Digestive System 3 histology

Endre Dobó

anatomical features:> Kerkring s valves (plicae circulares Kerkringi)

> approx. 1-cm-tall circular folds(cf. gastric rugae [folds], semilunar folds)

histological features:> intestinal villi (villi intestinales)

> approx. 1-mm-tall finger-like projections of themucous membrane into the lumen

Remarks: the microvilli are not considered to be specific feature, becausemicrovilli are present in another organs as well: e.g. ductus epididymidis, gallblader, kidney

functions> molecular breakdown of food> absorptions of small molecules

surface enlargement of small intestine> Kerkring s folds / valves (~ 1 cm)> intestinal villi (~ 1 mm)> microvilli (~ 1 µm)

> tunica mucosa (mucous membrane)

> lamina epithelialis mucosae

> lamina propria mucosae

> lamina muscularis mucosae

> tela submucosa

> tunica muscularis

> stratum circulare

> stratum longitudinale

> tela subserosa

> tunica serosa (serous membrane)

> lamina propria serosae

> lamina epithelialis serosae

in the retroperitoneal duodenum the serousa is replaced with adventia (!)

> the Kerkring s valve is formedby the relatively short longitudinalm. layer of the tunica muscularis

> in its core there is telatelasubmucosasubmucosa

lamina muscularis mucosae

telatela submucosasubmucosa

tunica muscularis

tunica serosa

inte

stin

alvi

lliin

test

inal

glan

ds(c

rypt

sof

Lieb

erku

hn)

lam

ina

prop

riam

ucos

ae

lam

ina

mus

cula

rism

ucos

ae

goblet cells

blood capillary

smooth muscle

enterocytes sloughing off

lymphatic capillary (lacteal)

smooth muscle

intraepithelial lymphocytes

enterocytes

striated border

enteroendocrine cells

lymphocytes

smooth musclegoblet cells

mitotic figures

Paneth cells

lamina muscularis mucosae

duodenum jejunum ileum

intestinal villi

intestinal glands

(crypts ofLieberkühn)

du

od

enal

du

od

enal

gla

nd

sg

lan

ds

lamina proprialamina proprialamina propria

folliculi lymphatici aggregati(Peyer s patches)

enterocytes

M cells

lymphatic follicle

cryp

tso

fL

ieb

erkü

hn

inte

stin

alvi

lli

gastricpit

gastricgastric

glandgland

stomach large intestinesmall intestine

lamina muscularis mucosae

inte

stin

alvi

lli

inte

stin

alg

lan

ds

inte

stin

alg

lan

d

lamina propria

goblet cell

enteroendo-crine cell

enterocyte

anatomical (macroscopic) features

> taeniae coli

> longitudinal layer of muscularis is split into 3 bands

> absent from the appendix and rectum

> haustra coli (colic sacculations)

> outpocketings between two semilunar folds

> appendices epiploicae / appendices omentales

> serosa-covered appendages contatining adipose tissue

general histological (microscopic) features

> (1) concomitant special properties:

> has intestinal glands (crypts of Lieberkühn)

> lacks intestinal villi

> (2) ratio of goblet cells to enterocytes is much larger in the largeintestine than in the small intestine

histological (microscopic) feature of appendix

> aggregated lymphatic follicles (folliculi lymphatici aggregati)

> are found as a complete ring in the wall of the appendix

(tela subserosa and / or lamina propria mucosae)

ileumappendix

vermiformis

mesentery meso-appendix

the last segment of the rectum

> proximal boundary

> beginning of anal / rectal column of Morgagni

(anorectal line)

(> pelvic diaphragm; levator ani muscle)

> distal boundary

> anus

> portions of anal canal (different covering epithelia)

> zona columnaris

> zonazona intermediaintermedia / / haemorrhoidalishaemorrhoidalis

> zona cutanea

external anal sphincter (striated m.)

middle rectal v.

venous plexus in the submucosa

adipose tissue

anal column

anal sinus

columnariscolumnaris--haemorrhoidalishaemorrhoidalis boundaryboundary

perineal skin

anus, skin

levator ani m. (striated m.)

internal anal sphincter (smooth m.)

longitudinal layer (smooth m.)

circular layer (smooth m.)

inferior rectal v.

haemorrhoidalishaemorrhoidalis--cutaneacutanea boundaryboundary