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Essentials of Anatomy and Physiology
Fifth edition
Seeley, Stephens and Tate
Chapter 18: Urinary System
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 2.1
General Information
 Waste products of metabolism are toxic
(CO2, ammonia, etc.)
 Removal from tissues:
by blood and lymph
 Removal from blood by:
Respiratory system
Urinary system
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.1a
Functions of the Urinary System
 Elimination of waste products
 Nitrogenous wastes
 Toxins
 Drugs
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.1a
Functions of the Urinary System
 Regulate homeostasis
 Water balance
 Electrolytes
 Acid-base balance in the blood
 Blood pressure
 Red blood cell production
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.1b
Organs of the Urinary system
 Kidneys
 Ureters
 Urinary bladder
 Urethra
Figure 15.1a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.2
Location of the Kidneys
 Retroperitoneally
 Lateral to vertebral column
 The right kidney is slightly lower than
the left
 Atop each kidney is an adrenal gland
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.3
Organs of the Urinary system
 Kidneys
Figure 15.1a
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.2
Coverings of the Kidneys
 Renal capsule
 Surrounds each kidney
 Adipose capsule
 Surrounds the kidneys
 Provides protection to the kidneys
 Helps hold kidneys in place
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.4
Regions of the Kidney
 Renal cortex:
outer region
 Renal medulla:
pyramids and
columns
 Renal pelvis:
collecting system
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 15.2b
Slide 15.5
Kidney Structures
 Medullary pyramids – triangular regions
of tissue
 Renal columns – cortical material
between pyramids
 Calyces (sing. Calyx)
cup-shaped structures
collect urine
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.6
Structures involved in Urine Formation
 Vascular Components
 Afferent arteriole
 Glomerulus
 Efferent arteriole
 Peritubular capillaries
 Tubular Components
 Bowman’s capsule
 Proximal convoluted tubule
 Loop of Henle
 Distal convoluted tubule
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.6
Blood Flow in/to the Kidneys
• Is extensive!!!
Figure 15.2c
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.7
Nephrons
 The structural and functional units of the
kidneys
 Responsible for forming urine
 Components of the nephrons
 Renal corpuscle
 Glomerulus and Bowman’s capsule
 Renal tubules
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.8
Glomerulus (“a ball of yarn”)
 A specialized
capillary bed
 Attached to
arterioles on both
sides
 Wide afferent
arteriole
 Narrow efferent
arteriole
Figure 15.3c
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.9a
Glomerulus
 Covered by
glomerular capsule
 first part of the
renal tubule
 AKA Bowman’s
capsule
Figure 15.3c
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.9b
Renal Tubule
 Bowman’s
capsule
 Proximal
convoluted
tubule
(PCT)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 15.3b
Slide 15.10
Renal Tubule
 Loop of Henle
 Distal
convoluted
tubule
 DCT
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 15.3b
Slide 15.10
Peritubular Capillaries
 Arise from efferent arteriole
 Attached to a venule distally
 Surround renal tubule
 Reabsorb substances from tubules into
blood
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.12
Renal Tubule
 Peritubular
capillaries
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 15.3b
Slide 15.10
Urine Formation Processes
 Filtration
 Reabsorption
 Secretion
Figure 15.4
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.13
Filtration
 Nonselective passive process
Depends on hydrostatic pressure
Stops if B.P. falls too low
 Water and some solutes (no proteins)
forced through capillary walls
Taken out of blood
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.14
Filtration
 Blood cells cannot pass
 Filtrate is collected in the glomerular
capsule
 This will become urine
 Leaves capsule through the renal tubule
 Alterations to filtrate occur in tubule
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.14
Reabsorption
 Moving reusable material back into the
blood
 The peritubular capillaries reabsorb
several materials
 Some water
 Glucose
 Amino acids
 Ions
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.15
Reabsorption, con’t…
 Some is passive, most is active
 65% of reabsorption occurs in the PCT
 Glucose, Na+, Ca++, Cl-, HCO3 Water (by osmosis)
 Amino acids (by pinocytosis)
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.15
Reabsorption, con’t…
 Loop of Henle
 15% more filtrate reabsorbed
 Descending limb:
 Water, by osmosis
 Ascending limb:
 Cl- by active transport
 Na+ by diffusion
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.15
Materials Not Reabsorbed
 Nitrogenous waste products
 Urea
 Uric acid
 Creatinine
 Excess water
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.16
Secretion: Reabsorption in Reverse
 Some materials move from peritubular
capillaries into renal tubules
 Hydrogen and potassium ions
 Creatinine
 Most secretion occurs in DCT
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.17
Secretion: Reabsorption in Reverse
 What’s left?? Urine!
 Moving urine out of kidneys: tubules 
 collecting duct
 minor calyces
 major calyces
 renal pelvis
 ureter
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.17
Formation of Urine
Figure 15.5
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Slide 15.18
Normal components of Urine
 Straw colored (pale yellow)
 Sterile
 Slightly aromatic 
 Normal pH of around 6
 Specific gravity of 1.001 to 1.035
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.19
Normal volume of Urine
 0.6 – 2.5 liters/day. Depends on:
Adequate B.P.
Fluid intake
Temperature, humidity
Activity levels
<30cc/hour output = kidney failure
Average is 115-125 ml/hr
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.19
Abnormal components of Urine
 Glucose
 Ketones
 Hemoglobin/blood cells
 Proteins
 pH <4 or >8
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.19
Ureters
 Tubes attaching kidney to urinary
bladder
 Continuous with the renal pelvis
 Enter the posterior aspect of the bladder
 Retroperitoneal
 Peristalsis, gravity move urine
Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings
Slide 15.20