RT Book, Section A1 Barrett, Kim E. A1 Barman, Susan M. A1 Brooks, Heddwen L. A1 Yuan, Jason X.-J. SR Print(0) ID 1159055770 T1 Renal Physiology: Introduction T2 Ganong's Review of Medical Physiology, 26e YR 2019 FD 2019 PB McGraw-Hill Education PP New York, NY SN 9781260122404 LK accessmedicine.mhmedical.com/content.aspx?aid=1159055770 RD 2024/03/28 AB The kidneys, the bladder, and the ureters make up the urinary system. Within the kidney, the functional unit is the nephron and each human kidney has approximately 1 million nephrons. The kidneys play an essential role in the regulation of water homeostasis, electrolyte composition (eg, Na, Cl, K, HCO3), regulation of extracellular volume (thus blood pressure), and acid–base homeostasis (Chapter 39). The kidneys filter the plasma of the blood and produce urine, which allows the kidneys to excrete metabolic waste products (eg, urea; ammonium; and foreign chemicals, such as drug metabolites) from the body. The kidneys are responsible for the reabsorption of glucose and amino acids from the plasma filtrate in addition to regulated calcium and phosphate uptake (high in children). The kidneys play a role in gluconeogenesis and during fasting can synthesize and release glucose into the blood, producing almost 20% of the liver’s glucose capacity. The kidneys are also endocrine organs, making kinins (see Chapter 32), 1,25-dihydroxycholecalciferol (see Chapter 21), erythropoietin (see Chapter 37), and making and secreting renin (see Chapter 38).