The Heart

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The Heart

• At the very heart of things is your heart

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• The heart is the pump of the circulatory system
• Functions of circulatory system
• Blood carries oxygen and nutrients to cells
• Carries waste products away

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Organs of the circulatory system

• Heart-
• Arteries
• Thick walled
• Veins
• Thin walled
• Capillaries
• Walls are one cell thick to permit the exchange
  of gas, waste

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• Arteries carry blood away from the heart
• Veins carry blood back to the heart
• There are two major blood circuits
• General (systemic) circulation throughout the
  body
• Cardiopulmonary from heart to lungs, and back

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• Location Thoracic cavity, middle of chest.
  Between the lungs, above the diaphragm
• About the size of a closed fist
• 5 inches long, 3.5 wide, weighing less than a
  pound

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Structure

• Encased in the pericardium- double layer of
  fibrous tissue. Between the layers is a
  lubricating fluid called pericardial fluid
• Myocardium- cardiac muscle tissue
• Septum- a thick muscular wall separating the
  right half from the left

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• Two upper chambers are the atria- right atrium
  and left atrium
• Two lower chambers are the ventricles- right and
  left.
• The deoxygenated blood enters the right side of
  the heart through the superior and inferior vena
  cava

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• Tricuspid valve located between the right atria
  and ventricle. Cordae tendinae keep it closed.
• Blood flows from the right ventricle through the
  pulmonary artery. The pulmonary semi-lunar valve
  keeps blood from flowing back into the ventricle
• Pulmonary artery takes deoxygenated blood to the
  lungs

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The return trip

• Oxygenated blood is carried back from the lungs
  via the pulmonary veins- right and left.
• Both deposit oxygenated blood into the left
  atria. When this blood flows into the left
  ventricle, it is the bicuspid valve that snaps
  shut between the left atria and ventricle

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• Oxygenated blood leaves the left side of the
  heart through the massive contraction of the left
  ventricle, via the aorta. The aortic semi-lunar
  valve keeps blood flowing in the right direction
• Aorta is the bodys largest vessel-about the size
  of a garden hose!

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• The heart is a side-by-side double pump with 4
  chambers. Each time the right ventricle contacts
  to send blood to the lungs pulmonary artery, the
  right ventricle contracts sending blood into the
  aorta.
• The familiar lubb-dupp are the valves closing

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Control of heart contractions

• A heart removed from the body will continue to
  beat- the heart has tissue which controls its own
  beating!
• This group of tissue is where the superior vena
  cava joins the right atrium- called the
  sinoatrial node or pacemaker

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• The SA node sends out an electrical signal- atria
  contract or depolarize.
• Signal travels from the SA node to the AV node,
  down through the AV bundle. AV bundle further
  divides into smaller units-Perkinje fibers.
  Ventricles contract.

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• Contraction depolarization systole
• Relaxation repolarization diastole
• The cardiac cycle takes 0.8 seconds- the average
  heart beats 72-80 times per minute

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• The electrical activity can be tracked with an
  electrocardiogram, a.k.a. EKG or ECG
• P wave atrial depolarization
• QRS ventricular depolarization
• T wave ventricular repolarization

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• Diagnostic tests
• Cardiac catheterization- uses a catheter to
  deliver dye to hearts vascular system
• Stress test- EKG on a treadmill
• Echocardiogram
• Holter monitor
• Troponin, CPK and LDH enzymes

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Symptoms of heart disease

• Arrhythmia- irregular heart beat
• Bradycardia- slow heart beat lt60 beats/min
• Tachycardia- rapid heart beat gt100 beats/min
• Murmur-defect in the valves of the heart
• Systolic murmur
• Diastolic murmur

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Heart disease

• Myocardial infarction, a.k.a an MI or heart
  attack, is caused by a lack of blood to the heart
  muscle -the myocardium
• Causes arteriosclerosis (hardening of the
  arteries)
• Arteriolosclerosis collagen
• Atherosclerosis cholesterol plaque

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• Result damage to the heart muscle due to lack of
  oxygen
• Symptoms crushing, severe chest pain radiating
  to the left shoulder, arm, neck and jaw. Nausea,
  increased perspiration, fatigue and dyspnea.
• Treatment clot dissolving drugs such as tPA
  (tissue plasminogen activator), anticoagulants
  and digitalis
• Angioplasty and bypass surgery may be considered