1. Chapter 19
The Kidneys

2. About this Chapter Anatomy of the excretory system
How the kidney is organized
How the nephron works to filter blood, recycle, secrete, and excrete
How filtration is regulated
Urination reflex

4. Kidney Functions: Overview
Homeostatic regulation: ECF volume, osmolarity, ion & pH balance
Excretion: Metabolic wastes & foreign molecules
Regulating hormones & enzymes

5. Kidney Functions: Overview
Figure 19-3: The excretion of a substance depends on the amount that was filtered, reabsorbed, and secreted

6. Excretory System: Anatomy Review
Kidney
Cortex
Medulla
Pelvis
Nephrons
Ureter
Bladder
Urethra
Figure 19-1: Anatomy Summary: The Urinary System

7. Nephron Functions: Overview
Figure 19-2: Filtration, reabsorption, secretion, and excretion

8. Glomerulus & Bowman's Capsule: Blood Filtration
Capillaries
Podocytes
Mesanglial cells
Bulk flow
Solutes
Water
(Few proteins)
(Not cells)

9. Glomerulus & Bowman's Capsule: Blood Filtration
Figure 19-4: Structure of the renal corpuscle

10. Glomerular Flow Rate (GFR)
Capillary
Hydrostatic pressure
Colloidal
Capsule pressure
Back pressure
Net Filtration p
GFR  180L/day (about 1% is excreted)
Figure 19-6: Filtration pressure in the renal corpuscle

11. Glomerular Flow Rate (GFR)
Figure 19-5: The filtration fraction

12. Regulation of GFR Autoregulation Myogenic stretch
Tubuloglomerular feedback
Macula densa
J G cells
ANS-Sympathetic
Arteriole vasoconstriction
Hormones/paracrines
Angiotensin II
Prostaglandins

13. Figure 19-9: The juxtaglomerular apparatus
Regulation of GFR
Figure 19-9: The juxtaglomerular apparatus

14. Reabsorption: 10 Active Transport
(Passive diffusion in)
Active Transport
Na+ to ECF
K+ into cell
ATP-ase
Uses energy
Na+ ECF peritubular capillaries
Reabsorption  blood

15. Reabsorption: 10 Active Transport
Figure 19-11: Sodium reabsorption in the proximal tubule

16. Reabsorption: Secondary Active Transport
Na+ linked 20 transport
Symport
Glucose
Ions
Amino acids
Proximal tubule, key site
Figure 19-12: Sodium-linked glucose reabsorption in the proximal tubule

17. Reabsorption: Passive Transport & Trancytosis
Passive Transport of urea
Na+ pumped out
H2O follows
Passive
 [urea]
[urea] higher than ECF
passive diffusion to ECF
Trancytosis of proteins

18. Reabsorption: Passive Transport & Trancytosis
Figure 19-13: Passive reabsorption of urea in the proximal tubule

19. Reabsorption: Receptors can Limit
Transport maximum
Saturation (# of receptors)
Competition
Specificity
Renal Threshold
Example: glucosuria

20. Reabsorption: Receptors can Limit
Figure 19-15: Glucose handling by the nephron

21. Secretion: From Peritubular Blood vessels & ECF
Figure 19-2 : Filtration, reabsorption, secretion, and excretion

22. Solute Clearance: Rate of removal from the Blood
Information on Kidney Function
GFR
Reabsorption rates
Secretion rates
Figure 19-16: Inulin clearance

23. Excretion: All Filtration Products that are not reabsorbed
Excess ions, H2O, molecules, toxins, "foreign molecules"
"nitrogenous waste": NH4+ and excess urea
Kidney Ureter  bladder urethra out of body

24. Excretion: All Filtration Products that are not reabsorbed
Figure 19-5: The filtration fraction

25. Urination: Micturation reflex
Bladder:
smooth muscles
internal sphincter
external sphincter
Regulation

26. Urination: Micturation reflex
Figure 19-18: The micturition reflex

27. Summary Kidney produces urine, ureter bladder urethra
Nephron filters, reabsorbs, secretes and excretes
Arteriole pressure dictates GFR through autoregulation, ANS and hormonal influences
Most filtrate is reabsorbed & returned via peritubular blood vessels; excess & toxic remains are excreted
Urination reflex uses involuntary and voluntary paths