1. The Circulatory System

2. Circulatory System The Circulatory System has two major subdivisions: 1.The cardiovascular system: The heart 1.The lymphatic system: Pumpless system of vessels and lymphoid organs that aids the cardiovascular system

3. Cardiovascular System

4. Location and Size Location and size: -Approximately the size of a person’s fist, the hollow, cone-shaped heart weighs less than a pound -The heart is located within the bony thorax and is in between the lungs

5. Location and Size Location : -Its more pointed apex is directly toward the left hip and rests on the diaphragm, approximately at the level of the fifth intercostal space -Its base, from which the great vessels of the body emerge, points toward the right shoulder and lies beneath the second rib

6. Coverings and wall The heart is enclosed by a double sac of membrane, the pericardium: -The thin visceral pericardium, or epicardium, tightly hugs the external surface of the heart and is actually part of the heart wall -The fibrous layer, parietal pericardium, helps protect the heart and anchors it to surrounding structures, such as the diaphragm and the sternum

7. Coverings and wall A slippery lubricating fluid is produced by the pericardial membranes: -This fluid allows the heart to beat easily in a relatively frictionless environment as the pericardial layers slide smoothly across each other

8. Pericarditis Inflammation of the pericardium, often results in a decrease in the amount of fluid This causes the pericardial layers to bind and stick to each other, forming painful adhesions that interfere with heart movements

9. Heart Wall - Myocardium The heart walls are composed of three layers: -The outer epicardium, the myocardium, and the innermost endocardium The myocardium consists of thick bundles of cardiac muscle twisted and whorled into ring like arrangement -It is the layer that actually contracts -It is reinforced internally by a dense, fibrous connective tissue network called the “ skeleton of the heart”

10. Heart Wall - Endocardium The endocardium is a thin, glistening sheet of endothelium that lines the heart chambers It is continuous with the linings of the blood vessels leaving and entering the heart

11. Lungs Body cells Our circulatory system is a double circulatory system. This means it has two parts parts. the right side of the system: carries deoxygenated blood away from the heart, to the lungs, and returns oxygenated blood back to the heart the left side of the system: carries oxygenated blood away from the heart to the body, and returns deoxygenated blood back to the heart Pulmonary Circulation: Systemic Circulation

13. Aorta right pulmonary artery Left pulmonary artery Right atrium Left atrium Right ventricle Left ventricle Superior Vena Cava Inferior Vena Cava Interventricular septum right pulmonary veins Left pulmonary veins Tricuspid valve Pulmonary semilunar valve Aortic semilunar valve Bicuspid valve

14. Valves – AV valves The atrioventricular or AV valves are located between the atrial and ventricular chambers on each side The AV valves prevent backflow into the atria when the ventricles contract The left AV valve -Bicuspid (mitral) valve: consist of 2 cusps, or flaps, of endocardium The right AV valve -Tricuspid valve: has 3 cusps Tiny white cords, the chordae tendineae (heart strings), anchor the cusps to the walls of the ventricles

15. Valves – semilunar valves The semilunar valves guards the bases of the two large arteries leaving the ventricular chambers Thus, they are known as the pulmonary and aortic semilunar valves Each semilunar valve has 3 cusps that fit tightly together when the valves are closed When the ventricles are contracting and forcing blood out of the heart, the cusps are forced open and flattened against the walls of the arteries

16. Stage 1 Blood enters the heart through a vein known as the vena cava. The blood is low in oxygen. The first chamber it goes into is the right atrium. Stage 2 The heart pumps the blood from the right atrium into the right ventricle. Stage 3 The heart pumps the blood from the right ventricle through the pulmonary artery towards the lungs. Stage 4 The blood returns from the lungs with lots of oxygen and re-enters the heart through the left atrium. Stage 5 The heart pumps the blood from the left atrium into the left Stage 6 The heart then pumps the blood from the left ventricle out of the heart to the rest of the body through the aorta.

17. Cardiac Circulation In reality, blood enters and exits both sides of the heart at the same time. blood from the body blood from the lungs The heart beat begins when the heart muscles relax and blood flows into the atria.

18. The atria then contract and the valves open to allow blood into the ventricles. The valves close to stop blood flowing backwards. The ventricles contract forcing the blood to leave the heart. At the same time, the atria are relaxing and once again filling with blood.

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