About This Chapter

• Functions of the kidneys • Anatomy of the urinary system • Overview of kidney function • Filtration • Reabsorption • Secretion • Excretion • Micturition

© 2016 Pearson Education, Inc. 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

© 2016 Pearson Education, Inc. Anatomy of the Urinary System

• Kidneys, ureters, bladder, and urethra • Kidneys – Bean-shaped organ – Cortex and medulla

© 2016 Pearson Education, Inc. Anatomy of the Urinary System

• Functional unit is the nephron – Glomerulus in the Bowman’s capsule – Proximal tubule – The loop of Henle • Descending limb and ascending limb twisted between arterioles forming the juxtaglomerular apparatus – Distal tubule – Collecting ducts

© 2016 Pearson Education, Inc. Figure 19.1b Anatomy summary

The kidneys are located retroperitoneally at the level of the lower ribs.

Inferior Diaphragm vena cava Aorta

Left adrenal gland

Left kidney Right kidney Renal artery

Renal vein

Ureter

Peritoneum Urinary Rectum (cut) bladder (cut)

© 2016 Pearson Education, Inc. Figure 19.1c Anatomy summary

© 2016 Pearson Education, Inc. Figure 19.1d Anatomy summary

© 2016 Pearson Education, Inc. Figure 19.1f-h Anatomy summary

Some nephrons dip deep into the medulla. One nephron has two arterioles and two sets of capillaries that form a portal system.

Efferent arteriole Arterioles Peritubular Juxtaglomerular capillaries The cortex apparatus contains all Bowman’s Nephrons Afferent capsules, arteriole Glomerulus proximal Juxtamedullary nephron and distal (capillaries) with vasa recta tubules.

Peritubular capillaries Glomerulus

The medulla contains loops of Henle and Vasa recta collecting ducts. Collecting duct

Loop of Henle

© 2016 Pearson Education, Inc. Kidney Function

• Filtration from blood into the lumen of the nephron • Reabsorption from the filtrate in the lumen of the tubule back into the blood • Secretion from blood into lumen of tubule • Excretion from lumen to out of the body • Capillary pressure causes filtration • Hydrostatic pressure (blood pressure) • Colloid osmotic pressure

© 2016 Pearson Education, Inc. Kidney Function

• Fluid pressure created by fluid in Bowman’s capsule • Only 20% of the plasma that passes through the glomerulus is filtered • Less than 1% of filtered fluid is excreted

© 2016 Pearson Education, Inc. Figure 19.2 Nephron Function Slide 1

The four processes of the kidney are:

F = Filtration: movement from blood to lumen S = Secretion: from blood to lumen

R = Reabsorption: from lumen to blood E = Excretion: from lumen to outside the body

This model nephron has been untwisted so that fluid flows left to right.

Tubular Elements

Bowman’s capsule Proximal tubule Loop of Henle Distal tubule Collecting duct

R S R V Efferent S a arteriole s c u l Glomerulus F a End of r Loop of Henle Afferent E 18 L/day arteriole l ____% volume R Filtered e 100 mOsM m S 180 L/day e R n 100% volume t 300 mOsM s Peritubular capillaries R Start of Loop of Henle To renal vein 54 L/day 30% volume 300 mOsM End of Collecting duct Vasa recta 1.5 L/day ____% volume 50–1200 mOsM E

To bladder and external environment © 2016 Pearson Education, Inc. Figure 19.2 Nephron Function Slide 2

The four processes of the kidney are:

F = Filtration: movement from blood to lumen S = Secretion: from blood to lumen

R = Reabsorption: from lumen to blood E = Excretion: from lumen to outside the body

This model nephron has been untwisted so that fluid flows left to right.

Tubular Elements

Bowman’s capsule

V a s c u l Glomerulus F a r Afferent E l arteriole e Filtered m 180 L/day e n 100% volume t 300 mOsM s

© 2016 Pearson Education, Inc. Figure 19.2 Nephron Function Slide 3

The four processes of the kidney are:

F = Filtration: movement from blood to lumen S = Secretion: from blood to lumen

R = Reabsorption: from lumen to blood E = Excretion: from lumen to outside the body

This model nephron has been untwisted so that fluid flows left to right.

Tubular Elements

Bowman’s capsule Proximal tubule

R S V Efferent a arteriole s c u l Glomerulus F a r Afferent E l arteriole e Filtered m 180 L/day e n 100% volume t 300 mOsM s Peritubular capillaries

© 2016 Pearson Education, Inc. Figure 19.2 Nephron Function Slide 4

The four processes of the kidney are:

F = Filtration: movement from blood to lumen S = Secretion: from blood to lumen

R = Reabsorption: from lumen to blood E = Excretion: from lumen to outside the body

This model nephron has been untwisted so that fluid flows left to right.

Tubular Elements

Bowman’s capsule Proximal tubule Loop of Henle

R S V Efferent a arteriole s c u l Glomerulus F a r Afferent E l arteriole e Filtered m 180 L/day e R n 100% volume t 300 mOsM s Peritubular capillaries R Start of Loop of Henle 54 L/day 30% volume 300 mOsM

Vasa recta

© 2016 Pearson Education, Inc. Figure 19.2 Nephron Function Slide 5

The four processes of the kidney are:

F = Filtration: movement from blood to lumen S = Secretion: from blood to lumen

R = Reabsorption: from lumen to blood E = Excretion: from lumen to outside the body

This model nephron has been untwisted so that fluid flows left to right.

Tubular Elements

Bowman’s capsule Proximal tubule Loop of Henle

R S V Efferent a arteriole s c u l Glomerulus F a End of r Loop of Henle Afferent E 18 L/day arteriole l ____% volume Filtered e 100 mOsM m 180 L/day e R n 100% volume t 300 mOsM s Peritubular capillaries R Start of Loop of Henle 54 L/day 30% volume 300 mOsM

Vasa recta

© 2016 Pearson Education, Inc. Figure 19.2 Nephron Function Slide 6

The four processes of the kidney are:

F = Filtration: movement from blood to lumen S = Secretion: from blood to lumen

R = Reabsorption: from lumen to blood E = Excretion: from lumen to outside the body

This model nephron has been untwisted so that fluid flows left to right.

Tubular Elements

Bowman’s capsule Proximal tubule Loop of Henle Distal tubule

R S R V Efferent S a arteriole s c u l Glomerulus F a End of r Loop of Henle Afferent E 18 L/day arteriole l ____% volume Filtered e 100 mOsM m 180 L/day e R n 100% volume t 300 mOsM s Peritubular capillaries R Start of Loop of Henle 54 L/day 30% volume 300 mOsM

Vasa recta

© 2016 Pearson Education, Inc. Figure 19.2 Nephron Function Slide 7

The four processes of the kidney are:

F = Filtration: movement from blood to lumen S = Secretion: from blood to lumen

R = Reabsorption: from lumen to blood E = Excretion: from lumen to outside the body

This model nephron has been untwisted so that fluid flows left to right.

Tubular Elements

Bowman’s capsule Proximal tubule Loop of Henle Distal tubule Collecting duct

R S R V Efferent S a arteriole s c u l Glomerulus F a End of r Loop of Henle Afferent E 18 L/day arteriole l ____% volume R Filtered e 100 mOsM m 180 L/day S e R n 100% volume t 300 mOsM s Peritubular capillaries R Start of Loop of Henle 54 L/day 30% volume 300 mOsM

Vasa recta

© 2016 Pearson Education, Inc. Figure 19.2 Nephron Function Slide 8

The four processes of the kidney are:

F = Filtration: movement from blood to lumen S = Secretion: from blood to lumen

R = Reabsorption: from lumen to blood E = Excretion: from lumen to outside the body

This model nephron has been untwisted so that fluid flows left to right.

Tubular Elements

Bowman’s capsule Proximal tubule Loop of Henle Distal tubule Collecting duct

R S R V Efferent S a arteriole s c u l Glomerulus F a End of r Loop of Henle Afferent E 18 L/day arteriole l ____% volume R Filtered e 100 mOsM m 180 L/day S e R n 100% volume t 300 mOsM s Peritubular capillaries R Start of Loop of Henle To renal vein 54 L/day 30% volume 300 mOsM

Vasa recta

© 2016 Pearson Education, Inc. Figure 19.2 Nephron Function Slide 9

The four processes of the kidney are:

F = Filtration: movement from blood to lumen S = Secretion: from blood to lumen

R = Reabsorption: from lumen to blood E = Excretion: from lumen to outside the body

This model nephron has been untwisted so that fluid flows left to right.

Tubular Elements

Bowman’s capsule Proximal tubule Loop of Henle Distal tubule Collecting duct

R S R V Efferent S a arteriole s c u l Glomerulus F a End of r Loop of Henle Afferent E 18 L/day arteriole l ____% volume R Filtered e 100 mOsM m 180 L/day S e R n 100% volume t 300 mOsM s Peritubular capillaries R Start of Loop of Henle To renal vein 54 L/day 30% volume 300 mOsM End of Collecting duct Vasa recta 1.5 L/day ____% volume 50–1200 mOsM E

To bladder and external environment © 2016 Pearson Education, Inc. Figure 19.2 Nephron Function Slide 10

The four processes of the kidney are:

F = Filtration: movement from blood to lumen S = Secretion: from blood to lumen

R = Reabsorption: from lumen to blood E = Excretion: from lumen to outside the body

This model nephron has been untwisted so that fluid flows left to right.

Tubular Elements

Bowman’s capsule Proximal tubule Loop of Henle Distal tubule Collecting duct

V Efferent a arteriole s c u l Glomerulus F a r Afferent E l arteriole e Filtered m 180 L/day e n 100% volume t 300 mOsM s Peritubular capillaries

To renal vein

Vasa recta

To bladder and external environment © 2016 Pearson Education, Inc. Figure 19.2 Nephron Function Slide 11

The four processes of the kidney are:

F = Filtration: movement from blood to lumen S = Secretion: from blood to lumen

R = Reabsorption: from lumen to blood E = Excretion: from lumen to outside the body

This model nephron has been untwisted so that fluid flows left to right.

Tubular Elements

Bowman’s capsule Proximal tubule Loop of Henle Distal tubule Collecting duct

R R V Efferent a arteriole s c u l Glomerulus a r Afferent E l arteriole R e Filtered m e R n t s Peritubular capillaries R

To renal vein

Vasa recta

To bladder and external environment © 2016 Pearson Education, Inc. Figure 19.2 Nephron Function Slide 12

The four processes of the kidney are:

F = Filtration: movement from blood to lumen S = Secretion: from blood to lumen

R = Reabsorption: from lumen to blood E = Excretion: from lumen to outside the body

This model nephron has been untwisted so that fluid flows left to right.

Tubular Elements

Bowman’s capsule Proximal tubule Loop of Henle Distal tubule Collecting duct

S

V Efferent S a arteriole s c u l Glomerulus a r Afferent E arteriole l R e Filtered m S e n t s Peritubular capillaries

To renal vein

Vasa recta

To bladder and external environment © 2016 Pearson Education, Inc. Figure 19.2 Nephron Function Slide 13

The four processes of the kidney are:

F = Filtration: movement from blood to lumen S = Secretion: from blood to lumen

R = Reabsorption: from lumen to blood E = Excretion: from lumen to outside the body

This model nephron has been untwisted so that fluid flows left to right.

Tubular Elements

Bowman’s capsule Proximal tubule Loop of Henle Distal tubule Collecting duct

V Efferent a arteriole s c u l Glomerulus a r Afferent E arteriole l R e Filtered m S e n t s Peritubular capillaries

To renal vein

Vasa recta

E

To bladder and external environment © 2016 Pearson Education, Inc. Figure 19.2 Nephron Function Slide 14

The four processes of the kidney are:

F = Filtration: movement from blood to lumen S = Secretion: from blood to lumen

R = Reabsorption: from lumen to blood E = Excretion: from lumen to outside the body

This model nephron has been untwisted so that fluid flows left to right.

Tubular Elements

Bowman’s capsule Proximal tubule Loop of Henle Distal tubule Collecting duct

R S R V Efferent S a arteriole s c u l Glomerulus F a End of r Loop of Henle Afferent E 18 L/day arteriole l ____% volume R Filtered e 100 mOsM m S 180 L/day e R n 100% volume t 300 mOsM s Peritubular capillaries R Start of Loop of Henle To renal vein 54 L/day 30% volume 300 mOsM End of Collecting duct Vasa recta 1.5 L/day ____% volume 50–1200 mOsM E

To bladder and external environment © 2016 Pearson Education, Inc. Figure 19.4 The filtration fraction Slide 1

>99% of plasma entering kidney Efferent arteriole Peritubular returns to systemic capillaries circulation.

80% <1% of 20% of volume is >19% of fluid excreted to volume is reabsorbed. Afferent filters. external arteriole environment.

Bowman’s Remainder Plasma volume capsule of nephron entering afferent arteriole = 100%. Glomerulus

© 2016 Pearson Education, Inc. Figure 19.4 The filtration fraction Slide 2

Efferent arteriole Peritubular capillaries

80%

Afferent arteriole

Bowman’s Remainder Plasma volume capsule of nephron entering afferent arteriole = 100%. Glomerulus

© 2016 Pearson Education, Inc. Figure 19.4 The filtration fraction Slide 3

Efferent arteriole Peritubular capillaries

80% 20% of volume Afferent filters. arteriole

Bowman’s Remainder Plasma volume capsule of nephron entering afferent arteriole = 100%. Glomerulus

© 2016 Pearson Education, Inc. Figure 19.4 The filtration fraction Slide 4

Efferent arteriole Peritubular capillaries

80% 20% of >19% of fluid volume is reabsorbed. Afferent filters. arteriole

Bowman’s Remainder Plasma volume capsule of nephron entering afferent arteriole = 100%. Glomerulus

© 2016 Pearson Education, Inc. Figure 19.4 The filtration fraction Slide 5

>99% of plasma entering kidney Efferent arteriole Peritubular returns to systemic capillaries circulation.

80% 20% of >19% of fluid volume is reabsorbed. Afferent filters. arteriole

Bowman’s Remainder Plasma volume capsule of nephron entering afferent arteriole = 100%. Glomerulus

© 2016 Pearson Education, Inc. Figure 19.4 The filtration fraction Slide 6

>99% of plasma entering kidney Efferent arteriole Peritubular returns to systemic capillaries circulation.

80% <1% of 20% of volume is >19% of fluid excreted to volume is reabsorbed. Afferent filters. external arteriole environment.

Bowman’s Remainder Plasma volume capsule of nephron entering afferent FIGURE QUESTION arteriole = 100%. Glomerulus If 120 mL of plasma filter each minute and the filtration fraction is 20%, what is the daily renal plasma flow?

© 2016 Pearson Education, Inc. Figure 19.6a Glomerular Filtration Rate

© 2016 Pearson Education, Inc. Glomerular Filtration Rate (GFR)

• Rate is relatively constant • Influenced by two factors – Net filtration pressure • Hydrostatic pressure – colloid osmotic pressure – fluid pressure – Filtration coefficient • Surface area of glomerular capillaries available for filtration • Permeability of interface between the capillary and Bowman’s capsule

© 2016 Pearson Education, Inc. GFR Regulation

• Myogenic response – Intrinsic ability of vascular smooth muscle to respond to pressure changes – Similar to autoregulation in other systemic arterioles • Tubuloglomerular feedback – Paracrine control • Hormones and autonomic neurons – By changing resistance in arterioles – By altering the filtration coefficient

© 2016 Pearson Education, Inc. Figure 19.7a-b The juxtaglomerular apparatus

The nephron loops back on itself so that the The macula densa cells sense distal tubule flow ascending limb of the loop of Henle passes and release paracrines that affect afferent between the afferent and efferent arterioles. arteriole diameter. Bowman’s Efferent arteriole capsule

Glomerulus

Ascending limb of loop of Henle

Macula densa cells Proximal tubule Endothelium

Granular cells secrete renin, an enzyme Afferent involved in salt and water balance. arteriole

© 2016 Pearson Education, Inc. Figure 19.7c The juxtaglomerular apparatus

Tubuloglomerular feedback helps GFR autoregulation.

Glomerulus Distal tubule GFR increases. Efferent arteriole

Flow through tubule increases. Bowman’s capsule

Flow past macula densa increases. Macula densa

Granular cells Paracrine from macula Afferent arteriole densa to afferent arteriole

Proximal Afferent arteriole constricts. tubule

Resistance in afferent arteriole increases. Collecting duct

Hydrostatic pressure in glomerulus decreases. Loop of Henle GFR decreases.

© 2016 Pearson Education, Inc.