Chapter 20 THE CARDIOVASCULAR SYSTEM: THE HEART

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Chapter 20THE CARDIOVASCULAR SYSTEM THE HEART

• Lecture Outline

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INTRODUCTION

• The cardiovascular system consists of the blood,
  heart, and blood vessels.
• The heart is the pump that circulates the blood
  through an estimated 60,000 miles of blood
  vessels.
• The study of the heart and diseases associated
  with it is known as cardiology.

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Location of the heart

• The heart is situated between the lungs with
  about two-thirds of its mass to the left of the
  midline.
• It is about the size of your closed fist.

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Pericardium

• The heart is enclosed and held in place by the
  pericardium, a membrane.
• It confines the heart in its position in the
  chest
• It also allows movement during contraction
• An inflammation of the pericardium is known as
  pericarditis. It is caused by a virus and causes
  pain. Treatment includes draining fluid through a
  needle.

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Layers of Heart Wall

• The wall of the heart has 3 layers
• Epicardium
• Thin, transparent outer layer
• Myocardium
• cardiac muscle layer is the bulk of the heart,
  it does the pumping
• Endocardium
• Very thin, lines the chambers and vessels

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Chambers and Sulci of the Heart

• Four chambers
• 2 upper atria (right and left atrium)
• 2 lower ventricles (right and left)
• Sulci - grooves on surface of heart containing
  coronary blood vessels and fat

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Right Atrium

• Blood from the body returns to the heart and goes
  into the right atrium.
• This is shown as blue because the oxygen has been
  used up
• Receives blood from 3 sources
• superior vena cava, inferior vena cava and
  coronary sinus

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Right Ventricle

• Blood from the right atrium then flows into the
  right ventricle
• Blood leaves the right ventricle through
  pulmonary valves, it then goes into the pulmonary
  artery to pick up oxygen

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Left Atrium

• Forms most of the base of the heart
• Shown as red because it has oxygen
• Receives blood from lungs through 4 pulmonary
  veins

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Left Ventricle

• Forms the apex (bottom) of heart
• It has oxygenated blood (red)
• Blood from the left atrium flows through the left
  ventricle and into the aorta, where it is pumped
  through the body.

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Myocardial Thickness and Function

• Thickness of myocardium varies according to the
  function of the chamber
• Atria are thin walled, deliver blood to adjacent
  ventricles

• Ventricle walls are much thicker and stronger
• right ventricle supplies blood to the lungs
  (little flow resistance)
• left ventricle wall is the thickest to supply
  systemic circulation

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HEART VALVES AND CIRCULATION OF BLOOD

• Valves open and close in response to pressure
  changes as the heart contracts and relaxes.
• Atrioventricular (A/V)
• Semilunar

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Atrioventricular Valves Open

• A-V valves open and allow blood to flow from
  atria into ventricles when ventricular pressure
  is lower than atrial pressure

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Atrioventricular Valves Close

• A-V valves close preventing backflow of blood
  into atria

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Semilunar Valves

• SL valves open with ventricular contraction
• allow blood to flow into pulmonary trunk and
  aorta
• SL valves close with ventricular relaxation
• prevents blood from returning to ventricles,
  blood fills valve cusps, tightly closing the SL
  valves

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Flow of Blood

• Oxygen enters the body through the lungs
• Pulmonary veins carry it to the left atrium (red)
• It then goes through the left ventricle (red)
• The aorta pumps it into the body through arteries
  (red)
• The body uses up the oxygen (red to blue)
• Blood returns to the heart through veins (blue)
• It enters the right atrium (blue)
• It goes through the right ventricle (blue)
• Then it goes into pulmonary arteries to get more
  oxygen from the lungs and the process starts over
  (blue to red)

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Blood Circulation

• Blood flow
• blue deoxygenated
• red oxygenated
• Heart ? arteries ? arterioles ? capillaries ?
  venules ? veins ? heart

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Project Part 1

• Get a poster. Divide it in half.
• On todays half, draw and color a picture of the
  heart.
• Refer to page 687.
• Include the following
• Both atria and ventricles
• Vena cava
• Aorta
• Pulmonary arteries
• Pulmonary veins

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Autorhythmic Cells The Conduction System

• Cardiac muscle cells are autorhythmic cells
  because they are self-excitable. They repeatedly
  generate spontaneous action potentials that then
  trigger heart contractions.
• These cells act as a pacemaker to set the rhythm
  for the entire heart.
• They form the conduction system, the route for
  propagating action potential through the heart
  muscle.

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Electrocardiogram

• A recording of the electrical changes that
  accompany each cardiac cycle (heartbeat) is
  called an electrocardiogram (ECG or EKG).
• The ECG helps to determine if the conduction
  pathway is abnormal, if the heart is enlarged,
  and if certain regions are damaged.

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THE CARDIAC CYCLE

• A cardiac cycle consists of the systole
  (contraction) and diastole (relaxation) of both
  atria, rapidly followed by the systole and
  diastole of both ventricles.
• Pressure and volume changes during the cardiac
  cycle
• This is what is measured when blood pressure is
  taken.

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Auscultation

• The act of listening to sounds within the body is
  called auscultation, and it is usually done with
  a stethoscope.
• The first heart sound (lubb) is created by blood
  turbulence associated with the closing of the AV
  valves.
• The second heart sound (dupp) represents the
  closing of the semilunar valves.

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CARDIAC OUTPUT

• Cardiac output (CO) is the volume of blood
  ejected from the left ventricle into the aorta
  each minute.
• Cardiac reserve is the ratio between the maximum
  cardiac output a person can achieve and the
  cardiac output at rest.

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Regulation of Heart Rate

• Nervous control from the cardiovascular center in
  the medulla
• Heart rate is also affected by hormones
• And by ions (Na, K, Ca2)
• And by age, gender, diet, physical fitness, and
  temperature

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Clinical Problems

• MI myocardial infarction
• death of area of heart muscle from lack of O2
• replaced with scar tissue
• results depend on size location of damage
• Blood clot
• use clot dissolving drugs streptokinase or t-PA
  heparin
• balloon angioplasty

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Risk Factors for Heart Disease

• Risk factors in heart disease
• high blood cholesterol level
• high blood pressure
• cigarette smoking
• obesity lack of regular exercise.
• Other factors include
• diabetes
• genetic predisposition
• male gender
• high blood levels of fibrinogen (blood clotting
  factor)
• left ventricular hypertrophy

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Desirable Levels of Blood Cholesterol for Adults

• TC (total cholesterol) under 200 mg/dl
• LDL under 130 mg/dl
• HDL over 40 mg/dl
• Normally, triglycerides are in the range of
  10-190 mg/dl.
• Among the therapies used to reduce blood
  cholesterol level are exercise, diet, and drugs.

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EXERCISE AND THE HEART

• A persons cardiovascular fitness can be improved
  with regular exercise.
• Aerobic exercise (any activity that works large
  body muscles for at least 30 minutes, preferably
  3 5 times per week) increases cardiac output
  and elevates metabolic rate.
• Regular exercise also decreases anxiety and
  depression, controls weight.

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Coronary Artery Disease

• Heart muscle receiving insufficient blood supply
• Caused by narrowing of vessels
• Risk factors for development of CAD include high
  blood cholesterol levels, high blood pressure,
  cigarette smoking, obesity, diabetes, type A
  personality, and sedentary lifestyle.
• Treatment
• drugs, bypass graft, angioplasty, stent

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Arrhythmia

• Arrhythmia (disrhythmia) is an irregularity in
  heart rhythm resulting from a defect in the
  conduction system of the heart.

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Congestive Heart Failure

• Congestive heart failure is a chronic or acute
  state that results when the heart is not capable
  of supplying the oxygen demands of the body.
• Causes of CHF
• coronary artery disease, hypertension, valve
  disorders, congenital defects
• Left side heart failure
• less effective pump so more blood remains in
  ventricle
• heart is overstretched even more blood remains
• blood backs up into lungs as pulmonary edema
• suffocation lack of oxygen to the tissues
• Right side failure
• fluid builds up in tissues as peripheral edema

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Murmurs

• A heart murmur is an abnormal sound that consists
  of a flow noise that is heard before, between, or
  after the lubb-dupp or that may mask the normal
  sounds entirely.
• Some murmurs are caused by turbulent blood flow
  around valves due to abnormal anatomy or
  increased volume of flow.
• Not all murmurs are abnormal or symptomatic, but
  most indicate a valve disorder.

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Project Part 2

• On the other side of your poster, you will
  describe a cardio vascular disease or disorder.
• Include the following
• Name of disease
• Type of disease (genetic, dietary etc)
• Risk Factors
• Population Affected
• Signs/Symptoms
• Treatments
• Prognosis

• Disease by Last Name
• A ? Heart Murmurs
• B ? Arrhythmias
• C ? D Heart Attack (MI)
• F ? K Hypertension
• L ? M Coronary Artery Disease
• N ? P Arteriosclerosis
• R ? S Congenital Heart Defects