Internal Anatomy of the Kidney

In the frontal section, the kidney shows the renal cortex, renal medulla, and renal pelvis.

The outermost layer — the renal cortex — is characterized by its light red color and grainy texture.

The renal medulla is the inner, darker, reddish-brown section of cone-like tissue groups known as renal or medullary pyramids.

These pyramids, along with the renal cortex, form the parenchyma, which is the functional part of the kidney.

About eight extensions of the cortex, known as renal columns, separate these pyramids.

Each pyramid has a wide base facing the cortex and an apex called a renal papilla facing the renal hilum. 

The papillae are encased by the minor calyces, which merge to form a major calyx.

The major calyces form two to three branches that merge to form a funnel-like tube called the renal pelvis. 

The calyces continuously drain urine from the papillae, collecting and transferring it to the renal pelvis.

From the renal pelvis, the urine is transported to the ureter and finally to the bladder.