1. Fenestrated Endothelium of the Glomerular Capillaries: This layer has pores that allow most components of the blood to pass through but prevent large cells and proteins from passing.
2. Basement Membrane: This layer is a thin, acellular layer composed of collagen and other proteins that acts as a barrier to large molecules. It also has a negative charge, further inhibiting the passage of negatively charged proteins.
3. Podocytes: These are specialized cells with foot-like projections called pedicels that wrap around the capillaries. The spaces between the pedicels, called filtration slits, are covered by a thin membrane called the slit diaphragm. This structure helps to regulate the passage of small molecules.
These three structures work together to create a highly selective barrier that allows water, small solutes, and waste products to pass from the blood into the nephron, while preventing larger molecules, like proteins and blood cells, from entering the filtrate.
