What is filtered through the glomerulus

Some substances can also pass through tiny spaces in between the renal epithelial cells, called tight junctions. As filtrate passes through the nephron, its osmolarity ion concentration changes as ions and water are reabsorbed. Finally, in the distal convoluted tubule and collecting duct, a variable amount of ions and water are reabsorbed depending on hormonal stimulus.

The final osmolarity of urine is therefore dependent on whether or not the final collecting tubules and ducts are permeable to water or not, which is regulated by homeostasis.

Reabsorption throughout the nephron : A diagram of the nephron that shows the mechanisms of reabsorption. Hydrogen, creatinine, and drugs are removed from the blood and into the collecting duct through the peritubular capillary network. Tubular secretion is the transfer of materials from peritubular capillaries to the renal tubular lumen; it is the opposite process of reabsorption. This secretion is caused mainly by active transport and passive diffusion. Usually only a few substances are secreted, and are typically waste products.

Urine is the substance leftover in the collecting duct following reabsorption and secretion. The mechanisms by which secretion occurs are similar to those of reabsorption, however these processes occur in the opposite direction. Renal secretion is different from reabsorption because it deals with filtering and cleaning substances from the blood, rather than retaining them.

The substances that are secreted into the tubular fluid for removal from the body include:. Many pharmaceutical drugs are protein-bound molecules thatDiagram showing the basic physiologic mechanisms of the kidney and the three steps involved in urine formation.

Tubular secretion occurs throughout the different parts of the nephron, from the proximal convoluted tubule to the collecting duct at the end of the nephron. The movement of these ions also helps to conserve sodium bicarbonate NaHCO 3. The typical pH of urine is about 6. Urine that is formed via the three processes of filtration, reabsorption, and secretion leaves the kidney through the ureter, and is stored in the bladder before being removed through the urethra.

At this final stage it is only approximately one percent of the originally filtered volume, consisting mostly of water with highly diluted amounts of urea, creatinine, and variable concentrations of ions. Privacy Policy. Skip to main content. Urinary System. Search for:. Physiology of the Kidneys. Overview of Urine Formation Urine is formed in three steps: filtration, reabsorption, and secretion. Learning Objectives Summarize the steps in urine formation.

Key Takeaways Key Points Filtration involves the transfer of soluble components, such as water and waste, from the blood into the glomerulus. Reabsorption involves the absorption of molecules, ions, and water that are necessary for the body to maintain homeostasis from the glomerular filtrate back into the blood.

Secretion involves the transfer of hydrogen ions, creatinine, drugs, and urea from the blood into the collecting duct, and is primarily made of water. Blood and glucose are not normally found in urine.

Key Terms urine : A liquid excrement consisting of water, salts, and urea, which is made in the kidneys then released through the urethra. Glomerular Filtration Glomerular filtration is the renal process whereby fluid in the blood is filtered across the capillaries of the glomerulus.

Learning Objectives Explain the process of glomerular filtration in the kidneys. Key Takeaways Key Points The formation of urine begins with the process of filtration. Fluid and small solutes are forced under pressure to flow from the glomerulus into the capsular space of the glomerular capsule. Blood entering the glomerulus has filterable and non-filterable components.

Filterable blood components include water, nitrogenous waste, and nutrients that will be transferred into the glomerulus to form the glomerular filtrate. Non-filterable blood components include blood cells, albumins, and platelets, that will leave the glomerulus through the efferent arteriole.

Glomerular filtration is caused by the force of the difference between hydrostatic and osmotic pressure though the glomerular filtration rate includes other variables as well.

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. Urinary System Structures. Give It Up for the Kidneys. Urine Storage and Elimination. Common Diseases and Disorders. When you select "Subscribe" you will start receiving our email newsletter. Use the links at the bottom of any email to manage the type of emails you receive or to unsubscribe.

See our privacy policy for additional details. Learn Site. The Glomerulus Filters Water and Other Substances from the Bloodstream Each kidney contains over 1 million tiny structures called nephrons. Your kidneys also remove acid that is produced by the cells of your body and maintain a healthy balance of water, salts, and minerals—such as sodium , calcium , phosphorus , and potassium —in your blood.

Watch a video about what the kidneys do. Each of your kidneys is made up of about a million filtering units called nephrons. Each nephron includes a filter, called the glomerulus , and a tubule.

The nephrons work through a two-step process: the glomerulus filters your blood, and the tubule returns needed substances to your blood and removes wastes.

As blood flows into each nephron, it enters a cluster of tiny blood vessels—the glomerulus. The thin walls of the glomerulus allow smaller molecules, wastes, and fluid—mostly water—to pass into the tubule. Larger molecules, such as proteins and blood cells, stay in the blood vessel. A blood vessel runs alongside the tubule.

As the filtered fluid moves along the tubule, the blood vessel reabsorbs almost all of the water, along with minerals and nutrients your body needs.

The tubule helps remove excess acid from the blood. The remaining fluid and wastes in the tubule become urine. Blood flows into your kidney through the renal artery.

This large blood vessel branches into smaller and smaller blood vessels until the blood reaches the nephrons. In the nephron, your blood is filtered by the tiny blood vessels of the glomeruli and then flows out of your kidney through the renal vein.