Block 11 MicroAna LOs PDF

1. Embryologic origins a. Endoderm-derived - epithelial mucosa, liver and pancreas, and associated glands b. Mesoderm-derived - submucosa, muscle layers, serosa, mesentery c. Ectoderm-derived - stratified squamous epithelium of oral cavity and anus, and nerve plexi 2. List the f...

1. Embryologic origins a. Endoderm-derived - epithelial mucosa, liver and pancreas, and associated glands b. Mesoderm-derived - submucosa, muscle layers, serosa, mesentery c. Ectoderm-derived - stratified squamous epithelium of oral cavity and anus, and nerve plexi 2. List the four tunics possible in a generic tubular organ, the three possible layers of the tunica mucosa, two plexuses found in some tubular viscera, surface modifications found in tubular viscera, and tissues found in tubular viscera. a. Mucosa i. Inner epithelium - glandular simple columnar ii. Middle lamina propria - loose connective tissue, VANs and lymphatics, smooth muscle cells iii. Muscularis mucosa - smooth muscle b. Submucosa - blood vessels, nerve plexus, facilitates the motility of mucosa, loose connective tissue, can contain glands and lymph nodules c. Muscularis - can be smooth or skeletal muscle, controls lumen size, contains myenteric nerve plexus i. Inner circular ii. Outer longitudinal d. Serosa - mesoepithelium = fat and loose connective tissue, continuous with the mesentery, omentum, and peritoneum e. Adventia - loose/dense connective tissue ONLY when the organ is connected to something else 3. Define: mucous membrane, villi, and microvilli. a. Mucous membrane - membrane that lines various cavities in the body and covers the surface of internal organs b. Villi - any of the fingerlike or threadlike projections from the surface of certain membranous structures, typically serving to increase surface area and facilitate the passage of fluid or nutrients c. Microvilli - microscopic cellular membrane protrusions that increase the surface area for diffusion and minimize any increase in volume, and are involved in a wide variety of functions, including absorption, secretion, cellular adhesion, and mechanotransduction 4. List and describe the components of the digestive system. a. Oral cavity i. Mucosa - stratified squamous epithelium 1. Keratinized or non-keratinized ii. Submucosa iii. Has salivary glands and tonsils b. Salivary glands i. Major glands - parotid (serous), sublingual (mostly mucous), mandibular 1. Stroma - connective tissues, VANs and lymph 2. Parenchyma a. Secretory units (adenomere) b. Ducts ii. Minor glands - lingual, palatal, labial, buccal, zygomatic (carnivores), molar (cats) iii. Types of secretions - mixed, serous, mucous c. Tongue i. Mucosa - stratified squamous epithelium, keratinized on dorsal side 1. Dorsal aspect has gustatory and mechanical papillae ii. Muscularis - skeletal muscle in 3 directions: longitudinal, transverse and vertical d. Teeth i. Layers 1. Enamel - covers entire external surface above the gumline a. Ameloblasts - forms enamel, simple columnar 2. Cementum - covers entire external surface below the gumline a. Cementoblasts - forms cementum 3. Dentin - beneath enamel and cementum a. Odonotoblasts - forms dentin 4. Pulp - loose connective tissue and VANs 5. Periodontal ligament a. Fibroblasts - forms the ligament ii. Types of teeth 1. Brachydont - short and cease to grow after eruption a. Contains a crown and neck with one or more roots b. All teeth in carnivores, incisors of ruminants, all teeth in pigs except incisors 2. Hypsodont - tall and continue to grow after eruption a. All teeth in horses, cheek teeth of ruminants, canine teeth of pigs e. Esophagus i. Epithelium - non-keratinized strat. squamous ii. Lamina propria iii. Muscularis mucosa iv. Submucosa - contains mucous glands v. Muscularis - skeletal or smooth muscle depending on the species vi. Adventitia f. Stomach  i. Gastric pit - indentations in the stomach which denote entrances to the tubular shaped gastric glands ii. Rugae - folds in the mucosal layer of the glandular stomach to increase surface area iii. Glandular stomach 1. Mucosa - simple columnar with gastric pits 2. Muscularis a. Inner oblique b. Middle circular c. Outer longitudinal 3. Serosa 4. Regions a. Cardia region - entrance into the stomach i. Lots of mucus glands b. Fundus - magic happens here i. Proper gastric glands ii. Chief cell 1. Secretes pepsinogen - stains basophillic iii. Parietal cell 1. Secretes HCl - stains eosinophillic iv. Endocrine G cell 1. Produces gastrin - requires special staining c. Pylorus region - exit to the duodenum i. Mucus glands and endocrine g cells g. Small intestine i. Layers 1. Epithelium - simple columnar (enterocytes and goblets) 2. Lamina propria - creates the villi and microvilli a. Intestinal crypts at base of villi (kinda like the gastric pits) 3. Mucularis ii. Function - nutrient absorption and mucus secretion iii. Areas 1. Duodenum - a. Brunner's glands in the submucosa that produces alkaline mucus to protect from acidic chyme from stomach 2. Jejunum 3. Ileum - peyer’s patches (lymphatic system) h. Large intestine i. Water absorption ii. Simple columnar epithelium iii. NO villi - intestinal crypts present i. Rectum i. Simple columnar epithelium ii. Stores feces, secretes mucus j. Anus - stratified squamous epithelium k. Liver i. Components 1. Hepatocytes a. Polygonal epithelial cells b. Function  i. Detox ii. Bile synthesis iii. Gluconogenesis iv. Energy storage 2. Intrahepatic biliary tree a. Canals and ducts lined by cuboidal epithelium b. Bile ducts in the portal triad c. Oval cells - pluripotent stem cells 3. Kupffer cells a. Phagocytes of the liver b. Located within the blood sinusoids c. Remove aged blood cells (hemosiderin), pathogens, some toxins 4. Sinusoid a. Capillaries of the liver with discontinuous basement membrane and epithelium b. Pit cells - resident granular leukocytes c. Ito cells - Vit. A metabolism, collagen production; contain large rounded lipid vacuoles d. Perisinusoidal space (space of Disse): Site of exchange between blood and hepatocytes 5. Central vein a. Found at the center of hepatic lobules b. Function - receive the blood mixed in the liver sinusoids and return it to circulation via the hepatic veins ii. Connective tissue 1. Each lobe is surrounded by mesothelium 2. Organized into lobules separated by connective tissue l. Gallbladder i. Concentrating/modifying reservoir for bile that dumps into the duodenum via major and minor papillae ii. Horse has NO gall bladder iii. Mucosa 1. Bile ducts lined by short columnar epithelium 2. Gall bladder lined by tall columnar epithelium iv. Smooth muscle v. Serosa m. Pancreas i. Stroma 1. Thin connective tissue capsule, trabeculae with VANs and lymph vessels (pacinian corpuscles) ii. Parenchyma 1. Exocrine - 95% of the parenchyma a. Serous acinar glands producing zymogen granules (eosinophilic) b. Secretes i. Trypsinogen ii. Chymotrypsinogen iii. Lipase iv. amylase 2. Endocrine - 5% of the parenchyma  a. Islet of langerhans b. Secretes i. Insulin ii. Glucagon iii. Somatostatin iv. Pancreatic polypeptide 5. Describe the mucosa of the ruminant stomach and explain the function of rumenal papillae. a. Rumen i. Non-glandular keratinized strat. squamous containing papillae ii. Largest compartment iii. Function - absorption of volatile fatty acids, mixing, regurge, eructation, movement of ingesta b. Reticulum i. Non-glandular keratinized strat. squamous, honeycombed shape mucosa ii. Function - absorption of volatile fatty acids, mixing, regurge, eructation, movement of ingesta c. Omasum i. Non-glandular keratinized strat. Squamous ii. Function - squeezes ingesta, liquifies and moves it to the abomasum d. Abomasum i. Glandular stomach 6. Define: M cell, intestinal crypt, absorption, goblet cell, lacteal, submucosal gland, myenteric plexus/submucosal plexus, colostrum. a. M cell - specialized epithelium that sample antigens from the lumen environment b. Absorption - the movement of nutrients, water and electrolytes from the lumen of the small intestine into the cell, then into the blood c. Goblet cell - a type of intestinal mucosal epithelial cell d. Lacteal - blind ended lymphatic vessels in the intestinal villi e. Submucosal gland - secrete mucus to facilitate the movement of particles along the body's various tubes f. Myenteric plexus - major nerve supply to the gastrointestinal tract and controls GI tract motility 7. Recognize anorectal junction (line), sphincters, circumanal glands, anal sacs. a. Anorectal junction  b. Circumanal glands - present in the subcutis around the anus in dogs c. Anal sacs - reservior for anal gland material i. Keratinized, stratified squamous epithelium ii. Located between the smooth muscle of the internalanal sphincter and the skeletal muscle of the external anal sphincter d. Anal glands - apocrine secretion in dogs and sebaceous and apocrine in cat 8. Define: hepatic lobule/portal lobule/hepatic acinus. a. Hepatic acinus - supplies oxygenated blood to hepatocytes i. Zones 1. Zone 1 (periportal) a. hepatocytes closest to O2 & nutrient rich arterial & portal inflow b. More susceptible to direct-acting toxins 2. Zone 3 (centrilobular) a. Nearest to venule - more susceptible to hypoxia b. Detoxification enzymes - susceptible to metabolites from toxins b. Hepatic lobule - drains portal triad to the central vein c. Portal lobule - drains bile from hepatocytes to bile ducts 9. Trace the flow of bile from the portal lobule to the duodenum. a. Formed by hepatocytes -> bile duct -> gall bladder -> bile duct to duodenum via major and minor papillae 10. List the components and function of the portal triad. a. Portal vein - deoxy blood away b. Portal artery - nutrients to hepatocytes c. Bile duct - get bile out to gall bladder