Simple Cuboidal Epithelium of Proximal Convoluted Tubule

Structure and/or Key Feature(s)

Glomerular filtrate from the urinary space passes from Bowman’s capsule into the proximal convoluted tubule. Cuboidal epithelial cells line this tubule and exhibit elaborate surface specializations to enhance the major functions of the tubule which are reabsorption and fluid transport. These specializations include:

—a “brush border” characterized by long, straight and closely packed microvilli;

—a junctional complex that prevents continuity between the intercellular space and tubule lumen;

—zonula adherens, which establish strong adhesion between adjacent cells;

—significant folding and interdigitations of both lateral and basal plasma membrane of the adjacent cell;

—basal striations, which appear as elongated, vertically oriented mitochondria accumulate at the basal surface of the cells (Ross and Pawlina, 2006).

Basal interdigitating processes of the adjacent cells contain numerous microfilaments 6 nm in diameter.

Anatomical Relations

Simple cuboidal epithelium lines the proximal convoluted tubule.

Function

Cuboidal cells of the proximal convoluted tubule reabsorb about 65% of the fluid from the glomerular filtrate due to the NA+/K+-ATPase pumps and aquaporin-1 (AQP-1) transmembrane proteins. Most small polypeptides, amino acids, and glucose are also reabsorbed across the proximal convoluted tubules. The microfilaments regulate fluid movement from the basolateral extracellular space across the basal lamina to a nearby capillary (Ross and Pawlina, 2006).

References

Ross, M. H. and Pawlina, W. (2006) Histology: A text and atlas. Lippincott Williams & Wilkins.