Unformatted text preview: eep them anchored as part of sheet, keep them from drifting away! 3) Partially restrict diffusion of substances
through the epithelium, in either direction
Help prevent material from diffusing willy nilly through epithelia! Capillaries never penetrate basement membranes of epithelia, i.e., epithelia
are always avascular no matter how thick they are.
GENERAL RULE OF EPITHELIA: NEVER VASCULARIZED THEMSELVES!!!!!!!! NEVER CROSS OTHER EPITHELIA -- CAN'T
GROW THROUGH ONE ANOTHER. SO CAPILLARIES NEVER GROW TO AN EPITHELIA, NO MATTER HOW THICK THEY GET.
NERVE FIBERS CAN CROSS EPITHELIA…BUT NEVER CAPILLARIES/BLOOD VESSELS. A basement membrane has two major parts: basal lamina and
laminin, type 4 collagen assoc. with
basal lamina -- and made by epithelia Important components of the basal lamina
• laminin, attached to integrin proteins in
the epithelial cell membranes
• type IV collagen, forming a felt-like sheet
associated with the layer of laminin
• perlecan, a glycoprotein that helps lin...
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- Spring '14
- Epithelial cells, Epithelia, basement membrane