Circulatory System Section 14.1

I. The Circulatory System The circulatory (cardiovascular) system includes the: *heart * blood vessels (arteries, capillaries & veins) *blood

II. Functions Deliver oxygen and food Remove waste (CO2) Fight disease (WBCs) Clot blood (platelets) Pump, pump, pump

III. The Heart Heart Structure 1. Upper receiving chambers – atria 2. Lower pumping chambers - ventricles 3. Septum separates the right and left sides (made of cardiac muscle)

4. Pacemaker: cells on the right atrium which stimulate the heart to contract.

5. Four Valves separate * atria from ventricles * ventricles from vessels leaving the heart.

B. How the heart works Phase 1: Heart relaxes and fills with blood. Phase 2: Heart contracts and pumps blood to the lungs and body. **Why does the LV contract more strongly than the RV?

IV. The Two Loops Loop 1: Back to the heart from the body  to the lungs to get O2  back to the heart

Loop 2: From the heart (aorta)  to the body to deliver O2 (capillaries) then back to the heart (veins)

V. Blood Vessels Arteries 1. Branch off Aorta 2. Have thick muscular walls 3. Carry oxygenated blood away from heart 4. Expand when blood flows through  pulse 5. Become arterioles then capillaries

1. Microscopic, one cell thick walled vessels. B. Capillaries 1. Microscopic, one cell thick walled vessels. 2. Place where deliveries of oxygen and food are made 3. Pick up of waste and CO2 4. Collect to form venules then veins

C. Veins 1. Thin walls 2. Move blood using valves, pressure of blood from behind and muscular squeezing. 3. Carry deoxygenated blood to the heart. 4. Enter heart through superior and inferior _______ ________.

VI. Blood Pressure Blood pressure is the force of blood against the walls of the vessels and is measured by a sphygmomanometer in mm Hg. Normal is 120 (ventricles contract) 80 (ventricles relax)