Epithelia of the gut Flashcards
What are the types of gut epithelia?
- Stratified squamous - found in the oesophagus and distal anus
- Non - keratinised
- Found in areas where there maybe mechanical or
chemical abrasion/stress. - Simple columnar - found from the stomach to the proximal anus.
Describe the epithelia of the stomach
- Surface mucous cells line gastric mucosa and dip down to form gastric pits.
- Gastric pits are connected to gastric glands in the lamina propria of the stomach.
- Mucous cells secrete mucus/HCO3 that forms a barrier to stomach acid.
What are neck mucous cells?
- Found at the bottom of gastric pits.
-Smaller cells with irregular shape due to compression by surrounding cells.
What are the adaptations of the small intestine to help it absorb nutrients?
- Permanent folds mean that gut does not have a flat internal surface.
- This increases the surface area over which absorption can happen.
- Villi
- Microvilli
- Epithelia is only one cell thick.
What is the predominant cell of the small intestine and colon?
- Enterocyte
Describe the structure of the small intestine epithelia
- Enterocytes
- Apical membrane
- Basolateral membrane
- Blood vessels and lymphatics lie immediately below the enterocyte in the lamina propria.
What is the function of goblet cells in the small intestine?
- Secrete mucus
- Found scattered in between enterocytes, increasing in number from duodenum to colon.
- Have a narrow base and larger apical size due to enterocytes squishing the cells.
- Mucus compresses nucleus to the base of the goblet cell.
Why is mucus important in the small intestine?
Protects epithelia from:
- Friction
-Chemical damage (acidic environment)
- Bacterial inflammation
What is found in the crypts of the small intestine?
- Enteroendocrine cells
- Stem cells
- Paneth cells
What is the function of the enteroendocrine cells in the crypts of the small intestine?
- Secrete hormones that control the function of the gut.
- E.g. gastrin, cholecystokinin, secretin
What is the function of the stem cells found in the crypts of the small intestine?
- Constantly divide to replace epithelia.
- Needs to happen every 2-4 days to maintain an intact and fully functioning barrier.
What is the function of the paneth cells located at the base of the crypts?
- Secrete antibacterial proteins to protect stem cells
What is the role of Brunner’s Glands found in the duodenum?
- Found in the proximal duodenum which receives very acidic material from the stomach.
- Glands are located partly within deep mucosa and also in submucosa.
- They produce an alkaline mucoid material.
- This material is secreted into the sides or bases of the crypts to neutralise acidic chyme.
How are different key nutrients absorbed in the small intestine?
- Proteins and carbohydrates are absorbed directly into the blood.
- Fats are absorbed into lymph capillaries that lie in the submucosa.
What cells make up the epithelium of the colon?
- Tall columnar epithelia interspersed with much larger mucus producing goblet cells.
