Gibneys + Dreyfus. - Histo Of Alimentary Canal Flashcards
How does The muscularis externa change depending on which part of the esophagus you are in?
Upper - all skeletal
Middle - half skeletal half smooth
Lower - all smooth
What kind of epithelium in the esophagus?
Stratified squamous
What type of epithelium does the stomach have?
Simple columnar with no goblet cells and villi. 3 layers of muscularis externa as opposed to the esophagus that had 2.
- Has pits and glands
What is the location called that we switch from stratified squamous to simple columnar?
Gastoesophageal junction
Cardiac of the stomach
- mostly mucous secreting glands
- glands are tubular, coiled, and perhaps branched
- 1:1 ratio of Piti to gland
Fundus of the stomach
- most colorful area due to staining o chief and parietal cells.
- 1:3 ratio of pit to glands
WHAT COLOR DO parietal cells stain? Chief cells?
Parietal - red stain
Chief - blue
What does a chief cell secrete?
Pepsinogen
What does an Inactive parietal cell secrete?
HCl, HCO3-, IF
- lots of mitochondria and tubules and vesicles termed the “membrane reserves”
Pyloric stomach
- mostly mucous secreting glands
- no chief or parietal cells
- glands are branched, coiled tubular glands with a wide lumen
- 3:1 pit to gland ratio.
What part of the stomach can you find the chief and parietal cells?
Fundus
Gastroduodenal junction
Stomach - no goblet cells
Duodenum - yes goblet cells
Stomach - no villi
Duodenum - yes villi
Stomach - 3 layers of muscularis externa
Duodenum - 2 layers of muscularis externa
Histological features of the SI
- goblet cells
- villi
- simple columnar epithelium
- crypts of Lieberkuhn
Plicae circularis
Sub mucosal folds in the intestines that increase surface area
KEy feature of the duodenum
Brunners glands - produce alkaline secretion to neutralize acidity of stomach.
- in mucosal layer
Key feature of the jejunum
Long villi
Lacteals
Found in the villi.
- Processing of lipids into chylomicrons occurs in the enterocytes and is then discharged into the lacteals.
Key feature of the Ileum
Peyers Patches - lymphoid nodules
- short and fat villi
M-cell
Specialized epithelial cell that takes up antigens which are then transported by transcytosis to present immunocompetent B lymphocytes.
- Essentially responsible for getting rid of invading microbes/pathogens in the ileum.
- found in the peters patches.
DNES cells
- found throughout the digestive system
- secretes hormones such as gastrin, glucagon, somatostatin, and motility.
- secretes these hormones directly into the blood circulation.
- influences motility and digestion
- can be open or closed
Paneth cells
Located at the bottom of crypts. They monitor microbial flora.
- they produce lysozyme, tumor necrosis factor-alpha, and defensins/cryptidins
4 layers of the GI tract
Mucosa - epithelium, lamina, propria, muscularis mucosae
Sub mucosa
Muscularis externa - Circular + Longitudinal
(Serosa)
- More Sweet Chili Langert
Key features of the colon
No villi
Increase in goblet cells
Taenia coli
Plicae semilunar
Submucoal fold in the large intestine
Appendix
Same epithelial lining as the colon
Differs. From colon in that it has a uniform layer of longitudinal muscle in the muscularis externa
Key feature - many lymph nodules with germinal centers
Recto-anal junction
Simple columnar with goblet cells –> stratified squamous epithelium
What is a key feature of the esophagus
Mucous glands are found in the lamina propria or th submucosa. These glands lubricate the esophagus so that food can pass down.
What are the 6 cells of the stomach?
Surface mucous cells Neck Mucous cells Stem cells Parietal cells Chief cells DNES (enteric doctrine) cells
Surface mucous cells
- granules contain glycoproteins (mucins) that combine with water on the surface to form a protective and insoluble gel. They produce HCO3- that diffuses into surface mucous gel
Neck mucous cells
Produce soluble mucous
What hormones regulate acid secretion
Acetylcholine, histamine, and gastrin
- parietal cells have receptors for all three of these.
Why does pH go up after eating a large. Meal
In order for Cl to be excreted from parietal cells, it first has to be taken up. It does this through a Cl-/HCO3- swap. This way, we still have a H+ left over from the break down of H20 and CO2 to be sent out into the lumen.
What activates chief cells?
Acetylcholine or secretin.
What activates Pepsinogen?
H+
Stem cells
- in base of gastric pits
- give rise to mature epithelium in 4-5 days
- replace damaged cells rom the gastric lumen
What 5 things act in a protective role of the GI epithelium?
Bicarbonate mucus Prostaglandins that increase local circulation and secretion of HCO3- Tight junctions Pepsinogen Stem cells
6 cells of the SI
Enterocytes Goblet cells Paneth cells immune cells Stem cells DNES cells
Enterocytes
Absorption of lipids in order to make chylomicrons. .
- also absorbs sugars, AAs, vitamins, minerals, ions, and water.
- makes enzymes associated with glycocalyx
What are the names of the two arteriolar systems in the villi? What other part of the circulatory system is in the villi?
Capillary villus plexus - supplies the tip of the villi
Pericryptal capillary plexus - supplies the crypt
- Also has a lacteal
