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Renal Physiology: Chapter Goals. After studying this chapter, students should be able to . . . 1. describe the different regions of the nephron tubules and explain the anatomic relationship between the tubules and the gross structure of the kidney.
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Renal Physiology: Chapter Goals After studying this chapter, students should be able to . . . 1. describe the different regions of the nephron tubules and explain the anatomic relationship between the tubules and the gross structure of the kidney. 2. describe the structural and functional relationships between the nephron tubules and their associated blood vessels. 3. describe the composition of glomerular ultrafiltrate and explain how it is produced. 4. explain how the proximal convoluted tubule reabsorbs salt and water. 5. describe active transport and osmosis in the loop of Henle and explain how these processes produce a countercurrent multiplier system. 6. explain how the vasa recta function in countercurrent exchange. 7. describe the role of antidiuretic hormone (ADH) in regulating the final urine volume. 8. describe the mechanisms of glucose reabsorption and explain the meanings of the terms transport maximum and renal plasma threshold.
Renal Physiology: Chapter Goals 9. define the renal plasma clearance, and explain why the clearance of inulin is equal to the glomerular filtration rate. 10. explain how the clearance of different molecules is determined and how the processes of reabsorption and secretion affect the clearance measurement.. 11. explain the mechanism of Na+ reabsorption in the distal tubule and why this reabsorption occurs together with the secretion of K+. 12. describe the effects of aldosterone on the distal convoluted tubule and how aldosterone secretion is regulated. 13. explain how activation of the renin-angiotensin system results in the stimulation of aldosterone secretion. 14. describe the interactions between plasma K+ and H+ concentrations and explain how this affects the tubular secretion of these ions. 15. describe the role of the kidneys in the regulation of acid-base balance. 16. describe the different mechanisms by which substances can act as diuretics and explain why some cause excessive loss of K+.
Renal Physiology • Functional Relationships • Urinary System Anatomy • Nephron
Urinary System Anatomy • Kidneys • Nephrons
Nephron Function • Filtration • Tubular Secretion • Selective Reabsorption
Filtration • Analysis of Glomerular Capillary Dynamics • Blood Pressure =55.0 mm Hg O (vs 35 normally) • Plasma Coll O.P. =30.0 mm Hg I • BC Hydrostatic P. =15.0 mm Hg I 10.0 mm Hg O = Filtration Pressure Table 14-1
Filtration (cont’d) • Regulation of Filtration Pressure - via juxtaglomerular apparatus
Tubular Secretion/Selective Reabsorption • Tubular Maximum • Urine = (Filtration - reabsorption) + Secretion
Regulation of Blood Composition • 1. Electrolytes and Solutes • a. Na+ high in blood; low in cells • b. K+ high in cells; low in blood • c. Aldosterone (from adrenal gland) Na+ uptake and K+ uptake (into blood)
Saving Sodium 14-18
Losing Sodium 14-20
Regulation of Blood Composition • 2. pH: too low - H+ to tubule; too high - H + to blood • a. Definition - pH = -log [H+] • b. How buffers work - e.g. tie up H+ from a strong acid with the salt of a weak acid, which forms a weak acid.
Regulation of Blood Composition 3. Water • 80% reabsorbed by elevated osmotic pressure of blood in capillaries of efferent renal arteriole following filtration by the glomerulus • Countercurrent Mechanism - salvages water from glomerular filtrate, so produces a concentrated urine
Water Reabsorption 17-22
Countercurrent Mechanism • i. Produce Na+ concentration gradient via active transport in ascending branch of the Loop of Henle. • ii. Maintain Na+ concentration gradient against tendency to diffuse. • iii. Use Na+ concentration gradient to salvage water
Countercurrent Mechanism 14-27