Bowman's capsule

Bowman's capsule
Glomerulus. (Bowman's capsule not labeled, but visible at top.)
Details
Precursor	Metanephric blastema
Identifiers
Latin	capsula glomeruli
MeSH	Bowman+Capsule
Dorlands /Elsevier	12211408
FMA	15626
Anatomical terminology []

Bowman's capsule (or the Bowman capsule, capsula glomeruli, or glomerular capsule) is a cup-like sack at the beginning of the tubular component of a nephron in the mammalian kidney that performs the first step in the filtration of blood to form urine. A glomerulus is enclosed in the sac. Fluids from blood in the glomerulus are collected in the Bowman's capsule (i.e., glomerular filtrate) and further processed along the nephron to form urine. This process is known as ultrafiltration. The Bowman's capsule is named after Sir William Bowman, who identified it in 1842.

Outside the capsule, there are two "poles":

Inside the capsule, the layers are as follows, from outside to inside:

A - Renal corpuscle
B - Proximal tubule
C - Distal convoluted tubule
D - Juxtaglomerular apparatus
1. Basement membrane (Basal lamina)
2. Bowman's capsule - parietal layer
3. Bowman's capsule - visceral layer
3a. Pedicels (podocytes)
3b. Podocyte or sometimes called Bowman's cells
4. Bowman's space (urinary space)
5a. Mesangium - Intraglomerular cell
5b. Mesangium - Extraglomerular cell
6. Granular cells (Juxtaglomerular cells)
7. Macula densa
8. Myocytes (smooth muscle)
9. Afferent arteriole
10. Glomerulus Capillaries
11. Efferent arteriole

The process of filtration of the blood in the Bowman's capsule is ultrafiltration (or glomerular filtration), and the normal rate of filtration is 125 ml/min, equivalent to 80 times the daily blood volume.

Any proteins under roughly 30 kilodaltons can pass freely through the membrane, although there is some extra hindrance for negatively charged molecules due to the negative charge of the basement membrane and the podocytes.

Any small molecules such as water, glucose, salt (NaCl), amino acids, and urea pass freely into Bowman's space, but cells, platelets and large proteins do not.