GI Tract Flashcards
What are the 5 major phases of food breakdown
- ingestion
- fragmentation
- digestion
- absorption
- elimination
Where is Auerbach plexus found?
What does it do ?
Found between inner and outer layers of muscularis extena
Provides motor innveration to muscularis
What is the stoamch rugae ?
Ridges produced by folding of internal surface of stomach
Allow stomach to expand to accommodate food
What do the parietal cells do ?
Secrete HCL via canaliculi in response to gastrin
Secrete intrinisic factors for vitamin B12 absorption
What do the chief cells do ?
Main cells in lower regions of gastrin glands
Release zymogen granules containing lipase and protease in repsonse to gastrin
What is the small intestine made up of ?
- duodenum
- jejunum
- ileum
What does the inner lining make up ? What does it do?
Plicae circularis
Increase surface area for absorption
What maintains the microvilli shape?
Actin filaments anchored to cell membrane
Base of actin filaments form part of terminal web
What does the microvili form ?
Brush boarder on apical side of enterocyte with glycocalyx
What are glycocalyx ?
Coating of glycoproteins and glycolipids projecting from plasma membrane
Protect from autodigestion and site of absorption of pancreatic enzymes
What are the epithelial cell types of the same intestine ?
- enterocytes
- goblet cells
- panetch cell
- endocrine cell
- stem cell
What are enteroctes ?
Tall columnar absorptive cells
Basely located nuclei
Have between 2000-3000 microvilli with glycocalyx
What do goblet cells do ?
Produce mucus for protection and lubrication
What do paneth cells do ?
Where are they found ?
Found in crypts
Release protective enzymes e.g lysozyme, phospholipase A and peptides
Secretions help destroy parasites and bacteria
What do enteroendocrine cells do ?
Where are they found ?
In lower part of crypts
Secrete hormones
Has the acidic chime neutralised ?
- CCK or CCK-PZ inhibits gastric emptying and stimulates acinar cells to secrete enzymes
- gall bladder releases bile to emulsify fats via ducts in duodenum
- secretin stimulates Brunner glands + pancreatic centroacinar cells to release bicarbonate to neutralise acidic chime
- liver makes bile
- parietal cells reduce acid secretion
Where do the ducs of Brunner glans deliver secretion to ?
Crypts of Lieberkuhn
What are distincit features of the jejnum :
- have the tallest vili
- no Brunner glands
- few lymphoid follicles
- some enteroendocrine cells producing CCK and secrtin
What are distinct features of the illeum ?
- short villi
- lots of lymphoid tissue forms Peyers patches
What is mucosa associated lymphoid tissue (MALT)
- defence mechanism of gut
- provides local immune survelliance
What is Peyers Patch ?
- Gut Associated Lymphoid Tissue
- lymphoid follicles that buldge into gut lumen
- contain many lymphocytes to fight infection
What are the cell types found in Peyers Patches ?
- goblet cells + M cells take up antigens
- mature B lymphocytes + T lymphocytes
- dendritic cells + macrophages
- immune cells
What is the large intestine made up of ?
- appendix
- cecum
- ascending colon
- transverse colon
- descending colon
- sigmoid colon
- rectum
- anal canal
Describe the appendix :
- small blind ended sac
- lamina propria of mucosa and sub mucosa heavily infiltrated with lymphocytes
- lymphoid tissue can form follicles with germinal center
Describe the colon :
- made of up 4 sections Ascending Transverse Descending Sigmoid - function is to absorb water and electrolytes
Describe the rectum :
- short dilated terminal portion of large intestine
- has tubular glands and goblet cells
What happens at the recto-anal junction ?
Sharp transition from simple columnar to stratified squamous epithelium
