1. Comparative Respiratory Systems
The function of animal respiratory systems is to…
AND to…
It’s all about DIFFUSION!!!
Get Oxygen (O2(g)) into the body
Get Carbon Dioxide (CO2(g)) out of body

2. Skin Diffusion (in Invertebrates)
Thin layer of skin cells
Moist/wet for gas diffusion
Blood vessels close to the skin
Gas exchange by diffusion
Oxygen in
Carbon Dioxide out
Example Organisms:
Flat worms
Round worms
Segmented worms
Jellies
Sponges
Mollusks
Bivalves
Snails
Cephalopods

3. Gills (in Annelids) Small thin branches Lined with blood vessels
Gas exchange by diffusion
Oxygen in
Carbon Dioxide out
Example Organisms:
segmented worms
leaches
earthworms

4. Mantle Cavity Gills (in Mollusks)
Feathery structure just under the mantle (under the shell)
Lined with blood vessels
Gas exchange by diffusion
Oxygen in
Carbon Dioxide out
Example organisms:
Mollusks:
Bivalves (clams, mussels, etc.)
Gastropods (snails, slugs)
Cephalopods (octopus, squid, etc.)

5. Respiratory System (of Insects)
Spiracles
Holes along abdomen
How air gets into the body
Tracheal Tubes/Tracheoles
Tubes that carry air throughout body
Air Sacs
Reservoirs of air; push air through tracheal tubes when contracted
Gases are moved, to a large extent, by pumping actions of the body segments; no blood flow needed.
Respiratory System (of Insects)

6. Respiratory System (of Insects)
Hemolymph (i.e. arthropod blood) seeps into tracheoles in periods of low activity.
Fluid/gas interface gas exchange
Hemolymph pulled out of tracheoles in high activity
Gas exchange is nearer to cells
Respiratory system of insects is what restricts their body size.
(i.e. this system is only efficient for small sizes up to diameter of 3 cm.

7. Book Lung (in Arachnids)
Found inside an air-filled cavity (atrium) in underside of the abdomen.
Hemolymph (i.e. arthropod blood) flows between the layers of air pockets (lamellae) for gas exchange.
Stacks of alternating lamellae and tissue filled with hemolymph look similar to a folded book.

8. Gills (in Fish)
The Gills of a Tuna fish

9. Gills (in Fish) Gills have a highly-folded feathery structure
Gill filaments are hair-like projections
Filaments extend off 3-7 gill arches
Lined with capillaries (smallest blood vessels)
Counter current for efficient gas exchange
Operculum
Flap that covers/protects gills
Opens when water is pushed through gills
Buccal cavity (mouth)
Forces water past gills

10. Amphibian Skin (only in water) & Gills (sometimes)
Skin: similar to invertebrate structure and function
Gills: similar to fish in structure and function

11. Increase surface area! Amphibian Lungs Lungs modified air sacs
Folded inner surface to…
Lined with small blood vessels
Gas exchange
Increase surface area!

12. Avian (bird) Respiratory System
The Avian respiratory system is similar to that of Mammals, with two key differences:
Air sacs (9 of them) which expand on inhalation and contract on exhalation, allowing for…

13. Avian (bird) Respiratory System
One-way flow: air moving through lungs is constant “fresh” air with higher O2 content.
Avian lungs are the only site of gas exchange, air sacs just move the air through the system.

14. Mammalian Respiratory System
The nasal cavity is lined with hair to filter inhaled air; also warms and humidifies air.
Air is directed to alveoli (air sacs in the lungs) through branching network of tubes
Trachea, Bronchi, Bronchioles
Alveoli have very thin layer of cells (1 or 2 deep) with capillaries all around for maximized gas exchange.

15. References http://www.bozemanscience.com/respiratory-system
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