Lecture 47 - Gastrointestinal Physiology: Function of the GI Tract

Question 1

Describe the major function of the digestive system, and the main processes involved.

Answer 1

o To break down food mechanically and chemically into smallest absorbable components
o To absorb nutrients into the body

Question 2

summary of gastric function

Answer 2

o Ingestion
o Mechanical processing
o Digestion
o Secretion
o Propulsion
o Absorption
o Excretion

Question 3

Describe, in general terms, how digestive secretions and motility are controlled by nerve reflexes

Answer 3

o Extrinsic nervous system
 Intrinsic to the walls of the ENS are sensory. Mtor and inter neurons
 Give short reflex and control local peristalsis, secretion, in response to arrival of bolus

Question 4

Role of the autonomic nervous system

Answer 4

o PSNS = increased muscle tone, increased gland secretion
o SNS = muscle relaxation. Decreased gastric blood flow

Question 5

mouth

Answer 5

 Mechanical = mastication or chewing forming bolus
 Chemical = amylase action of carbohydrates, lingual lipase action on triglycerides

Question 6

stomach

Answer 6

 Mechanical = Highly acidic, cells secrete HCl, Motility involved in mechanical breakdown of food, turns bolus into chyme
 Chemical = protein digestion begins by HCl denaturing proteins and HCl transforming pepsinogen into pepsin which helps break peptide bonds. Fat digestion continues by gastric lipase, HCl kills microbes in food

Question 7

small intestines

Answer 7

 Mechanical = weak peristalsis and segmentation
 Chemical = turning macromolecules into monomers, assisted by release of digestive enzymes from accessory organs exocrine pancreas and liver

Question 8

pancreas

Answer 8

 Accessory organ of digestive system
 Endocrine = release of insulin. And glucagon
 Exocrine = release of enzymes that aid digestion directly into the lumen of the small intestine

Question 9

liver

Answer 9

 Produces bile
 Bile aids in fat absorption by breaking large fat droplets into small micelles

Question 10

large intestines

Answer 10

 Chemical = no enzymes, bacteria ferment, bacteria produce vitamin K and B in colon, flatus (gas)
 Mechanical = peristaltic waves, haustral churning, gastrolienal reflex, gastrocolic reflex

Question 11

Brush boarder enzymes: polypeptides to amino acids

Answer 11

o Polypeptides to amino acid breakdown via pancreatic enzymes in chyme
o These polypeptides are digested into smaller di and tripeptides that can be absorbed at the brush boarder

Question 12

Brush boarder enzymes: disaccharides to monosaccharides

Answer 12

Via pancreatic amylase enzyme and also absorbed at brush boarder

Question 13

Function of mucous cells

Answer 13

Protect stomach walls from being digested with 1-3mm thick layer of mucous