Renal corpuscle
Encyclopedia
In the kidney
, a renal corpuscle is the initial blood-filtering component of a nephron
. It consists of two structures: a glomerulus
and a Bowman's capsule
. The glomerulus is a small tuft of capillaries containing two cell types. Endothelial cells, which have large fenestrae, are not covered by diaphragms. Mesangial cells are modified smooth muscle cells that lie between the capillaries and the glomerulus. They regulate blood flow by their contractile activity and secrete extracellular matrix, prostaglandins, and cytokines. Mesangial cells also have phagocytic activity, removing proteins and other molecules trapped in the glomerular basement membrane or filtration barrier. The Bowman's capsule has an outer parietal layer composed of simple squamous epithelium. The visceral layer, composed of modified simple squamous epithelium, is lined by podocytes. Podocytes have foot processes, pedicels, that wrap around glomerular capillaries. These pedicels interdigitate with pedicels of adjacent podocytes forming filtration slits.
The renal corpuscle filtration barrier is composed of: the fenestrated endothelium of glomerular capillaries, the fused basal lamina of endothelial cells and podocytes, and the filtration slits of the podocytes. This barrier permits passage of water, ions, and small molecules from the bloodstream into Bowman's space (the space between the visceral and parietal layers). Large and/or negatively charged proteins are prevented from passing into Bowman's space, thus retaining these proteins in the circulation. The basal lamina is composed of 3 layers: lamina rara externa, lamina densa, and lamina rara interna. The lamina rara externa is adjacent to the podocyte processes. The lamina densa is the central layer consisting of type IV collagen and laminin. This layer acts as a selective macromolecular filter, preventing the passage of large protein molecules into Bowman's space. The lamina rara interna is adjacent to endothelial cells. This layer contains heparan sulfate, a negatively charged glycosaminoglycan that contributes to the electrostatic barrier of the glomerular filter.
There are two poles in the renal corpuscle, a vascular pole, and a urinary pole. The vascular pole is where the afferent and efferent arterioles communicate with the glomerulus. The urinary pole is where the corpuscle opens into the lumen of the proximal convoluted tubule.
Fluid from blood in the glomerulus is collected in the Bowman's capsule to form "glomerular filtrate", which is then further processed along the nephron to form urine
.
, named after
Marcello Malpighi
(1628–1694), an Italian physician
and biologist
. This name is not used widely anymore, probably to avoid confusion with a Malpighian corpuscle in the spleen
.
Kidney
The kidneys, organs with several functions, serve essential regulatory roles in most animals, including vertebrates and some invertebrates. They are essential in the urinary system and also serve homeostatic functions such as the regulation of electrolytes, maintenance of acid–base balance, and...
, a renal corpuscle is the initial blood-filtering component of a nephron
Nephron
The renal tubule is the portion of the nephron containing the tubular fluid filtered through the glomerulus. After passing through the renal tubule, the filtrate continues to the collecting duct system, which is not part of the nephron....
. It consists of two structures: a 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...
and a 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 glomerulus is a small tuft of capillaries containing two cell types. Endothelial cells, which have large fenestrae, are not covered by diaphragms. Mesangial cells are modified smooth muscle cells that lie between the capillaries and the glomerulus. They regulate blood flow by their contractile activity and secrete extracellular matrix, prostaglandins, and cytokines. Mesangial cells also have phagocytic activity, removing proteins and other molecules trapped in the glomerular basement membrane or filtration barrier. The Bowman's capsule has an outer parietal layer composed of simple squamous epithelium. The visceral layer, composed of modified simple squamous epithelium, is lined by podocytes. Podocytes have foot processes, pedicels, that wrap around glomerular capillaries. These pedicels interdigitate with pedicels of adjacent podocytes forming filtration slits.
The renal corpuscle filtration barrier is composed of: the fenestrated endothelium of glomerular capillaries, the fused basal lamina of endothelial cells and podocytes, and the filtration slits of the podocytes. This barrier permits passage of water, ions, and small molecules from the bloodstream into Bowman's space (the space between the visceral and parietal layers). Large and/or negatively charged proteins are prevented from passing into Bowman's space, thus retaining these proteins in the circulation. The basal lamina is composed of 3 layers: lamina rara externa, lamina densa, and lamina rara interna. The lamina rara externa is adjacent to the podocyte processes. The lamina densa is the central layer consisting of type IV collagen and laminin. This layer acts as a selective macromolecular filter, preventing the passage of large protein molecules into Bowman's space. The lamina rara interna is adjacent to endothelial cells. This layer contains heparan sulfate, a negatively charged glycosaminoglycan that contributes to the electrostatic barrier of the glomerular filter.
There are two poles in the renal corpuscle, a vascular pole, and a urinary pole. The vascular pole is where the afferent and efferent arterioles communicate with the glomerulus. The urinary pole is where the corpuscle opens into the lumen of the proximal convoluted tubule.
Fluid from blood in the glomerulus is collected in the Bowman's capsule to form "glomerular filtrate", which is then further processed along the nephron to form urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
.
Eponym
A renal corpuscle is also known as a Malpighian corpuscleMalpighian corpuscle
There are at least two anatomical structures called a Malpighian corpuscle. They are also known as:* Renal corpuscles — the initial filtering component of nephrons in the kidneys...
, named after
Eponym
An eponym is the name of a person or thing, whether real or fictitious, after which a particular place, tribe, era, discovery, or other item is named or thought to be named...
Marcello Malpighi
Marcello Malpighi
Marcello Malpighi was an Italian doctor, who gave his name to several physiological features, like the Malpighian tubule system.-Early years:...
(1628–1694), an Italian physician
Physician
A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...
and biologist
Biologist
A biologist is a scientist devoted to and producing results in biology through the study of life. Typically biologists study organisms and their relationship to their environment. Biologists involved in basic research attempt to discover underlying mechanisms that govern how organisms work...
. This name is not used widely anymore, probably to avoid confusion with a Malpighian corpuscle in the spleen
Spleen
The spleen is an organ found in virtually all vertebrate animals with important roles in regard to red blood cells and the immune system. In humans, it is located in the left upper quadrant of the abdomen. It removes old red blood cells and holds a reserve of blood in case of hemorrhagic shock...
.