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PowerLecture:

Chapter 8

Circulation - The Heart

and Blood Vessels

Learning Objectives

List the basic components of the human circulatory system.

Trace the routes of blood flow in the human cardiovascular system.

Look at the structure and function of blood vessels.

Describe the major cardiovascular disorders.

The Cardiovascular System – Moving Blood Through the Body

The heart and blood vessels make up the cardiovascular system.  The cardiovascular system has two major elements:

• (^) The heart is the muscular pump that generates the

pressure required to move the blood through the

body.

• (^) Blood vessels are the distribution tubes of varying

diameters.

 The route of circulation: heart >>> arteries >>> arterioles >>> capillaries >>> venules >>> veins and finally back to the heart.

jugular veins superior vena cava pulmonary veins hepatic portal vein renal vein inferior vena cava iliac veins femoral vein carotid arteries ascending aorta pulmonary arteries coronary arteries renal artery brachial artery abdominal aorta iliac arteries femoral artery Fig. 7. heart

Section 2

The Heart: A Double

Pump

right lung left lung

diaphragm heart

rib cage

1 2 3 4 5 6 7 8 Fig. 7.

© 2007 Thomson Higher Education superior vena cava right semilunar valve right pulmonary veins right atrium right AV valve (opened) right ventricle inferior vena cava septum (partition that divides the heart into two halves) aorta trunk of pulmonary arteries left semilunar valve left pulmonary veins left atrium left AV valve (opened) left ventricle endothelium, connective tissue pericardium Fig. 7. muscles that keep valve from pointing wrong way myocardium

three cusps two cusps left atrioventricular valve (bicuspid or mitral valve) left semilunar valve (between left ventricle and aorta) right atrioventricular valve (tricuspid) right semilunar valve (between right ventricle and pulmonary arteries)

front of chest

Fig. 7.

© 2007 Thomson Higher Education aorta (left pulmonary artery) (left pulmonary veins) cardiac vein left coronary artery (superior vena cava) right coronary artery cardiac vein (inferior vena cava) Fig. 7.

© 2007 Thomson Higher Education superior vena cava right semilunar valve right pulmonary veins right atrium right AV valve (opened) right ventricle inferior vena cava septum (partition that divides the heart into two halves) aorta trunk of pulmonary arteries left semilunar valve left pulmonary veins left atrium left AV valve (opened) left ventricle endothelium, connective tissue pericardium Fig. 7 muscles that keep valve from pointing wrong way myocardium

The Heart: A Double Pump

In a “heartbeat,” the heart’s chambers contract, then relax.  The cardiac cycle is a sequence of contraction ( systole ) and relaxation ( diastole ).

• (^) As the atria fill, the ventricles are relaxed.
• (^) Pressure of the blood in the atria forces the AV

valves open; the ventricles fill as the atria contract.

• (^) When the ventricles contract, the AV valves close,

and blood flows out through the semilunar valves.

Cardiac Cycle

Blood flow follows pressure differences. Valves don’t allow back flow. Arteries expand and return as blood flows (pulse)

Fig. 7. Heart sounds Atria, contract, and fluid pressure in ventricles rises sharply. 1 Fluid pressure in filling atria opens AV valves; blood flows into ventricles 4 Ventricles relax even as the atria begin to fill and start another cycle. 3 Ventricles contract; blood is pumped into the pulmonary artery and the aorta 2

Section 3

The Two Circuits of

Blood Flow