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stage 1 Gastrointestinal tract > GI3 Gastric function > Flashcards

GI3 Gastric function Flashcards

1
Q

Givw the function of the following:

1) mouth
2) pharynx and oesophagus
3) Stomach
4) small intestine
5) large intestine
6) rectum and anus

A

1) mastication
2) transport
3) o storage
o mechanical disruption
o chemical disruption
o protection

4)o	chemical digestion
o	mechanical digestion 
o	major site of nutrient absorption
5)o	absorb water
o	electrolytes 
6) defecation
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2
Q

What occurs in the mouth? what is the result of this i.e. =

A
  1. Mechanical digestion (mastication or chewing)
    =breaks into pieces
    =mixes with saliva = forms a bolus
  2. Chemical digestion
    o α-amylase
    = begins starch digestion
    o lingual lipase= begins breakdown of triglycerides into fatty acids and glycerol
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3
Q

What is the pH of the mouth?

2) What enzyme works well at this pH?
3) The enzyme is denatured in the stomach, what is the pH of the stomach?

A

1) 6.5 - 7.0
2) alpha-amylase and lingual lipase
3) 2.5

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4
Q

1) What part of stomach holds food until needed?
2) What storage property mean the stomach can regulate and prevent?
3) What part of the stomach does digestion?
4) What is chemical digested in the stomach?

A

1) upper part
2)  Stomach regulates the rate food enters small intestine
 Prevents wastage and malabsorption
3) the lower part
4) lipids and proteins

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5
Q

Describe protein digestion in the lower part of the stomach:

A

o HCl denatures (unfolds) protein molecules
o HCl transforms pepsinogen (inactive form) into pepsin 9active form) that breaks peptides bonds between certain amino acids

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6
Q

Describe lipid digestion in the lower part of the stomach:

2) When is lipid digestion most effective?-why?
3) What cell type secretes gastric lipase?

A

o gastric lipase splits the triglycerides in milk fat

2) infancy: pH 5 to 6 (infant stomach)
3) Secreted by chief cells on gastric gland.

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7
Q

Describe the mechanical digestion in the stomach:

1) pylorus
2) elsewhere

A

1) intense waves, that open pyloric spincter allowing 1-2teaspoons out every wave
2) gentle (these happen every 15-25 secs , they form chime as they mix the bolus with 2 litres of gastic juices per day) and more vigorous waves( body of stomach to pyloric region)

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8
Q

How does the stomach protect?

2) What can result from and infection or driniking alcohol?

A

acid secretions kills microbes
AND
gastric mucosal secretions containing mucus (physical barrier) and bicarbonate (chemical barrier)
2) increased mucus secretions

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9
Q

What 2 things control mucus secretions:

A

CNS via long (cephalic) reflexes and enteric nervous systems via short reflexes
Also: Paracrine hormones released from near by cells

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10
Q

Describe how ENS controls mucus secretions of the stomach:

not that important

A

stimulus detected (e.g. pH, stretch, osmolarity or products of digestion
2)sensory receptors and neurons detect
2) input to inter-neurons within ENS “little brain”
3) efferent neurons signal response to secretory or smooth muscle
4) If smooth mm= contraction or relaxation
If gland= exocrine secretion ((enzyme, mucus , acid , bicarbonate), paracrines
or endocrine secretions

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11
Q

Describe how CNS controls mucus secretions of the stomach:

not that important

A

stimulus detected (e.g. pH, stretch, osmolarity or products of digestion
2)sensory receptors and neurons detect
2) input to cephalic brain, cephalic brain also receives input from sensory receptros detecting sight, small )
3) cephalic brain inputs to efferent neurons signal response to secretory or smooth muscle via VAGUS nn
4) If smooth mm= contraction or relaxation
If gland= exocrine secretion ((enzyme, mucus , acid , bicarbonate), paracrines
or endocrine secretions

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12
Q

Regulation of Gastric Secretion and Motility is via:

A

Cephalic phase
 Gastric phase
 Intestinal phase

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13
Q

What are the phases of the stomach and what do they mean?

A
  1. Cephalic Phase = “Stomach Getting Ready”
  2. Gastric Phase = “Stomach Working”
  3. Intestinal Phase = “Stomach Emptying”
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14
Q

Describe how the CNS and ENS integrate together to get the stomach redy in the CEPHALIC PHASE:

A

CNS. Medulla oblongata sends preganglionic efferents to enteric plexus via vagus nn.
ENS. Sensory input to enteric plexus is initiated by detection of distension or peprides and amino acids in lumen of stomach)
Enteric Plexus: outflows postganglionic parasympathetic and intrinsic enteric neurons to effector cells
RESULT: motility and sectretion

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15
Q

What is the effect of sympathetic input on the stomach:

A

reduces activity of the stomach

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16
Q

1) What keeps the stomach working in the gastric phase?
2) What does 1st answer cause the stomach to do?
3) What does the 2nd answer cause the stomach to do?

A

1) Nervous control keeps stomach active, it recieves info from stretch receptors & chemoreceptors
AND  Endocrine influences over stomach activity
2) NS causes a) vigorous peristalsis and glandular secretions continue
b) chyme is released into the duodenum
3)  distension and presence of caffeine or protein cause G cells secretion of gastrin into bloodstream

 GASTRIN hormone increases stomach churning and sphincter relaxation
AND
gastrin hormone increases stomach glandular secretion

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17
Q

What hormone is secreted during gastric phase of stomach?

2) From where is it excreted?
3) What causes it’s secretion?

A

1) gastrin
2) G cells secretion of gastrin into bloodstream
3) distension and presence of caffeine or protein

18
Q

How does the enteric Nervous system effect the stomach during the gastric phase (working) of stomach?

A

1) amino acids and peptides in lumen of stomach stimulate enteric sensory neurons which synapse in enteric plexus outflow stimulates G cells = gastric secreted
2) H+ ions in lumen stimulate enteric sensory neurons inputing to enteric plexus, outflow of enteric plexus stimulates chief cells that secrete pepsinogen

19
Q

A) How does the central Nervous system effect the stomach during the gastric phase (working) of stomach?
B) describe how stimulated cells interact and influence stomach contents

A

enteric plexus receives nput via vagus nn. , it outflows and stimulates :
1) G cells
2) ECL cells
3) Parietal cells
B) G cells release gastrin, gastrin causes direct stimulation of parietal cells to release H+ or indirectly via ECL cells which secrete histamine activating parietal cells

20
Q

How is pepsin formed?

A

chief cells secrete pepsinogen and is activated to pepsin by presence of H+ ions

21
Q

How does the NS mediate :

Intestinal Phase = “Stomach Emptying”

A

Duodenum stretch recepetors slow stomach activity & increase intestinal activity
2) distension, fatty acids and sugar detected, medulla outflows via sympathetic, slow stomach activity

22
Q

How do hormones +names mediate:

Intestinal Phase = “Stomach Emptying”

A

 Secretin hormone decreases stomach secretions
 Cholecystokinin (CCK) decreases stomach emptying
 Gastric inhibitory peptide (GIP) decreases stomach secretions, motility & emptying

23
Q

What do the following cells secrete:

1) mucus cells
2) parietal cells
3) Enterochromaffin like (ECL) cell

A

1) mucus & bicarbonate
2) Gastric acid & Intrinsic factor
3) histamine

24
Q

What do the following cells secrete:

1) Chief cells
2) D cell
3) G cell

A

1) Pepsinogen & Gastric lipase
2) Somatostatin
3) Gastrin

25
Q

What secretes :

1) Pepsinogen & Gastric lipase
2) Somatostatin
3) Gastrin

A

1) Chief cells
2) D cell
3) G cell

26
Q

What stimulates release of

1) a) Pepsinogen
b) Gastric lipase
2) Somatostatin
3) Gastrin

A

1) Acetylcholine, secretin, acid
2) acid in the stomach
3) Acetylcholine, peptides

27
Q

What is the function of

1) a) Pepsinogen
b) Gastric lipase
2) Somatostatin
3) Gastrin

A

Protein digestion
Lipid digestion
Inhibits acid
Stimulates acid secretion

28
Q

What cell secretes:

1) mucus & bicarbonate
2) Gastric acid & Intrinsic factor
3) histamine

A

1) mucus cells
2) parietal cells
3) Enterochromaffin like (ECL) cell

29
Q

What stimulates the following cells:

1) a)mucus
b) bicarbonate
2) a) Gastric acid
b) Intrinsic factor
3) histamine

A

1) a) irritation
b) secreted with mucus
2) Acetylcholine, gastrin histamine
3) Acetylcholine, gastrin

30
Q

What is the function of the following:

1) a)mucus
b) bicarbonate
2) a) Gastric acid
b) Intrinsic factor
3) histamine

A

1) a) Physical barrier
b) Chemical protection
3) Activates pepsin, denatures protein, kills bacteria
4) Vitamin B12 absorption

31
Q

What is the effect of fat on the stomach?

A

 Fat content in the stomach slows the passage of alcohol to the intestine where absorption is more rapid

32
Q

What is absorbed in the stomach:

2) How do are the cells adapted to absorb alcohol:

A

1) Water especially if it is cold
Electrolytes
Some drugs (especially aspirin) & alcohol
2)  Gastric mucosal cells contain alcohol dehydrogenase that converts some alcohol to acetaldehyde (more of this enzyme found in males than females)

33
Q

Who is more likely to suffer from palatal and lingual tooth erosion?

A

patient suffers reflux

34
Q

Who should not be put in supine (lay down) position

A

 Patients who suffer gastro-oesophageal reflux

35
Q

What is a risk of putting patients with reflux under General anaesthetic?

A

aspiration of stomach contents

36
Q

List ulecer healing drugs and antacids:

A

o H2 receptor antagonists – competitor for histamine H2 receptors – reduce acid production
o Proton pump inhibitors – block the H+/K+ ATPase (parietal cells)
o Chelates and complexes – protect mucosa by coating
o Prostaglandin analogues – stimulate mucus and bicarbonate production and inhibit cAMP production
o Antacids - Inhibit acid, increase mucus and bicarbonate

37
Q

What do the following drugs do:
o H2 receptor antagonists
o Proton pump inhibitors
o Chelates and complexes

A

o H2 receptor antagonists – competitor for histamine H2 receptors – reduce acid production
o Proton pump inhibitors – block the H+/K+ ATPase (parietal cells)
o Chelates and complexes – protect mucosa by coating

38
Q

What do the following drugs do:
oProstaglandin analogues
o Antacids

A

o Prostaglandin analogues – stimulate mucus and bicarbonate production and inhibit cAMP production
o Antacids - Inhibit acid, increase mucus and bicarbonate

39
Q

Desribe bad drug interactions of the following:

1) antacids
2) Omeprazole
3) Sufralcate (chelator)–

A

o Antacids – reduce absorption of tetracycline
o Omeprazole – reduce absorption of antifungal drugs – ketoconazole
o Sufralcate (chelator)– inhibits absorption of amphotericin, ketoconazole and tetracycline

40
Q

What is the 2nd messenger involved in histamoine production:

A

cAMP

stage 1 Gastrointestinal tract (12 decks)

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