What is the primary function of the glomerulus?

• A. Filtration of blood to form urine
• B. Reabsorption of glucose
• C. Secretion of hormones
• D. Storage of urine

Answer: (A)

The glomerulus acts as the kidney’s filtration unit. Blood enters the glomerular capillaries and, across a filtration barrier made of the fenestrated endothelium, the glomerular basement membrane, and podocyte slit diaphragms, small solutes and water pass into Bowman's space to form filtrate. Large proteins and blood cells stay in the circulation, so the filtrate is essentially plasma minus those large components. This filtrate is the starting point for urine and is later modified by the tubules through reabsorption and secretion. So the primary function is filtration of blood to form urine. Reabsorption of glucose happens mainly in the proximal tubule, hormones are secreted by various tissues and parts of the nephron, and urine storage occurs in the bladder.