The various tubular transverse sections are labelled as follows: thick (A) and thin (B) segments of Henle’s loops and collecting ducts (C).

Table II. Identification criteria for tubules and ducts in the kidney medulla
Cell types	Staining	Cell apex*	Lateral cell wall**
Thick descending limb of Henle's loop	Acidophilic	Brush border present	Indistinct
Thin segments of of Henle's loop	Pale	No brush border	Indistinct
Thick ascending limb of Henle's loop	Lightly acidophilic	Brush border less prominent	Indistinct
Collecting ducts	Pale	No brush border	Distinct
*All cells show apical microvilli. In the case of "brush borders," the microvilli are long and abundant. In the case of "invisible brush borders," the microvilli are small and sparse. **The lateral cell walls are "distinct" when the cytoplasmic membranes are clearly visible from the base to the apex of the epithelial cells. The lateral cell walls are "indistinct" when the plasma membranes present numerous lateral projections and are thus not visible with the light microscope.

Stain: H–­­E
Magnification: ×800