Crypts of the small intestine

Mohamed Issam

Objectives:1. Def.2. Histological structure of included

cell:1. Site2. LM/EM3. Function

1. Definition:Type: simple tubularExtend: from base of the villi

To: muscularis mucosa

Length: 100-200µm

2.Histological structure:Lining cells

1.Absorptive epithelium2.Stem (mitotic) cell3.Goblet cell4.APUDA cell5.Paneth cell6.Caveolate cells7.M cell

1. Absorptive epithelium:

Most common cells in the crypt

Tall columnar

Prominent striated border of microvilli (brush burder)

Have a thick coat of glycocalyx, protecting it from corrosive

chemicals

2. Mitotic cell: Site: at the base of the crypt among Paneth cells LM:

short columnar, basal oval nucleus,

basophilic cytoplasm EM:

rERPloyribosomessmooth lateral border

Function:

3. Paneth cell: Site: grouped at the base of the crypt LM:

Triangular with narrow apex Basal rounded pale nucleus Basal basophilia Apical acidophilia

EM: rER Golgi apparatus Electron dense granules

Function

4. M (microfold, membrane-like) cell Site: highly specialized epithelial cells

that cover the Peyer’s patches and large lymphatic nodules.

Shape: Dome shaped Basal cavity containing WBCs

EM: Short microvilli Attached to neighboring by junctional

complex Discontinuous basement membrane

Function:

5. Caveolated cell

Rare cellLarge columnar Free border shows deep tubular invagination

Act as a receptor

6. APUD (amine precursor uptake and decarboxylation) cells – Enteroendocrine cell

Site: scattered throughout the epithelium of the villi and intestinal glands.

Same as the villi: D S E-G E KCC MO N