1. Renal (Urinary) System
Chapter 17

2. Function Maintains homeostasis in ECF
Removing metabolic waste (except CO2)
e.g. ammonia, urea, uric acid
Removing foreign compounds
e.g. drugs, food additives, pesticides
Regulating salt concentrations, fluid volume, and pH

3. Anatomy Fig 17.1 Kidneys (2) Ureters (2) Urinary bladder Urethra
process plasma into urine
Ureters (2)
tubes that carry urine to bladder
Urinary bladder
storage of urine
Urethra
carries urine to exterior
Fig 17.1

4. Anatomy Fig 17.2 Cortex Medulla Renal Pelvis Renal artery and vein
outer granular region
Medulla
inner striated region
renal pyramids
Renal Pelvis
central collecting cavity
Renal artery and vein
Fig 17.2

5. Anatomy Fig 17.2 Nephron 1 million per kidney
functional unit of the kidney
smallest unit capable of forming urine
Fig 17.2

6. Nephron Fig 17.5 Vascular Component Renal Artery Afferent Arteriole
conducts blood
Renal Artery
Afferent Arteriole
Glomerulus
Efferent Arteriole
Peritubular Capillaries
Venules
Renal Vein
Fig 17.5

7. Nephron Fig 17.5 Tubular Component Bowman’s capsule
forms urine
Bowman’s capsule
Proximal Convoluted Tubule
Loop of Henle
Distal Convoluted Tubule
Collecting duct
Fig 17.5

8. Urine Formation Urine - water and waste solutes
Nephrons conduct three processes to convert blood plasma into urine
filtration
filter blood plasma to retain cells/proteins
reabsorption
remove valuable materials from filtrate
secretion
transfer additional wastes to filtrate

9. Filtration Figs 17.8-17.10 Occurs in the glomerulus
Fenestrated capillaries
3 layers of podocytes form capillary walls
Small pores (fenestrae)
filters plasma
proteins + cells stay in blood
forms ultrafiltrate
Figs

10. Filtration Fig 17.10 Filtration driven by blood pressure
Glomerular filtration is non-selective
Small particles pass (glucose, Na+, urea, H2O)
Large ones do not
20% of plasma enters tubule
plasma filtered 65x/day
Fig 17.10

11. Reabsorption Fig 17.12 Occurs in remainder of nephron tubule
Selective movement of substances from tubule into plasma
Return of valuable substances to peritubular caps
Active or passive
Passive (no energy)
Active transport (requires energy)
Fig 17.12

12. Secretion Fig 17.21 Also occurs in tubules
Additional materials transported from plasma in peritubular capillaries into tubule
excess K+, Ca2+ and H+, uric acid
foreign compounds
By passive diffusion or active carrier transport
Fig 17.21

13. Proximal Tubule Figs 17.2, 17.5 Proximal Tubule Reabsorbs:
2/3 of plasma Na+
2/3 of plasma Cl-
2/3 of plasma H2O
100 % of plasma glucose
Figs 17.2, 17.5

14. Active Transport in the Proximal Tubule
Na+ actively transported from cell to blood
Creates Na+ gradient favoring Na+ flow from lumen
Na+ gradient used to transport glucose against concentration gradient (cotransport)
Glucose diffuses into blood passively
Fig 17.13

15. Passive Reabsorption in the Proximal Tubule
Cl- to be reabsorbed passively along electrical gradient
Water reabsorbed along osmotic gradient
Fig 17.14

16. Acid Base Balance
Proximal tubule also secretes H+ and absorbs HCO3-
used to regulate pH
with  pH,  H+ secretion and HCO3- reabsorption
Fig 17.28

17. Loop of Henle Fig 17.16 Kidneys produce a hyperosmotic urine
less H2O than blood plasma
concentrating mechanism occurs in the Loop of Henle
Fig 17.16

18. Loop of Henle Countercurrent Multiplication
generates osmotic gradient that draws H2O out of the tubules to be reabsorbed
due to active reabsorption of Na+ & Cl-
Exchange = 30
Exchange = 50

19. Loop of Henle Fig 17.16 descending limb ascending limb
permeable to water
no active transport
ascending limb
impermeable to water
lined w/ Na+-K+ pumps
Fig 17.16

20. Loop of Henle
Pumping of ions out of ascending limb creates osmotic gradient
Water flows out of descending limb
Absorbed by peritubular capillaries
Fluid becomes more concentrated as it passes down descending limb
Figs 17.16, 17.17

21. Loop of Henle
Removal of ions without water causes fluid to become less concentrated in the ascending limb
Less concentrated than blood in distal convoluted tubule
25% of initial Na+ and water reabsorbed by loop of Henle
Fig 17.16

22. Distal Convoluted Tubule and Collecting Duct
Secretion of K+ and H+
Reabsorption of Na+ and water
Generation of hyperosmotic urine
final ~8% of water and Na+ reabsorbed
Figs 17.19, 17.27

23. Hormonal Regulation of Reabsorption
Aldosterone
increases Na+ reabsorption and K+ secretion by distal & collecting tubules
 salt retention and BP (H2O retention)
ADH
induces implantation of aquaporins (water channels) into tubule cell membranes
 permeability of Distal and Collecting tubules to water
 H2O reabsorption =  urine volume

24. Triggering of Aldosterone Release
release induced by juxtaglomerular apparatus
region of afferent arteriole that comes into contact w/ascending limb of Loop of Henle
releases renin (enzyme) into blood in response to BP
renin converts angiotensinogen  angiotensin I
Fig 17.26

25. Triggering of Aldosterone Release
angiotensin I converted to angiotensin II (fully activated) by angiotensin converting enzyme in lungs
angiotensin II stimulates aldosterone release
Fig 17.26

26. Urination Fig 17.1 Ureters Urinary Bladder Two sphincters
transfer urine to pelvic region
Urinary Bladder
Stores urine
smooth muscle, stretchable walls
Two sphincters
internal urethral sphincter (involuntary)
external urethral sphincter (voluntary)
Fig 17.1

27. Urination Fig 17.1 Urination Reflex:
Stretch receptors in bladder wall  spinal cord
efferents to smooth muscle  contraction
Internal sphincter relaxes
External sphincter relaxes
Fig 17.1