Histology Flashcards
What are the four layers of the GIT?
Mucosa
Submucosa
Muscularis propria
Adventitia (serosa)
What are the three layers of mucosa in the GIT?
Epithelium, lamina propria and muscularis mucosae
What is the submucosa made of and what does it contain?
Mase of loose collagenous tissue containing blood vessels, lymphatics, nerve submucosal plexus and lymphoid aggregates
What are the two layers of the muscularis propria and what lies between them?
Inner circular muscle and outer longitudinal
The myenteric plexus lies between these two layers
When do you have adventitia and serosa and what is it comprised of?
Sersoa when intraperitoneal and adventitia when retroperitoneal
It is an outer layer of loose supporting tissue conducting major vessels, nerves and contains variable amounts of adipose tissue.
What lines the oesophagus?
Stratified squamous epithelium
What occurs in Barretts oesophagus?
There is metaplasia (change in cell type) from stratified squamous to columnar epithelium which is usually found in the intestine. occurs in response to acid reflux
What occurs at the gastro-oesophageal junction?
Change from stratified squamous epithelium to simple columnar
What is the role of surface mucous cells?
Secrete bicarbonate to protect the epithelium from acidic gastric juices
What is the role of parietal cells?
secrete gastric acid and intrinsic factor
What is the role of chief cells?
secrete pepsin
What is the distinguishing feature of the muscularis propria in the stomach?
There is an additional layer of muscle (inner oblique)
What can helicobacter pylori cause?
gastritis, adenocarcinoma, lymphoma and gastric ulcers
What occurs at the gastro-duodenal junction
change from simple columnar epithelium to villous mucosa lined by columnar mucosa with goblet cells
What is the function of the villi and what are the spaces in-between them called
Increase the surface area for absorption
In-between there are the crypts of Lieberkuhn which extend down to the muscularis mucosae
What is the feature unique to the duodenum?
Brunners glands in the submucosa that secrete a thin alkaline mucus in response to chyme that will protect the duodenal mucosa from auto digestion
what does chyme stimulate?
Brunners glands and release of CCK and secretin from neuroendocrine cells which will stimulate pancreatic secretions and gallbladder contractions
What are enterocytes?
Absorptive cells with microvilli that line the villi and crypts
What is the role of goblet cells?
to produce mucin for lubrication and protection - scatted amongst the enterocytes
what are paneth cells, where are they found and what is their function?
Found at the base of the crypts and are distinguished by their prominent eosinophilic apical granules - defensive function
Where are the stem cells found?
at the base of the crypts and can divide to form all 4 cell types
What occurs at the ileo-caecal junction?
change from villous mucosa to simple columnar which forms tubular glands (crypts)
What are the two cell types in the large intestine?
Goblet cells
Absorptive cells
What are the differences between small and large intestine?
Small: finger like villi and crypts (not as many goblet cells)
Large: deep crypts without villi (lots of goblet cells)
