Midgut and Hindgut Flashcards
what is the anatomical transition from fore- to midgut?
duodenum
what do the jejunal arteries supply?
distal duodenum and jejunum
what does the caudal pancreaticoduodenal artery supply?
right pancreatic lobe + middle of duodenum
what do the ileocolic, cecal and right colic arteries supply?
ascending colon
cecum
right colic fixture (curve between ascending and transverse colon)
what does the middle colic artery supply?
first 2/3 of the transverse supply
what is digestion?
breakdown of complex nutrients into simple molecules
what is absorption?
transporting those molecules across intestinal epithelium
what are plica circulares/circular folds and what do they do?
in duodenum
non-distensible –> meaning do not flatten out with distension
covered with intestinal villi and act to increase surface area of the proximal small intestine by approximately 10-14x
what are lacteal?
specialized lymph –> carries absorbed fats away from surface epithelium
describe small intestine mucosal epithelium
simple columnar epithelium with microvilli (as brush border)
evaginates into villi
invaginations into short intestinal glands
villi, microvilli, glands increase surface area for absorption
what are the 2 types of enterocyte functions?
absorptive: tall microvilli, tight junctions (containment of luminal contents), lateral enfoldings
digestive: glycocalyx enzymes, glycoproteins mixed with mucous creating a coating that traps molecules near the apical membrane
what do brunner’s glands secrete
peptide hormone urogastrone that inhibits HCl secretion
mucous-alkaline glycoprotein
describe the cells in the proximal part of the duodenum (closest to pylorus)
specialized mucous-secreting glands to protect the duodenal lining from the highly acidic chyme delivered from the stomach
tall cuboidal epithelial cells
brunner’s glands
what are fenestrated capillaries?
transport of proteins, carbs
what are lymphatic capillaries?
called lacteals
transport of dietary fats
how does the lamina propria provide host defense?
GALT: gut-associated lymphatic tissue
aggregated nodules of lymphoid tissue are concentrated in the ileum
what is the muscularis mucosa?
smooth muscle layer in deepest mucosa
smooth muscle organized in inner circular and outer longitudinal layers that during contraction move the mucosa, forming ridges and valleys that facilitate absorption and secretion
what are 2 notable exceptions against why the submucosa is similar along the GI tract
1) brunner’s glands (only in duodenum) secrete alkaline fluid to raise pH of incoming chyme
2) plicae circulares - envaginated submucosa covered with mucosa increases surface area for absorption –> cannot flatten
how does the material pass into the large intestine?
ileal orifice and annular fold
what does the cranial rectal artery supply?
distal descending colon and cranial half of the rectum
what does the left colic artery supply?
descending colon and part of transverse colon
what does the colon absorb?
water, vitamins, electrolytes
describe the mucosal epithelium of the large intestine
-simple columnar with short microvilli
-invagination into long straight intestinal glands/crypts
-enterocytes –> absorb water, dehydrate feces
INVAGINATIONS = STRAIGHT AND REGULAR
how is the cecum specialized in non-ruminant herbivores
houses microfauna to ferment and break down cellulose, functionally similar to forestomachs to ruminants
no villar expansion, intestinal crypts open at the surface
goblet cells
describe the lamina propria in the colon
provides host defense (GALT via isolated nodules)
no lymphatic capillaries –> colon cancers slow to spread
describe the muscularis mucosa in the colon
smooth muscle
contract intestinal glands
contractions shake loose lodged feces
describe the submucosa in the colon
dense irregular CT
blood and lymphatic vessels
describe the equine large intestine makeup
ascending colon:
-L and R ventral
-L and R dorsal
-transverse colon
descending colon
describe the importance of the haustrae in cows and horses
narrows the diameter of the colon and makes fecal matter smaller
describe the rectum/anal canal histology make up
stratified squamous epithelium for protection
mucous glands for lubrication
skeletal and smooth muscle
what is a potential origin for the portal vein
cranial mesenteric vein
what drains into the cranial mesenteric vein
-jejunal
-cranial pancreaticoduodenal
-ileocolic
-right colic
what is the largest lymphatic vessel of the lymphatic system and what does it drain to?
thoracic duct
drains to the left brachiocephalic vein, returns lymph to systemic drainage
what is intestinal volvulus
complete twisting of a loop of intestine around its mesenteric attachment site
endangers blood supply –> can lead to necrosis of affected bowel
