Chapter 36: pp. 665 - 678
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10th Edition
Sylvia S. Mader
Body Fluid Regulation
& Excretory Systems
BIOLOGY
© Georgette Douwma/Photo Researchers, Inc.
PowerPoint® Lecture Slides are prepared by Dr. Isaac Barjis, Biology Instructor
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1
2
• 2.D.2: Homeostatic mechanisms reflect both common
ancestry and divergence due to adaptation in different
environments. (36.1)
• 2.D.3: Biological systems are affected by disruptions to
their dynamic homeostasis. (36.2)
• 4.B.2: Cooperative interactions within organisms promote
efficiency in the use of energy and matter. (36.2)
3
Nitrogenous Waste Products
• Ammonia (N2 waste) is the byproduct of
catabolizing amino acids. Toxic to most animals.
• Aquatic animals excrete ammonia directly.
• Terrestrial animals must convert ammonia to urea or
uric acid.
• Urea needs lots of water per unit of nitrogen.
• Mammals and amphibians
• Uric acid requires much less water per unit of nitrogen excreted.
• Reptiles, birds, and arthropods
• Can live in arid environment.
4
Nitrogenous Wastes
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proteins
amino acids
NH2
most fishes and
other aquatic
animals
adult amphibians,
sharks, and
mammals
Insects, birds, and
reptiles
ammonia
urea
uric acid
O
H
N
O
H
H2N
C
HN
NH2
C
H
C N
C
O
C
H
water needed to excrete
energy needed to produce
C N
N
H
H
O
5
Body Fluid Regulation
• An excretory system regulate body fluid
concentrations and is dependent on conc. of
minerals (sodium, potassium…)
• Obtain water by ingesting (food, drink) or
metabolism.
• Osmoregulation- maintaining proper water levels
and ion conc.
6
Aquatic Animals
• Bony Fishes
• Marine bony fishes
• Body fluids hypotonic to sea water, so they lose water through gills.
• Must constantly drink to compensate.
• Freshwater bony fishes have opposite problem
• Body fluids hypertonic to fresh water, so they gain water through gills.
• Eliminate excess water through copious urine.
7
Body Fluid Regulation in Bony Fishes
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passive loss
of water
through
gills
drinks seawater
salts actively
excreted by gills
scanty amount
of isotonic
urine contains
some salts
a. Marine bony fish
passive gain of
water through gills
does not drink
salts actively
taken up by gills
b. Freshwater bony fish
large amounts of hypotonic
urine contain few salts
8
Osmoregulation in a Shark
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Blood is isotonic to seawater.
No need to osmoregulate.
© Digital Vision Ltd
9
Terrestrial Animals
• Terrestrial animals lose water through excretion and
respiration.
• Must drink water to make up for loss.
• The environment the animal lives in dictates the method of
osmoregulation.
• i.e. Desert animals have a different system due to inadequate water
supply to replenish water loss through urine.
10
Adaptations of a Kangaroo Rat
to a Dry Environment
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Exhaled air is
cooled and dried
in long convoluted
air passages.
Animal fur prevents
evaporative loss of
water at skin.
Urine is the
most hypertonic
known among
animals.
Fecal pellets
are dry.
Oxidation of
food results in
metabolic water.
© Bob Calhoun/Bruce Coleman, Inc.
11
Adaptations of Marine Birds to a
High Salt Environment
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salt solution
exits here
salt solution
runs down
beak here
© Eric Hosking/Photo Researchers, Inc.
Human Urinary System
• Functions to filter the blood & rid the body of waste,
also homeostasis.
• Composed of bladder, ureters, urethra, & kidneys, but
works closely w/ circ. system.
Anatomy of Urinary System
1.
2.
3.
The ureters carry urine (excess water, waste, and
excess ions) to the bladder.
The bladder is a muscular bag that stores urine to
expel.
The urethra is a tube that takes waste out of the
body.
Anatomy of Urinary System
4. Kidneys- composed of the renal cortex, renal pelvis, and
renal medulla. Supplied by the renal artery & blood exits
via the renal vein.
a. Nephrons- unit of the kidney; tiny filters
15
Macroscopic & Microscopic
Anatomy of the Kidney
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nephrons
renal
pelvis
renal
cortex
renal
medulla
collecting
duct
ureter
renal artery
and vein
a. Gross anatomy
renal pyramid
in renal medulla
renal
pelvis
b. Two nephrons
b. Blood flows into glomerulus (bed of
capillaries); particles in the blood (glucose,
salt, vitamins, waste, AAs) flow into
Bowman’s capsule, which becomes loop of
Henle.
RLO: The Anatomy of the Kidneys
c. Water, ions, & glucose are
reabsorbed into the capillaries
surrounding the loop, waste remains in
tubules and is urine.
18
Processes in Urine Formation
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glomerular capsule
H2O
Glomerular Filtration
Water, salts, nutrient molecules, and
waste molecules move from the
glomerulus to the inside of the glomerular
capsule. These small molecules are
called the glomerular filtrate.
urea
glucose
amino
acids
uric
acid
salts
proximal
convoluted
tubule
Tubular Reabsorption
Nutrient and salt molecules are actively
reabsorbed from the convoluted tubules
into the peritubular capillary network, and
water flows passively.
glomerulus
efferent
arteriole
Tubular Secretion
Certain molecules (e.g., H+ and
penicillin) are actively secreted from the
peritubular capillary network into the
convoluted tubules.
afferent
arteriole
distal
convoluted
tubule
renal
artery
renal
vein
venule
collecting
duct
peritubular
capillary
network
loop of the
nephron
H2O
urea
uric acid
salts
NH4+
creatinine
19
Reabsorption of Salt and Water
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C1-
Na+
Increasing solute concentration in renal medulla
H2O
Renal
cortex
Outer
medulla
ascending
limb
Na+
H2O
H2O
C1-
descending
limb
Urea
H2O
H2O
Inner
medulla
loop of the
nephron
collecting
duct
20
Urine Formation and Homeostasis
• Important to excrete water, but maintain
homeostasis at the same time.
• Water and salt are reabsorped in the loop of the nephron.
• Antidiuretic hormone (ADH)
• Released by the posterior lobe of the pituitary
• ↑ ADH, ↑ water reabsorption.
• Renal Physiology
21
The Renin-Angiotensin-Aldosterone System
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liver
kidneys
adrenal cortex
secrete
renin
blood vessel
stimulates
secretes
secretes
speeds
angiotensin I
angiotensin II
angiotensinogen
aldosterone
Facts
1.
2.
3.
Important to remove urea & ammoniatoxic- jaundice.
Kidneys regulate pH, by regulating
osmotic pressure
Excess glucose is toxic- diabetes.