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# The Human Circulatory System ## Valves in the Heart - Blood moves from one place to another within the heart. - Valves prevent backflowing of the blood. - **Atrioventricular (AV)** valves are between the atria and ventricles. - **Tricuspid valve** - between right atrium and right ventricle....

# The Human Circulatory System ## Valves in the Heart - Blood moves from one place to another within the heart. - Valves prevent backflowing of the blood. - **Atrioventricular (AV)** valves are between the atria and ventricles. - **Tricuspid valve** - between right atrium and right ventricle. - **Bicuspid or mitral valve** - between the left atrium and left ventricle. - **Semilunar (SL)** valves are within the openings of the vena cava and the aorta: - **Pulmonic valve** - within the opening of the pulmonary artery - **Aortic valve** - within the opening of the aorta. - When the atria contract, blood from the atria moves toward the ventricles. - AV valves are open - SL valves are closed - When the ventricles contract, blood moves to their destination. - AV valves are closed - SL valves are open. ## Blood Vessels - The circulatory system is closed. - The blood remains confined within the network of blood vessels. - There are three types of blood vessels : arteries, veins and capillaries. ### Arteries - Thick-walled to cope with the high pressure of the blood flowing through them. - Transport oxygen-rich blood that moves away from the heart. - Starting from the aorta, the artery branches into smaller arteries called arterioles. ### Veins - Have thinner walls than arteries. - Convey blood coming from all parts of the body to the heart. - Starting from the vena cava, the vein branches out to veins and then to venules. - The openings of the veins are wider than the openings of arteries. - They are equipped with valves to prevent blood from flowing back. ### Capillaries - One-cell thick. - Allow gasses and nutrients to be exchanged between the blood and the cells. - Connect arterioles and venules. ## The Flow of the Blood in the Body - Oxygen-poor blood coming from the body goes back to the right heart through the vena cava. - The right atrium forces blood to move to the right ventricle. - When the right ventricle contracts, blood moves toward the lungs, passing through the pulmonary artery. - In the lungs, oxygenated (pulmonary circulat) blood goes to the left atrium by way of the pulmonary veins. ## Career in Focus: Cardiologist - Highly trained professionals in the field of the heart and blood vessels. - They also know how the circulatory system works. - A cardiologist in the Philippines becomes a cardiologist by completing a six to eight year program in any appropriate life science medical school to finish a four-year residency program.