Chapter 19a
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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

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Chapter 19a

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Chapter 19a

Chapter 19a

The Kidneys


About this chapter

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

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


Anatomy the urinary system

Anatomy: The Urinary System

THE URINARY SYSTEM

Kidney

Ureter

Urinary bladder

Urethra

(a) The urinary system

Figure 19-1a


Anatomy the urinary system1

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


Anatomy the urinary system2

Anatomy: The Urinary System

Nephrons

Cortex

Polycystic kidney

Medulla

Renal pelvis

Ureter

Capsule

(c) The kidney, in cross section.

Figure 19-1c


Anatomy the urinary system3

Anatomy: The Urinary System

Arterioles

Nephrons

Cortex

Medulla

(i) Some nephrons dip deepinto the medulla.

Figure 19-1i


Anatomy the urinary system4

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


Anatomy the urinary system5

Anatomy: The Urinary System

Figure 19-1d–e


Anatomy the urinary system6

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


Anatomy the urinary system7

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


Kidney function

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


Kidney function1

Kidney Function

Table 19-1


Kidney function2

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


The filtration fraction

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


The renal corpuscle

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


The renal corpuscle1

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


The renal corpuscle2

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


Forces that influence filtration

Forces that Influence Filtration

  • Hydrostatic pressure (blood pressure)

  • Colloid osmotic pressure

  • Fluid pressure created by fluid in Bowman’s capsule


Filtration

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


Filtration1

Filtration

  • Autoregulation of glomerular filtration rate takes place over a wide range of blood pressures

Figure 19-7


Filtration2

Filtration

  • Resistance changes in renal arterioles alter renal blood flow and GFR

Figure 19-8a


Filtration3

Filtration

Figure 19-8b


Filtration4

Filtration

Figure 19-8c


Gfr regulation

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


Juxtaglomerular apparatus

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


Tubuloglomerular feedback

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)


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