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The Circulatory System Anatomy The Circulatory System is the major transportation system in the body. It includes the heart, blood vessels (capillaries, arteries ) and the blood. Important in the exchange between cells of tissues, organs and systems. The Heart • This is the motor (pump) that makes the system work. • Organ made up of muscle tissue. • Size of a fist • Located between the two lungs, on the left side and is protected by the rib cage. The Heart continued • In adults, it beats between 65 and 85 times per minute. • Over a lifetime it will beat about 2,500,000,000 times, twenty-four seven, never stopping, just slowing down. • Movement of blood relies on the heart because it propels blood with sufficient pressure The Heart Chambers (4) The heart has four chambers Right and Left Atrium in the upper part of the heart where blood enters the heart. Right and Left ventricles in the lower part contract to send blood out of the heart. Bigger then atria! Left atrium Right atrium Right ventricle Left ventricle (very muscular) Functions of the Heart chambers 1. The right atrium: receives deoxygenated blood from the entire body. 2.The right ventricle: pushes blood to the lungs so it is thinner then the left 3. The left atrium: receives oxygenated blood from the lungs. 4. The left ventricle: wall thicker then right ventricle because pushes blood to the entire body. (larger chamber) The heart also has valves which control blood flow from one chamber to the other and prevent back flow. Each atrium opens into the ventricle located just below it through these valves. Blood Vessels of the Heart • Blood vessels are the channels that blood uses to circulate through the body Two vessels leave the ventricles: • Pulmonary trunk which divides into: Right and left pulmonary arteries : brings deoxygenated blood from the heart (right ventricle) to the lungs • Aorta brings oxygenated blood from the heart (left ventricle) to the entire body. • These are the larger vessels of the heart. Two other blood vessels empty blood into the atria of the heart • Right and left pulmonary veins bring oxygenated blood from the lungs to the heart (left atrium) • Superior and inferior vena cava bring deoxygenated blood from the body (organs) back to the heart (right atrium); Other blood vessels are called coronary vessels which supply blood to the heart. They provide the heart with nutrients and oxygen it needs to rid it of waste. Main blood vessels Aorta (blood to body) Superior vena cava (blood from the upper body) Pulmonary artery (blood to the lungs) ri Inferior vena cava (blood from the lower body) Pulmonary vein (blood from the lungs) Septum Blood vessels of the body: • Their role is to distribute blood to different parts of the body • Arteries and arterioles(small arteries): carry blood AWAY from the heart to the organs of the body. • Have thick, muscular, elastic walls to withstand high pressure. • Starts with the aorta(largest artery) which begins at the left ventricle. • Divide into small arteries and arterioles until they reach capillary network. • Capillaries: small branches at the ends of arteries linking them to veins. • They are permeable and have thin walls of a single layer of epithelial cells so gas exchange can happen through diffusion between blood and cells. • Veins and venules(small veins): • • • • • carry blood from the organs to the heart. Thinner walls and less elastic then arteries because there is less pressure. To help blood flow from the extremities such as the legs, veins have one way valves that prevent back flow. Blood flows in the same direction from arteries to arterioles, to the capillaries, to the venules and veins. Leg muscle contractions help pump blood back to heart. Capillaries turn into venules, enlarging into veins and returning to the left atrium from the large Vena Cava. The Circulatory System Physiology: How it works!! • Blood vessels of body make up a network that carry blood to all parts of the body. • Two components form a double pump – Pulmonary circulation = lungs – Systemic circulation = all other organs Function of the Heart in Circulation: Contractions of the heart muscle causes blood to circulate through the entire body. Right and left sides of heart pump blood into separate circuits at the same time. For blood to enter the two atria, the muscles must be at rest (muscles must be relaxed) For blood to exit the atria, the two atria must contract at the same time forcing blood to empty into ventricles Then the two ventricles contract at the same time to push blood into arteries and towards body organs or lungs Pulmonary Circulation • Carries blood that contains carbon dioxide(deoxygenated blood) from the heart to the lungs, where it gets rid of the waste and is resupplied with oxygen and returned to the heart. Carbon dioxide diffuses out of the blood and into the alveoli Oxygen diffuses into the blood (gas exchange) When a heart beats, it contracts the atria first and then the ventricles. 1. Deoxygenated blood from the body returns under pressure via the Vena Cava into the relaxed right atrium. 2. Contraction of right atrium forces blood into the right ventricle. * 3. The contractions of the right ventricles forces blood through the Pulmonary artery (only aretery carrying deoxygenated blood) into both lungs. Blood travels through smaller arteries then arterioles and finally the capillaries in single file. The capillaries surround the alveoli and allow the exchange of gases. Oxygenated blood leaves the lungs, first through the venules, then veins returning to the left atrium via the pulmonary vein. * Thus during pulmonary circulation the hearts contractions pump the blood from: • Right Atrium>Right ventricle pulmonary arteries (lead to the two lungs) smaller arteries arterioles pulmonary capillaries (gas exchange/diffusion) venules larger venules pulmonary veins left atrium of heart. Coloring of Veins and Arteries • Pulmonary • Arteries are blue because blood is deoxygenated and the arteries are sending the blood to the lungs and veins going back to heart are red because blood has become oxygenated • Systemic • Arteries leaving heart are red, and veins returning to right ventricle are blue Systemic Circulation • Carries oxygenated blood to the cells from the heart to supply them with oxygen and nutrients and collects their waste such as carbon dioxide and water and brings them back to the heart, • Distance traveled by blood is greater than in pulmonary circulation. • Gas exchange – O2 out of blood, CO2 into blood, occurs in the cells The Contractions of the left atrium push blood toward starting point of systemic circulation into the left ventricle. 4. Contraction of the left ventricle forces the blood through the Aorta and then throughout the body. Arteries branch off the aorta and supply various organs and tissues with oxygenated blood. * During Systemic Circulation the heart contractions pump blood from: Left ventricle aorta smaller arteries arterioles capillaries capillary networks surrounding cells(exchanges/diffusion) venules veins inferior and superior vena cava right atrium of the heart. • Right atrium contracts, pushing blood in it’s chambers back to the starting point of pulmonary circulation (right ventricle) The walls of the left ventricle are thicker (more muscular) than those of the right ventricle because the left ventricle has to push blood into the entire body, whereas the right ventricle only has to push blood as far as the lungs. BLOOD ALWAYS LEAVES THE VENTRICLES, GOES THROUGH THE BODY AND COMES BACK INTO THE ATRIUMS!! Blood Pressure • Measures force with which blood pushes against the walls of the arteries; • It is measured in mm of mercury (mm Hg ) Blood Pressure has two types, Systolic and Diastolic. • Systolic pressure is when the ventricular pressure is at its maximum. During the contractions of the ventricles, the arteries must expand under pressure of the blood that is being pumped out. • Diastolic pressure is when the pressure is at its lowest when the heart is not contracting (at rest). • Blood pressure is represented by the systolic pressure(higher number)/ diastolic pressure(lower pressure); • Normal blood pressure is 113 mm Hg/ 65 mm Hg for adolescents. Incompressibility of Blood • Blood like water is an incompressible fluid, • Liquid will move when pressure is applied to it. • Blood is an incompressible fluid that exerts pressure on the walls of the arteries in which it circulates. This is why it is called blood pressure. Heart rate • What can affect your heart rate? • Activity • Emotions • CO – slows your heart • Drugs Heart Health • A healthy heart needs: movie Heart Health (movie) • If blood pressure is to high, you have Hypertension, to low, Hypotension. • Hypertension is usually caused by a narrowing of blood vessels due to cholesterol build up. How to avoid high blood pressure: Healthy diet, less salt Exercise to lower stress Decrease tobacco and Alcohol consumption Summary movie