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The Heart. Cardiology. Physical Characteristics. Situated between the lungs in the mediastinum About the size of a clenched fist Cone or pyramid shape, tilting to the left Apex - inferior portion Base - superior portion. Pericardium - 3 layers. Fibrous pericardium - outer layer

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the heart

The Heart

Cardiology

physical characteristics
Physical Characteristics
  • Situated between the lungs in the mediastinum
  • About the size of a clenched fist
  • Cone or pyramid shape, tilting to the left
  • Apex - inferior portion
  • Base - superior portion
pericardium 3 layers
Pericardium - 3 layers
  • Fibrous pericardium - outer layer
  • Serous pericardium - inner layer
    • parietal layer
    • visceral layer (epicardium)
  • Pericardial cavity - space between the parietal and visceral layers that is filled with pericardial fluid
  • Pericardial fluid - lubrication,reduces friction
heart wall
Heart Wall
  • Epicardium - outermost layer
    • visceral pericardium
  • Myocardium - middle layer
    • cardiac muscle
    • involuntary, striated, short, branched cells
    • intercalated discs
  • Endocardium - inner layer
    • lines the chambers and covers the valves
    • simple squamous epithelium
heart chambers
Heart Chambers
  • Two upper atria ; two lower ventricles
  • Atria are the receiving chambers
  • Ventricles are the distributing chambers
  • Interatrial septum separates atria
  • Interventricular septum divides ventricles
  • Auricles are external flaps
  • Left ventricle very thick
heart valves
Heart Valves
  • Atrioventricular valves
    • tricuspid (right)
    • bicuspid or mitral (left)
    • chordae tendineae
    • papillary muscle
  • Semilunar valves
    • aortic semilunar
    • pulmonary semilunar
    • three pocketlike cusps
valve disorders
Valve Disorders
  • Rheumatic Fever - group A, B-hemolytic Streptococcus pyogenes
  • Heart Mumur
    • stenosis
    • incompetent valves
    • Mitral valve prolapse (MVP)
blood flow through the heart
Blood Flow through the Heart
  • The heart receives blood from the superior vena cava, inferior vena cava and the coronary sinus
  • Right atrium->tricuspid valve->right ventricle-> pulmonary semilunar valve-> pulmonary trunk>pulmonary arteries-> lungs-> pulmonary veins->left atrium->mitral valve->left ventricle>aortic semilunar valve -> aorta
pulmonary systemic circulation
Pulmonary & Systemic Circulation
  • Pulmonary circulation - refers to blood going through the right side of the heart to the lungs
  • Systemic circulation - involves the left heart. Oxygenated blood from the lungs flows into the left atrium, enters the left ventricle, out through the aorta into the body’s tissue, and back via systemic veins to the right atrium
coronary circulation
Coronary Circulation
  • The aorta branches into the left and right coronary arteries
blood flow through myocardium
Blood flow through myocardium
  • Left coronary artery
    • Anterior interventricular artery
    • Circumflex artery
  • Right coronary artery
    • Posterior interventricular artery
    • Marginal artery
  • Arterial anastomoses
venous drainage
Venous Drainage
  • Great cardiac veins
  • Coronary sinus
  • Right atrium
cardiac conduction system
Cardiac Conduction System
  • Sinoatrial (SA) node
    • Pacemaker of the heart
  • Atrioventricular (AV) node
  • Atrioventricular bundle (Bundle of His)
  • Left and right bundle branches
  • Purkinje fibers
  • Modification by the ANS and hormones
electrocardiogram ecg
Electrocardiogram - ECG
  • P wave - atrial depolarization
  • QRS complex - ventricular depolarization
  • T wave - ventricular repolarization
  • Atrial repolarization is masked by the larger QRS complex
arrhythmias abnormal heart rhythms
Arrhythmias Abnormal Heart Rhythms
  • Heart block - blockage in the AV node
  • Tachycardia - >100 beats per minute
  • Bradycardia - <60 beats per minute
  • Fibrillation - uncoordinated quivering
  • Flutter - rapid contractions
  • PVC - premature ventricular contraction
  • PAC - preatrial contraction
terms
Terms
  • Myocardial infarction (MI) - heart attack
  • Infarction - tissue death due to loss of blood supply
  • Ischemia - decreased blood flow causing hypoxia
  • Angina pectoralis - chest pain related to coronary problems
cardiac cycle
Cardiac Cycle
  • Cardiac cycle consists of one complete cycle of contraction and relaxation
  • Contraction phase - systole
  • Relaxation phase - diastole
  • Complete cycle - 0.8 seconds
  • Phases : relaxation period, ventricular filling, ventricular systole
  • Normal heart rate - 75 beats/minute
cardiac output
Cardiac Output
  • CO = Stroke volume x Heart rate
    • Amount of blood passing through a ventricle in 1 minute
  • SV = Amount of blood that is pumped by a ventricle per beat (approx. 70 ml)
  • HR = number of beats per minute
examples
Examples
  • Rest - CO = 70ml/beat x 75 beats/min

= 5250ml/minute

=5.25 liters/minute

  • Exercise -
  • CO = 140ml/beat x 150 beats/min

= 21,000ml/minute

= 21 liters /minute

factors influencing stroke volume
Factors influencing stroke volume

“Frank - Starling law of the heart”

  • Critical factor = stretch of cardiac muscle
  • Preload - how much blood enters a ventricle during diastole
  • Contractility - forcefulness of a contraction
  • Afterload - pressure needed before ventricle ejection occurs
regulation of heart rate
Cardiovascular Center

Medulla

Sympathetic nervous system

Cardiac accelerator nerves

Parasympathetic nervous system

Vagus nerve

Baroreceptors - monitor pressure

aortic arch

carotid arteries

Chemoreceptors - monitor chemicals

aortic/carotid bodies

Hormones, age, fitness,gender

Regulation of Heart Rate