1. Circulation and Gas Exchange
Ch 42 Notes
Circulation and Gas Exchange

2. Circulation
Used to get nutrients and Oxygen in through cell membranes and waste products out through same cell membrane
Direct Exchange – Occurs in single celled organisms, sponges
Gases and nutrients move directly from environment into and out of cells

3. Gastrovascular Cavity
Single Opening – Only 2 cell layers in body
Inner and Outer Tissue bathed by fluid
Nutrients, Gases and Waste move by diffusion
Cnidarians, Planarians/Flatworms

4. Circulatory System Animals with many cell layers
Fluid transported in Circulatory System connected to body cells
3 Parts to System
Circulatory Fluid
Interconnecting Tubes
Muscular Heart to Pump

5. Open Circulatory System
Circulatory fluid bathes organs directly (no vessels)
Fluid called Hemolymph
Heart (s) pump hemolymph through vessels into sinuses surrounding organs
Chemical exchange occurs
Don’t need much energy
Arthropods, mollusks

6. Closed Circulatory System
Fluid (blood) confined to vessels
Blood is separate from interstitial fluid (fluid that surrounds cells)
One or more hearts pumps blood into large vessels, leads to smaller vessels, then to cells
Allows for higher activity levels
Annelids, Cephalopods (squid/octopus) and all Vertebrates

8. Vertebrate Circulatory Systems
Cardiovascular System
Extensive network of vessels
Arteries - carry blood away from heart (arterioles – small arteries)
Capillaries – tiniest vessels (one cell layer thick) where exchange of gas and nutrients occurs – right next to cells
Veins – bring blood back to heart (venule – small vein)

9. Single Circulation 2 – chambered heart One atrium and one ventricle
Blood enters heart through atrium, moves into ventricle, pumped to gills (Oxygen into blood, CO2 out, Artery carries blood to body cells, vein returns it to heart
Fish, Sharks, Rays

10. Double Circulation Heart has 2 pumps for coordination
Right side – Pulmonary Circuit – Oxygen poor blood goes to gas exchange tissue (lungs) and gets O2 and gets rid of CO2
Blood returns to Left side of heart – Systemic Circuit – gets pumped to the rest of body through arteries – capillaries (oxygen and nutrients given to cells, waste picked up) and returns to right side through veins

11. Amphibians Three chambered Heart – 2 atria and one ventricle
Get some mixing of blood with and without oxygen
Gas exchanged through both skin and lungs

12. Reptiles
Three chambered heart with septum partially dividing the ventricle
Better separation of blood with and without oxygen

13. Mammals and Birds 4 Chambered Heart – 2 atria, 2 ventricles
Complete separation of blood with and without oxygen
Allows them to be endothermic because the heart is more efficient at delivering oxygen and fuel to cells

15. Mammalian Circulation
Right Atrium
Tricuspid Valve
Right Ventricle
Pulmonary Semilunar Valve
Pulmonary Artery
Lungs (pick up Oxygen, release Carbon Dioxide
Pulmonary Vein
Left Atrium
Bicuspid Valve
Left Ventricle
Aortic Semilunar Valve
Aorta
Arteries
Arterioles
Capillaries (give Oxygen and nutrients to cells, pick up waste)
Venules
Veins
Vena Cava
Start over

17. Gas Exchange
Uptake of Molecular Oxygen and discharge of Carbon Dioxide
Can be through air (easier) or water (more difficult)
Warmer/Saltier water holds less oxygen than fresh water

18. Respiratory Surfaces Always Moist Exchange occurs by Diffusion
Exchange is fast when area for diffusion is large and surface is thin
Sponges/Cnidarians – direct gas exchange
Earthworms/Some Amphibs – thru skin
Aquatic Vertebrates – Gills
Insects – Tracheal Tube system
Terrestrial Vertebrates - Lungs

20. Alveoli Site of Gas Exchange in Mammals Millions inside each lung
Large Surface Area
Found close to capillaries to make gas exchange easier

21. Breathing - Mammals Use Negative Pressure – pulls air in
Diaphragm – Muscle beneath lungs
Diaphragm Contracts
Thoracic cavity increase (pressure decreases)
air pulled in (inhalation)
Diaphragm relaxes
Thoracic cavity decreases (pressure increases)
air pushed out (exhalation)

22. Control Of Breathing
Medulla Oblongata (in brain) – sets rhythm of breathing
Pons (in brain) – controls inhale/exhale tempo
CO2 concentration changes the pH of blood which signals to the medulla how fast breathing should occur
More CO2 = lower pH = faster breathing
Less CO2 = higher pH = slower breathing