Midgut and Hindgut

Question 1

what is the anatomical transition from fore- to midgut?

Answer 1

duodenum

Question 2

what do the jejunal arteries supply?

Answer 2

distal duodenum and jejunum

Question 3

what does the caudal pancreaticoduodenal artery supply?

Answer 3

right pancreatic lobe + middle of duodenum

Question 4

what do the ileocolic, cecal and right colic arteries supply?

Answer 4

ascending colon
cecum
right colic fixture (curve between ascending and transverse colon)

Question 5

what does the middle colic artery supply?

Answer 5

first 2/3 of the transverse supply

Question 6

what is digestion?

Answer 6

breakdown of complex nutrients into simple molecules

Question 7

what is absorption?

Answer 7

transporting those molecules across intestinal epithelium

Question 8

what are plica circulares/circular folds and what do they do?

Answer 8

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

Question 9

what are lacteal?

Answer 9

specialized lymph –> carries absorbed fats away from surface epithelium

Question 10

describe small intestine mucosal epithelium

Answer 10

simple columnar epithelium with microvilli (as brush border)

evaginates into villi
invaginations into short intestinal glands
villi, microvilli, glands increase surface area for absorption

Question 11

what are the 2 types of enterocyte functions?

Answer 11

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

Question 12

what do brunner’s glands secrete

Answer 12

peptide hormone urogastrone that inhibits HCl secretion
mucous-alkaline glycoprotein

Question 13

describe the cells in the proximal part of the duodenum (closest to pylorus)

Answer 13

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

Question 14

what are fenestrated capillaries?

Answer 14

transport of proteins, carbs

Question 15

what are lymphatic capillaries?

Answer 15

called lacteals

transport of dietary fats

Question 16

how does the lamina propria provide host defense?

Answer 16

GALT: gut-associated lymphatic tissue

aggregated nodules of lymphoid tissue are concentrated in the ileum

Question 17

what is the muscularis mucosa?

Answer 17

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

Question 18

what are 2 notable exceptions against why the submucosa is similar along the GI tract

Answer 18

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

Question 19

how does the material pass into the large intestine?

Answer 19

ileal orifice and annular fold

Question 20

what does the cranial rectal artery supply?

Answer 20

distal descending colon and cranial half of the rectum

Question 21

what does the left colic artery supply?

Answer 21

descending colon and part of transverse colon

Question 22

what does the colon absorb?

Answer 22

water, vitamins, electrolytes

Question 23

describe the mucosal epithelium of the large intestine

Answer 23

-simple columnar with short microvilli
-invagination into long straight intestinal glands/crypts
-enterocytes –> absorb water, dehydrate feces

INVAGINATIONS = STRAIGHT AND REGULAR

Question 24

how is the cecum specialized in non-ruminant herbivores

Answer 24

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

Question 25

describe the lamina propria in the colon

Answer 25

provides host defense (GALT via isolated nodules)
no lymphatic capillaries –> colon cancers slow to spread

Question 26

describe the muscularis mucosa in the colon

Answer 26

smooth muscle
contract intestinal glands
contractions shake loose lodged feces

Question 27

describe the submucosa in the colon

Answer 27

dense irregular CT
blood and lymphatic vessels

Question 28

describe the equine large intestine makeup

Answer 28

ascending colon:
-L and R ventral
-L and R dorsal
-transverse colon
descending colon

Question 29

describe the importance of the haustrae in cows and horses

Answer 29

narrows the diameter of the colon and makes fecal matter smaller

Question 30

describe the rectum/anal canal histology make up

Answer 30

stratified squamous epithelium for protection

mucous glands for lubrication

skeletal and smooth muscle

Question 31

what is a potential origin for the portal vein

Answer 31

cranial mesenteric vein

Question 32

what drains into the cranial mesenteric vein

Answer 32

-jejunal
-cranial pancreaticoduodenal
-ileocolic
-right colic

Question 33

what is the largest lymphatic vessel of the lymphatic system and what does it drain to?

Answer 33

thoracic duct

drains to the left brachiocephalic vein, returns lymph to systemic drainage

Question 34

what is intestinal volvulus

Answer 34

complete twisting of a loop of intestine around its mesenteric attachment site

endangers blood supply –> can lead to necrosis of affected bowel