| Bowman's capsule | |
| Latin: | capsula glomeruli |
| Precursor: | Metanephric blastema |
| Location: | Nephron of kidney |
Bowman's capsule (or the Bowman capsule, capsula glomeruli, or glomerular capsule) is a cup-like sac 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.
Outside the capsule, there are two "poles":
Inside the capsule, the layers are as follows, from outside to inside:
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. It is a major site for blood filtration (including glomerulus)
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.
As a result, the filtrate leaving the Bowman's capsule is very similar to blood plasma (filtrate or glomerular filtrate is composed of blood plasma minus plasma protein i.e. it contains all the components of blood plasma except the proteins) in composition as it passes into the proximal convoluted tubule.
Measuring the glomerular filtration rate (GFR) is a diagnostic test of kidney function.[1]
A decreased GFR may be a sign of kidney failure.
A number of diseases can result in various problems within the glomerulus. Examples include acute proliferative (endocapillary) glomerulonephritis, mesangioproliferative glomerulonephritis, mesangiocapillary (membranoproliferative) glomerulonephritis, acute crescentic glomerulonephritis, focal segmental glomerulonephritis, and diabetic glomerulosclerosis.
Bowman's capsule is named after Sir William Bowman (1816–1892), a British surgeon and anatomist.[2] However, thorough microscopical anatomy of kidney including the nephronic capsule was first described by a Ukrainian surgeon and anatomist from the Russian Empire, Prof. Alexander Schumlansky (1748–1795), in his 1782 doctoral thesis "De structura renum" ("About Kidney Structure", in Latin); thus, much prior to Bowman.[3]
Together with the glomerulus it is known as a renal corpuscle, or a Malpighian corpuscle, named after Marcello Malpighi (1628–1694), an Italian physician and biologist. This name is not used widely anymore, probably to avoid confusion with Malpighian bodies of the spleen.
