What is the difference between tubular fluid and filtrate

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.

Key Terms glomerulus : A small, intertwined group of capillaries within nephrons of the kidney that filter the blood to make urine. It is the primary force that drives glomerular filtration. Learning Objectives List the conditions that can affect the glomerular filtration rate GFR in kidneys and the manner of its regulation.

Key Takeaways Key Points Glomerular filtration is occurs due to the pressure gradient in the glomerulus. Increased blood volume and increased blood pressure will increase GFR. Constriction in the afferent arterioles going into the glomerulus and dilation of the efferent arterioles coming out of the glomerulus will decrease GFR.

Water tends to follow proteins based on an osmotic pressure gradient. This enhances the kidney's ability to eliminate certain wastes and toxins. It is also essential to regulation of plasma potassium concentrations and pH. See Fluid and electrolyte balance. Excretion is what goes into the urine, the end result of the above three processes.

In individual nephrons flow-dependent reabsorption cannot always be observed even when it appears that GTB is preserved in that kidney.

Flow dependency of tubular fluid reabsorption might be attributed to some properties or constituents in tubular fluid rather than to some intrinsic characteristics of the tubular epithelium. Because flow dependence and tubular fluid transport are homogeneous along the tubule, fluid reabsorption might be controlled by a mechanism akin to a flow reactor.

Filtrate osmolarity changes drastically throughout the nephron as varying amounts of the components of filtrate are reabsorbed in the different parts of the nephron. Filtrate The fluid filtered from blood, called filtrate, passes through the nephron, much of the filtrate and its contents are reabsorbed into the body.

Mechanisms of Reabsorption Tubular secretion : Diagram showing the basic physiologic mechanisms of the kidney and the three steps involved in urine formation. The mechanisms of reabsorption into the peri-tubular capillaries include: Passive diffusion—passing through plasma membranes of the kidney epithelial cells by concentration gradients.

Cotransport—this process is particularly important for the reabsorption of water. Water can follow other molecules that are actively transported, particularly glucose and sodium ions in the nephron.