Loop of Henle

The loop of Henle consists of the straight proximal tubule, the thin loop and the straight distal tubule. 

The straight proximal tubule (pars recta) comprises the descending thick segment and the straight distal tubule comprises the ascending thick segment.  
The thin loop cells are very low cuboidal and contain no brush border. 
They look similar to the capillaries which are often seen juxtaposed.

Although the thin loop cells are low cuboidal and the capillary cells are simple squamous, often the best way to distinguish the loop cells from the vascular endothelial cells is to look for red blood cells. If they are present then you have found a vessel.  
 

The length of the thin loop varies depending on the location of the nephron. 
Cortical loops only extend a short descending thin portion whereas juxtamedullary loops extend an extensive descending and ascending thin loop of Henle. 
 

The thick limb loop of Henle cells, which resemble proximal and distal tubule cells, from the capillaries. 
But deeper in the medulla, the loop cells are much thinner, and harder to distinguish from the capillaries.