Exam 1 Flashcards
Salivary glands - functions
Protection of oral cavity and teeth
Lubricate dry ingesta
Provide fluid for rumen and pH adjustment
source of IgA from adjacent plasma cells and perhaps hormones
production of digestive enzymes
regulation of electrolyte balance
GI tract - functions
movement of ingesta thru the tube
digestion - mechanical and chemical
absorption of simple nutrients
secretion of enzymes, hormones, and mucin
Esophagus
T. mucosa: stratified squamous epithelium, keratinized in herbivores and pigs; muscularis mucosa with longitudinal orientation - absent cranially, increases in thickness caudally
T. submucosa - tubuloacinar glands: mostly mucous with some serous demilune cells. Glands are only found cranially, except in the dog
T. muscularis - inner circular and outer longitudinal layers; ruminants and dog - striated ms. entire length; cat, pig, horse - striated cranially, smooth caudally; circular layers form physiological sphincter at pharyngeal-esophageal and esophageal-gastric junctions
T. adventitia - covers most length of esoph
T. serosa - appears in a small area adjacent to stomach
Stomach - functions
storage and mixing
mechanical and chemical digestion
secretion of mucous, enzymes, H2O, electrolytes, hormones
Simple Stomach/ruminant abomasum
T. mucosa - thrown into gastric folds with gastric areas (elevations) and gastric pits (depressions); at base of pits, epith = tall columnar, mucus secreting, simple branched or coiled tubular gastric glands in lamina propria; mitosis occurs at base of gastric pit with older cells toward stomach lumen
Lamina propria - sparse with fine collagen fibers and free cells b/t gastric glands, diffuse lymphoid tissue
Subglandular layer in carnivores - at border of lamina propria and muscularis mucosae, consists of stratum granulosum (cellular) and stratum compactum (packed collagen fibers)
Muscularis mucosae - 3 layers of smooth ms - strands of sm. ms. from innermost layer extend b/t glands toward mucosal surface
T. submucosa - coarse CT, abundant free cells, largest blood vessels and the submucosal plexus
T. muscularis - 3 layers of smooth muscle: inner oblique, middle circular layer (–> sphincters), outer longitudinal; myenteric plexus is b/t middle and outer layers
T. serosa - covers outermost surface of stomach
Gastric mucosal barrier - made of alkaline mucus and HCO3 secreted by epith cells and tight junctions b/t cell apices; protects mucosa from acid stomach contents/physical damage
Ruminant forestomach
Epithelium - same in all compartments - stratified squamous, slightly cornified (protection), desmosomes attach adjacent cells; swollen b/t st. corneum and st. granulosum; wide intercellular spaces (absorption), metabolically active, highly permeable (VFAs are absorbed and metabolized)
L. propria - highly vascular
T. muscularis - in all compartments - 2 layers
T. serosa - present
Rumen
Fermentation vat
Luminal surface - small tongue like papillae (^ SA; size varies from area to area and w/nutrition)
No muscularis mucosae
Reticulum
mechanical digestion
surface folds form honey-comb network of ridges w/muscularis mucosae in free edge only
secondary papillae extend from the fold
reticular groove - channel from esophagus to omasum; made of sm. ms. of muscularis mucosae, floor had t. muscularis intermixed with skel. ms
Omasum
mechanical digestion
long, leaf-like folds with small, horny papillae
muscularis mucosae/t. muscularis occupy center of larger folds
Small intestine
T. mucosa - contain villi = leaflike projections of t. mucosa (epithelium and l. propria) that ^ SA
lymphatic in center of villus = central lacteal - transports chylomicrons into circulation and surrounded by capillaries
strands of sm. ms. from muscularis mucosae extend into villus - rhythmic contrxn of this pumps lymph out of lacteal and into larger lymph vessels
intestinal mucosal glands/crypts - fill l. propria, lined by epithelium continuous surface epithelium, open b/t villi
L. propria - reticular fibers, many free cells
lymph nodules thruout SI and increase caudally
aggregated nodules (peyer’s patches) on antimesenteric side = characteristic of ileum
stratum compactum/subglandular layer - in carnivores
muscularis mucosae = 2 layers of sm. ms.
T. submucosa
aggregated lymph nodules in ileum
intestinal submucosal glands - cranial SI - simple branched tubuloacinar glands, open into base of intestinal mucosal glands, secretory cells (mucous, serous, or mixed with protective substances to buffer stomach acid) have apical membrane-bound granules, basal RER; secretions are part of intestinal mucosal barrier (with goblet cell secretions and apical jnctnl complexes) that protects epith
location of submucosal nerve plexus
t. muscularis - 2 layers of sm. ms. & myenteric n. plexus
T. serosa - visceral peritoneum
Large intestine - functions
site of microbial action
epithelium absorbs/secretes H2O and electrolytes, absorbs fermentation products in non-ruminants, secretes mucus
forms fecal mass
Large intestine - structure
T. mucosa - longitudinal folds, no villi, smooth epith, deep mucosal glands open unto luminal surface; abundant goblet cells, enterocytes, enteroendocrine cells; l. propria with many free cells and lymph nodules, large venous plexuses occur in rectum
T. submucosa - may accumulate fat
T. muscularis - outer longitudinal layer forms bands in cecum and colon of horse and pig, many elastic fibers
T. serosa - covers large intestine except for most of rectum (t. adventitia)
Other features:
ruminants - longitudinal mucosal folds in rectum (rectal columns; alternate with rectal sinuses)
dogs - solitary lymph nodules w/epith depressions over them = rectal pits
