5 Once leaving the heart, the blood must make its way back: Left Ventricle Aortic Semilunar Valve Aorta Arteries Arterioles (O2) Systemic Capillaries (Gas Exchange: O2 /CO2)Venules (DeO2) Veins Superior & Inferior Vena Cavae (Cava-s) Right Atrium
6 Differences in Vessels Arteries (“A” for “away”)ALWAYS carry blood AWAY from the heartUSUALLY carry oxygenated bloodHave thicker walls than veinsVeinsALWAYS carry blood TO the heartUSUALLY carry deoxygenated bloodHave valves
7 Differences in vessels, cont’d Capillaries:Exchange O2 for CO2 at body cells and CO2 for O2 at the lungsAre microscopic, walls only one cell thick--allowing for the above
8 Arteries usually carry oxygenated blood, veins usually carry deox - what’s the exception? Heart pulmonary artery(deO2) pulmonary arterioles (deO2 ) capillaries of lungs, where blood becomes oxygenatedCapillaries of Lungs pulmonary venules (O2) pulmonary veins (O2) heart
9 Finalize the loopNow that you have been introduced to all components of the circulatory loop, put them all together to show exactly where blood travels.Indicate whether the blood is oxygenated (O2) or deoxygenated (DeO2) and where gas exchange occurs.
10 The Loop Right Atrium (deoxygenated) Tricuspid Valve Right Ventricle Pulmonary Semilunar ValvePulmonary ArteryPulmonary ArteriolesPulmonary Capillaries (CO2 dropped off O2 picked up)Pulmonary Venules (oxygenated)Pulmonary Veins>>>>Left AtriumBicuspid/Mitral ValveLeft VentricleAortic Semilunar ValveAortaSystemic ArteriesSystemic ArteriolesSystemic Capillaries (O2 dropped off, CO2 picked up)Systemic Venules (deoxygenated)Systemic VeinsSuperior/Inferior Vena Cava
13 Looking at this loop…Why do you think that it is important that arteries have thicker walls than veins?Arteries have thicker walls to withstand the high pressure of the blood coming from the heart -- caused by the heart’s contractions.
15 Looking at this loop…Why do you think that it is important that veins have valves?By the time blood reaches the veins, its velocity and pressure have decreased. Valves prevent the backflow of blood.
17 Blood return to the heart is affected by ValvesA strongly beating heartAdequate arterial blood pressure“Milking action” of skeletal muscle contractionChanging pressures in the chest cavity caused by breathing
18 The heart & blood vessels are important in supplying the cells of the body with O2. But… What about the cardiac tissue itself? How does the heart get the O2 that it needs?