Transcript Chapter 8: Cardiovascular system

Chapter 8: Cardiovascular system
• Chapter objectives:
– To learn the structures of the heart and their functions
– To understand the heart’s conduction system
– To learn about the flow of blood through the heart and
body
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Chapter 8: Cardiovascular system
• Functions:
– Supply life-sustaining oxygen and nutrients to the body’s
cells
– Remove metabolic waste products
– Carry hormones from one part of the body to another
• Structures:
– Heart
– Blood vessels
– Lymphatics
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Chapter 8: Cardiovascular system
Heart
• Lies beneath the sternum in the mediastinum, between the 6th
and 7th ribs
• Consists of two pumps: the right side pumps blood to the
lungs, and the left side pumps blood to the rest of the body
• Heart structure
– Pericardium—sac surrounding the heart
• Consists of fibrous pericardium (tough, white, fibrous
tissue) and serous pericardium (thin, smooth inner
portion)
• Pericardial space—space between the fibrous and
serous pericardia; contains pericardial fluid, which
lubricates the heart
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Chapter 8: Cardiovascular system
Heart
• Heart structure (continued)
– Heart wall
• Epicardium—outer layer
• Myocardium—middle layer
• Endocardium—inner layer
– Heart chambers
• Right atrium—receives blood from the superior and
inferior venae cavae
• Left atrium—receives blood from the two pulmonary
veins
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Chapter 8: Cardiovascular system
Heart
– Heart chambers (continued)
• Interatrial septum—separates the right and left atria
• Right ventricle—pumps blood to the lungs
• Left ventricle—pumps blood to all other vessels in the
body
• Interventricular septum—separates the right and left
ventricles
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Chapter 8: Cardiovascular system
Heart
– Heart valves
• Atrioventricular valves:
– Tricuspid valve—prevents backflow from the right
ventricle into the right atrium
– Mitral valve—prevents backflow from the left
ventricle into the left atrium
• Semilunar valves:
– Pulmonic valve—prevents backflow from the
pulmonary artery into the right ventricle
– Aortic valve: prevents backflow from the aorta into
the left ventricle
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Chapter 8: Cardiovascular system
Heart
• Conduction system
– Causes blood to move throughout the body
– Pacemaker cells—specialized cells in the heart with unique
characteristics:
• Automaticity—ability to generate an electrical impulse
automatically
• Conductivity—ability to pass the impulse to the next cell
• Contractility—ability to shorten fibers in the heart when
receiving the impulse
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Chapter 8: Cardiovascular system
Heart
• Conduction system (continued)
– Sinoatrial (SA) node—normal pacemaker of the heart;
results in atrial contraction; generates 60-100
impulses/minute
– Atrioventricular (AV) node—slows the impulse between the
atria and ventricles, allowing time for blood filling before
ventricular contraction
– Bundle of His—conducts the impulse from the AV node;
branches off into right and left bundles
– Purkinje fibers—distal portions of the right and left
bundles; initiate contraction of the ventricles
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Chapter 8: Cardiovascular system
Heart
• Conduction system (continued)
– Safety system
• SA node fails to fire—AV node generates 40-60
impulses/minute
• SA and AV nodes fail—ventricles generate 20-40
impulses/minute
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Chapter 8: Cardiovascular system
Heart
• Cardiac cycle
– Period from the beginning of one heartbeat to the
beginning of the next
– Electrical and mechanical events occur in sequence and to
proper degree to provide blood flow
– Systole—ventricular contraction
– Diastole—recovery period
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Chapter 8: Cardiovascular system
Conduction system
• Cardiac cycle (continued)
– Cardiac output—amount of blood the heart pumps in
1 minute
– Stroke volume—amount of blood ejected with each
heartbeat; affected by:
• Preload—stretching of muscle fibers in the ventricles
• Contractility—ability of the myocardium to contract
normally
• Afterload—pressure needed to overcome the pressure in
the aorta
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Chapter 8: Cardiovascular system
Conduction system
• Cardiac cycle (continued)
– Events of cycle
• Isovolumetric ventricular contraction—tension in the
ventricles increases; AV valves close
• Ventricular ejection—ventricular pressure exceeds aortic
and pulmonary arterial pressures; semilunar valves
open; blood is ejected
• Isovolumetric relaxation—all valves are closed
• Ventricular filing—AV valves open; ventricles fill 70%
• Atrial systole (“atrial kick”)—adds additional 30% of
blood to ventricles
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Chapter 8: Cardiovascular system
Blood flow
• Blood vessels
– Five types:
• Arteries—thick, muscular walls; accommodate higher
speed blood flow and pressure
• Arterioles—thinner walls than arteries; constrict or
dilate to control blood flow to capillaries
• Capillaries—have walls made up of a single layer of
endothelial cells
• Venules—thin walls; gather blood from the capillaries
• Veins—thin walls but large diameters; return blood to
the heart
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Chapter 8: Cardiovascular system
Blood flow
• Circulation
– Three methods to transport blood through the body:
• Pulmonary—unoxygenated blood travels from the right
atrium via the pulmonary arteries, exchanges carbon
dioxide for oxygen at the alveoli level, and transports
oxygenated blood to the left atrium via the pulmonary
veins
• Systemic—oxygenated blood is ejected from the left
ventricle to the aorta, which branches off to other
vessels to transport blood to organs
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Chapter 8: Cardiovascular system
Blood flow
• Circulation (continued)
• Coronary—blood flows out of the heart during diastole
and through the cardiac arteries to nourish heart
muscle
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Chapter 8: Cardiovascular system
Blood flow
– Coronary vessels
• Right coronary artery—supplies the right atrium, most
of the right ventricle, and the inferior part of the left
ventricle
• Left coronary artery—splits into the anterior descending
artery and circumflex artery; supplies the left atrium,
most of the left ventricle, and most of the
interventricular septum
• Coronary sinus—largest coronary vein; opens into the
right atrium; most coronary veins empty into it
• Anterior cardiac veins—do not empty into the coronary
sinus; empty into the right atrium
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins
Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins