Lecture 22 - Alimentary 2 Flashcards
(30 cards)
how does water, electrolytes, proteins and carbohydrates get absorbed?
through enterocytes of villi in the small intestine and into the venules that lead to the hepatic portal vein
how do fats get absorbed?
through enterocytes of villi in the small intestine and into the lymphatic vessels via lacteals
what is the consequence of lacteals having no muscular walls, and what is the body’s solution to this?
lamina propria contains smooth muscle cells that contract and squeeze the lacteals, as if they are ‘milking’ the lacteal
- also mixes the solution when smooth muscle contracts
where does nutrient-rich deoxygenated blood go from the small intestine?
to the liver via the hepatic portal vein
what is the consequence that being old has on the small intestine?
elderly have poorer circulation, therefore leading to malabsorption
what effect does coeliac disease have on absorption of nutrients
causes the body to attack its own villi, so there is less villous atrophy and less nutrient absorption
describe the epithelium on villi and intestinal glands of the small intestine
all simple columnar
- villi have microvilli brush border and goblet cells with no microvilli
- intestinal glands have no microvilli/apical specialisations and other specialised cell types
where do lymphatic vessels eventually drain into?
venous system
what is the role of the studded enzymes of enterocytes?
Glycosidases break down carbohydrates
enterokinases activate pancreatic enzymes
where are studded kinases of enterocytes found?
at the plasma membrane
describe the structure and function of enterocytes
structure: elongated nuclei, microvilli
function: absorption
what does smooth muscle underlying the enterocytes in the lamina propria do?
when it contracts, it moves the lamina propria, and since that is connected to the actin cytoskeleton via the basement membrane, the microvilli move
where do undifferentiated cells divide?
upwards to replace most intestinal gland cells
downwards to replace paneth cells
what do paneth cells do
they are unique cells to intestines that sit at the bottom of the gland and has a major protection role.
- secretion of lysozyme to destroy bacterial membranes and kill bacteria
what triggers enteroendocrine cells to secrete hormones?
- amino acid fragments (digested protein)
- fatty acid fragments
- acidic chyme
what three main things do the hormones of the enteroendocrine cells have an effect on?
- gall bladder to release bile
- pancrease to secrete more enzymes
- ductal cells to release more HCO3-
rank the regions of the small intestine from longest to shortest
1: Ileum
2: jejunum
3: duodenum
what part of the small intestine is C shaped?
duodenum
what increased the pH of intestinal contents in the duodenum from pH1-2 in the stomach to pH7-8?
the brunner glands, which secrete HCO3- rich mucus to neutralise the acidic chyme
what is the unique, distinguishable feature of the duodenum?
brunners glands
describe the jejunum
2.5m long, mostly does digestion (has lots of studded enzymes) and absorption
what is the main function of the ileum?
protection/defense
what is the distinguishable feature of the ileum?
PEYER’S PATCHES
lymphatic aggregates that are macroscopically visible (visible to naked eye)
why does the ileum require a defensive role?
it forms the gateway to the large intestine, which has a high density of bacteria
