Digestion 2 Flashcards
What is chyme?
Fine particles of undigested material
Is chyme acidic or alkaline?
Acidic
What is in chyme?
Protein and polysaccharide fragments and fat
Role of exocrine pancreas
Provides main digestive fluid of the small intestine
What is the structure of the exocrine pancreas?
Similar to salivary gland
What is secreted by the pancreas?
Water, HCO3- and enzymes
What do parasympathetic nerves control for the pancreas?
ACh and VIP (vasoactive intestinal peptide)
What do gut hormones control in the pancreas?
HCO3- and enzyme rich secretion
Role of enterokinase
Catalyses trypsinogen to trypsin
Role of trypsin
Catalyses conversion of all enzymes to active forms
What does the liver receive?
All blood leaving the gastrointestinal tract
What does the liver produce?
Bile and important plasma proteins
What does the metabolic control centre store?
Carbohydrates, amino acids and fats
What can the metabolic control centre convert amino acids to?
Other amino acids or sugars
What does the metabolic control centre monitor?
Blood levels
What does the liver do with old red blood cells?
Destroys them and breaks down the haemoglobin
How does the liver improve blood quality?
Removes toxins and foreign components
Role of bile salts
Aid absorption of fats
Examples of bile salts
Cholic and chenodeoxycholic acid
Role of bile pigments
Breakdown products of haemoglobin
Examples of bile pigments
Biliverdin and bilirubin
How do bile salts cause fats to be absorbed?
Form a hydrophilic shell around the fat to diffuse through villus tip
What causes contractions of the gall bladder?
Cholecystokinin
Role of gall bladder
Release stored bile into duodenum
What is the final site of chemical breakdown and absorption of food?
Small intestine
Role of enterocytes
Absorption across walls of villi
How long to enterocytes live for?
2-3 days
What happens when enterocytes differentiate?
They develop brush borders, digestive enzymes and transporter proteins
What are propulsive movements?
Shifts material along the gut
Role of mixing movements
Mixes digesta with secretions and ensures material is close to villi
What is peristalsis?
Propulsive movement coordinated by enteric nerves
How is peristalsis initiated?
Stretching of intestinal walls
What occurs to muscles during peristalsis?
Muscle behind digesta contracts and muscle in front relaxes
What causes segmentation of the digesta?
Stretching of the intestine
How does segmentation occur?
Contractions of muscle at regular intervals of the digesta
Role of segmentation
Easier absorption
Parts of the large intestine
Colon
Cecum
Appendix
Rectum
Role of colon
Stores material and absorbs water and salt
What are bowel movements?
Slow contractions that mix materials
What are mass movements?
Large contractions that push faeces down the colon
What is the gastrocolic reflex?
Mass movements that occur when food enters the stomach
What is the defecation reflex?
Faeces entering rectum causes internal anal sphincter to relax
What must occur before defecation?
Relaxation of external anal sphincter
What causes disruption of the digestive system?
Emotional problems
Vomiting
Diarrhoea
Constipation
How do emotions effect gastric motility?
Autonomic nerves alter gastric smooth muscle excitability
How does vomiting occur?
Action of the diaphragm and abdominal muscles
What causes diarrhoea?
Excessive intestinal motility and osmotically active particles in digestive tract
