W3 - Upper GI tract Flashcards
What two types of epithelium do we tend to see in the GI?
Stratified squamous and simple columnar
What two parts of the GI tract have stratified squamous epithelium and what is it’s function?
Oesophagus and rectum, it has a protective function
What type of epithelium covers the majority of the GI tract and what is it’s function?
Simple columnar, secretion and absorption (can sometimes be protective - more immune cells in gut than anywhere else)
What is difference between the squamous epithelium in the oesophagus and the skin?
It’s non-keratinised
Which layer of the Oes contains oesophageal glands for lubrication and protection?
The submucosa
What is different about the cells at the bottom of the Oes glands compared to the surface of the Oes?
They are columnar and not squamous
Why is the highly proliferating basal layer of the Oes squamous epithelium at the bottom?
So they are protected and to not expose the lamina propria to infection
What are the proliferative cells usually around in the Oes squamous epithelium?
The papillae
Oesophageal glands produce mucin to aid movement of food from oes to stomach, where are these more typically located in this case?
Distal oesophagus
Other than lubrication, what is the other function of oesophageal glands and why?
They produce antimicrobial peptides to help fight infection
There are two parts to an oesophageal submucosal gland, the duct (connecting to gland) and the secretory part - gland, which is squamous and which is columnar?
Duct - squamous, Gland - columnar
At the gastro-oesophageal junction what does the epithelium change from and to?
Protective to secretory
Secretion of acids, digestive enzymes, mucous and lysozymes in the stomach are controlled by HMs but what triggers the release of these HMs?
The stretching of the rugae when food is ingested sends a signal to release HMs for digestion (switches off when food leaves stomach)
What is the primary function of the rugae folds?
Allow for expansion of the stomach
Foveolar cells in the cardia produce muc5AC, what is it’s very important function?
Stops the stomach acid and enzymes from digesting the stomach
what do mucous secreting cells produce fro lubrication in the cardia?
Mucin6
The body of the stomach have parietal cells within the gland, they produce HCl, how are the glands in the body more complex in structure than those in the cardia?
They are branched and are comprised of a base, a neck and an isthmus
Unlike the stem cells in the oesophagus, where do the stem cells sit in the glands of the stomach’s body?
In the middle (isthmus)
Foveolar cells are common to all parts of the stomach, what is a characteristic of these cells that makes sense considering they secrete muc5AC?
They are resistant to degradation
In the glands in the body of the stomach, do all stem cells differentiate/migrate upwards?
No some up (foveolar) some down (parietal + chief)
Mucous neck cells secrete trefoil factors and are protective, how are they found?
Clusters/single cells
Parietal cells are large and round with eosinophilic cytoplasm, what do parietal cells have a lot of? (‘fried egg cells’)
Mitochondria and intracellular canaliculi
Chief (zymogenic) cells or predominantly in the lower tubular gland in the stomach body, what do they secrete (other than lipids) and what does this convert to in the presence of an acid?
Pepsinogen (inactive enzyme), pepsin (active proteolytic enzyme)
Zymogenic cells have a lot of rER, where is their nuclei positioned?
Base
Neuroendocrine cells are found in the isthmus of the glands, what are the two HMs that they produce + what are their functions?
Gastrin by G cells (activates parietal cells to secrete HCl) and somatostatin by D cells (inhibits release of gastrin)
What stimulates the release of gastrin and the release of somatostatin?
The parasympathetic signalling from rugae stretching (gastrin), presence of HCl (somatostatin)
The gastric pits are larger in the pylorus than the body of the stomach, what does this mean about the HMs secreted?
There are more neuroendocrine cells and therefore more HMs secreted in the pylorus than the body
What is another word for a gastric pit of a gland?
Foveolus
Why are the gastric pits/foveoli in the pylorus deeper than the rest of the stomach?
Due to gravity, most of the food is at the base of the stomach so you need more of everything (especially muc5AC)
