i. circulation a. circulatory systems 1. gastrovascular cavity - very simple - flatworms

I. CirculationA. Circulatory systems

1. gastrovascular cavity- very simple- flatworms

2. open circulation- blood pumped through open-ended vessels- “bathes” the tissues- many mollusks and all arthropods

3. closed circulation

3. closed circulation- arteries (carry blood away from the heart)- veins (carry blood back to the heart)

4. functionsa. transportb. regulation

- hormones- temperature

c. protection- white blood cells- antibodies

B. Heart1. peristaltic pump to:

2. fish (tube-like heart with two adjacent chambers)a. atrium (collects just enough blood to fill ventricle)b. ventricle (thick-walled muscular pump)c. single circuitd. loses force in the gills (slows down)

3. amphibiansa. double circulation

- pulmonary circuit- systemic circuit- pump blood to muscles at higher force

b. three-chambered heart (mixing of blood in ventricle)(won’t damage the lungs)

- some transcutaneous gas exchange

4. reptilesa. three-chambered heartb. partial septum in ventricle (less mixing)

4. mammals, birds, crocodiliansa. four-chambered heartb. complete separation of the ventriclesc. no mixing (much more efficient)d. birds and mammals evolved independently

C. Blood1. plasma

a. transport of nutrients/wastesb. proteins

- clotting factors- antibodies

2. cellsa. red blood cellsb. white blood cellsc. platelets

3. stem cells

II. RespirationA. Gas exchange

II. RespirationA. Gas exchange

1. direct diffusion- primitive

2. transcutaneous respiration- most practitioners are small- requires water

3. gills- thin sheets of tissue- contain blood vessels- countercurrent flow

4. tracheal systema. insectsb. spiracles

- reduces water loss

c. tracheoles penetrate the body and provide gas exchange- insects don’t use circulatory system to deliver O2

5. lungs- have small sacs (alveoli) lined with thin layer of fluid

B. Gill apparatus1. fish “gulps” water2. water passes over gills, then exits through gill slit3. countercurrent flow (allows countercurrent exchange)

a. water and blood flow in opposite directionsb. very efficient method of gas exchange

C. Amphibian lung1. very small without much surface area for gas exchange

- not very efficient2. rely on transcutaneous respiration 3. may lack lungs completely (some salamanders)

D. Reptiles1. more efficient than amphibian

- increased surface area for gas exchange2. most have lower metabolic rate than mammals

- less need for high-volume gas exchange

E. Mammals1. many tiny air sacs (alveoli)2. greatly increased surface area for gas exchange

- about 100 m2 in human lungs3. air conduction system lined with ciliated cells

- mucus elevator

F. Birds1. posterior and anterior air sacs2. one way flow of air through lungs3. countercurrent flow

- but 90˚, not 180˚ as in fish4. highest efficiency of land animals