What is zonulae?

What is zonulae?

Tight junctions, also known as occluding junctions or zonulae occludentes (singular, zonula occludens) are multiprotein junctional complexes whose canonical function is to prevent leakage of solutes and water and seals between the epithelial cells.

What is paracellular diffusion?

What is Paracellular Diffusion? Paracellular transport is the movement of substances across the epithelium through the intercellular space between the cells. This movement is a type of passive diffusion. Therefore, there is no requirement of energy as the diffusion occurs through a concentration gradient.

What is Zona Occludens?

ZO (zonula occludens) proteins are scaffolding proteins providing the structural basis for the assembly of multiprotein complexes at the cytoplasmic surface of intercellular junctions. In addition, they provide a link between the integral membrane proteins and the filamentous cytoskeleton.

What is the paracellular pathway?

The paracellular pathway is an aqueous, extracellular route across endothelia and epithelia that is followed by substances according to their size and charge. Although under certain circumstances it may be traversed by objects as large as leukocytes, it is generally used by water and small solutes.

How many Occludins are there?

Occludin’s structure can be broken down into 9 domains. These domains are separated into two groups.

What is the Paracellular pathway?

Where does Paracellular transport occur?

Paracellular transport refers to transport that occurs in between cells, passing through an intercellular shunt pathway. Paracellular transport appears to be exclusively passive and downhill, occurring by diffusion or convection, and driven by existing transepithelial gradients.

What is the difference between transcellular and paracellular?

Paracellular transport refers to the transfer of substances across an epithelium by passing through the intercellular space between the cells. It is in contrast to transcellular transport, where the substances travel through the cell, passing through both the apical membrane and basolateral membrane.

What is desmosome and Hemidesmosome?

Desmosomes facilitate adhesion between adjacent epithelial cells, whereas hemidesmosomes, named for their ultrastructural resemblance to half a desmosome, mediate adhesion between basal cells of epithelial tissues and the substratum.

What is paracellular reabsorption?

Paracellular reabsorption of Cl− is driven by a lumen negative potential through the tight junction in the collecting duct of the kidney. Two claudin proteins – claudin-4 and claudin-8 make the paracellular pathway for Cl− permeation.

What is a paracellular pathway?

paracellular pathway The route between cells. For example, substances can travel through epithelia by a paracellular pathway if the tight junctions between constituent cells are not fully continuous (i.e. ‘leaky’), as in the proximal tubule of a kidney nephron. Paracellular pathways lack any means of active transport,…

What is paracellular transport?

Paracellular transport refers to the transfer of substances across an epithelium by passing through the intercellular space between the cells.

What is the primary barrier to paracellular transport?

Tight junctions (TJs) located between adjacent Type I epithelial cells are the primary barrier to paracellular transport. Tight junctions (TJs) are a junctional complex between epithelial cells sealing the paracellular space across the epithelia.

What is the role of Paracellular absorption in glucose absorption?

Paracellular absorption therefore plays only a minor role in glucose absorption, although there is evidence that paracellular pathways become more available when nutrients are present in the intestinal lumen.