Function of Alimentary Tract

Question 1

What aids helps grinding motions?

Answer 1

Stomach has oblique layer of smooth muscle inside the circular layer

Question 2

How stomach STORES?

Answer 2

• Remains ~1hr unmixed - reservoir
• Fundus + body (thinner muscle tone) relaxes –> large volume ~1.5L
• Vagal reflex ❌smooth muscle tone – mechanoreceptors–>fundic relaxation VIP+NO
• Antral mixes/grinds food w gastric secretions–>digestion

Question 3

What does colon STORE?

Answer 3

digestive residues + faeces

Question 4

Where gastric secretions stored + how much?

Answer 4

Stomach 2-3L /24hrs

Question 5

What’s mucus?

Answer 5

goblet + mucus neck cells ⇶

lubricated barrier protects stomach + colon

Question 6

What’s lipase?

Answer 6

triglycerides→FA+glycerol

Question 7

What’s pepsin?

Answer 7

chief cells ⇶

🐟 digestion

Question 8

What’s instinsic factor?

Answer 8

parietal cells ⇶

vit B12 absorption

Question 9

What’s HCl?

Answer 9

parietal cells ⇶

defence

Question 10

What are paracrine secretions?

Answer 10

“local hormones”
⇶ from cells in the mucosa + acts on adjacent cells via interstitial fluid
eg somatostatin ❌ gastrin release

Question 11

What are exocrine secretions?

Answer 11

⇶from many glands w ducts enter gut lumen:

• Salivary glands: mucus-lubrication for mastication +speech
• Gastric glands: HCl, pepsin, mucus
• Pancreas: bicarbonate ions, 𝔼 amylase- (starch→sugars), lipase, carboxypeptidase (hydrolyses peptide bond at C-terminal of 🐟)
• Liver: bile acids

Question 12

What are endocrine secretions?

Answer 12

hormones synthesised by ductless glands ➩blood stream ➩target tissue to bind to specific receptors

• Gastrin: ⇶G cells in antrum
• Secretin: ⇶from S cells in duodenal mucosa
• Pancreozymin-cholecystokinin⇶from duodenal mucosa
• Insulin: pancreas (β cells)

Question 13

How colon does fluid absorption?

Answer 13

absorbs 90% of H2O ↓v to 200ml of semi-solid faecal matter

Question 14

What’s motility?

Answer 14

movements of mostly smooth muscle except extreme ends of the upper oesophagus/rectum

Question 15

What is motility vital for?

Answer 15

Movement- from 1 region→ another (law of gut)
Storage- proximal stomach, descending colon
Mechanical degradation- antrum
Mixing lumen contents-small intestine
🚌 of U+E

Question 16

Diff ways of excretion?

Answer 16

Saliva
Bile
Faeces
(Vomit)

Question 17

Why does the small intestine need defence mechanisms?

Answer 17

large lymphoepithelial organ + mucosal surface ∴ most exposed to environmental antigens, if breach of barrier then toxin ➩blood

Question 18

What are the defence mechanisms?

Answer 18

• 👁, 👃,👅 alerts to harmful food
• Vomit reflex
• HCl kills harmful 🐛
• Normal flora prevents colonisation of harmful 🐛
• Aggregation of lymphoid tissue eg Peyer’s patches responds to food-borne antigens - analyse +respond to pathogens

Question 19

Where are Peyer’s patches?

Answer 19

in the lamina propria layer (beneath epithelium) of the mucosa extending➩ submucosa of ileum

Question 20

What’s the liver?

Answer 20

in abdominal cavity, 1.3kg

does carb, N and lipoprotein metabolism + bile production + bilirubin excretion

Question 21

Functions of GI?

Answer 21

Storage + digestion
Motility
Storage of waste
Defence
Secretions: exocrine, endocrine, paracrine
Excretion

Question 22

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Answer 22

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