Chapter 19a
The Kidneys
About this Chapter
• Anatomy of the urinary system• Overview of kidney function• Homeostasis• pH• Electrolytes• fluid• Filtration• Reabsorption• Secretion• Excretion
• Micturition
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
Figure 19-1a
Kidney
Ureter
Urinary bladder
Urethra
(a) The urinary system
THE URINARY SYSTEMAnatomy: The Urinary System
Figure 19-1b
Ureter
Diaphragm
Aorta
Inferior vena cava
Right kidney Left kidney
Renal artery
Renal vein
(b) The kidneys are located retroperitoneallyat the level of the lower ribs.
Urinarybladder
Peritoneum(cut)
Rectum(cut)
Left adrenal gland Anatomy: The Urinary System
Figure 19-1c
Cortex
Medulla
Renal pelvis
Ureter
Capsule
(c) The kidney, in cross section.
Nephrons
Anatomy: The Urinary System
Polycystic kidney
Figure 19-1i
Cortex
Medulla
Arterioles
Nephrons
(i) Some nephrons dip deepinto the medulla.
Anatomy: The Urinary System
Figure 19-1g–h
Glomerulus(capillaries)
Peritubularcapillaries
Juxtaglomerularapparatus
(g) One nephron has two arteriolesand two sets of capillaries.
Efferent arteriole
Afferentarteriole
(h) Juxtamedullary nephronwith vasa recta
Glomerulus
Peritubularcapillaries
Vasa recta
Loop ofHenle
Collectingduct
Anatomy: The Urinary System
Figure 19-1d–e
Anatomy: The Urinary System
Figure 19-1f
(f) The capillaries of the glomerulus form aball-like mass.
Cut edge ofnephron tubule
STRUCTURE OF THE NEPHRON
Glomerulus
Anatomy: The Urinary System
Figure 19-1j
Bowman’scapsule
Distal tubuleProximal tubule
Collectingduct
Ascendinglimb
Descendinglimb
Loop ofHenle
(j) Parts of a nephron
Descendinglimb of loop
begins
Ascendinglimb of loopends
To bladder
Anatomy: The Urinary System
Figure 19-2
Collectingduct
Distal tubule
Afferentarteriole
Loopof
Henle
Efferentarteriole
Glomerulus
Peritubular capillaries
ProximaltubuleBowman’s
capsule
To renalvein
To bladder andexternal environment
KEY
= Filtration: blood to lumen
= Reabsorption: lumen to blood
= Secretion: blood to lumen
= Excretion: lumen to externalenvironment
Kidney Function
• Filtration, reabsorption, secretion, and excretion
Table 19-1
Kidney Function
Figure 19-3
– + =
Efferentarteriole
Afferentarteriole
Glomerulus
Bowman’scapsule
Peritubularcapillaries To renal vein
To bladder andexternal environment
amount of soluteexcreted
Amountfiltered
Amountreabsorbed
Amountsecreted
Tubule
Kidney Function
• The urinary excretion of substance depends on its filtration, reabsorption, and secretion
Figure 19-4
>19% of fluidis reabsorbed.
Plasma volumeentering afferentarteriole = 100%
<1% ofvolume isexcreted toexternalenvironment.
Remainderof nephron
Bowman’scapsule
Glomerulus
>99% of plasmaentering kidneyreturns to systemiccirculation.
Efferent arteriole Peritubularcapillaries
Afferentarteriole
20% ofvolumefilters.
80%
1
2 3
4
5
The Filtration Fraction
Figure 19-5a
Bowman’scapsule
Capsularepithelium
Podocyte
GlomerularcapillaryLumen ofBowman’scapsule
Proximaltubule
Efferentarteriole
Afferentarteriole
Thickascending
limb ofloop ofHenle
(a) The epithelium around glomerularcapillaries is modified into podocytes.
The Renal Corpuscle
Figure 19-5d
Filtration slit
Basal lamina
Filteredmaterial
(d) Filtered substances passthrough endothelial poresand filtration slits.
Foot processof podocyte
Lumen ofBowman’scapsule
Capillarylumen
Pores inendothelium
The Renal Corpuscle
Figure 19-5c
(c) Podocyte foot processes surround eachcapillary, leaving slits through which filtrationtakes place.
Lumen ofBowman’s
capsule
Podocytefoot
processes
Glomerularcapillary
Podocyte
Mesangialcell
Capillaryendothelium
The Renal Corpuscle
Forces that Influence Filtration
• Hydrostatic pressure (blood pressure)• Colloid osmotic pressure• Fluid pressure created by fluid in Bowman’s
capsule
Figure 19-6
Filtration
• Filtration pressure in the renal corpuscle depends on hydrostatic pressure, and is opposed by colloid osmotic pressure and capsule fluid pressure
Afferentarteriole Glomerulus
Bowman’scapsule
PH = Hydrostatic pressure (blood pressure) = Colloid osmotic pressure gradientdue to proteins in plasma but notin Bowman’s capsulePfluid = Fluid pressure created by fluid inBowman’s capsule
PH – – = net filtration pressure
55 30– – = 10mm Hg15
KEY
Efferentarteriole 15 mm Hg
30 mm Hg
55 mm HgPH
Pfluid
Net filtrationpressure =10 mm Hg
Pfluid
Figure 19-7
Filtration
• Autoregulation of glomerular filtration rate takes place over a wide range of blood pressures
Figure 19-8a
Filtration
• Resistance changes in renal arterioles alter renal blood flow and GFR
Figure 19-8b
Filtration
Figure 19-8c
Filtration
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
Figure 19-9
Juxtaglomerular Apparatus
Bowman’s capsule
Proximal tubule
Granular cells
Efferent arteriole
Afferent arteriole Endothelium
Ascendinglimb of loop
of Henle
Glomerulus
Macula densa cells
(a) (b)
Figure 19-10, steps 1–5 (4 of 4)
Tubuloglomerular FeedbackGFR increases.
Flow through tubule increases.
Flow past macula densa increases.
Paracrine from maculadensa to afferent arteriole
Afferent arteriole constricts.
Resistance in afferentarteriole increases.
Hydrostatic pressurein glomerulus decreases.
GFR decreases.
Efferent arteriole
Granular cells
Afferent arteriole
Bowman’s capsule
Glomerulus
Macula densa
Distal tubule
Collectingduct
Loopof
Henle
Proximaltubule
1
2
3
4
5
1
23
45