Upper GI Histology Flashcards
Parietal cells produce what two things?
Intrinsic factor
HCl
On their basolateral sides, the parietal cells have ______________ to maintain pH balance.
chloride-bicarb
The part of the GI tract that has villi and crypts is _____________.
the small intestine
The crypts in the small intestine are called ______________.
crypts of Lieberkuhn
Most of the intestinal absorption occurs in ____________.
enterocytes of the small intestine (which have microvilli)
In the small intestine, where are the goblet cells?
In the villi, next to enterocytes
Brunner’s glands are within _____________ of the duodenum. What do they do?
crypts of Lieberkuhn; secrete bicarbonate to neutralize the acid from the stomach
Paneth cells, within the crypt of Lieberkuhn, secrete ____________.
defensins and lysozymes
What are lacteals?
Lymphatic vessels of the small intestines that absorb fats
Why is fat broken down and absorbed as chylomicrons?
Because fat globules could clog small vessels if absorbed in raw, unmanageable form
What four integral membrane proteins are found on the surface of enterocytes (that we need to know for this class, of course)?
- Enterokinase: an enzyme that acts on trypsinogen from the pancreas (which initiates the cleavage of procarboxypeptidase and chymotrypsin)
- Lactase: degrades lactose to glucose and galactose
- Maltase: degrades maltose (a breakdown product of starch)
- Sucrase: degrades sucrose to glucose and fructose
Explain why it is beneficial to have the sugar-degrading enzymes on the surface of enterocytes (as opposed to floating in the lumen).
Gut bacteria also eat sugar. If sugar were allowed to float freely in the lumen, then much of it would be eaten by bacteria before getting eaten.
IgA has its secretory component added by _______________.
membrane proteins on enterocytes
True or false: microvilli have microtubules in their cores.
False. They have actin.
The lumen of the crypts in the _____________ are narrower.
large intestine (as compared to the small intestine)
