Chapter 19a

1. Chapter 19a The Kidneys

2. About this Chapter • Anatomy of the urinary system • Overview of kidney function • Homeostasis • pH • Electrolytes • fluid • Filtration • Reabsorption • Secretion • Excretion • Micturition

3. Functions of the Kidneys • Regulation of extracellular fluid volume and blood pressure • Regulation of osmolarity • Maintenance of ion balance • Homeostatic regulation of pH • Excretion of wastes • Production of hormones

4. Anatomy: The Urinary System THE URINARY SYSTEM Kidney Ureter Urinary bladder Urethra (a) The urinary system Figure 19-1a

5. Anatomy: The Urinary System Diaphragm Left adrenal gland Inferior vena cava Left kidney Right kidney Renal artery Ureter Aorta Renal vein Urinarybladder Rectum(cut) Peritoneum(cut) (b) The kidneys are located retroperitoneallyat the level of the lower ribs. Figure 19-1b

6. Anatomy: The Urinary System Nephrons Cortex Polycystic kidney Medulla Renal pelvis Ureter Capsule (c) The kidney, in cross section. Figure 19-1c

7. Anatomy: The Urinary System Arterioles Nephrons Cortex Medulla (i) Some nephrons dip deepinto the medulla. Figure 19-1i

8. Anatomy: The Urinary System Efferent arteriole Peritubularcapillaries Peritubularcapillaries Juxtaglomerularapparatus Glomerulus Afferentarteriole Glomerulus(capillaries) Vasa recta Collectingduct Loop ofHenle (h) Juxtamedullary nephronwith vasa recta (g) One nephron has two arteriolesand two sets of capillaries. Figure 19-1g–h

9. Anatomy: The Urinary System Figure 19-1d–e

10. Anatomy: The Urinary System STRUCTURE OF THE NEPHRON Glomerulus Cut edge ofnephron tubule (f) The capillaries of the glomerulus form aball-like mass. Figure 19-1f

11. Anatomy: The Urinary System Bowman’scapsule Proximal tubule Distal tubule Ascendinglimb of loopends Descendinglimb of loopbegins Collectingduct Descendinglimb Ascendinglimb (j) Parts of a nephron Loop ofHenle To bladder Figure 19-1j

12. Kidney Function • Filtration, reabsorption, secretion, and excretion Distal tubule Peritubular capillaries Efferentarteriole Glomerulus Afferentarteriole Proximaltubule Bowman’scapsule KEY Collectingduct LoopofHenle To renalvein = Filtration: blood to lumen = Reabsorption: lumen to blood = Secretion: blood to lumen To bladder andexternal environment = Excretion: lumen to externalenvironment Figure 19-2

13. Kidney Function Table 19-1

14. Kidney Function • The urinary excretion of substance depends on its filtration, reabsorption, and secretion Glomerulus Efferentarteriole Peritubularcapillaries To renal vein Tubule Afferentarteriole Bowman’scapsule To bladder andexternal environment Amountreabsorbed Amountfiltered Amountsecreted amount of soluteexcreted – = + Figure 19-3

15. The Filtration Fraction 4 >99% of plasmaentering kidneyreturns to systemiccirculation. Efferent arteriole Peritubularcapillaries 5 <1% ofvolume isexcreted toexternalenvironment. 80% 2 20% ofvolumefilters. >19% of fluidis reabsorbed. 3 Afferentarteriole Bowman’scapsule Remainderof nephron 1 Plasma volumeentering afferentarteriole = 100% Glomerulus Figure 19-4

16. The Renal Corpuscle Thickascendinglimb ofloop ofHenle Efferentarteriole Bowman’scapsule Capsularepithelium Podocyte Proximaltubule Glomerularcapillary Afferentarteriole Lumen ofBowman’scapsule (a) The epithelium around glomerularcapillaries is modified into podocytes. Figure 19-5a

17. The Renal Corpuscle Foot processof podocyte Filtration slit Pores inendothelium Basal lamina Capillarylumen Filteredmaterial Lumen ofBowman’scapsule (d) Filtered substances passthrough endothelial poresand filtration slits. Figure 19-5d

18. The Renal Corpuscle Podocyte Lumen ofBowman’scapsule Glomerularcapillary Podocytefootprocesses Capillaryendothelium Mesangialcell (c) Podocyte foot processes surround eachcapillary, leaving slits through which filtrationtakes place. Figure 19-5c

19. Forces that Influence Filtration • Hydrostatic pressure (blood pressure) • Colloid osmotic pressure • Fluid pressure created by fluid in Bowman’s capsule

20. Efferentarteriole 15 mm Hg Pfluid Net filtrationpressure =10 mm Hg  30 mm Hg PH 55 mm Hg Afferentarteriole Bowman’scapsule Glomerulus  PH – – Pfluid = net filtration pressure 55 – 30 – 15 = 10mm Hg KEY PH = Hydrostatic pressure (blood pressure)  = Colloid osmotic pressure gradientdue to proteins in plasma but notin Bowman’s capsule Pfluid = Fluid pressure created by fluid inBowman’s capsule Filtration • Filtration pressure in the renal corpuscle depends on hydrostatic pressure, and is opposed by colloid osmotic pressure and capsule fluid pressure Figure 19-6

21. Filtration • Autoregulation of glomerular filtration rate takes place over a wide range of blood pressures Figure 19-7

22. Filtration • Resistance changes in renal arterioles alter renal blood flow and GFR Figure 19-8a

23. Filtration Figure 19-8b

24. Filtration Figure 19-8c

25. GFR Regulation • Myogenicresponse • Similar to autoregulation in other systemic arterioles • Tubuloglomerularfeedback • Paracrinecontrol by macula densa • Hormones and autonomic neurons • By changing resistance in arterioles • By altering the filtration coefficient • Surface area

26. Juxtaglomerular Apparatus Bowman’s capsule Efferent arteriole Ascendinglimb of loopof Henle Glomerulus Macula densa cells Proximal tubule Granular cells Afferent arteriole Endothelium (a) (b) Figure 19-9

27. Tubuloglomerular Feedback Glomerulus Distal tubule 1 GFR increases. Efferent arteriole 2 Flow through tubule increases. Bowman’s capsule 3 4 Flow past macula densa increases. 1 Macula densa 5 Granular cells 4 Paracrine from maculadensa to afferent arteriole Afferent arteriole 2 3 Proximaltubule 5 Afferent arteriole constricts. Resistance in afferentarteriole increases. Collectingduct Hydrostatic pressurein glomerulus decreases. LoopofHenle GFR decreases. Figure 19-10, steps 1–5 (4 of 4)