filtration

(noun)

In bulk flow, this refers to the movement of proteins or other large molecules from the blood into the interstitium.

Related Terms

Examples of filtration in the following topics:

  • Glomerular Filtration

    • Glomerular filtration is the renal process whereby fluid in the blood is filtered across the capillaries of the glomerulus.
    • Glomerular filtration is the first step in urine formation and constitutes the basic physiologic function of the kidneys.
    • The positively charged podocytes will impede the filtration of negatively charged particles as well (such as albumins).
    • The process by which glomerular filtration occurs is called renal ultrafiltration.
    • These factors will influence the glomeruluar filtration rate, along with a few other factors.

  • Bulk Flow: Filtration and Reabsorption

    • Capillary fluid movement occurs as a result of diffusion (colloid osmotic pressure), transcytosis, and filtration.
    • The movement of materials across the capillary wall is dependent on pressure and is bidirectional depending on the net filtration pressure derived from the four Starling forces.
    • When moving from the bloodstream into the interstitium, bulk flow is termed filtration, which is favored by blood hydrostatic pressure and interstitial fluid oncotic pressure.
    • This indicates that capillaries are normally in a state of filtration along their entire length.

  • Overview of Urine Formation

    • Urine is a waste byproduct formed from excess water and metabolic waste molecules during the process of renal system filtration.
    • Urine formation occurs during three processes: filtration, reabsorption, and secretion.
    • These filterable components accumulate in the glomerulus to form the glomerular filtrate.
    • Normally, about 20% of the total blood pumped by the heart each minute will enter the kidneys to undergo filtration; this is called the filtration fraction.
    • The end product of all these processes is urine, which is essentially a collection of substances that has not been reabsorbed during glomerular filtration or tubular reabsorbtion.

  • Regulation of Glomerular Filtration Rate

    • Glomerular filtration rate (GFR) is the measure that describes the total amount of filtrate formed by all the renal corpuscles in both kidneys per minute.
    • The glomerular filtration rate is directly proportional to the pressure gradient in the glomerulus, so changes in pressure will change GFR. 
    • Osmotic pressure is the force exerted by proteins and works against filtration because the proteins draw water in.
    • GFR is the rate at which is this filtration occurs.
    • List the conditions that can affect the glomerular filtration rate (GFR) in kidneys and the manner of its regulation

  • Tubular Reabsorption

    • As the fluid filtered from blood, called filtrate, passes through the nephron, much of the filtrate and its contents are reabsorbed into the body.
    • As filtrate passes through the nephron, its osmolarity (ion concentration) changes as ions and water are reabsorbed.
    • The filtrate entering the proximal convoluted tubule is 300 mOsm/L, which is the same osmolarity as normal plasma osmolarity.
    • In the proximal convoluted tubules, all the glucose in the filtrate is reabsorbed, along with an equal concentration of ions and water (through cotransport), so that the filtrate is still 300 mOsm/L as it leaves the tubule.
    • The filtrate osmolarity drops to 1200 mOsm/L as water leaves through the descending loop of henle, which is impermeable to ions.

  • Glomerular Diseases

    • The Bowman's capsule empties the filtrate into a tubule that is also part of the nephron.
    • A glomerulus and its surrounding Bowman's capsule constitute a renal corpuscle, the basic filtration unit of the kidney.
    • The glomerular filtration rate (GFR) is the rate at which blood is filtered through all of the glomeruli, and, thus, the measure of the overall renal function.

  • Movement of Fluid Among Compartments

    • The solution to the equation is known as the net filtration or net fluid movement.
    • If positive, fluid will tend to leave the capillary (filtration).

  • Capillary Dynamics

    • The movement of materials across the wall is dependent on pressure and is bi-directional depending on the net filtration pressure derived from the four Starling forces that modulate capillary dynamics.
    • The net filtration pressure derived from the sum of the four forces described above determines the fluid flow into or out of the capillary.
    • In conditions where plasma proteins are reduced (e.g. from being lost in the urine or from malnutrition), or blood pressure is significantly increased, a change in net filtration pressure and an increase in fluid movement across the capillary result in excess fluid build-up in the tissues (edema).

  • Renal Clearance

    • Each substance has its own specific clearance that depends on its unique filtration characteristics.
    • Clearance is a function of glomerular filtration, secretion from the peritubular capillaries to the nephron, and reabsorption from the nephron back to the peritubular capillaries.

  • Spleen

    • Red Pulp:the site of blood filtration in the spleen.
    • The primary function of the spleen is blood filtration.
    • Describe the roles of the spleen in the filtration and storage of red blood cells