1. THE CIRCULATORY SYSTEM
Section 3.2

2. CIRCULATION
The circulatory system uses blood vessels to carry oxygen to the cells and picks up carbon dioxide to be eliminated from the body
No cell is more than 2 cells away from a blood vessel

3. CIRCULATION
There are two types of systems utilized by multicellular organisms:
Open system: blood carrying oxygen and nutrients is pumped into body cavities where it bathes the cells. The heart relaxes and blood is taken back to the heart through open ended pores. (ex. snail, clam)
Closed system: blood is contained within blood vessels moving to and from the heart. (ex. worm, human)

4. The body has 96 000 km of blood vessels (the earth is 40, 075
The body has km of blood vessels (the earth is 40, km around…. So that is MORE then twice around the earth!!

5. PARTS OF THE CIRCULATORY SYSTEM
Arteries: blood vessels that carry blood away from the heart
have thick muscular walls
Veins: blood vessels that carry blood back to the heart
have valves so that the blood only flows one way
Capillaries: small blood vessels that connect arteries and veins
so small that blood cells must travel single file

6. Major Veins & Arteries

7. THE HEART 2 parallel pumps separated by a wall of muscle
4 chambers  two atria (singular atrium) and two ventricles

8. HOW THE HEART WORKS

9. The heart contains 4 sets of valves that operate as one-way doors (keep blood flowing in one direction in the heart)
 valves closing makes “lubb” heart sound
 when ventricles relax some gives the “dubb” heart sound