Structure Proximal tubule

1 structure

1.1 brush border cell
1.2 divisions

1.2.1 proximal convoluted tubule (pars convoluta)
1.2.2 proximal straight tubule (pars recta)

structure

the distinctive characteristic of proximal tubule brush border, known striated border.

brush border cell

the luminal surface of epithelial cells of segment of nephron covered densely packed microvilli forming border readily visible under light microscope giving brush border cell name. microvilli increase luminal surface area of cells, presumably facilitating resorptive function putative flow sensing within lumen.

the cytoplasm of cells densely packed mitochondria, largely found in basal region within infoldings of basal plasma membrane. high quantity of mitochondria gives cells acidophilic appearance. mitochondria needed in order supply energy active transport of sodium ions out of cells create concentration gradient allows more sodium ions enter cell luminal side. water passively follows sodium out of cell along concentration gradient.

cuboidal epithelial cells lining proximal tubule have extensive lateral interdigitations between neighboring cells, lend appearance of having no discrete cell margins when viewed light microscope.

agonal resorption of proximal tubular contents after interruption of circulation in capillaries surrounding tubule leads disturbance of cellular morphology of proximal tubule cells, including ejection of cell nuclei tubule lumen.

this has led observers describe lumen of proximal tubules occluded or dirty-looking, in contrast clean appearance of distal tubules, have quite different properties.

divisions

the proximal tubule part of nephron can divided 2 sections, pars convoluta , pars recta. differences in cell outlines exist between these segments, , therefore presumably in function too.

regarding ultrastructure, can divided 3 segments, os1, s2, , s3:

proximal tubule cell showing pumps involved in acid base balance, left lumen of tubule


proximal convoluted tubule (pars convoluta)

the pars convoluta (latin convoluted part ) initial convoluted portion.

in relation morphology of kidney whole, convoluted segments of proximal tubules confined entirely renal cortex.

some investigators on basis of particular functional differences have divided convoluted part 2 segments designated s1 , s2.

proximal straight tubule (pars recta)

the pars recta (latin straight part ) following straight (descending) portion.

straight segments descend outer medulla. terminate @ remarkably uniform level , line of termination establishes boundary between inner , outer stripes of outer zone of renal medulla.

as logical extension of nomenclature described above, segment designated s3.