Digestive System: Small intestines Flashcards
(45 cards)
What are the general functions of the small intestines (SI)?
Digestion
Absorb nutrients
Produce intestinal hormones using DNES cells (produce CCK)
What 3 surface adaptations increase surface area by a factor of 400+?
- Plicae circulares (valves of Kerckring)
- Villi
- Microvilli
What are the plicae circulares?
Permanent folds affecting the mucosa and submucosa; found throughout duodenum, jejunum, and proximal ileum
Where are the microvilli?
On the luminal cell surface
What is the surface epithelium of the intestinal mucosa?
Simple columnar
What cell types are present in the surface epithelium of the mucosa?
Surface absorptive cells (enterocytes) Goblet cells DNES cells (Type I, Type K, Type S) Regenerative cells Paneth cells M (microfold) cells
What are the main functions of the surface absorptive cells/enterocytes?
Absorb water and nutrients
Terminal digestion in glycocalyx; cells produce the enzymes and absorb the monosaccharides and peptides created
What do the surface absorptive cells/enterocytes contain?
Microvilli
How are the goblet cells distributed in the SI?
Few in duodenum, most in ileum
How many DNES cell types are present in the SI?
11 types (we only need to know 3)
What do Type I DNES cells produce and do?
Produces cholecystokinin (CCK) to stimulate GB contraction and pancreatic secretion of enzymes from serous acini
What do Type K DNES cells produce and do?
Produces GIP (gastric inhibitory peptide) which inhibits HCL release
What do Type S DNES cells produce and do?
Produces Secretin which stimulates pancreatic secretion of bicarbonate from the pancreatic ducts; secretin also inhibits HCL release and the movement of chyme into SI
How long do the regenerative cells of the SI live? Where are they found?
5-7 days
Found in crypts (intestinal gands)
How long do the Paneth cells of the SI live? Where are they found?
20 days, they are long lived
Found in base of crypts (intestinal glands)
What is the function of the Paneth cells of the SI?
Produce lysozyme
Where are the M (microfold) cells found in the SI?
Ileum epithelium over Peyer’s patches
What is the cell structure of the M (microfold) cells?
Contain large intracellular pockets that are fairly open to the LP; M cells sample foreign antigens in gut lumen and transfer antigens to lymphocytes and dendritic cells that have entered the M cell pockets
What is the function of the M (microfold) cells?
Promote humoral immunity; results in plasma cells producing IgA which is then transferred to epithelial cells and released into gut lumen. M cells are also important in maintaining appropriate gut flora
What is the lamina propria of the SI made up of?
Loose areolar CT
Where is the villus core located?
In the lamina propria
What is found in the villus core?
Lacteals
Vascular components
Some longitudinal smooth muscle
What are lacteals and what’s their function?
They are lymphocyte capillaries
Function in most lipid absorption
Are the vascular components of the villus core larger or smaller blood vessels?
Smaller
