Understanding the Kidney and Its Filter System

These terms all refer to the same organ. “Kidney” is used here for clarity.

Kidneys are bean-shaped and weigh about 150–200g (men) or 125–135g (women).
Each kidney contains ~1 million nephrons, the key filtering units.
They receive 20% of the heart’s blood flow — showing their crucial role in filtering fluids.

Each nephron has a glomerulus (filter) and a tubule.

• The glomerulus is a cluster of tiny blood vessels.
• Its outermost layer has podocytes, special cells that prevent protein loss.

Podocytes can’t regenerate. We’re born with a set number, and they decline with age.
They keep proteins like albumin in the blood.
Albumin in the urine (albuminuria) means podocytes are being lost — a sign of kidney injury.

Medications like ACE inhibitors, ARBs, MRAs, and SGLT2 inhibitors help lower pressure inside the glomerulus, reducing podocyte loss and preserving kidney function.