L85b: microanatomy of large intestines

MCQ: what mucosal feature is common to both small and large intestines?

intestinal glands within the lamina propria

what do all segments of the large intestine lack?

1. villi

2. paneth cells

3. plicae circulares

what does the cecum have a substantial number of?

lymphatic nodules

where are lymph nodes concentrated in the cecum of pigs. ruminants, and dogs?

around the ileal ostium

where are lymphatic nodules concentrated in the cecum of horses and cats?

near the apex of the cecum

what is 1?

intestinal crypts

what is 3?

goblet cells

what is 8?

inner circular layer of tunica muscularis

what is 10?

lamina muscularis

what is 12?

tunica submucosa

why is the mucosa of the colon thicker than that of the small intestine?

due to the increased length of the intestinal glands

what happens to the submucosa of the colon?

often distended by lymphatic tissue which disrupts the lamina muscularis and can extend gland into submucosa

what is unique about the colon in pigs and horses?

outer longitudinal layer of tunica muscularis of cecum and colon form taenia ceci and taenia coli

what does the cecum and ventral colon of the horse have more of?

more elastic fibers than smooth muscle

what is 19?

taenia coli in colon of pig

what layer of the rectum is thickened in carnivores?

outer longitudinal layer of tunica muscularis

in which animals are elastic fibers most prominent in the rectum?

horses and cattle

in which animals are elastic fibers the least prominent in the rectum?

sheep and goats

which layer of the tunica muscularis contains more elastic fibers?

outer longitudinal layer

what covers the cranial portion of the rectum?

serosa

what surrounds the retroperiotoneal portion of the rectum?

adventitia which blends with the pelvic fascia

green circle

gland

blue lining

lamina muscularis

2

tunica submucosa

3

tunica muscularis

rectal columns

longitudinal folds of rectal mucosa to allow for stretch and facilitate passage of fecal matter

where does the outer longitudinal layer of the tunica muscularis of the rectum terminate?

at the anorectal junction

where does the inner circular layer of the anal canal terminate?

internal anal sphincter muscle

external anal sphincter

composed of skeletal muscle, covers the internal anal sphincter muscle

what happens at the anorectal line of the anal canal?

simple columnar epithelum of rectum changes abruptly to non keratinized stratified squamous epithelium

which species lack glands in teh mucosa of the anal canal?

ruminants and horses

which species is the anal mucosa divided into three zones?

pigs and carnivores

columnar zone of anal canal

contains longitudinal folds, anal columns, and anal sinuses

MCQ: the taenia coli of the large intestine is an organ-specific specialization of what layer of the intestinal wall?

tunica muscularis

what lines the mucosa of both the columnar and intermediate zones?

non-keratinized stratified squamous epithelium, and modified tubuloalveolar sweat gland

where is the intermediate zone of the anal canal?

between the columnar zone and cutaneous zone

where do anal glands occupy in the anal canal?

propria-submucosa of intermediate zone

which animals is the secretion of the anal glands a lipid secretion?

dogs and cats

which animals is the secretion of the anal glands mucuous?

pigs

where does the cutaneous zone of the anal canal begin?

acutaneous line

what lines the cutaneous zone of the anal canal?

keratinized stratified squamous epithelium

where do the ducts of the anal sacs open at in carnivores?

at the junction of the intermediate and cutaneous zones

what does teh mucosa of the outermost part of the cutaneous zone contain in dogs?

1. large modified sebaceous glands

2. circumanal glands