Biology, Seventh Edition
Solomon • Berg • Martin
Chapter 46
Osmoregulation and
Disposal of Metabolic
Wastes
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Osmoregulation
• The active regulation of osmotic
pressure of body fluids so that
homeostasis is maintained
• Excretory systems
• Help maintain homeostasis by
regulating the concentration of
body fluids
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Principal waste products of
animal metabolism
• Water
• Carbon dioxide
• Nitrogenous wastes
–Ammonia (excreted mainly by aquatic
animals)
–Urea
–Uric acid
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Osmoconformers
• Includes most marine invertebrates
• Salt concentration of their body
fluids varies with changes in the
seawater
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Osmoregulators
• Marine invertebrates that inhabit
coastal habitats
• Maintain an optimal salt
concentration despite changes in
the salinity of their surroundings
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Nephridial organs
• Include protonephridia and
metanephridia
• Function in osmoregulation and
waste disposal
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Protonephridia
• Found in flatworms and
nemerteans
• Tubules with no internal openings
• Interstitial fluid enters their blind
ends, which consist of flame cells
• Beating of the cilia propels fluid
through the cilia
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
Protonephridia of a
flatworm
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Metanephridia
• Found in annelids and mollusks
• Tubules open at both ends
• As fluid from the coelom moves
through the tubule, materials are
reabsorbed by capillaries
• Urine exits the body through
nephridiopores
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
Metanephridia of an
earthworm
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Malpighian tubules
• Extensions of the insect gut wall
• Have blind ends that lie in the
hemocoel
• Cells of the tubule actively
transport uric acid, etc., into the
tubule
• Water follows by diffusion
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Malpighian tubules, cont.
• Contents of the tubule pass into the
gut and water and some other
solutes are reabsorbed in the
rectum
• Malpighian tubules effectively
conserve water
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
Malpighian tubules
of an insect
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Freshwater fishes
• Take in water osmotically
• Excrete a large volume of dilute
urine
• Marine bony fishes
• Lose water osmotically
• Compensate by drinking seawater
and excreting salt through gills
• Produce a small volume of urine
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Sharks and other marine
cartilaginous fishes
• Retain large amounts of urea
• Take in water osmotically through
the gills
• Excrete a large volume of urine
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
Osmoregulation
in fishes
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Marine mammals
• Ingest seawater with their food
• Produce a concentrated urine
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Terrestrial vertebrates
• Must conserve water
• Endotherms have high metabolic
rate
• Produce a large volume of
nitrogenous wastes
• Conserve water through efficient
kidneys and other adaptations
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
Excretory
organs in
terrestrial
vertebrates
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Vertebrate kidney
• Functions in excretion and
osmoregulation
• Is vital in maintaining homeostasis
• Its structure and function are
adapted to the lifestyle of the
animal
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Organs of the mammalian urinary
system
• Kidney
–Key organ of the urinary system, the
principal excretory system in humans
and other vertebrates
–In mammals, the kidney produces
urine
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Organs of the mammalian urinary
system, cont.
• Urine passes through the ureters to
the urinary bladder
• During urination, the urine is
released through the urethra
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
The human urinary
system
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Structure of the kidney
• Outer portion is the renal cortex
• Inner portion is the renal medulla
–Contains eight to ten renal pyramids
–Tip of each pyramid is a renal papilla
–Urine flows into collecting ducts, which
empty through a renal papilla into the renal
pelvis
• Functioning unit is a nephron
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
Structure of the kidney
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
Structure of the nephron
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
Detailed view of Bowman’s capsule
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Urine formation is accomplished
by the
• Filtration of plasma
• Reabsorption of needed materials
• Secretion of substances such as
potassium and hydrogen ions into
the renal tubule
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
General regions of filtration, reabsorption, and
secretion
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
Filtration membrane of the kidney
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
Movement of water, ions, and urea through the
renal tubule and collecting duct
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
Concentration of the filtrate as it moves
through the nephron
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Urine volume is regulated by ADH
• Released by the pituitary gland in
response to an increase in osmotic
concentration of the blood
• ADH increases the permeability of
the collecting ducts to water
• As a result, more water is
reabsorbed
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
Regulation of urine
volume by ADH
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• Aldosterone andatrial natriuretic
peptide work antagonistically
• When blood pressure decreases,
cells of the juxtaglomerular
apparatus secrete renin, which
leads to production of angiotensin II
• Angiotensin II stimulates
aldosterone release, which raises
blood pressure
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
• When blood pressure increases
• Atrial natriuretic peptide (ANP)
increases sodium excretion
• Inhibits aldosterone secretion
• These actions increase urine
output and lower blood pressure
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Biology, Seventh Edition
CHAPTER 46 Osmoregulation and Disposal of Metabolic Wastes
Hormonal control of kidney function
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