Kidney: Cortex and medulla

The image on the left is taken from an area similar to that outlined by the black rectangle. 

The cortex is subdivided into convoluted portions and medullary rays, which present an alternating striped appearance within the cortex.

The convoluted portions contains renal corpuscles, convoluted portions of proximal and distal tubules, and collecting tubules, which are the beginnings of collecting ducts.

Medullary rays contain straight portions of proximal and distal tubules, as well as cortical portions of collecting ducts.  A medulla ray can be identified by the linearity of its tubules and by its lack of renal corpuscles.  Tubules in the medullary rays are directly continuous with similar tubules in the medulla.

The medulla is composed of the straight portions of the proximal and distal tubules, the thin limbs of the loops of Henle, and collecting tubules, including the ducts of Bellini.  The medulla can be identified by the linearity of the tubules traversing it and by its lack of renal corpuscles.

The conical renal pyramids are composed of medullary tissue with their bases abutting the cortex and their apices forming a papillae.

Renal columns are cortical tissue that is interposed between the pyramids.

Arcuate blood vessels separate the cortex from the medulla.

The next image is similar to that enclosed by the blue rectangle.