Lecture 33: Abdomen VI Midgut And Hindgut Flashcards
Where does the vagus nerve stop
End of midgut
Topography of midgut/hindgut
-right side: duodenum and ascending colon
-mediolateral: transverse colon
-left side: descending colon
What travels within the mesentery to sustain jejunum and ileum
Mesenteric vessels and innervation
What are arcades
Loops of artery
Vasa recta
Straight arteries out to organ
Mesenteric vs anti Mesenteric sides/edges
Antimesenteri = opposite to side attached to Mesentery
What arteries supply distal duodenum and jejunum
Jejunal arteries
What artery supplies right pancreatic lobe and middle of duodenum
Caudal pancreaticoduodenal
Blood supply to ascending colon and terminal end of ileum
Ileocolic artery
2 branches of ileocolic artery
Cecal
Right colic
Cecal artery supplies
Cecum
Right colic artery supplies
Right colic flexure (between ascending and transverse colons)
Blood supply to first 2/3 of transverse colon
Middle colic
What structures are absent in colon
-villi
-digestive glands
Function of goblet cells in colon
Secrete mucous to lubricate feces for passage
Where are goblet cells located (specific colon)
Transverse colon
Alimentary canal definition
Continuous tube
Esophagus —> colon
What tissue layer differs the most along alimentary canal
Mucosa
Which tissue layer contracts mucosa for mobility
Muscularis mucosa
Plica circulares: features and function
-circular folds
-non distensible
-covered with villi to increase surface area of proximal small intestine
What happens to size and number of plica circulares along small intestine (jejunum to ileum)
Decrease
specializations for absorptive function along small intestine (duodenum, jejunum, ileum)
-intestinal villi
-goblet cells and microvilli within simple columnar epithelial cells
-lacteal
what are lacteals
specialization lymphatic structure within each villus of small intestine (lymphatic capillaries)
carry absorbed fats away from small intestine
what structure covers surface of each plica circularis
intestinal villi
what is each intestinal villus covered with
goblet cells and simple columnar epithelial cells with microvilli
predominant function of small intestine
absorption
2 hallmarks of small intestine mucosal epithelium
-villi
-intestinal crypts
enterocytes definition
cell of intestinal lining
2 functions of enterocytes
-absorption
-digestion
what 3 features allow for enterocytes absorptive function
-tall microvilli
-tight junctions to contain luminal contents
-lateral enfoldings
what 2 features allow for enterocytes digestive function
-glycocalyx enzymes
-glycoproteins mixed with mucous creates coating that traps molecule near apical membrane
what structure is present specifically in the proximal portion of the duodenum (closest to pylorus)
brunner’s glands
brunner’s glands: definition and function
-specialized mucous secreting glands
-protect duodenal lining from acidic chyme delivered from stomach
-secrete peptide hormone urogastrone that inhibits HCl secretion
what kind of epithelium is found in brunners glands
tall cuboidal
2 structures/features within lamina propria: small intestine
-fenestrated capillaries for transport of proteins and carbs
-lacteals for transport of dietary fats
what tissue layer of small intestine provides critical host defense
lamina propria
what is GALT
gut associated lymphoid tissue
aggregated nodules of lymphoid tissue
peyer’s patches
aggregates of GALT
where is GALT concentrated
lamina propria of ileum
Paneth cells: location and function
base of crypts of lierbukuhn in small intestine (ileum)
in GALT
innate immunity
what 2 cells/structures are in lamina propria of ileum that provides host defense
-GALT
-paneth cells
what kind of muscle is muscularis mucosa
smooth
how is muscularis mucosa organized
inner circular layer
outer longitudinal layer
function of muscularis mucosa in small intestine
-move mucosa and lymph
where are brunner’s glands only found
duodenum
where is plicae circularis found (2)
jejunum and ileum
plicae circularis vs rugae
plicae circulares can’t flatten
where does material pass through from small intestine to ascending colon (2 structures)
ileal orifice and annular fold
does the cecum have any specialized functions in carnivorans
no
shape of cecum
spiral
where does ileum/small intestine end
ileocolic junction
rectum and cranial 1/4 of anal canal at end of hindgut: blood supply and innervation
hindgut
cranial rectal and left colic
what supplies distal descending colon and cranial half of rectum
cranial rectal
what supplies descending colon and part of transverse colon
left colic
anastamoses at splenic flexure occurs between
middle colic and left colic
hallmark of large intestine/colon cross section
intestinal glands are straight and regular
5 features of mucosal epithelium: colon
-simple columnar epithelium
-short microvilli
-invagination into long straight intestinal glands/crypts
-enterocytes
-goblet cells
function of enterocytes: colon
absorb water
dehydrate feces
surface area is __________ in large intestine
reduced
is absorption important in colon
not really
specialized cecum in horses
-microfauna for microbial fermentation of cellulose
-very large cecum
equine cecum similar to
forestomach in ruminants
functions of lamina propria: colon
-host defense
-GALT
-no lymphatic capillaries
functions of muscularis mucosa: colon
contract intestinal glands
shake loose lodged feces
smooth muscle
features of submucosa” colon
blood and lymphatic vessels
dense irregular CT
lamina propria vs submucosa in colon: spread of cancer
-rapidly in submucosa due to lymphatic vessels/capillaries
-no lymphatic vessels in lamina propria
2 key features of equine large intestine/colon
-haustra
-tenia coli
haustra: definition and formed by
sacs/segments of colon in equines
formed by specialized muscularis externa
created because tenia coli is shorter than large intestine = bunches up
tenia coli
outer longitudinal layer reduced to 3 strips (smooth muscle)
function of muscularis externa in colon
compaction of feces
what structure is formed by specialized muscularis externa in colon
haustrae
how does fecal mass pass through colon (4 processes)
-peristalsis
-antiperistalsis
-rhythmic segmentation
-mass movement
composition of feces (6)
-water and fiber
-mucus
-dead and living bacteria
-contents of anal sacs
-sloughed intestinal cells
-stercobilin pigment
what type of epithelium lines rectum and anal canal (and why)
stratified squamous epithelium
protection
3 features of rectum and anal canal
-stratified squamous epithelium
-mucous glands
-skeletal and smooth muscle
what kind of muscle are internal and external anal sphincters
skeletal muscle
where do foregut lymph nodes drain to
cisterna chyli
what is the largest lymphatic vessel of lymphatic system
thoracic duct
where does thoracic duct drain to
-left brachiocephalic vein
what 3 veins drain into gastroduodenal vein
-right gastric
-cranial pancreaticoduodenal
-right gastroepiploic
what vein drains into splenic vein
left gastroepiploic
what 3 veins drain into caudal mesenteric vein (hindgut)
-middle colic
-left colic
-cranial rectal
what 4 veins drain into cranial mesenteric vein (midgut)
-jejunal
-caudal pancreaticoduodenal
-ileocolic
-right colic
