Digestion Physiology - Secretion, Absorption and Fermentation Flashcards
What are gastric pits?
Small indentations in the stomach lining that lead to tubular gastric glands
What are gastric glands?
Are glands in the stomach which are responsible for secreting gastric acid and other substances essential for digestion,
What is glandular mucosa?
The inner lining composed of specialised cells that produce digestive juices and protect the stomach wall
What do parietal cells do?
Are specialised stomach cells that secrete hydrochloric acid
What are chief cells?
Are cells that in the stomach secrete pepsinogen which is a precursor to the digestive enzyme pepsin
What is gastrin?
A peptide hormone primarily responsible for stimulating gastric acid secretion and promoting gastric mucosal growth
What is the pancreas?
A gland with exocrine digestive and endocrine metabolic functions
How does the pancreatic cell protect itself from protein digesting enzymes?
The proteins are synthesised as zymogens which means they are inactive until activated
What do high levels of acid in the duodenum cause?
The release of secretin from epithelial cells in the duodenum
What does the release of secretin do?
Causes copious secretion of pancreatic juices and bicarbonate
What role does the liver have in digestion?
To secrete bile
Why is bile important for digestion?
It is used in lipid digestion
Where is bile secreted from?
The hepatocytes in the liver and then it flows into the bile duct system
What are the three major functional components of bile?
- Phospholipids
- Cholesterol
- Bile acids
What colour is bile and what makes it this colour?
It is green and the colour i given by bilirubin
What is enterohepatic recirculation?
The process where substances, including drugs and bile salts, are excreted into the bile, travel through the intestines, are reabsorbed, and then return to the liver via the portal circulation and re excreted in the bile
What does amylase act on?
Carbohydrates
What does pepsin act on?
Proteins
What does trypsin act on?
Proteins
What does lipase act on?
Fats
What are the two phases of digestion?
- Luminal phase digestion
- Membranous phase digestion
What is the luminal phase digestion?
- Breakdown of food
- Gastric and pancreatic enzymes
- Results in solublised fat and shot chain peptides
What is the membranous phase digestion?
- Enzymic digestion of CHO and protein
- Enzymes are produced by enterocytes
Where does fat get absorbed into?
The lymphatic system
Which vein carries the majority of blood from the intestines?
The hepatic portal vein
What are advantages of fermentative digestion?
- Allows the use of fibrous diets
- Access to cellulose in plant material
- High value microbial protein from low value plant protein
What are disadvantages of fermentative digestion?
- Spend a large part of day chewing
- Fermentation vat must be kept working
- Must use end products of fermentation
What are the three primary VFA’s?
- Acetic acid
- Propionic acid
- Butyric acid
What is regurgitation in rumination?
Extra contraction of rumen to get the soupy content of the rumen into the mouth
What is eructation in rumination?
The removal of gases of fermentation
What organs perform the role of the rumen in hind gut fermentors?
The caecum and colon
How is the nitrogen recycling different in ruminants and hind gut fermentors?
In ruminants microbial protein nitrogen recovered in small intestine in hind gut fermentors most of it is lost in faeces
