Intestines-histo Flashcards
what is the function of the SI
absorption
What are the 3 magnitudes of folding of the SI
microvilli, villi and plicacirculares
describe microvilli
cytoplasmic projections of cell membrane- simple columnar epitheliums
What is the structure of villi
evaginations of mucosa with a core of lamina propria that project into the lumen
what do villi look like in the 3 parts of SI
duodenum- broad short and leaf like
jejunum- tongue like projections
in ileum- tall, narrow, finger-like projections
what is the structure of plicae circulares
circular folds of entire mucosa with a core of submucosa
permanent projections into lumen
where are plicae circulares most prominent
distal duodenum and proximal jejunum
what are the 3 categories of glands in SI
exocrine, submucosal and intestinal crypts
what are the exocrine glands of the SI
pancreas and liver
what are the submucosal glands of the SI
duodenal
Whar are the intestinal crypts of the SI
epithelium invaginating into lamina propria in small and large intestine
Whar type of epithelium is the SI
simple columnar epithelium replaced every 3-7 days
what cells are present in SI epithelium
absorptive columnar with microvilli goblet cells lymphocytes enteroendocrine cells paneth cells M cells
What are enteroendocrine cells
secrete product into vascular channels in lamina propria
What products do enteroendocrine cells secrete
incretins (K cells) GIP (L cells) serotonin (enterochromaffin cells) somatostatin motilin cholecystokinin neurotensin VIP substance P endorphins
where are paneth cells found
in the base of intestinal crypts
describe characterizations of paneth cells
large acidophilic granules
what do paneth cells secrete
lysozyme and peptide defensins
what is the role of lysozymes and peptide defensins
degrade bacterial cell wall components
What are M cells and what is their role
specialized cells in epithelium that are part of innate and classic immune system because the actively capture and transport Ag to APCs and B cells in lamina propria
describe the lamina propria structure and function of AI
loose CT prone to lymphoid infiltration so have lots of plasma cells that can produce IgA
also have lots of capillaries”lacteals” that begin blindly in the villi
have lymph nodules called peyers patches
where are peyers patches most prominent in SI
ileum and maybe lower jejunum
Where are M cells most prevalent in SI
ileum and l=maybe lower jejunum
Describe the layers of the SI wall
submucosa with lymphocytes and peyers patches
muscularis externa
serosa
describe the serosa of the 3 parts of SI
duodenum has serosa anteriorly because retroperitoneal
ileum and jéjunum have serosa continuous with supporting mesentery
What is the ileocecal junction
ileum joins large intestine
what structures make up the ileocecal junction
folds of mucosa and submucosa supported by muscularis externa
the cecum is structurally identical to what part of gut
large intestine- colon
What type of cells are found in the appendix
intestinal crypts of enteroendocrine cells and paneth cells
describe the epithelium of appendix
simple columnar epithelium with goblet cells
describe layers of appendix wall
muscularis mucosa is incomplete
submucosa is thick
thin 2 layered muscularis externa
typical serosa
Are there villi on the large intestine
no
What are the intestinal crypts called in large intestine
crypts of lieberkuhn
describe the intestinal crypts of the large intestine
longer and more closely packed than in SI
have some enteroendocrine cells and no paneth cells
What is the surface epithelium like in the large intestine
simple columnar but many many goblet cells and no digestive enzymes are secreted
why are there numerous goblet cell sin large intestine compared to small
fecal matter is solidified now and needs lubrication
instead of plica circulates, what is in the large intestine
plica semilunares that form haustra
describe the muscularis externa layer of the large intestine
inner layer completely encircles submucosa
outer longitudinal layer in 3 longitudinal bands
what is the name of the 3 longitudinal bands of the outer layer of muscularis externa
taeniae coli
describe the serosa of the large intestine
on anterior surface but not posterior
what is the name of the small sacs of fat on the large intestine
epiploic appendages
describe the muscularis externa of the rectum
complete and there are no taeniae coli anymore because form outer m layer
describe serosa of rectum
upper 1/3 is intraperitoneal and has serosa
anterior surface in middle 1/3 has serosa becase retroperitoneal
lower 1/3 does not have serosa because extraperitoneal now
What are the plicae transversales of the rectum
transverse folds of mucosa that bulge into lumen
2 on left
1 on right
where is the rectoanal junction
where rectum pierces perineum
Describe the changes at the rectoanal junction
intestinal crypts decrease in number till they disappear and the mucous membrane forms longitudinal folds known as rectal columns
how does epithelium change across pectinate line
simple columnar becomes stratified squamous non cornfield and becomes continuous with the skin
describe the submucosal Ct of the anal canal
subepithelial circumanal glands
longitudinal thin walled vv
(hemorrhoidal vv)
Describe the muscularis externa of the anal canal
internal layer thickens to form internal anal sphincter
external sphincter is formed by skel m
Where is the anal verge
caudal portion of anal canal
what is the epithelium like at the anal verge
stratified squamous keratinized with sweat glands, hair follicles, sebaceous glands
