Urine: Filtered urea, some water + some blood plasma salts
Ultrafiltration
High bp in glomerulus
Afferent arteriole wider diameter than efferent
Forces water + small solutes - any w/ relative molecular mass of <69,000 - out
Filtrate crosses 3 barriers
1st layer: Glomerular capillary wall
Single-cell endothelium
Large pores/fenestrations between cells
Filtrate forced through by bp
2nd Layer: Basement membrane
Collagen fibres + glycoproteins
Underlies/supports endothelium
True filter
3rd layer: Podocytes
Specialised epithelial cells
Long finger-like membrane extensions
Primary + secondary processes
Slit pores between secondary
Forms glomerular filtrate
Water, glucose, amino acids, urea + ions
Filtration pressure
High bp forces glomerular filtrate into Bowman's capsule
Higher hydrostatic pressure than Bowman's capsule
Net pressure favours glomerular filtrate formation
