Specialized structures of epithelial

Cilia, microvilli are located at the free space of epithelial cells.

basement membrane, membrane infolding are located at the basal surface of epithelial cells.

tight junction, intermediate junction, desmosome, gap junctions are located at the lateral surface of epithelial cells.

Figure 1.  epithelial cells surfaces

microvilli

microvilli is type of projection in the plasma membrane. They can be found on the apical surface of some of the epithelial cells.

• Striated border—on the surface of the columnar cells of small intestinal mucosa.

• Brush border—on the surface of the proximal tubule cells of kidney.

Function: Increase the area of surface so as to improve the absorption metabolites.

Figure 2. Striated border on small intestinal mucosa

cilia

cilia like microvilli is type of projection in the plasma membrane. They can be found on the apical surface of some of the epithelial cells.

Function: Undulating motion to clear out the secretions , bacteria and exotic materials.

figure 3. cilia of trachea

Cell junctions

we will talk about three major types of cell junctions. Tight junctions, desmosomes, gap junctions.

tight junctions 

impermeable junctions prevent molecules from passing through the intercellular space.

Desmosomes 

anchoring junction bind adjacent cells together like a molecular velcro and help from an internal tension-reducing network of fibers.

Gap junctions 

communicating junctions allow ions and small molecules to pass for intracellular communication.

figure 4. cell junctions

figure 5. EM snapshots of junctions

basement membrane

located between epithelium and the underlying connective tissue, and constituted of reticular fibers and matrix.

Function: supporting , junction and act as a semipermeable membrane in material exchange.

figure 6. basement membrane

Membrane infolding

located at base surface of epithelial cells of renal proximal tubules and distal tubules. The cell membrane of base surface infolding deeply into the cytoplasm.

Function: increase the area of basal surface to facilitate the transmissions of water and electrolytes.

figure 7. membrane infolding

Join Art of Medics

Become Part of Art of Medics for further scientific purposes