By the fifth week, the genital ridges differentiate into an outer cortex and an inner medulla, and are called indifferent gonads.

Tissue osmolarity increases from cortex (outer layar of a nephron), to inner renal medulla (middle layer of a nephron).

Each adrenal gland has two distinct structures, the outer adrenal cortex and the inner medulla, both of which produce hormones.

All ganglia consist of an outer cortex containing the nuclei and an inner medulla.

The hair fiber is composed of a cuticle that is continuous with the root sheath, an intermediate cortex, and an inner medulla.

The subsequent buildup of urea in the inner medulla is critical to the process of urinary concentration.

All three layers of the inner medulla were highly immunoreactive.

The Kokko and Rector model is a theory to explain how a gradient is generated in the inner medulla of the kidney.

But it has been proven that this cannot be the case in the inner medulla, since there are no salt pumps, and the cell membrane is too permeable to salt.

The Kokko and Rector model suggests that in the inner medulla the driving force for salt reabsorption is urea accumulation.