Animal Physiology

1. Respiratory System
Gas exchange

2. RESPIRATION

3. Cellular respiration is the aerobic breakdown of
glucose in the mitochondria to make ATP.
Respiratory systems are the organs in animals that
exchange gases with the environment.
“Respiration” is an everyday term that is often
used to mean “breathing.”

4. Respiration in animals
• Whether they live in water or on land, all animals must
respire.
– To respire means to take in oxygen and give off carbon
dioxide.
• Some animals rely of simple diffusion through their
skin to respire.
• While others…
• Have developed large complex organ systems for
respiration.

5. Invertebrate respiration
• Invertebrate respiratory organs have
–large surface areas
–contact with air or water
–If require diffusion they must be moist.
Aquatic invertebrates : have naturally moist respiratory
surfaces, and some respire through diffusion through
their skin.
– Example: jellyfish and anemones
• Some larger aquatic animals like worms and annelids
exchange oxygen and carbon dioxide through gills.
– Gills are organs that have lots of blood vessels that bring blood
close to the surface for gas exchange.

6. Terrestrial Invertebrates
• Terrestrial invertebrates have respiratory surfaces
covered with water or mucus. (reduces water loss)
• There are many different respiratory specialized
organs in terrestrial invertebrates.
– Spiders use parallel book lungs
– Insects use openings called spiracles where air
enters the body and passes through a network of
tracheal tubes for gas exchange
– Snails have a mantel cavity that is lined with moist
tissue and an extensive surface area of blood vessels.

7. Section 29-2
Mollusk
Insect
Spider
Gill
Siphons
Movement of water
Book
lung
Airflow
Tracheal
tubes
Spiracles
Invertebrate Respiratory Systems

8. Vertebrate respiratory systems
• Chordates have one of two basic structures
for respiration:
– Gills – for aquatic chordates
• Example: tunicates, fish and amphibians
– Lungs - for terrestrial chordates
• Examples: adult amphibians, reptiles, birds, and
mammals

9. Aquatic Gills
• Water flows
through the mouth
then over the gills
where oxygen is
removed
• Carbon dioxide and
water are then
pumped out
through the
operculum

10. Vertebrate lungs
• As you move from amphibians to mammals the
surface area of the lungs increases
– Insures a greater amount of gas exchange (or a two way
flow of air).
• Birds, by contrast have lungs and air sacs which
have only a one-way flow of air.
– This allows for them to have constant contact with fresh
air.
– This adaptation enables them to fly at high altitudes
where there is less oxygen.

11. Section 33-3
Salamander Lizard Pigeon
Primate
Nostrils, mouth, and
throat
Trachea
Lung
Air sac
Vertebrate Lungs

12. Gas exchange by Diffusion
• Some animals simply allow gases to diffuse
through their skins.

13. Fick’s Law of Diffusion
• Gas exchange involves the diffusion of gases across a
membrane
• Rate of diffusion (R) is governed by Fick’s Law:
• R = DA p
d
D= diffusion constant (size of molecule, membrane permeability, etc)
A= area over which diffusion occurs
p = pressure difference between sides of the membrane
d = distance across which diffusion must occur

14. Fick’s Law of Diffusion
R = DA p
d
To maximize diffusion, R can be increased by:
Increasing A (area over which diffusion occurs)
Increasing p (pressure difference between sides of
the membrane)
Decreasing d (distance across which diffusion must occur)
Evolutionary changes have occurred to maximize R

15. Figure 42.18 The role of gas exchange in bioenergetics

16. GAS EXCHANGE in “Animals”
• The part of the organism across which gases
are exchanged with the environment is the
respiratory surface
• Must be moist
–plasma membranes must be surrounded
by water to be stable
• Must be sufficiently large
–maximize A in Fick’s Law

17. 1. Integument/skin – Protozoa – Annelids;
Echinoderms - Dermal papulae - starfish
2. Gills – Mollusca – Fishes -Aquatic Insects and amphibians
Mollusks - Monopectinate – Pila; Bipectinate – Freshwater mussel
Crustacean (Prawn) – Arthrobranch, Pleurobranch & Podobranch
Tracheal gills - aquatic insects
Prochordates – Pharyngeal gills
3. Trachea - Insects
4. Lungs – Amphibian – Mammals (advanced in Aves)
Diffusion lungs: Book lungs – Arachnids – Spiders & Scorpions
Ventilating lungs: Inspirational type - mammals and birds
Expirational – Amphibians & reptiles (except crocodiles)
MAJOR RESPIRATORY STRUCTURES IN ANIMALS

18. OTHER TYPES
1. Swim bladder – air breathing fishes
2. Alimentary mucosa - fishes
3. Labyrinthine organ – wavy plates in fish operculum
4. Arborescent organ – respiratory trees operculum
5. Epipodite – Crustaceans – prawn – Y shaped respiratory
filaments
6. Tracheal gills – Aquatic insects
7. Book gills – Limulus; Holothurians
8. Water lungs - Molluscans
9. Pulmonary chamber – empty sac lined with vascularized
membranes within mantle cavity - gastropods

20. ?

21. The branchiostegite has been cut
to reveal the six podobranchs
and the epipodites connected to
them. The arthrobranchs are not
visible as they lie beneath the
podobranch. E, epipodite; F,
filament; G, gill; S,
Scaphognatite. Bar = 1 mm.
?

22. ?

23. ?

24. ?

25. ?

26. Comparative Respiratory
Systems
• Cell Membranes
– in unicellular organisms
– some simpler animals (sponges, cnidarians,
flatworms)

27. Comparative Respiratory Systems
Respiratory surface = a single layer of epithelial cells separates outer
respiratory medium (air or water) from the organism’s transport
system (blood)

28. – Skin must be moist
– organisms with flat or
wormlike bodies so skin in
sufficient surface area
– or in frogs and some turtles
to supplement respiration
using lungs
• Skin (cutaneous respiration)

29. • Specialized region of body is folded and branched to
provide large surface area
• This maximizes A in Fick’s Law
• Also decrease d by bringing the respiratory medium
close to the internal fluid
• Three such systems:
– Gills (Aquatic organisms)
– Trachea (insects)
– Lungs (terrestrial vertebrates)

31. Diversity in the structure of gills, external body surfaces in gas exchange

32. Gills
• most aquatic organisms
• outfoldings of the body surface specialized
for gas exchange
• Water is the respiratory medium

33. Water as Respiratory Medium
• Respiratory surface always moist
• Oxygen content of water is much less than
that of air
• denser medium so harder to ventilate

34. Ventilation
• Any method that increases the flow of the
respiratory medium across the respiratory
surface
• This maximizes p in Fick’s Law
– By constantly have new air or new water with
more oxygen

35. Ventilation
• requires a lot of energy to ventilate gills b/c
water is denser than air
• pumping operculum, ram ventilation
Buccal cavity Operculum
Gills Opercular
cavity
Oral valve
Mouth opened,
jaw lowered
Water
Mouth closed,
operculum opened
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36. Water flow
Water
flow
Gill arch
Operculum Gills
Gill
filaments
Gill
filament
Oxygen-
deficient blood
Oxygen-
deficient
blood
Oxygen-
rich
blood
Oxygen-
rich
blood
Gill raker
Blood flow
Lamellae with
capillary networks
Water
flow
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

37. Countercurrent Exchange
• Enhances gas exchange in the gills of fish
• blood is continually loaded with O2 b/c it
meets water with increasing O2
concentration
– Increases p in Fick’s Law

38. Blood (0%
O2 saturation) Water (15%
O2 saturation)
Blood (85%
O2 saturation)
Water (100%
O2 saturation)
Blood (50%
O2 saturation)
60%
Blood (0%
O2 saturation) Water (100%
O2 saturation)
Water (50%
O2 saturation)
No further
net diffusion
40%
30% 70%
20% 80%
10% 90%
Countercurrent Exchange Concurrent Exchange
15%
30%
40%
50%
60%
70%
80%
90%
100%
10%
20%
30%
40%
50%
60%
70%
80%
85%
a. b.
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50%
50%

39. Air as respiratory medium
• Higher oxygen concentration
• ventilation is easier b/c air is less dense
• respiratory surface loses water to air by
evaporation

40. Air as respiratory medium
• Solution…
– fold respiratory surface inside the body

41. Trachea
• Air tubes that branch throughout the body
• finest tubes (tracheoles) extend to nearly
every cell in the body
• gas diffuses across moist epithelium that
lines the terminal ends

42. Figure 42.22 Tracheal systems

43. Trachea
• Found in insects
• Open Circulatory system of insects is NOT
involved in transporting gases
• Ventilation
– diffusion
– body movements

44. Lungs
• Localized in one area of body
– circulatory system must transport gases

45. Section 33-3
Salamander Lizard Pigeon
Primate
Nostrils, mouth, and
throat
Trachea
Lung
Air sac
Vertebrate Lungs

46. Lungs
• Ventilation
– Positive pressure breathing - frogs

47. Lungs
Esophagus
Air
External
nostril
Buccal cavity
Nostrils
open
Nostrils
closed
a.
b.
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Air

48. Lungs
• Ventilation
– Negative pressure breathing- mammals

49. Negative pressure breathing

50. Expiration
Inspiration
Muscles
contract
Lungs
Air
Sternocleido-
mastoid muscles
contract
(for forced
inspiration)
Diaphragm
contracts
Muscles
relax
Diaphragm
relaxes
a.
b.
Abdominal
muscles contract
(for forced expiration)
Air
Negative pressure breathing

51. Nasal cavity
Nostril
Larynx
Trachea
Right lung Left lung
Pharynx
Left
bronchus
Glottis
Diaphragm
Pulmonary
venule
Pulmonary
arteriole
Blood flow
Bronchiole
Alveolar
sac
Alveoli
Capillary
network on
surface
of alveoli
Smooth muscle
Lungs

52. Section 37-3
Flowchart
Oxygen and
carbon dioxide
exchange at
alveoli
Oxygen-rich
air from
environment
Bronchioles
Nasal
cavities
Pharynx Trachea Bronchi
Bronchioles
Alveoli
Pharynx
Nasal
cavities
Carbon
dioxide-rich
air to the
environment
Bronchi
Trachea
Movement of Oxygen and Carbon Dioxide In
and Out of the Respiratory System

53. In the alveolus
• The respiratory
surface is made
up of the alveoli
and capillary
walls.
• The walls of the
capillaries and the
alveoli may share
the same
membrane.

54. Gas exchange
• Air entering the lungs
contains more oxygen
and less carbon
dioxide than the blood
that flows in the
pulmonary capillaries.

55. Oxygen transport
• Hemoglobin
binds to oxygen
that diffuses into
the blood
stream.

56. Carbon dioxide transport
• Carbon dioxide
can dissolve in
plasma, and about
70% forms
bicarbonate ions.
• Some carbon
dioxide can bind to
hemoglobin for
transport.

57. Lungs
• Ventilation
– air sacs act as bellows in birds
• air flows in one direction during both inhalation &
exhalation

58. Anterior
air sacs Posterior
air sacs
Parabronchi of lung
Trachea
Inspiration Expiration
Inspiration Expiration
Cycle 2
Cycle 1
Trachea
Anterior
air sacs
Lung
Posterior
air sacs
a. b.
Lungs of Birds

59. Transport of Gases
• Occurs in the circulatory system when
needed

60. Transport of Gases
• O2 is transported by respiratory pigments
– hemoglobin on red blood cells or hemocyanin
in the plasma

62. Transport of Gases
• CO2 is transported by respiratory pigments
and dissolved in the plasma and in red
blood cells as bicarbonate ion (HCO3
-)