Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Blood transfusion wikipedia , lookup
Autotransfusion wikipedia , lookup
Schmerber v. California wikipedia , lookup
Plateletpheresis wikipedia , lookup
Blood donation wikipedia , lookup
Jehovah's Witnesses and blood transfusions wikipedia , lookup
Hemorheology wikipedia , lookup
Men who have sex with men blood donor controversy wikipedia , lookup
10.4 The Vascular Pathways The circulatory system includes two circuits. • Pulmonary circuit: circulates blood through the lungs • Systemic circuit: circulates blood to the body tissues The Pulmonary Circuit Pulmonary circuit: circulates blood to lungs • Blood from all regions of the body first collects in the right atrium. • Blood passes into the right ventricle, which pumps it into the pulmonary trunk. • Pulmonary trunk divides into right and left pulmonary arteries, which branch into arterioles. • Arterioles take blood to the pulmonary capillaries, where gas exchange occurs. • Blood passes through pulmonary venules, which lead to pulmonary veins that enter the left atrium. The Systemic Circuit Systemic circuit: circulates blood to body tissues. • The aorta and venae cavae serve as the major pathways for blood in the systemic circuit The path of systemic blood to any organ in the body begins in the left ventricle. Trace the path of blood to and from the legs: • left ventricle aorta common iliac artery femoral artery leg capillaries femoral vein common iliac vein inferior vena cava right atrium Blood Pressure As blood passes through the blood vessels in the body, it exerts pressure against the vessel walls (blood pressure). • Systolic pressure: results from blood being forced into arteries when ventricles contract (ventricular systole) • Diastolic pressure: results from pressure in the arteries when ventricles fill with blood (ventricular diastole) o Blood pressure can be measured with a sphygmomanometer, which has a pressure cuff that determines the amount of pressure required to stop the flow of blood through an artery o Expressed in millimetres of mercury as a fraction of systolic pressure over diastolic pressure (e.g., 120/80 mm Hg) Blood pressure decreases as blood flows from the aorta into the arteries, arterioles, and capillaries. • Blood is under minimal pressure in capillaries since capillaries have a high total cross-sectional area. Blood pressure in the veins is low. • Valves prevent the backward flow of blood in veins, and muscle contraction is sufficient to move blood toward the heart. Figure 10.18 Cross section of a valve in a vein. a. Pressure on the walls of a vein, exerted by skeletal muscles, increases blood pressure within the vein and forces the valve open. b. When external pressure is no longer applied to the vein, blood pressure decreases, and back pressure forces the valve closed. Closure of the valve prevents the blood from flowing in the opposite direction.