Cardiovascular

• The cardiovascular system is the system responsible for delivering blood to different parts of the body. It consists of the following organs and tissues.
• The heart: A muscular pump that forces blood around the body.
• Arteries: Vessels that carry blood away from the heart.
• Veins: Vessels that bring blood back to the heart.
• Capillaries: Tiny vessels that branch off from arteries to deliver blood to all body tissues.
• systemic circulatory system the main blood circulatory system that transports blood to the organs, tissues, and cells throughout the body.
• pulmonary circulatory system: blood passes through the lungs and returns to the heart. It is where oxygen enters the blood and carbon dioxide leaves the blood.
• Blood lacking oxygen returns from the body and enters the right atrium via the inferior vena cava and superior vena cava veins.
• From right atrium blood flows through the tricuspid valve and enters the right ventricle.
• The right ventricle pumps blood through the pulmonary valve and out of the heart via the main pulmonary artery.
• The blood then flows through the left and right pulmonary arteries into the lungs. Here, the process of breathing draws oxygen into the blood and removes carbon dioxide. As a result, the blood is now rich in oxygen.
• As the blood is now rich in oxygen again the blood returns to the heart and flows into the left atrium via four pulmonary veins.
• From right atrium blood flows through the mitral valve and enters the left ventricle .
• The left ventricle pumps the blood through the aortic valve into a large artery called the “aorta.” This artery delivers blood to the rest of the body.
• Cardiac Cycle:  first phase is diastole, in which the ventricles fill with blood.
• First phase: It begins when the aortic or pulmonary valve closes and ends when the mitral or tricuspid valve closes. During diastole, blood vessels return blood to the heart in preparation for the next contraction of the ventricles.
• Cardiac Cycle: second phase is systole, in which the ventricles contract and eject blood.
• Second phase: It begins when the mitral or tricuspid valve closes and ends when the aortic or pulmonary valve closes. The pressure inside the ventricles becomes greater than the pressure inside adjacent blood vessels, thereby forcing the blood from the ventricles to the vessels.
• semilunar valves are located between the ventricles and outflow vessels. 
• Semilunar valve: Pulmonary valve, located at the opening between the right ventricle and the pulmonary trunk.
• Semilunar valve: Aortic valve, located at the opening between the left ventricle and the aorta.
• The atrioventricular valves are valves that connect the atrium to the ventricles
• The mitral valve is located on the left side of the heart, between the left atrium and the left ventricle. This valve has two leaflets that allow blood to flow from the lungs to the heart.
• The tricuspid valve is located on the right side of the heart, between the right atrium and the right ventricle.