distal convoluted tubule (purple: found in the renal cortex)
collecting tubule (black: in the medulla)
collecting duct black: (in the medulla)
The shape and cross-sectional structure of the different parts of the tubules differs, according to their functions.
First, theproximal convoluted tubule - which is the longest part of the renal tubule - has a simple tall cuboidal
epithelium, with a brush border (microvilli). The epithelium almost fills the lumen, and the microvilli increases the surface area by 30-40 fold.
This part of the nephron is hard to tell apart from adjacent capillaries, except that there are no red blood cells in the lumen.
Finally, the distal convoluted tubule.
These tubules are less numerous than the proximal convoluted tubules. The epithelial cells are cuboidal, with very few microvilli. The cells stain more palely than those of the proximal convoluted tubule. Click here to see an EM of the DCT.
Collecting tubules are not part of the nephron.
The epithelium of these tubules consist of cuboidal or columnar cells. They empty into collecting ducts that are easy to recognise, because they have large lumens, with pale staining columnar epithelium.
Collecting tubules have two main functions:
1. resorb water in response to the hormone vasopressin.
2. resorb sodium in response to the hormone aldosterone.
From these descriptions, try to find renal corpuscles, proximal and distal convoluted tubules and loops of Henle in this eMicroscope section of the cortex from the kidney.