The Small Intestine. Flashcards
What 2 major processes occur in the small intestine?
Digestion and absorption.
What are the 4 major functions of the small intestine?
To further propel chyme through the intestine.
To buffer acidic chyme.
To further digest acidic chyme.
To absorb micronutrients, water and electrolytes.
What 2 modes of contraction are carried out by the small intestine?
Persitalsis.
Mixing.
What prevents the flow of chyme into the large intestine from the small intestine?
The ileocecal sphincter.
What are the small projections that project off the wall of the small intestine known as?
Intestinal villi.
What is the function of the intestinal villi?
They increase the surface area of the intestine and aid with absorption.
They also secrete digestive enzymes.
What is found in between each intestinal villi?
A crypt of lieberkuhm.
What is found in the crypts of lieberkuhn?
Different cells at different levels with stem cells at the bottom.
What happens to the stem cells at the bottom of the crypts of Lieberkuhn?
They differentiate into the cells that are located at the lowest level of the crypt.
They are then pushed upwards by more developing cells.
As they are pushed up they turn into cells that are found at the higher levels of the crypt.
Is there a very high turnover of cells in the crypts of Lieberkuhn?
Yes, they are replaced roughly every 5 days.
What is the order of cells found in the crypt of Lieberkuhn from youngest to oldest?
Intestinal stem cells.
Paneth cells.
Transit amplifying cells.
Goblet cells.
Enteroendocrine cells.
Enterocytes.
What are the secretory cells of the crypts of Lieberkuhn?
The enterocytes.
What age are the secretory cells that are found in the crypts of Lieberkuhn?
The young enterocytes.
Where are the enterocytes located on the intestinal villi?
At the end of the intestinal villi.
What is the function of the young enterocytes of the intestinal villi?
They secrete intestinal fluid into the lumen.
What is the function of intestinal fluid that is secreted by the young enterocytes of the intestinal villi?
Cl- is secreted into the gut lumen.
Na+ follows the gradient into the lumen and water follows.
The water dilutes the chyme.
What cells are the absorptive cells of the intestinal villi?
The mature enterocytes.
What is the function of the mature enterocytes of the intestinal villi?
They develop microvilli called a brush border membrane and this contains digestive enzymes and absorptive mechanisms.
What will break down the partially digested macromolecules in the chyme of the small intestine?
BBM enzymes.
What disorder can affect the young enterocytes of the intestinal villi?
Diarrhoea as this leads to more water secretion into the intestine.
What is the difference between luminal and membranous digestion in the small intestine?
Luminal digestion occurs is due to enzymes that were released in the mouth and stomach.
Membranous digestion is due to BBM enzymes.
What enzymes carry out hydrolysis in the small intestine?
Enzymes from the luminal phase of digestion.
Enzymes from the membranous phase of digestion.
Bile salts and B12 are absorbed in what part of the small intestine?
In the ileum.
How are starch and glycogen broken down in the luminal phase of digestion?
Amylase breaks large polysaccharides down into oligopeptides etc.