Glomerular basement membrane
Encyclopedia
The glomerular basement membrane (GBM) is the basal lamina
l portion of the glomerulus
. The Glomerular capillary endothelial cells, the GBM and the filtration slits
between the podocytes perform the filtration function
of the glomerulus, separating the blood in the capillaries from the filtrate that forms in Bowman's capsule
. The GBM is a fusion of the endothelial cell and podocyte basal laminas.
Basal lamina
The basal lamina is a layer of extracellular matrix secreted by the epithelial cells, on which the epithelium sits. It is often confused with the basement membrane, and sometimes used inconsistently in the literature, see below....
l portion of the glomerulus
Glomerulus
A glomerulus is a capillary tuft that is involved in the first step of filtering blood to form urine.A glomerulus is surrounded by Bowman's capsule, the beginning component of nephrons in the vertebrate kidney. A glomerulus receives its blood supply from an afferent arteriole of the renal...
. The Glomerular capillary endothelial cells, the GBM and the filtration slits
Filtration slits
Foot processes of podocytes interdigitate with one another forming filtration slits that, in contrast to those in the glomerular endothelium, are spanned by slit diaphragms.-Structure:...
between the podocytes perform the filtration function
Ultrafiltration (renal)
In biological terms, ultrafiltration occurs at the barrier between the blood and the filtrate in the renal corpuscle or Bowman's capsule in the kidneys. The Bowman's capsule contains a dense capillary network called the glomerulus. Blood flows into these capillaries through a wide afferent...
of the glomerulus, separating the blood in the capillaries from the filtrate that forms in Bowman's capsule
Bowman's capsule
The Bowman's 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...
. The GBM is a fusion of the endothelial cell and podocyte basal laminas.
Layers
The GBM contains three layers:| Layer | Location | Composition | >- | lamina rara externa | adjacent to podocyte processes | heparan sulfate Heparan sulfate Heparan sulfate is a linear polysaccharide found in all animal tissues. It occurs as a proteoglycan in which two or three HS chains are attached in close proximity to cell surface or extracellular matrix proteins... |
>- | dark central zone | type 4 collagen Collagen Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content... and laminin |
69,000) >- | lamina rara interna |
adjacent to endothelial cells | heparan sulfate Heparan sulfate Heparan sulfate is a linear polysaccharide found in all animal tissues. It occurs as a proteoglycan in which two or three HS chains are attached in close proximity to cell surface or extracellular matrix proteins... |
blocks by charge |
Pathology
- Goodpasture's syndromeGoodpasture's syndromeGoodpasture’s syndrome is a rare disease characterized by glomerulonephritis and hemorrhaging of the lungs...
is also known as "anti-glomerular basement membrane disease". Capillaries become inflamed as a result of damage to the basement membrane by antibodies to type 4 collagen.
- Nephrotic syndromeNephrotic syndromeNephrotic syndrome is a nonspecific disorder in which the kidneys are damaged, causing them to leak large amounts of protein from the blood into the urine....
is a change in the structure of the glomerular filtration mechanism usually in the glomerular basement membrane. Some symptoms include proteinuriaProteinuriaProteinuria means the presence of anexcess of serum proteins in the urine. The protein in the urine often causes the urine to become foamy, although foamy urine may also be caused by bilirubin in the urine , retrograde ejaculation, pneumaturia due to a fistula, or drugs such as pyridium.- Causes...
, hypoalbuminaemia, oedema, and hyperlipidemiaHyperlipidemiaHyperlipidemia, hyperlipoproteinemia, or hyperlipidaemia is the condition of abnormally elevated levels of any or all lipids and/or lipoproteins in the blood...
.
- Diabetic glomerulosclerosisGlomerulosclerosisGlomerulosclerosis refers to a hardening of the glomerulus in the kidney. It is a general term to describe scarring of the kidneys' tiny blood vessels, the glomeruli, the functional units in the kidney that filter urine from the blood....
is a thickening of the basement membrane, which can become up to 4-5 times thicker than normal. Can be caused by insulin deficiencyInsulinInsulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....
or resultant hyperglycemiaHyperglycemiaHyperglycemia or Hyperglycæmia, or high blood sugar, is a condition in which an excessive amount of glucose circulates in the blood plasma. This is generally a glucose level higher than 13.5mmol/l , but symptoms may not start to become noticeable until even higher values such as 15-20 mmol/l...
.