Intro to Functions of Alim Tract

Question 1

Describe pancreatic secretions

Answer 1

Exocrine, include watery secretions eg. bicarbonate* for essential neutralisation of acidic chyme.

Question 2

What are organs with storage function?

Answer 2

Prox Stomach - Food remains ~1hr unmixed

Desc Colon - faeces/residues

Question 3

How does stomach allow for food storage?

Answer 3

Fundus and body relax, allowing accommodation to 1.5L for storage. The Vagal reflex INHIBITS smooth muscle tone - mechanoreceptors detect -> fundic relaxation - VIP + NO

Question 4

Give an example of digestion in the stomach

Answer 4

Antral region mixes/grinds food with gastric secretions

Question 5

What’s the volume of an empty stomach (fasting)?

Answer 5

~50ml

Question 6

Describe gastric secretions

a) Where produced from?
b) Purpose?

Answer 6

2-3L of gastric juice / 24 hrs

Consist of: mucus, lipase, pepsin, intrinsic factor + HCl

Question 7

Describe paracrine secretions + give an example

Answer 7

‘Local hormones’, act locally on adjacent cells via the INTERSTITIAL FLUID.

Eg. Somatostatin - produced from D cells, inhibits G cells + gastrin release

Question 8

Describe exocrine secretions + give examples

Answer 8

Secretions from glands with DUCTS

• Salivary glands: mucus (lube for mastication/speech)
• Gastric glands: HCl, pepsin, mucus (barrier to trauma)
• Pancreas: HCO3-, enzymes
• Liver: bile acids

Question 9

Describe endocrine secretions + give examples

Answer 9

Hormones synthesised by DUCTLESS glands enter BLOOD, travel to target tissue(s) + bind to specific receptors.

• Gastrin: stomach (G cells/antrum)
• Secretin: Duo mucosa -> pancreatic sec
• CCK: Duo mucosa -> bile sec
• Insulin: Pancreas (B-cells)

Question 10

Role of colon in absorption

Answer 10

Absorbs 90% of water, reducing vol to 200ml of semi-solid faecal matter

Question 11

What is motility?

Answer 11

The MOVEMENTS of the muscular wall (mostly smooth muscle except upper oes/rectum)

Question 12

Functions of motility

Answer 12

• Storage: (name the organs!)
• Movement (peristalsis)
• Mech Degradation: antrum
• Mixing lumen contents/segmentation (in SI)
• Transport of urea + electrolytes

Question 13

How do drugs/prods of metabolism leave the body?

Answer 13

Via; saliva, bile, faeces + vomit.

Indigestible food residues leave in faeces.

Question 14

Why is defence important within the gut?

Answer 14

The gut EPITHELIUM is an interface with the “contaminated” outside world. So unsterile basically.

Intestine = largest lympho-epithelial organ!

Question 15

Name defence mechanisms of the gut

Answer 15

• Peyer’s patches (lymph)
• Sight, smell, taste
• Vomit reflex
• HCl in stomach kills bacteria
• Natural bacteria flora
• IgA

Question 16

What is a standard integrated response to a meal?

Answer 16

Ingestion -> Digestion & Absorption* -> Elimination

*Motor and secretory behaviour involved too