Kidney Filtration Cross-Section (2D)

Blood Supply

Mean arterial pressure 100 mmHg

Vessel Tone

Afferent arteriole tone Normal

Normal perfusion — glomerular capillary pressure holds GFR steady.

Live Readout

GFR

100 mL/min

Filtration fraction

19%

Glomerular P

60 mmHg

Urine output

1.0 mL/min

How it works

Blood enters the glomerulus — a tuft of capillaries inside Bowman's capsule — through the afferent arteriole and leaves through the narrower efferent arteriole. That narrowing keeps glomerular capillary pressure (~60 mmHg) far higher than in ordinary capillaries, which is what forces water, glucose, ions and waste through the filtration membrane into Bowman's space, while blood cells and large proteins are held back.

Net filtration pressure = glomerular pressure − (Bowman's capsule pressure + plasma oncotic pressure), and the glomerular filtration rate (GFR) scales with it. A healthy adult filters roughly 180 L of plasma per day at a GFR near 100–120 mL/min, yet excretes only about 1–2 L of urine — over 99% of the filtrate is reclaimed by reabsorption along the proximal tubule and loop of Henle, with final adjustments made by secretion in the distal tubule.

Real kidneys buffer this against blood-pressure swings via renal autoregulation: the afferent arteriole constricts when pressure rises and dilates when it falls, holding glomerular pressure — and therefore GFR — nearly constant across a wide range of systemic pressure. Turn autoregulation off here to see GFR rise and fall directly with pressure instead.

Blood flow Glucose / ions (filtered & reabsorbed) Water Urine (waste, concentrated)