Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Digestion And Metabolism > GIT secretions 2 > Flashcards

GIT secretions 2 Flashcards

1
Q

What are functions of pancreatic secretions?

A

– Digestion
– Protection
• Neutralizes the acidity of the contents leaving the stomach
• Optimal pH for enzyme activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the composition of pancreatic secretions?

A

• Composition:
– Same Na+ and K+ as plasma - isotonic

– high HCO3- concentrations (alkaline)

– low Cl-

– Enzymes: lipase, amylase and proteases

– Composition depends on flow rate:
• Low flow rates: isotonic – mostly Na+ and Cl-
• High flow rates: isotonic – mostly Na+ and HCO3-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe pancreatic secretions

A

• Acinar cells: low volume, NaCl, enzymes

• Ductal cells: modifies; absorbing Cl-, secreting HCO3-
via Cl HCO3- exchanger

• Pancreatic ductal cells are permeable to water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Describe the secretion of Secretin

A

Secreted from S cells of the dupdenum

Inresponse to protons in duodenal lumen

Cquses increases bicarbonate secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Describe the secretion of CCK

A

Secreted from I cells of duodenum

In response to small peptides, amino acids, fatty acids in duodenal lumen

Causes increased enzyme secretion and potentiates bicarbonate secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Describe the secretion of ACh

A

Secreted from vagus terminalis

In response to protons, small peptides, amino acids, fatty acids

Causes increased enzyme secretion and potentiates bicarbonate secretiom

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are the modulators of pancreatic acinar secretion?

A
  • increases Cl secretion = -ve lumen
  • increases Na and H2O follow passively into the lumen
  • increases Exocytosis - release of zymogen granules into SI lumen

A rise in calcium conc. Triggers Acinar cell secretion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe ion transporter naming conventions

A

• final letter:
– C – co-transporter/symporter • moves ions in same direction
– E – exchanger/antiporter

• exchanges ions, i.e. moves them in opposite directions

• preceding letters: – N – sodium (Na+)
– H – proton (H+)
– B – bicarbonate (HCO3-) – K – potassium (K+)
– C – chloride (Cl-)
• e.g. NKCC is the sodium (N) potassium (K) chloride (C) co-transporter (C)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe bicarbonate secretion by ductal cells

A

HCO3-
– produced by carbonic anhydrase
– secretion via HCO3- Cl exchanger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe bicarbonate secretion by ductal cells

A

HCO3-
– produced by carbonic anhydrase
– secretion via HCO3- Cl exchanger

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe Cl- secretion by ductal cells of the pancreas

A

– cellular Cl- can diffuse passively back into lumen through CFTR channel
– NKCC transporter also provides cellular Cl-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Describe Na+ and H2O secretion in ductal cells of the pancreas

A

follow passively para-cellularly down electrochemical gradient

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Describe H+ secretion in pancreatic ductal cells

A

– formed with HCO in the cell

– exits across basolateral membrane via Na-H exchanger, entering bloodstream and neutralizing the alkaline tide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is the pancreatic two component model?

A

Low Flow

  • mainly NaCl
  • from acinar cells

High Flow

  • mainly NaHCO3
  • from ductal cells
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe the cystic fibrosis

A 
• Defective CFTR (Cl- channel and eNaC regulator)
• Consequences: 
Decreases Cl- secretion
Decreases Lumen negativity
Decreases Na+ and H2O
movement
Decreases Ductal secretion
Decreases Enzyme action→
Malabsorption
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Describe the pancreatic secretion time course

A

Interdigestive (fasting) phase- basal secretion rate

  1. Cephalic —> increased secretion rate (25%)
  2. Gastric—> increased secretion rate (10%)
  3. Intestinal —> increased (50-80%)

Late digestive —> decreased

16
Q

Summarize pancreatic secretions of the cephalic phase

A

Cephalic phase—> increased vagal activity —> stimulates ductal and acinar cell

Ductal cells increase secretions of bicarbonate

Acinar cells—> increased secretion (enzym3s)

17
Q

Describe pancreatic secretions of gastric phase

A

Food in stomach—>

Gastric distension increases vagal response (ACh) + gastrin release

Protein in food stimulates CCK

ACh, Gastrin, CCK stimulates acinar cells enzyme release

18
Q

What is the rlevance of CCK to acinar cells?

A

• CCK release depends on content of meal – Fatty acids: large CCK response
– Amino Acids: intermediate CCK response
– Carbohydrates: minimal CCK response

  • Exocrine pancreas has large reserves of digestive enzymes for carbohydrates and protein, less for lipid digestion
  • Even lipid digestion is not affected until 80-90% of the pancreas is destroyed
19
Q

Describe the relevance of secretin to the pancreas

A

• acts on pancreatic duct cells to increase cAMP levels, activating HCO3- and fluid secretion

• food buffers gastric acidity
– pH drop in duodenum may not be enough to produce high secretin levels

• CCK and ACh potentiate the effect of secretin on ductal HCO3- and fluid secretion

20
Q

What are the functions of small intestines secretions?

A

Functions
– Protection
• Mucus prevents acid and protease damage to intestine
• Alkaline solutions neutralize chyme

 – Digestion
• Enzymes break down all major foodstuff
• Alkaline solutions neutralizes chyme
• Trypsin activates chymotrypsin and procarboxypeptidase 
• Bile emulsifies fat

– Control
• CCK and Secretin inhibit gastric motility and secretion
• CCK stimulates contraction of the gall bladder and relaxation of the hepatopancreatic sphincter
• Secretin stimulates secretion of bicarbonat

21
Q

What are the functions of intestinal fluid secretions?

A
  • Aids lubrication and motility (secretion failure = gut obstruction)
  • Provides a source of Na+ to absorb nutrients if a meal has low Na+ content
  • Vehicle for gut antibodies secreted from crypts
  • General response to irritation/infection to “wash out” the problem
22
Q

What are the steps in NaCl secretion in the small intestines?

A
  1. Na+-K+ pump in basolateral in membrane
  2. Low intracellular [Na+]
  3. Provides the energy for uptake of Cl- into the cell via the NKCC transporter in basolateral membrane
  4. [Cl-] increase so that Cl can exit passively through Cl channels in the apical me,brane
  5. Lumen becomes more negative
  6. Attracts Na+into the lumen down an electrical gradient
  7. H2O follows passively by osmosis
23
Q

Describe large Intestinal secretions

A

– Alkaline mucus solution containing bicarbonate and K+

24
Q

What are the functions of large intestinal secretions?

A

– Protection
• Resident bacteria release acid
• Mechanical damage by passage of feces

25
Q

What stimulates large intestinal secretions?

A

Stimulation:
– Acid and mechanical
– Mediated by long and short reflexes

26
Q

Describe distal colon NaCl Reabsorption

A

Na+ influx→ Lumen becomes more –ve. Cl- is absorbed paracellularly.

When body Na+ is low, aldosterone stimulates the ENaC pump to promote Na+ retention (similar in the kidney)

27
Q

Summarize secretion of K+ in the distal colon

A

Passive K+ secretion driven by –ve luminal potential

28
Q

Summarize K+ movement

A
  • Intestines can absorb or secrete K+
  • GIT plays a minor role in regulating K+ in the ECF.
  • The kidney is the major regulator of K+ levels.
  • K+ is absorbed in proximal segments of the GIT
  • K+ is secreted in distal segments of the GIT
  • Salivary, Gastric, Pancreatic and Biliary secretions: rich in K+
  • High K+ load is presented to the small intestine
  • Stool contains high levels of K+ (partly due to colonic secretion)
29
Q

What is the effect of aldosterone?

A

Active K+ secretion in the distal colon

30
Q

Summarize intestinal secretion & absorption

A 
Small Intestine 
• Net absorption
• H2O
• Na+
• Cl-
• K+• • Net secretion
• HCO3
Large intestine
Net absorption 
H2O
Na+
Cl- 
Net secretion
HCO3
K+
31
Q

Describe intestinal solute abd H2O balance

A
  • Secretory mechanisms are located in crypts
  • Absorption mechanisms are located in the villi
  • Cl- is the primary ion secreted
  • Transported through a chloride channel regulated by cAMP
  • Na+ secretion passively follows Cl-
  • H2O follows osmotically
32
Q

What is diarrhea?

A 
(an increase in the volume or frequency of defecation)
• Osmotic
– Ingestion of poorly absorbed substrate
– Malabsorption 
– carbohydrates

• Secretory
– Bacterial toxins
– Tumors, hormones

33
Q

What is secretory diarrhea?

A

Increased endogenous secretions of fluid and electrolytes from GIT

Enterotoxin, V. Cholera
E. Choli

Enterotoxin e.g., Clostridium Difficile

VIP., histamine, prostaglandins

ACh, 5-HT, Bradykinin

34
Q

What are the factors affecting Cl- secretion in SI?

A

Apical Cl- channels open in response to: ↑ cAMP ↑ Ca2+

Secretagogues induce apical Cl channel opening

Secretagogues: Hormones and neurotransmitters (ENS, VIP)

Products of immune cells (e.g. histamine)

Bacterial exotoxins (“enterotoxins”) Laxatives

Either by ↑cAMP
or ↑ Ca2+

Induction (recruitment and activation) of apical Cl- channels plays a major role in the pathophysiology of secretory diarrheas

35
Q

Describe diarrhea and ootassium balance

A

Bacterial exotoxins (“enterotoxins”) Laxatives

36
Q

What are the consequences of secretory diarrhea?

A

Loss of ECF type fluid from the GIT: up to 9L/day
1. ↓ Intravascular volume
↓ Arterial pressure
Circulatory collapse

  1. Loss of bicarbonate—> metabolic acidosis
  2. Loss of K+ - ->hypokalemia—> cardiac arryhthmias

Digestion And Metabolism (57 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions