histology of small duodenum Flashcards
what is the function of small intestine ?
principal site for absorption
what are the factors that provide an enormous surface area?
Length of small intestine
Pilcae circulares ( Valves of kerking )
Vili
Microvili
Crypts , called crypts of lieberkuhn
describe the pilcae circulares?
the mucosa and submucosa are thrown into circularly arranged folds
describe the villi?
projections on top of the plicae circulares
describe microvili ?
smaller vili’s and projections on top of plicae circulares
Forms the brush border
describe the crypts of lieberkuhn? / intestinal crypts
space between the villi projections called crypts
what happens in celiac disease ?
loss of intestinal villi —-> symptoms of malabsorption
describe the plicae circulare of jejunum?
empty food = highest absorption activity —> closely packed plicae
describe the mucosa of ileum?
it has patches —> peyers patches for protection ( pebble shape )
what are the layers of digestive tract?
Mucosa
submucosa
muscularis externa
Serosa/ adventitia
what are the components of mucosa?
Epithelium lining
Lamina propria
Muscularis mucosa ( MM )
describe the epithelium lining of mucosa?
Simple columnar
from the stomach to colon = Simple columnar
other areas = Stratified squamous
describe the lamina propria of the mucosa?
collagen and reticular fibers
blood vessels
nerve ending
glands and mucosa associated lymph tissue ( MALTS )
what is the function of MALTS?
monitor and produce an immune response to pathogens passing with food through GI tract
describe Muscularis mucosa (MM)?
very thin smooth muscle
made of inner circular layer and outer longitudinal layer of smooth muscle
Inner —> circular
Outer —-> longitudinal
what is the function of muscularis mucosa ? MM
Causes local folding of mucosal layers
what is the extension of Muscularis mucosa MM?
Extends into the mucosa but doesnt REACH THE VILLI
what are the modifications of the lumen surface that facilitates absorption ?
Circular folds –> Plicae circulares
Intestinal villi
Microvili
describe plicae circulares?
Transverse permanent folds of mucosa and submucosa
describe the intestinal villi?
Finger like projections of the mucosa
Contain central core of lamina propria with single lacteal , capillary loops
what is the function of intestinal villi?
absorb and breakdown products of fat
what covers the intestinal villi?
Simple columnar epithelium
describe microvilli?
make brush border
finger like projections of plasma membrane of absorptive columnar epithelial cells
where is the maximum amount of goblet cells found ?
in the ileum
As you go down from duodenum to the ileum it will increase in the amount
where is the longest villi found?
longest villi found in duodenum
Becomes shorter as you go down —> so shortest in ileum
what found in the submucosa of duodenum?
Brunners glands —> excretory ducts drain the secretion into the crypts of lieberkun
only present in duodenum
so if you see brunners glands + long villi = duodenum
leaflike shape villi
what present in the submucosa of jejunum?
nothing special
if u see nothing special in the submucosa + Finger like shape = jejunum
what found in the submucosa ileum?
peyers patch –> lymphoid aggregates forming large follicles extend throughout the lamina propria and submucosa
M cells –> antigen transporting cells
Villi are short
if you see short villi + peyers patch = ileum
what are the cells types found in the mucosa of small intestine ?
Crypt based columnar cell + stem cells
Transit amplifying cells
Paneth cells
Tuft cells / chemosensory cells
Neuroendocrine/ APUD cells
Goblet cells
Absorptive cells / enterocytes
Membrane epithelial / M cells
what is the location of crypt based columnar cells + stem cells?
base of the crypts
what is the function of crypt based columnar cells + stem cells?
divide continuously to replenish other epithelial cell types —-> has mitotic figures
what are transit amplifying cells ?
undifferentiated cells in transition between stem cells and differentiated cells
what is the location of paneth cells?
Base of the crypts
describe paneth cells?
prominent eosinophilic apical granules
defense : the granules contain antimicrobial enzymes to provide the first time of defense against any disease producing microbes which survive passage through the stomach
what are the cells responsible for sensing ?
Tuft cells
chemosensory cells
what is the location of neuroendocrine / APAUD cells?
in the crypts
what is the function of neuroendocrine/APUD cells?
produce locally acting hormones regulating GI motility and secretions
describe goblet cells?
scattered –> more as we get down
produce mucin for lubrications of the intestinal contents and protections of the epithelium
describe absorptive cells / enterocytes ?
tall columnar cells with oval basal nucleus lining the villi
apical surface with microvilli / brush border
each cell has 3000 microvilli for increased surface area
describe membranous epithelial / M cells?
Specialized epithelial cells —> have microfolds not microvilli ( NO MICROVILLI )
Overlying the peyers patches ( ON TOP OF IT)
peyers is in the ileum
what is the function M cells?
Sample antigen of the intestinal lumen and present them to the lymphocytes and macrophages of the underlying lymphatic nodules
in ileum
what does the submucosa contain ?
Loose areolar connective tissue
Elastic fibers
blood vessels
Lymphatic vessels
in duodenum —> brunners glands ( mucous glands )
in ILEUM —> peyers patches
Meissners plexus ( submucosal plexus )
what does muscular externa contain?
Two layers of smooth muscles : INNER circular and OUTER longitudinal
Myenteric plexus ( AUERBACH plexus )
what does adventitia contain ?
loose connective tissue
what is serosa?
mesothelial lining :
simple squamous layer / peritoneum on top of a layer of loose connective tissue THAT secretes slippery fluid
plenty of adipose tissue
describe the characteristics of large intestine MUCOSA ?
Mucosa has folds EXECEPT AT THE RECTUM AREA
NO VILLI
Epithelium :
Columnar with SHORT MICROVILLI
NUMEROUS GOLBET CELLS
Glands of lieberkuhn : CONTAIN goblet cells and FEW endocrine cells
Function of epithelium include water absorption , mucous , production and feces formation
Few crypts are present ( between the microvilli )
what is the content of lamina propria of large inestine ?
lymphoid cells and some nodules (SOLITAIRY LYMPHOID FOLLICLES )
because theres increased bacterial population
in Large intestine : solitary lymphoid follicles and HUGE AMOUNT OF GOBLET CELLS
in ileum : Peyers patches, fewer goblet cells
describe the muscular externa of large intestine ?
Inner circular layer
Outer longitudinal
what does outer longitudinal layer forms?
3 bands —-> teniae coli
what does the mucosa in the anal area have?
longitudinal folds
what happens to the mucosal epithelium 2 cm above the anus?
becomes stratified squamous
KERATINIZED to protect
in the esophagus ( stratified squamous non keratinized )
what is haustrations ?
sacculations of large intestines
describe the appendix ?
Retrocecal organ
Evagination of large intestine
Narrow lumen with abundant lymphoid follicles in the submucosa
Structure similar to large intestine
NO TENDIA COLI
how do differentiate between appendix , Large intestine , Ileum ?
Appendix : HUGE AMOUNT OF GOBLET + patches of lymphoid follicles + no tenaie coli
Large intestine : a lot of goblet cells + solitary lymphoid follicles + Tenaie foli
Ileum : Goblet cells + peyers patches
