Скачать с ютуб FORMATION OF URINE|| NEPHRON || HUMAN EXCRETORY SYSTEM || MOLECULAR MYSTERIES в хорошем качестве

FORMATION OF URINE|| NEPHRON || HUMAN EXCRETORY SYSTEM || MOLECULAR MYSTERIES

#trending #anatomy #humananatomy #humanbodyfacts #excretory_system #urine #urineformation #genetics #biologyatease #science #kidneyhealth #kidneyhealth #nephron FORMATION OF URINE|| NEPHRON || HUMAN EXCRETORY SYSTEM || MOLECULAR MYSTERIES Physiology of Urine Formation in the Nephrons Steps involved in urine formation are Glomerular filtration, Tubular reabsorption and Tubular secretion Glomerular Filtration: During filtration, blood enters the afferent arteriole and flows into the glomerulus where filterable blood components, such as water and nitrogenous waste, will move towards the inside of the glomerulus, and nonfilterable components, such as cells and serum albumins, proteins will exit via the efferent arteriole. These filterable components accumulate in the glomerulus to form the glomerular filtrate. Glomerular filtration filters out most of the solutes due to high blood pressure and specialized membranes in the afferent arteriole. The blood pressure in the glomerulus is maintained independent of factors that affect systemic blood pressure. The “leaky” connections between the endothelial cells of the glomerular capillary network allow solutes to pass through easily. All solutes in the glomerular capillaries, except for macromolecules like proteins, pass through by passive diffusion. There is no energy requirement at this stage of the filtration process. Glomerular filtration rate (GFR) is the volume of glomerular filtrate formed per minute by the kidneys. GFR is regulated by multiple mechanisms and is an important indicator of kidney function. Tubular Reabsorption and Secretion Tubular reabsorption occurs in the PCT part of the renal tubule. Almost all nutrients are reabsorbed, and this occurs either by passive or active transport. Reabsorption of water and some key electrolytes are regulated and can be influenced by hormones. Sodium (Na ) is the most abundant ion and most of it is reabsorbed by active transport and then transported to the peritubular capillaries. Because Na is actively transported out of the tubule, water follows it to even out the osmotic pressure. Water is also independently reabsorbed into the peritubular capillaries due to the presence of aquaporins, or water channels, in the PCT. This occurs due to the low blood pressure and high osmotic pressure in the peritubular capillaries. However, every solute has a transport maximum and the excess is not reabsorbed A U-shaped tube represents the loop of Henle. Filtrate enters the descending limb, and exits the ascending limb. The descending limb is water-permeable, and water travels from the limb to the interstitial space. As a consequence, the osmolality of the filtrate inside the limb increases from 300 milliosmoles per liter at the top to 1200 milliosmoles per liter at the bottom. The ascending limb is permeable to sodium and chloride ions. Because the osmolality inside bottom part of the limb is higher than the interstitial fluid, these ions diffuse out of the ascending limb. Higher up, sodium is actively transported out of the limb, and chloride follows. Countercurrent exchange in Loop of Henle In the loop of Henle, the permeability of the membrane changes. The descending limb is permeable to water, not solutes; the opposite is true for the ascending limb. Additionally, the loop of Henle invades the renal medulla, which is naturally high in salt concentration and tends to absorb water from the renal tubule and concentrate the filtrate. The osmotic gradient increases as it moves deeper into the medulla. Because two sides of the loop of Henle perform opposing functions, as illustrated in Figure 2, it acts as a countercurrent multiplier. The vasa recta around it acts as the countercurrent exchanger. The loop of Henle acts as a countercurrent multiplier that uses energy to create concentration gradients. The descending limb is water permeable. Water flows from the filtrate to the interstitial fluid, so osmolality inside the limb increases as it descends into the renal medulla. At the bottom, the osmolality is higher inside the loop than in the interstitial fluid. Thus, as filtrate enters the ascending limb, Na and Cl− ions exit through ion channels present in the cell membrane. Further up, Na is actively transported out of the filtrate and Cl− follows. By the time the filtrate reaches the DCT, most of the urine and solutes have been reabsorbed. If the body requires additional water, all of it can be reabsorbed at this point. Further reabsorption is controlled by hormones. Excretion of wastes occurs due to lack of reabsorption combined with tubular secretion. Undesirable products like metabolic wastes, urea, uric acid, and certain drugs, are excreted by tubular secretion. LINKS: For structure of kidney and nephron: https://studio.youtube.com/video/T35W... Thanks for watching Subscribe, Like and Share your ideas Parinita