3. crypt villus dynamics and small intestinal cell response SDL

Question 1

what are the arrows pointing to

Answer 1

crypts

Question 2

where is the muscularis mucosae and what does it do

Answer 2

In the small intestine, the muscularis mucosae is located within the mucosa, specifically situated deep to the lamina propria (connective tissue) and superficial to the submucosa. It forms a thin layer of smooth muscle fibers that run parallel to the surface epithelium.
- regulates mucosal fold shape
- controls local movements of the mucosa (aids in mixing of lumen contents)
- supports and protects mucosa by maintaining structural integrity
- facilitates nutrient absorption through movements

Question 3

in which parts of the GIT are villi found and what are their function

Answer 3

• extend into lumen of small intestine, most prominently in the jejunum and ileum
• function to increase surface area, absorb nutrients, secrete digestive enzymes, mix, absorb lymphatics

Question 4

where are cells lost from on the villi

Answer 4

1. stem cell division begins in crypts
2. as they divide the give rise to progenitor cells that migrate upwards or downwards where they can then differentiate into matture cells

Question 5

discuss how the process of the epithelial cell escalator of the villi maintain villus health and how damage to the villus can be repaired

Answer 5

• continuous renewal and tunrover of cells
• repair = activation of stem cells and migration and differentiation of cells

Question 6

where do you find goblet cells

Answer 6

• scattered among epithelial cells of vili but more abundant in ileum than duodenum
• also in large intestine

Question 7

what intracellular features of goblet cells allow them to secrete mucin

Answer 7

• mucin granules
• glycosylation
• release through exocytosis

Question 8

do goblet cells have any absorptive capacity

Answer 8

no
- dont have any absorptive structures (microvilli)

Question 9

what features do goblet cells lack which are most associated with absorption processes for amino acids and carbohydrates

Answer 9

• microvilli
• transport proteins
• enzymes for digestion
• mitochondrail density
• specialised tight junctions and barier function

Question 10

what stem cells fo goblet cels arise from and where are they located

Answer 10

stem cells from crypts of lieberkuhn

Question 11

how do goblet cells respond to inflammation

Answer 11

• increse mucin production
• alter mucin composition (glycosylation pattern changes viscosity patterns etc)

Question 12

what kind of feedback mechanism tells the crypt to work quickly to re form a damaged villi

Answer 12

• stem cell activation
• signalling pathways and growth factors
• immune response and inflamamtory signals
• feedbakc from microbiota