
Bile components
* water (~97%) * Bile salts (\<1%) * Bilirubin (\<1%) * Fats (\<1%)
41
Bile salts in biliary secretions
solubilize water-insoluble fats
42
Bilirubin in biliary secretions
Hemoglobin breakdown product; excreted
43
fats in biliary secretions
Includes cholesterol and lecithin (phospholipids); aid digestion
44
What happens when the sphincter of Oddi is closed?
The gallbladder also fills up when the sphincter of Oddi is closed, preventing its secretion into the duodenum
45
How is bile concentrated?
While in the gallbladder, water and NaCl are absorbed from it – making it more concentrated
46
How does the gallbladder respond to CCK?
In response to CCK, the gallbladder contracts and the sphincter of Oddi relaxes, allowing bile to be secreted into the duodenum
47
GI regulation phase of bile secretion
*Primarily an intestinal phase response*
48
Regulation of bile secretion
49
Daily intestinal secretions
approx. 1500 mL
50
intestinal secretion components
* water/electrolytes * mucus * enzymes
51
water/ electrolytes in intestinal secretions
Maintains fluidity of intestinal contents
52
mucus in intestinal secretions
Lubrication and protection of lining of epthelium
53
enzymes in intestinal secretions
aid digestion
54
what primarly drives secretion of water into the small intestine?
osmosis
55
Where does water secretion into SI occur?
Base of intestinal villi surrounded by invaginations of the intestinal wall called the crypts of Lieberkuhn * water follows the ions
56
*In general, villi are primarily \_\_\_\_\_\_\_\_, whereas crypts are \_\_\_\_\_\_\_\_\_*
absorptive, secretory
57
What can change water osmolarity?
Chyme leaving the stomach and entering the duodenum can change its osmolarity * A high concentration of solutes in chyme creates a hypertonic environment * Osmotic forces drive water from the plasma into the intestinal lumen
58
Approximately how much of total secretions are absorbed?
~6700 mL

PHYSL 210 Part 3 (46 decks)

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