Module 3 - GI tract

Question 1

what is salivary secretion composed of ?

Answer 1

1. mucus - for lubrication
2. Dilute solution of NaCl
   - allows to dilute food
   - this allows optimal ph to be reached for digestive enzymes
3. Digestive enzymes
   - Lingual lipase
   - a - amylase

Question 2

what are the functions of the salivary secretion ?

Answer 2

• Aids in talking and chewing and swallowing food
• Hygiene
• Digestion
  
  • dissolves food allows taste
    
    • lingual lipase - fats
      - a amylase - starch

Question 3

how is salivary secretion regulated ?

Answer 3

through nervous and autonomic nervous system

Nervous

• thought, smell, sight of food
• presence of food in mouth

Autonomic

• para
  
  • stimulates secretion of a lot of fluid
  • Sym
    
    • small volumes of viscous fluid

Question 4

composition of gastric secretion?

Answer 4

• mucous cells
• chief cels -pepsinogen
• parietal cells - intrinsic factors

Question 5

what are the functions of gastric secretion?

Answer 5

1. the mucus protects against abrasion and acid
2. Intrinsic factor
   - absorptive of vitamin b12
3. Pepsinogen
   starts the digestion of proteins
   - is converted into the active form of pepsin by acid
4. Gastric acid
   - dilutes food
   - denatures proteins
   - activates pepsinogen

Question 6

secretion of hcl

Answer 6

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Question 7

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Answer 7

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Question 8

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Answer 8

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Question 9

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Answer 9

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Question 10

how is gastric secretion regulated ?

Answer 10

this is coordinated with eating and arrival of food

- divided into 3 phases

Question 11

what are 3 phases through which gastric secretion is regulated

Answer 11

1. Cephalic phase
2. Gastric phase
3. Intestinal phase

Question 12

explain the cephalic phase?

Answer 12

20% of secretion associated with this phase

• this phase is where the body prepares for the arrival of the good

Stimuli
-the sight of food, the thought of food

Parasympathetic nervous system
- via the enteric nervous system it stimulates
- chief cells
- goblet cells
- parietal cells
it also stimulates the secretion of hormone gastrin which is released into the blood and this hormone also stimulates parietal and chief cells

Question 13

explain the gastric phase?

Answer 13

70% of secretion is associated with this phase

This phase ensures that their is sufficient to handle ingested food

Stimuli in stomach

• stretch of stomach wall
• elevated ph

Nervous and hormonal regulation

local nervous reflex
- enteric nervous system

external nervous reflex
- parasympathetic system

stimulates

• secretion
• gastrin secretion
• motility

Question 14

explain the intestinal phase ?

Answer 14

10% secretion

stimuli

• stretch of the duodenum
• the arrival of acid chyme, lipids and carbohydrates

Nervous and hormonal regulation

Hormones
- CCK, GIP, secretin

Nerves
- enterogastric reflex

Both inhibit secretion and motility

Question 15

what is the composition of pancreatic secretion?

Answer 15

consists of

• enzymes - acinar cells and chemical digestion of food
• Alkaline fluid
  
  • duct cells
  • neutralises acid
  • optimum ph for enzymes

Question 16

what is function of pancreatic enzymes?

Answer 16

luminal chemical digestion of food

Question 17

how is pancreatic secretion of enzymes stimulated ?

Answer 17

• secretion of digestive enzymes is by acinar cells which is stimulated by hormone CCK

Question 18

how is the secretion of alkaline fluid stimualted?

Answer 18

by hormone secretion, secretion of secretin stimulated by arrival of acid chyme in duodenum

Question 19

what are products associated with digestion in biliary secretion?

Answer 19

• bile salts

- HC03-

Question 20

what are the excretory products in biliary secretion?

Answer 20

bile pigment- waste products

cholestrol

Question 21

what is the function of biliary secretion?

Answer 21

bile salts - fat digestion
HC03- - neutralises acid
bile pigments - excretion

Question 22

how is biliary secretion regulated ?

Answer 22

• bile is secreted in the liver, it is delivered to the duodenum when the food arrives
• the initial delivery of bile is under hormonal control
  • CCK

Bile stimulates its won secretion
- enterohepatic circulation

Question 23

what does the CCK hormone do ?

Answer 23

• it is produced in response to products of digestion in duoder
• contraction of gall bladder
• relaxation of hepatopancreatic ampulla

Question 24

what is enterohepatic circulation

Answer 24

it is the process of reabsorbing 95% of the bile in the ileum

Question 25

what does the SI consist of and what do the components do?

Answer 25

• mucus for lubrication
• isosmotic fluid
  
  • alkaline - HELPS TO neutralise acid and dilutes food to aid digestion

digestive enzymes
- shed cells

Question 26

name the major nutrients in our food

Answer 26

• carbohydrates
• proteins
• fats

Question 27

what 2 monosaccharide is sucrose made out of ?

Answer 27

glucose and fructose

Question 28

what 2 monosaccharide is lactose made out of ?

Answer 28

glucose and galactose

Question 29

what 2 monosaccharide is maltose made out of ?

Answer 29

glucose and glucose

Question 30

what are sources of protein?

Answer 30

• 50% from the diet

- 50% endogenous proteins

Question 31

what are digestive enzymes?

Answer 31

• are extracellular
• are organic catalysts
• need different enzymes for different substrates
• have different optimal ph’s
  
  • salivary enzymes - alkaline
  • gastric enzymes - acidic
  • small intestinal - alkaline