Structure and Function of the Heart

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Structure and Function of the Heart

• Pathophysiology
• October 11, 2004

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Heart Facts

• Put your hand on your heart. Did you place your
  hand on the left side of your chest? Many people
  do, but the heart is actually located almost in
  the center of the chest, between the lungs. It's
  tipped slightly so that a part of it sticks out
  and taps against the left side of the chest,
  which is what makes it seem as though it is
  located there.

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• Your heart beats about 100,000 times in one day
  and about 35 million times in a year. During an
  average lifetime, the human heart will beat more
  than 2.5 billion times.
• The aorta, the largest artery in the body, is
  almost the diameter of a garden hose.
  Capillaries, on the other hand, are so small that
  it takes ten of them to equal the thickness of a
  human hair.

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• Your body has about 5.6 liters (6 quarts) of
  blood. This 5.6 liters of blood circulates
  through the body three times every minute. In one
  day, the blood travels a total of 19,000 km
  (12,000 miles)--that's four times the distance
  across the US from coast to coast.
• lub-DUB, lub-DUB, lub-DUB. Sound familiar? If you
  listen to your heart beat, you'll hear two
  sounds. These "lub" and "DUB" sounds are made by
  the heart valves as they open and close.

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Heart Anatomy

• Location mediastinum
• Surrounded by pericardial sac
• Composed of cardiac muscle
• Epicardium contains lubricating fluid to
  faciliate heart movement
• Mycardium is the cardiac muscle
• Endocardium is the inner layer that forms heart
  valves

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External Structure

• Four chambers
• 2 Upper Atria
• Blood enters the heart
• 2 Lower Ventricles
• Blood leaves the heart
• Two halves separated by the septum

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Internal Structure

• Atrioventricular (AV) valves separate the atria
  and ventricles
• Right tricuspid
• Left mitral (bicuspid)
• Semilunar valves at the exits of the aorta and
  pulmonary artery

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Blood Flow (Right side)

• Deoxygenated blood enters through the VENA CAVAE
• Passes through the RIGHT ATRIUM
• It then passes through the TRICUSPID VALVE and
  enters the RIGHT VENTRICLE
• It leaves the heart through the PULUMONARY
  ARTERIES where it goes to the lungs to pick up
  OXYGEN

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Blood Flow (Left side)

• Oxygen rich blood enters the heart through the
  PULMONARY VEINS
• It passes through the LEFT ATRIUM
• It moves through the MITRAL VALVE and enters the
  LEFT VENTRICLE
• It will leave the heart through the AORTA to
  deliver oxygen rich blood to the body

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Conduction System

• Electrical impulses from your heart muscle cause
  it to beat (contract).
• This electrical signal begins in the sinoatrial
  (SA) node, located at the top of the right
  atrium. The SA node is sometimes called the
  heart's "natural pacemaker."
• When an electrical impulse is released from this
  natural pacemaker, it causes the atria to
  contract.
• The signal then passes through the
  atrioventricular (AV) node. The AV node checks
  the signal and sends it through the muscle fibers
  of the ventricles, causing them to contract.

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The Heartbeat Two pumping Action

• When the SA Node causes the atria to contract,
  blood is pushed through the tricuspid and mitral
  valves into the resting ventricles.
• This part of the two-part pumping phase (the
  longer of the two) is called the diastole.

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• The second part of the pumping phase begins when
  the ventricles are full of blood. The electrical
  signals from the SA node travel along a pathway
  of cells to the ventricles, causing them to
  contract. This is called systole.