THE CIRCULATORY SYSTEM Section 3.2

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

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)

The body has 96 000 km of blood vessels (the earth is 40, 075 The body has 96 000 km of blood vessels (the earth is 40, 075.16 km around…. So that is MORE then twice around the earth!!

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

Major Veins & Arteries

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

HOW THE HEART WORKS

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