![nephron and concentrations of interstital fluid image nephron and concentrations of interstital fluid image](https://image.slidesharecdn.com/chp17physiologyofthekidneys-151015043055-lva1-app6891/95/physiology-of-the-kidneys-36-638.jpg)
The glomerulus forces solutes out of the blood by pressure.Aquaporin expression at the collecting duct membrane can be mediated by vasopressin. Aquaporins on the apical side of epithelial cells in the collecting ducts filter water out and the urine is concentrated here before it enters the ureters through the renal pelvis to go to the bladder. The collecting ducts collect filtrate coming from the nephrons and fuse in the medullary papillae. Osmolarity is given in units of milliosmoles per liter (mOsm/L).Īdditional solutes and wastes are secreted into the kidney tubules during tubular secretion (the last step), which is the opposite process of tubular reabsorption. Further up, Na+ is actively transported out of the filtrate and Cl- follows. Thus, as filtrate enters the ascending limb, Na+ and Cl- ions exit through ion channels present in the cell membrane. At the bottom, the osmolality is higher inside the loop than in the interstitial fluid. Water flows from the filtrate to the interstitial fluid, so osmolality inside the limb increases as it descends into the renal medulla. The vasa recta around the loop of Henle acts as the countercurrent exchanger. Because two sides of the loop of Henle perform opposing functions, it acts as a countercurrent multiplier. The osmotic gradient increases as it moves deeper into the medulla. It tends to absorb water from the renal tubule and concentrate the filtrate. Additionally, the loop of Henle invades the renal medulla, which is naturally high in salt concentration. The descending limb is permeable to water, not solutes the opposite is true for the ascending limb. In the loop of Henle, the permeability of the membrane changes. This occurs due to the low blood pressure and high osmotic pressure in the peritubular capillaries. Water is also independently reabsorbed into the peritubular capillaries due to the presence of aquaporins, or water channels, in the PCT. Because Na + is actively transported out of the tubule, water follows to even out the osmotic pressure. Sodium (Na +) is the most abundant ion most of it is reabsorbed by active transport and then transported to the peritubular capillaries. Reabsorption of water and key electrolytes are regulated and influenced by hormones. Almost all nutrients are reabsorbed this happens either by passive or active transport.
![nephron and concentrations of interstital fluid image nephron and concentrations of interstital fluid image](https://basicmedicalkey.com/wp-content/uploads/2016/09/B9780323088541000035_f03-04-9780323088541.jpg)
Tubular reabsorption occurs in the PCT ( proximal convoluted tubule) part of the renal tubule. The second step is the tubular reabsorption. Glomerular filtration rate (GFR) is the volume of glomerular filtrate formed per minute by the kidneys. There is no energy requirement at this stage of the filtration process. All solutes in the glomerular capillaries, including sodium ions and negatively and positively charged ions, pass through by passive diffusion the only exception is macromolecules such as proteins. The “leaky” connections between the endothelial cells of the glomerular capillary network allow solutes to pass through easily. The process of glomerular filtration filters out most of the solutes, particularly large solutes like proteins, due to the high blood pressure and specialized membranes in the afferent arteriole. The first step of the formation of the urine is glomerular filtration in the glomerules. It occurs through three steps: glomerular filtration, tubular reabsorption, and tubular secretion. The formation of urine takes place in the nephron, which is the structural and fundamental unit of the kidney.