Ultrafiltration ( renal ) - wikipedia Ultrafiltration ( renal ) This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. ( June 2011 ) Diagram showing the basic physiologic mechanisms of the kidney In renal physiology, ultrafiltration occurs at the barrier between the blood and the filtrate in the glomerular capsule ( Bowman 's capsule ) in the kidneys. As in nonbiological examples of ultrafiltration, pressure ( in this case blood pressure ) and concentration gradients lead to a separation through a semipermeable membrane ( provided by the podocytes ). The Bowman 's capsule contains a dense capillary network called the glomerulus. Blood flows into these capillaries through the afferent arterioles and leaves through the efferent arterioles. The high hydrostatic pressure forces small molecules in the tubular fluid such as water, glucose, amino acids, sodium chloride and urea through the filter, from the blood in the glomerular capsule across the basement membrane of the Bowman 's capsule and into the renal tubules. This process is called ultrafiltration ; the resulting fluid, virtually free of large proteins and blood cells, is referred to as glomerular filtrate, or ultrafiltrate. Further modification of ultrafiltrate, by reabsorption and secretion, transforms it into urine. Glomerular pressure is about 75 millimeters of mercury ( 10 kPa ). It is opposed by osmotic pressure ( 30 mmHg, 4.0 kPa ) and hydrostatic pressure ( 20 mmHg, 2.7 kPa ) of solutes present in capsular space. This difference in pressure is called effective pressure ( 25 mmHg, 3.3 kPa ). In hemodialysis centers, ultrafiltration takes place on the hemodialysis machines when the venous pressure is greater than the transmembrane pressure ( TMP ). This cleans whole blood while keeping its blood cells intact. Contents 1 Selectivity 2 Slow continuous ultrafiltration 3 See also 4 References Selectivity See also : Table of permselectivity for different substances The structures of the layers of the glomerulus determine their permeability - selectivity ( permselectivity ). For instance, small ions such as sodium and potassium pass freely, while larger plasma proteins, such as hemoglobin tetramers, haptoglobin bound hemoglobin and albumin have practically no permeability at all. Also, negatively charged molecules will pass through far less frequently than positively charged ones. Slow continuous ultrafiltration Slow Continuous Ultrafiltration ( SCUF ) is an artificial method which approximately mimics the ultrafiltration function of the kidneys. SCUF is a continuous renal replacement therapy ( CRRT ) generally used to remove fluid from fluid overloaded patients suffering acute renal failure. During SCUF blood is removed from the body and is passed through an extracorporeal circuit through a hemofilter and a predetermined percentage of plasma water is removed based upon a prescription. Typically, no more than 2 liters an hour of fluid is removed. The remaining blood is returned to the patient. Unlike hemodialysis, hemofiltration and hemodiafiltration, no dialysate or replacement fluids are used in SCUF. See also Ultrafiltration ( industrial ) Ultrafiltration Aquapheresis References Jump up ^ Koushanpour, Esmail ( 1986 ). Renal Physiology. New York : Springer - Verlag. pp. 53 -- 72. ISBN 978 - 0 - 387 - 96304 - 4. Jump up ^ Ronco C, Bellomo R, Ricci Z ( 2001 ). `` Hemodynamic response to fluid withdrawal in overhydrated patients treated with intermittent ultrafiltration and slow continuous ultrafiltration : role of blood volume monitoring ''. Cardiology. 96 ( 3 - 4 ) : 196 -- 201. doi : 10.1159 / 000047404. PMID 11805387. hide Physiology of the kidneys and acid - base physiology Renal function Secretion clearance Pharmacokinetics Clearance of medications Urine flow rate Reabsorption Solvent drag sodium chloride urea glucose oligopeptides protein Renal function Glomerular filtration rate Creatinine clearance Renal clearance ratio Urea reduction ratio Kt / V Standardized Kt / V Measures of dialysis Hemodialysis product PAH clearance ( Effective renal plasma flow Extraction ratio ) Filtration Renal blood flow Ultrafiltration Countercurrent exchange Filtration fraction Hormones Antidiuretic hormone Aldosterone Atrial natriuretic peptide Renin Erythropoietin Calcitriol Prostaglandins Acid - base balance Fluid balance Darrow Yannet diagram Body water : Intracellular fluid / Cytosol Extracellular fluid ( Interstitial fluid Plasma Transcellular fluid ) Base excess Davenport diagram Anion gap Arterial blood gas Winters ' formula Buffering Bicarbonate buffer system Respiratory compensation Renal compensation Other Fractional sodium excretion BUN - to - creatinine ratio Tubuloglomerular feedback Natriuresis Urine Retrieved from `` https://en.wikipedia.org/w/index.php?title=Ultrafiltration_(renal)&oldid=841574200 '' Categories : Renal physiology Hidden categories : Articles needing additional references from June 2011 All articles needing additional references Talk Contents About Wikipedia Español فارسی Bahasa Melayu Edit links This page was last edited on 16 May 2018, at 17 : 31. 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Question: where does ultrafiltration take place in the kidney
Answer: at the barrier between the blood and the filtrate in the glomerular capsule (Bowman's capsule) in the kidneys