Epithelia of small intestines Flashcards
What are the types of epithelia in the small intestines?
Enterocytes
Goblet cells
Enteroendocrine cells
Paneth cells
Stem cells
What type of epithelial cell is most common in the small intestine?
Enterocytes
What is the function of enterocytes in the small intestine?
Absorption
What is the function of goblet cells in the small intestine?
Produce mucus
What does mucus in the small intestine contain?
Bicarbonate ions
What are the functions of mucus in the small intestine?
Physical barrier between epithelia and bacteria, to prevent bacterial infection
Lubricate gut, so contents can pass through more easily
Neutralises acidity of chyme from the stomach
What is the structure of goblet cells?
Wider towards the top, contain mucus
Narrower towards the bottom, nucleus here
What is the function of paneth cells in the small intestine?
Secrete antibacterial proteins
What is the function of the antibacterial proteins in the small intestine?
Protect stem cells from damage by bacteria and their toxins
What is the function of stem cells in the small intestine?
Divide every 2-4 days
migrate upwards
differentiate as they do so
to replace epithelial cells further up
What are the types of enteroendocrine cells in the small intestine?
G cells
I cells
S cells
K cells
What is the function of G cells?
Produce gastrin hormone
What is the function of I cells?
Produce cholecystokinin hormone
What is the function of S cells?
Produce secretin hormone
What is the function of K cells?
Produce gastric inhibitory peptide hormone
What is the structure of the inner surface of the small intestine?
Has villi
Has crypts
What are villi?
Projections of mucosa of small intestine
into its lumen
What are the epithelial cells on the surface of villi?
Enterocytes
What are crypts?
Depressions of mucosa of small intestine to the muscularis mucosae
out of the lumen
What are the epithelial cells on the surface of crypts?
Towards top of crypt are enterocytes
then goblet cells and enteroendocrine cells
then paneth cells
then stem cells towards bottom of crypt
How is the small intestine adapted for absorption?
Its walls are folded into plicae circulares
plicae circulares are folded into villi
increases surface area
What are plicae circulares?
Projections of submucosa of small intestine into its lumen
How are enterocytes adapted for absorption?
Have microvilli on their apical domain
increases surface area
What is the brush border of the small intestine?
Microvilli on apical domain of enterocytes
What specific gland does the submucosa of the duodenum contain?
Brunner’s glands
What is the function of Brunner’s glands?
Produce mucus
Where do the ducts of the Brunner’s glands in the duodenum drain into?
Crypts of duodenum
How does the proportion of enterocytes change in the ileum?
Decreases
How does the proportion of goblet cells change in the ileum?
Increases
How does the proportion of Paneth cells change in the ileum?
Increases
How does the amount of lymphoid tissue change in the ileum?
Increases
What is the name of the lymphoid tissue in the ileum?
Peyer’s patches
Why does the ileum have more lymphoid tissue called Peyer’s patches?
Because it is adjacent to the colon
which contains many bacteria as part of the normal flora
whereas the ileum is sterile
so it has more lymphoid tissue to protect against infection
How does the number of villi change in the ileum?
Decreases
