Cardiovascular system

• The heart is found underneath the sternum to provide protection, and its surrounded by a thin layered sac which is called pericardium and this has a fluid to prevent friction
• There are 3 layers of the heart: Epicardium - Outer layer. Myocardium - Strong, middle layer of the hearts wall. Endocardium - inner layer .
• The septum of the heart has: A solid wall of muscle and keeps deoxygenated and oxygenated blood separated.
• The Aortic semi lunar valve: Situated between left ventricle and aorta, and prevents backflow of blood
• The pulmonary semi lunar valve is situated between the right ventricle and pulmonary artery
• The tricuspid valve: Situated between right ventricle and atrium and prevents blood flowing backwards
• The Bicuspid valve: Situated between left atrium and ventricle and allows blood to flow in correct direction
• The ventricles: They pump blood at high pressure, they have thick muscular walls than atria
• The structure of the blood vessels: Arteries - always transport blood away from the heart. Veins - transport blood towards the heart. Capillaries - Gaseous exchange happens. The blood vessels make sure to transport the blood to the whole body.
• Arteries and veins ( 3 layers ) Tunica externa - thin layer of connective tissue. Tunica media - middle layer of smooth muscle Tunica interna - thick layer of elastic tissue.
• Arteries: Always carry blood away from the heart, they have thick muscular walls, this helps to carry blood at higher pressure, do not have valves, small diameter. Have elasticity - Being able to stretch and go back to the original form. Have Contractility - measure of cardiac pump.
• Veins: Return the blood to the heart, large diameter, have thin walls, have valves to prevent blood backflow, carry blood at high pressure
• Capillaries: Blood pressure is high, gaseous exchange happens
• Arterioles: smaller version of arteries. Venules: Smaller version of veins
• Composition of blood: Plasma =55% RBC +WBC + Platelets =45%