The glomerulus is made up of a network of small blood vessels called a tuft
The glomerulus is made up of a network of small blood vessels called a tuft. It is located in the Bowman’s capsule at the beginning of the nephron located in the kidney. Blood gets filtered across capillaries walls of the tuft through the barrier of the glomerular filtrate. The structure glomerulus contains an afferent arteriole efferent arteriole that carries blood into and out of it, respectively. The capillaries of the glomerular contain a tube within the central lumen that is lined by endothelial cells. The capillaries also contain gaps called fenestrae.
Consequently, the glomerular walls contain pores between cells that allow for the filtration of blood plasma, fluids, protein, and solutes while preventing red blood cells, platelets, and the white blood cells from filtration. Glomerulus contains a glomerular basement membrane (GBM) that consists of a type IV collagen, nidogen, minis, and again, which gets synthesized and secreted by the podocytes and endothelial cells. The glomerular basement membrane is, therefore, located between the podocytes and the capillaries.
Mesangium
The mesangium is a continuous space with the arterioles’ smooth muscles. It is surrounded by capillaries, although it is located outside the capillary membrane. It forms a scaffold that supports the microvasculature of the glomerular. The cells of the mesangium are contractile cells that closely resemble vascular smooth muscle cells. The basement membrane surrounding the capillaries and the mesangium. It is located in the middle of the capillaries.
Blood supply
The afferent arteriole branching from renal arterial is the sole blood carrier that directs blood into the glomerulus. The blood leaves from the capillaries of the glomerular through the efferent arteriole rather than through the venules. A sufficient hydraulic pressure that happens within the glomerulus is caused by the efferent arterioles’ resistance, enhancing the ultrafiltration force. There is tight control over blood flow through the glomerulus that occurs during the exit through the efferent arteriole caused by the rapid dilation and constriction of the arterioles, as it happens more than in the venules. The blood enters into the renal venules from the efferent arteriole, then enters the renal interlobular vein as it moves forward into the renal vein. The filtrate passes through a filtration unit consisting of three and thereafter, enters the Bowman’s space. The filtrate is directed into the nephrons, made up of renal tubules following up a U-shaped path to the collecting duct, and finally inters the renal calyx in the form of urine. Juxtamedullary nephrons are cortical nephrons located near the junction of the corticomedullar. When blood leaves the afferent arteriole of the nephrons, it enters straight capillary branches called the vasa recta, delivering blood from the renal medulla. The vasa recta run directly adjacent to the loop of Henle that is both ascending and descending, and it supports the countercurrent exchange medullary system maintenance
Functions
Filtration
The first main function that the glomerulus performs is the filtration of plasma, producing a glomerular filtrate. The filtrate from the glomerulas passes in form of urine through the length of the nephrone. The rate of glomerular filtration from plasma is always higher as compared to that of systemic capillaries. The glomerulus is attached on both sides with the afferent and the efferent arterioles, which have high resistance essential for enabling the filtration. The arterioles are arranged in a series that enable the high hydraulic pressure posed on the capillaries of the glomerullar that favours the filtration into the Bowman’s capsule.
Permeability
The layers are structured in a way that determine the permselectivity (permeability-selectivity). There are factors that affect the permeability of the glomerulus include the negative charge contained in the podocytic epithelium and the basement membrane. Another factor affecting permeability is the pores of the glomerular walls which are effective enough to allow for permeability of the glomerulus. The resulting activity is that the negatively charged molecules are large making them unable to penetrate through the walls frequently, as compared to the positively charged small molecules that can pass through frequently. Filtration is resisted by the glomerular capillaries’ oncotic pressure. The walls of the glomerullar resists the filtration of the large negatively charged proteins into the Bowman’s capsule. Oncotic pressure increases in the walls of the glomerular capillaries as a result of the increase in the protein concentration as the glomerular capillaries filtrate the plasma. The concentration occurs due to inability of the proteins to penetrate through the walls as a result of their large-sized particles.
Blood pressure regulation
Smooth muscle cells that are specialized are contained within the walls of the afferent arteriole. The muscles cells therefore synthesize renin. The juxtaglomerular cells have a major role in the system of the renin-angiotensin that function to regulate blood pressure.