Circulation
The function of the circulation system is to transport necessary materials to the cells of an animalās body and transport waste products away from cells so they can be released into the environment.
The three basic types of circulatory systems are gastrovascular activity (cnidarians), open circulatory systems, closed circulatory system.
Open Circulatory Systems
Open circulatory systems are found in arthropods and some mollusks. The basic components of an open circulatory system is hemolymph, vessels, and one or more hearts. The vessels open into animalās body cavity. Nutrients and waste are exchanged by diffusion between hemolymph and body cells.
Closed Circulatory Systems
Closed circulatory systems are found in earthworms, cephalopods, and all vertebrates. Blood and interstitial fluid are physically separated. Larger, more active animals need a higher pressure to pump blood to all body cells. Some common features of animals with closed circulatory systems are blood remains within vessels for distribution, one or more contractile for muscular hearts, solutes exchanged with environment and body cells, contains disease-fighting cells and molecules, adjusted to match the animalās metabolic demands, capacity to heal themselves when wounded, and the system grows in size as the animal grows.
Cardiac Cycle
Cardiac Cycle: events that produce a single heartbeat
The cardiac cycle has two phases: diastole and systole.
Diastole: atria contract and ventricles fill (blood pressure is at itās lowest)
Systole: ventricles contract and blood is ejected from the heart (blood pressure is at itās highest)
The heart valves open and shut in response to pressure gradients.
Blood Vessels
Arteries: conduct blood away from the heart
Arterioles: constrict to control blood distribution
Capillaries: gas, nutrient, and waste exchange
Venules: small, thin extensions of capillaries
Veins: conduct blood back to the heart
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