1. Chapter 42- Circulation and Gas Exchange

2. Background
The lowest inverts (jellyfish, etc…) have only a gastrovascular cavity where circulation AND digestion take place simultaneously.

3. Open vs. Closed Open vs. Closed Circulatory System- All have:
- Circulatory fluid (blood)
- Tubes (blood vessels)
- Muscular pump (heart)

4. Open vs. Closed Open circulation- Insects/Arthropods/Mollusks
- Metabolically cheap
- Sinuses- Area surrounding the organs
- Blood bathes the organs

5. Open vs. Closed
Closed circulation- Blood is contained within vessels (all mammals)
- Metabolically expensive
- Called cardiovascular system in mammals
- Heart  Arteries Arterioles  Capillaries (site of gas exchange) 
Venules  Veins  Heart

7. Open vs. Closed - Fishes- Heart is 2 chambers
- Amphibians and Reptiles- 3 chambers
- Mammals and Birds- 4 chambers

9. The Heart
- Pathway of blood through heart (and body)

10. The Heart
- Cardiac cycle- The complete sequence of pumping and filling
- Contraction- systole
- Relaxation- diastole
- Valves in the heart prevent backflow
- SA Node- Pacemaker of the heart. Receives original signal then passes signal to the AV node, which delays the pulse and then sends it out

12. Blood Vessels Blood Vessels
- Veins have valves to prevent backflow, arteries do not
- Arteries are thicker than veins

13. Blood Vessels
- Layers of blood vessels (from the outside to the inside)
- Elastic connective tissue
- Smooth muscle
- Endothelium- Smooth surface for blood to flow over
- Capillaries only have a “basement membrane” and an endothelium

15. Blood Vessels
- Normal blood pressure 120 (systole)/70 (diastole) - Fluid is lost through the capillaries, but returns to the circulatory system by entering into the lymphatic system (direct connection to circulatory system)

16. Blood Blood- Called hemolymph and is a connective tissue
- 90% of it is water
- pH of 7.4
- Plasma is the fluid that all of the cells are suspended in

18. Blood - Cells found in blood - Erythrocytes (red blood cells)
- Carry oxygen by having hemoglobin proteins
- Each hemoglobin has 4 subunits each with a heme group and an associated iron atom. Iron binds to the O2

20. Blood
- Cooperative binding- when one O2 binds, it makes it easier for more O2 to attach and when one O2 leaves, it makes it easier for more O2 to leave
- Each erythrocyte can contain up to 250 million hemoglobin molecules and each can carry four O2 molecules = 1 billion O2 molecules per erythrocyte.

21. - The lower the pH, the lower the affinity to O2 = Bohr Shift
- The lower the pH, the lower the affinity to O2 = Bohr Shift. pH lowers when CO2 levels are high (ie: rigorous exercise) and hemoglobin will be more likely to release O2 to the tissue that needs it.

22. Blood Leukocytes (white blood cells)- Fight infection
Platelets- Blood clotting factor

23. Gas Exchange
- Gas exchange (O2 uptake and CO2 release- flow of molecules is because of diffusion)
- The “respiratory medium” is the source of O2
- The “respiratory surface” is the location of gas exchange
- Water must be present for the gas exchange to occur

24. Gas Exchange Groups of Animals and Gas Exchange
- Worms- Diffusion through skin (reason they are often flat and long)
- Aquatic animals- Gills. Countercurrent exchange

26. - Insects- Tracheal system (air tubes within body)

27. - Large animals and birds- Lungs - Tidal flow- The volume of air inhaled and then exhaled