GlomerulusBlood is filtered as it passes through these loops.
Glomerular capsuleIts outer wall is the parietal layer. The podocytes are its inner, visceral layer.
Capsular spaceThe filtrate collects here before it flows into the tubule.
PodocytesTheir foot processes wrap the capillaries and leave slits for the filtrate.
Afferent arterioleIt is wider than the efferent arteriole. That keeps the pressure in the loops high.
Efferent arterioleBlood leaves the glomerulus through it, not through a vein.
Juxtaglomerular cellsThey release renin when blood pressure falls.
Distal convoluted tubuleLater in the nephron it returns to touch its own corpuscle here.
Macula densaThey sense the salt in the fluid and signal the juxtaglomerular cells.
Mesangial cellsThey support the loops and can narrow them.
Proximal convoluted tubuleThe filtrate flows into it. Most of what the body keeps is taken back here.
The filtration barrier 4
FenestrationsThe pores let fluid out but keep blood cells in.
Basement membraneIt holds back most proteins.
PedicelsFoot processes of the podocytes, lying side by side.
Filtration slitsThe filtrate passes through them into the capsular space.
Forces of filtration 4
Glomerular blood hydrostatic pressureThe force that drives filtration. About 55 mm Hg in the textbook example.
Blood colloid osmotic pressureAbout 30 mm Hg: proteins kept in the blood draw water back.
Capsular hydrostatic pressureAbout 15 mm Hg: fluid already in the capsule pushes back.
Net filtration pressure55 minus (15 plus 30) leaves about 10 mm Hg. It pushes fluid out.
How this list was compiled: Every name checked on 2026-09-29 against OpenStax Anatomy and Physiology 2e, section 25.4 Microscopic Anatomy of the Kidney (glomerulus, Bowman's capsule with parietal and visceral layers, podocytes, pedicels and filtration slits, fenestrations, basement membrane, afferent and efferent arterioles, mesangial cells, juxtaglomerular cells, macula densa, proximal and distal convoluted tubules), https://openstax.org/books/anatomy-and-physiology-2e/pages/25-4-microscopic-anatomy-of-the-kidney, and section 25.5 Physiology of Urine Formation (Bowman's space; the forces GBHP, CHP and BCOP and NFP = 55 - [15 + 30] = 10 mm Hg, the values used here), https://openstax.org/books/anatomy-and-physiology-2e/pages/25-5-physiology-of-urine-formation; and against Wikipedia, text only: Renal corpuscle, Juxtaglomerular apparatus, Glomerulus (kidney) and Glomerular filtration rate (the hydrostatic and colloid osmotic pressures and the net filtration pressure). Licence: own work
The drawing: Drawn for this site on 2026-09-29 from plain geometry; nothing traced. Licence: own work
How it works
The top drawing is a renal corpuscle cut through: the glomerulus inside its capsule, the vessels at the top and the tubule leaving below. The bottom one enlarges the barrier between blood and capsule, with arrows for the pressures.
Read the full guide
Structures first, then the forces
Numbers 1 to 11 are the corpuscle: the loops, the capsule and its space, the podocytes, the two arterioles with the juxtaglomerular cells and the macula densa, the mesangial cells and the tubules. Numbers 12 to 15 are the layers of the barrier. Numbers 16 to 19 are the pressures: one pushes fluid out, two push it back, and the last is what is left.
Afferent arrives, efferent exits: the afferent arteriole brings blood in and is the wider of the two.
Questions and answers
What forces are involved in glomerular filtration?
Glomerular blood hydrostatic pressure pushes fluid out of the blood. Capsular hydrostatic pressure and blood colloid osmotic pressure push it back. In the textbook example that is 55 minus 15 minus 30, a net filtration pressure of about 10 mm Hg.
What is the renal corpuscle made of?
The glomerulus, a tuft of capillaries, and the glomerular (Bowman's) capsule around it. Together they filter the blood; the filtrate collects in the capsular space and flows into the proximal convoluted tubule.
What do podocytes do?
They wrap the glomerular capillaries with foot processes called pedicels. The narrow filtration slits between the pedicels let water and small solutes through but hold back blood cells and most proteins.