bio 7.4 - circuits and cross-sectional area

pulmonary circuit

• heart and lungs

• brings CO2 blood to lungs for clearing and O2 blood back to heart

• R.V. → pulmonary trunk → pulmonary arteries → lung capillaries → pulmonary veins → left atrium

systemic circuit

• carried O2 blood to the body tissues and returns CO2 blood to heart

• Vena cava → R.A → tricuspid valve → R.V. → pulmonary valve → pulmonary artery → lungs → pulmonary veins → L.A. → mitral valve → L.V. → aortic valve → aorta → body tissues

total Cross Sectional Area

• sum of cross-sectional area of all blood vessels of one type

• has major effect on blood flow

• as CSA increases, velocity of blood decreases

velocity of blood flow

• decreases from arteries to arterioles to capillaries

• increases from venules to veins

CSA and blood pressure

• as CSA increases, blood pressure decreases

• once blood pressure is lost in capillaries, it cant be regained even though CSA of individual venules and veins increases