What does the glomerulus allow to pass through?

The correct response is that the glomerulus allows small substances to pass through. The glomerulus is a network of tiny blood vessels (capillaries) located within the kidney's nephron. Its primary function is to filter blood and initiate the urine formation process.

When blood flows into the glomerulus, pressure forces water, electrolytes, and small molecules (such as glucose, amino acids, and urea) through its walls and into the Bowman's capsule, while larger molecules like large proteins and blood cells are too big to filter through and remain in the bloodstream. This selective filtration is essential for maintaining the balance of substances in the body while allowing waste to be collected for excretion.

Understanding the selective permeability of the glomerulus helps clarify how it differentiates between which components can pass into the urine-forming part of the nephron and which must remain in circulation for essential bodily functions.