Salivary Glands, Oesophagus and Stomach Microanatomy Flashcards
What are the layers of the gut wall?
Mucosa; Submucosa; Musclularis externa; Serosa/adventitia
What are the layers of the mucosa?
Epithelium: protection, secretion, absorption
Lamina Propria: Support (CT and BVs/nerves)
Muscularis mucosa: movement independent of peristalsis
What are the two nerve plexi of the gut ad where are they?
Submucosal nerve plexus in submucosa
Myenteric nerve plexus in muscularis externa
What are the three salivary glands, what are their secretions?
Parotid- Serous (25%)
Submandibular- Mixed (70%)
Sublingual- Mixed (5%)
What are the three different cell types of the glands?
Serous acinus
Mucous acinus
Striated duct
What is the structure of a serous acinus?
Central nuclei; darkly stained due to zymogin granules (amylase); surrounding myoepithelial cells which contract
What is the structure of a mucous acinus?
Peripheral nuclei; light colour due to mucous granules
What is the structure of a striated duct cell and what do they do?
Fenestrated with many mitochondria on the outside.
Metabolically active and controls flows on ions on secretions, particularly bicarbonate
What does mucous do in saliva?
Lubricates and prevents bacterial adhesion.
How do bicarbonate ions; lysozyme; lactoferrin and IgA protect saliva?
Bicarbonate: protects against bacterial secretions and acidic things i.e vomit.
Lysozyme: bacterial cell walls
Lactoferrin: iron dep. bacteria
IgA: bacteria and viruses.
How do amylase; lipases and kallikrein aid digestion?
Amylase: breaks down CHO at pH 4-11
Lipase at pH 4
Kallikrein: causes an increase in blood supply to the glands, meaning more saliva (PSNS)
How are salivary glands controlled by the ANS?
SNS: less, viscous saliva, dry mouth, high enzyme concentrate.
PSNS: More watery saliva, increased blood flow, myoepithelial cells contract.
What do the three different stomach glands secrete?
Cardia- mucous
Fundus- HCl, intrinsic facor, pepsinogen, somatostatin
Pylorus- Mucuous, pepsinogen, gastrin, somatostatin
What are the different stomach cell types?
Simple columnar mucuous cells; mucuous neck cells; undiff. stem cells; parietal cells; chief cells; enteroendocrine cells
What are the features of simple columnar mucous cells and what can affect them?
They secrete an insoluble, alkaline mucous coat that will trap HCO3-. Also have a dense layer of phospholipids. Both these are stimulated to be made by PROSTAGLANDIN E2.
Helicobacter pylori converts urea to ammonia by urease, damaging the mucuous coat, as well as toxins (ulcerogens) harm the cell.
What do mucous neck cells secrete?
Soluble acidic mucous.
What do parietals cells secrete and how are these important?
HCL: provide the acidic environemnt for pepsinogen to be converted to pepsin, and to sterilise food. Decreased HCl can cause a decrease in digestion (less pepsin) and/or not all bacteria are killed, causing potentially gastroenteritis.
Intrinsic factor: aids vitmain B12 absorption, which is important in RBC haemopoiesis. Decreased IF can causes pernicious anaemia.
What do chief cells produce?
pepsinogen
How do enteroendorcine cells work?
note that they secrete hormones int blood stream of LP
G cells will secret gastrin, which stimulates all stomach cells and ECL cells to secrete histamine.
Histamine will stimulate PARIETAL cells and D cells to secrete somatostatin.
Somatostatin inhibits G cells and ECL cells secreting gastrin and histamine.
Prostaglandin E2 will inhibit G cells and ECL cells, meaning decrease gastrin etc. NB PE2 can be inhibited by NSAIDs such as aspirin.
