Blood Flow: Human Heart

Fig c, p.560 superior vena cava (from head, upper limbs) right semilunar valve (shown closed); to the pulmonary trunk right pulmonary veins (from lungs) right atrium right AV valve (shown open) right ventricle (muscles that prevent valve from everting) inferior vena cava (from trunk, legs) septum (partition between heart's two halves) myocardiumheart’s apex arch of aorta trunk of pulmonary arteries left semilunar valve (shown closed); to aorta left pulmonary veins (from lungs) left atrium left AV valve (shown open) left ventricle endothelium and underlying connective tissue inner layer of pericardium

Circuits Systemic (transport of: O 2, CO 2, nutrients, waste), left side Pulmonary (respiratory interface: O 2, CO 2, exchange), right side –heart beats about 100,000 times every day or about 35 million beats per year

Systemic Circuit Longer loop that carries blood to and from body tissues capillary beds of head and upper extremities (to pulmonary circuit) aorta (from pulmonary circuit) heart capillary beds of other organs in thoracic cavity capillary bed of liver capillary beds of intestines

Pulmonary Circuit Short loop that oxygenates blood right pulmonary arteryleft pulmonary artery capillary bed of right lung pulmonary trunk capillary bed of left lung (to systemic circuit) pulmonary veins lungs (from systemic circuit) heart

Direction of Blood Flow 1.Superior and inferior vena cava 2.Right atrium 3.Right ventricle 4.Pulmonary artery (Pulmonary circuit) 5.Pulmonary veins (Pulmonary circuit) 6.Left atrium 7.Left ventricle 8.Aorta 9.Systemic Circuit ( Arteries [elastic], Arterioles, Capillaries, Venules, Veins ). Back to # 1

Figure 19.6

Cardiac Cycle All events associated with one heartbeat two atria contract –while two ventricles relax two ventricles contract –while two atria relax

Fig , p.561 Fluid pressure in filling atria opens AV valves; blood flows into ventricles. Ventricles contract; blood is pumped into the pulmonary artery and the aorta. Atria contract, and fluid pressure in ventricles rises sharply. Ventricles relax even as the atria begin to fill and start another cycle.

Summary Two simultaneous circuits: systemic and pulmonary Ventricles = muscular chambers of the heart that eject blood (aorta, pulmonary arteries) Atria = collecting chambers of the heart that contract to fill the ventricles left side pumps to systemic circuit right side pumps to pulmonary circuit