How is filtrate reabsorbed into the blood

A three stage process occurs in each nephron: filtration, selective reabsorption and finally excretion. The glomerulus filters the blood and removes water, glucose, salts and waste urea from it. The blood is under high pressure at the start of the nephron, which aids the filtration of the blood. These waste substances all pass from the capillaries in the glomerulus into the Bowman's capsule. This purifies the blood. These waste substances then move from the Bowman's capsule towards the loop of Henle.

Proteins are too large to pass through here and so remain in the blood. This process is called filtration. The kidneys must now reabsorb the molecules which are needed, while allowing those molecules which are not needed to pass out in the urine. Therefore, the kidneys selectively reabsorb only those molecules which the body needs back in the bloodstream.

The reabsorbed molecules include:. This reabsorption comes from the solution passing along the loop of Henle from the Bowman's capsule. This reabsorption of vital nutrients from the filtrate is the second step in urine creation.

The filtrate absorbed in the glomerulus flows through the renal tubule, where nutrients and water are reabsorbed into capillaries. At the same time, waste ions and hydrogen ions pass from the capillaries into the renal tubule.

This process is called secretion. The secreted ions combine with the remaining filtrate and become urine. The urine flows out of the nephron tubule into a collecting duct. It passes out of the kidney through the renal pelvis, into the ureter, and down to the bladder. The nephrons of the kidneys process blood and create urine through a process of filtration, reabsorption, and secretion. Nitrogenous wastes excreted in urine include urea, creatinine, ammonia, and uric acid.

Ions such as sodium, potassium, hydrogen, and calcium are also excreted. Download Nephrons Lab Activity. See more from our free eBook library. The Body Online. Glomerular filtration removes solutes from the blood; it is the first step of urine formation. In tubular reabsoption, the second step of urine formation, almost all nutrients are reabsorbed in the renal tubule by active or passive transport. Tubular secretion is the last step of urine formation, where solutes and waste are secreted into the collecting ducts, ultimately flowing to the bladder in the form of urine.

Key Terms arteriole : one of the small branches of an artery, especially one that connects with capillaries countercurrent : a current that flows against the prevailing one electrolyte : any of the various ions such as sodium or chloride that regulate the electric charge on cells and the flow of water across their membranes.

Glomerular Filtration The formation of urine occurs through three steps: glomerular filtration, tubular reabsorption, and tubular secretion. 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.

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