1. Chapter 19a
The Kidneys

2. Anatomy of the urinary system Overview of kidney function
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
Kidney
Ureter
Urinary bladder
Urethra
(a) The urinary system
Figure 19-1a

5. Anatomy: The Urinary System
Diaphragm
Left adrenal gland
Inferior vena cava
Right kidney
Left kidney
Renal artery
Ureter
Aorta
Renal vein
Peritoneum (cut)
Urinary bladder
Rectum (cut)
(b) The kidneys are located retroperitoneally at 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 deep into the medulla.
Figure 19-1i

8. Anatomy: The Urinary System
Efferent arteriole
Peritubular capillaries
Peritubular capillaries
Juxtaglomerular apparatus
Glomerulus
Afferent arteriole
Glomerulus (capillaries)
Vasa recta
Collecting duct
Loop of Henle
(g) One nephron has two arterioles and two sets of capillaries.
(h) Juxtamedullary nephron with vasa recta
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 of nephron tubule
(f) The capillaries of the glomerulus form a ball-like mass.
Figure 19-1f

11. Anatomy: The Urinary System
Bowman’s capsule
Proximal tubule
Distal tubule
Descending limb of loop begins
Ascending limb of loop ends
Collecting duct
Descending limb
Ascending limb
(j) Parts of a nephron
Loop of Henle
To bladder
Figure 19-1j

12. To bladder and external environment
Kidney Function
Filtration, reabsorption, secretion, and excretion
Peritubular capillaries
Distal tubule
Efferent arteriole
Glomerulus
Afferent arteriole
Proximal tubule
Bowman’s capsule
KEY
Collecting duct
= Filtration: blood to lumen
Loop of Henle
To renal vein
= Reabsorption: lumen to blood
= Secretion: blood to lumen
To bladder and external environment
= Excretion: lumen to external environment
Figure 19-2

13. Kidney Function
Table 19-1

14. Peritubular capillaries amount of solute excreted
Kidney Function
The urinary excretion of substance depends on its filtration, reabsorption, and secretion
Glomerulus
Efferent arteriole
Peritubular capillaries
To renal vein
Tubule
Afferent arteriole
Bowman’s capsule
To bladder and external environment
Amount filtered
Amount reabsorbed
Amount secreted –
amount of solute excreted + =
Figure 19-3

15. The Filtration Fraction4
>99% of plasma entering kidney returns to systemic circulation.
Efferent arteriole
Peritubular capillaries 5
<1% of volume is excreted to external environment.
80% 2
20% of volume filters. 3
>19% of fluid is reabsorbed.
Afferent arteriole
Bowman’s capsule
Remainder of nephron 1
Plasma volume entering afferent arteriole = 100%
Glomerulus
Figure 19-4

16. Thick ascending limb of loop of Henle
The Renal Corpuscle
Thick ascending limb of loop of Henle
Efferent arteriole
Bowman’s capsule
Capsular epithelium
Podocyte
Proximal tubule
Glomerular capillary
Afferent arteriole
Lumen of Bowman’s capsule
(a) The epithelium around glomerular capillaries is modified into podocytes.
Figure 19-5a

17. The Renal Corpuscle Foot process of podocyte Filtration slit
Pores in endothelium
Basal lamina
Capillary lumen
Filtered material
Lumen of Bowman’s capsule
(d) Filtered substances pass through endothelial pores and filtration slits.
Figure 19-5d

18. Lumen of Bowman’s capsule Podocyte foot processes
The Renal Corpuscle
Podocyte
Lumen of Bowman’s capsule
Glomerular capillary
Podocyte foot processes
Capillary endothelium
Mesangial cell
(c) Podocyte foot processes surround each capillary, leaving slits through which filtration takes 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. Filtration
Afferent arteriole
Glomerulus
Bowman’s capsule
PH = Hydrostatic pressure (blood pressure)
 = Colloid osmotic pressure gradient due to proteins in plasma but not in Bowman’s capsule
Pfluid = Fluid pressure created by fluid in Bowman’s capsule PH – 
= net filtration pressure 55 30
= 10mm Hg 15
KEY
Efferent arteriole
15 mm Hg
30 mm Hg
55 mm Hg
Pfluid
Net filtration pressure = 10 mm Hg
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. Resistance changes in renal arterioles alter renal blood flow and GFR
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. Tubuloglomerular feedback Hormones and autonomic neurons
GFR Regulation
Myogenic response
Similar to autoregulation in other systemic arterioles
Tubuloglomerular feedback
Paracrine control 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
Ascending limb of loop of 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
Flow past macula densa increases. 4
Macula densa 1 5
Granular cells 4
Paracrine from macula densa to afferent arteriole
Afferent arteriole 2 3
Proximal tubule 5
Afferent arteriole constricts.
Resistance in afferent arteriole increases.
Collecting duct
Hydrostatic pressure in glomerulus decreases.
Loop of Henle
GFR decreases.
Figure 19-10, steps 1–5 (4 of 4)