Introduction to the Renal System PDF

Introduction to the Renal System Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Role of the Kidneys v Influence blood pressure control v Release renin to activate the renin–angiotensin system v Leads to increased blood pressure and volume v Increased blood flow to the...

Introduction to the Renal System Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Role of the Kidneys v Influence blood pressure control v Release renin to activate the renin–angiotensin system v Leads to increased blood pressure and volume v Increased blood flow to the kidney v Can lead to water retention or excretion Copyright © 2020 Wolters Kluwer All Rights Reserved Components of the Renal System v Kidneys v Organs of the Urinary Tract o Ureters o Urinary bladder o Urethra Copyright © 2020 Wolters Kluwer All Rights Reserved Major Functions of the Renal System v Maintaining the volume and composition of body fluids within normal ranges v Regulating vitamin D activation v Regulating blood pressure through the renin–angiotensin system v Regulating red blood cell production through the production and secretion of erythropoietin Copyright © 2020 Wolters Kluwer All Rights Reserved The Kidney and Organs of the Urinary Tract Copyright © 2020 Wolters Kluwer All Rights Reserved The Nephron Copyright © 2020 Wolters Kluwer All Rights Reserved Components of the Nephron v Bowman’s Capsule v Ascending Loop of Henle v Distal Convoluted Tubule v Collecting Ducts v Renal Pelvises Copyright © 2020 Wolters Kluwer All Rights Reserved Processes Involved in the Functioning of the Nephrons v Glomerular Filtration o Straining fluid into the nephron v Tubular Secretion o Actively removing components from the capillary system and depositing them into the tubule v Tubular Reabsorption o Removing components from the tubule to return them to the capillary system and circulation Copyright © 2020 Wolters Kluwer All Rights Reserved Maintenance of Volume and Composition of Body Fluids v The kidneys regulate the composition of body fluids by balancing the levels of the key electrolytes. v They secrete or absorb these electrolytes to maintain the desired level within the body. v The volume of body fluids is controlled by diluting or concentrating the urine. Copyright © 2020 Wolters Kluwer All Rights Reserved Sodium Regulation v Body major cations v Filters through the glomerulus and enters the renal tubule, then is actively reabsorbed in the proximal convoluted tubule to the peritubular capillaries v As sodium is actively moved out of the filtrate it takes chloride ions and water with it v This occurs by passive diffusion as the body maintains the osmotic and electrical balance on both sides of the tubule Copyright © 2020 Wolters Kluwer All Rights Reserved Aldosterone v Influences the sodium levels v Is a hormone produced in the adrenal gland v Is released into the circulation in response to high potassium levels, sympathetic stimulation, or angiotensin III v Stimulates the sodium-potassium exchange pump in the cells of the distal tubule Copyright © 2020 Wolters Kluwer All Rights Reserved Countercurrent Mechanism v It further regulates sodium absorption in the medullary nephrons in the loop of Henle. v Sodium is actively reabsorbed into the surrounding peritubular tissues, and water flows out of the tubule into this sodium rich tissue to maintain osmotic balance. v The filter at the end of the descending loop of Henle is concentrated in comparison to the rest of the filtrate. Copyright © 2020 Wolters Kluwer All Rights Reserved Factors Stimulating Release of ADH v Falling Blood Volume v Sympathetic Stimulation v Rising Sodium Levels Copyright © 2020 Wolters Kluwer All Rights Reserved Antidiuretic Hormone v Produced by the Hypothalamus v Stored in the Posterior Pituitary Gland v Important in Maintaining Fluid Balance Copyright © 2020 Wolters Kluwer All Rights Reserved Carbonic Anhydrase v Catalyst that influences the sodium reabsorption v Allows carbon dioxide and water to combine v This combination forms carbonic acid Copyright © 2020 Wolters Kluwer All Rights Reserved Chloride Regulation v Chloride is an important negatively charged ion that helps to maintain electrical neutrality with the movement of cations across the cell membrane. v Chloride is primarily reabsorbed in the loop of Henle, where it promotes the movement of sodium out of the cell. Copyright © 2020 Wolters Kluwer All Rights Reserved Potassium Regulation v Potassium is another cation that is vital to proper functioning of the nervous system, muscles, and cell membranes. v About 65% of the potassium that is filtered at the glomerulus is reabsorbed at Bowman’s capsule and the proximal convoluted tubule. v Another 25% to 30% is reabsorbed in the ascending loop of Henle. v If potassium levels are very high the retention of sodium exchange for potassium also leads to a retention of water and a dilution of blood volume. Copyright © 2020 Wolters Kluwer All Rights Reserved Regulation of Vitamin D Activation v The absorption of calcium from the gastrointestinal (GI) tract is regulated by vitamin D. v Vitamin D must be activated in the kidneys to a form that promotes calcium absorption. v Once absorbed, calcium levels are maintained within a very tight range by parathyroid hormone (PTH) and calcitonin. Copyright © 2020 Wolters Kluwer All Rights Reserved Functions of Calcium v Absorption of calcium from the gastrointestinal (GI) tract is regulated by vitamin D ingested as part of the diet. The vitamin then must be activated in the kidneys to a form that will promote calcium absorption for the following o Muscle Function o Blood Clotting o Bone Formation o Contraction of Cell Membranes o Muscle Movement Copyright © 2020 Wolters Kluwer All Rights Reserved Nephrons and Points of Regulation Copyright © 2020 Wolters Kluwer All Rights Reserved Renin–Angiotensin System Copyright © 2020 Wolters Kluwer All Rights Reserved