The Heart

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The Heart

• and blood flow

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Heart Facts

• Your heart is about the same size as your fist
• An average adult body contains about five quarts
  of blood (1.25 gallons)
• All the blood vessels in the body joined end to
  end would stretch 62,000 miles or two and a half
  times around the earth.

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Heart Facts continued.

• The heart circulates the bodys blood supply
  1000 times each day
• The heart pumps the equivalent of 5,000 to 6,000
  quarts of blood each day
• The heart beats about 42,075,904 times per YEAR
  imagine a lifetime?

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3 Layers of the Heart

• Pericardium protection, exterior, serous
  membrane
• Myocardium cardiac muscle tissue, involuntary
  contractions
• Endocardium interior layer, lines heart chambers

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Blood Flow

• Pulmonary Circulation carries deoxy-genated
  blood away from the heart, to the lung, and
  returns oxygenated blood back to the heart

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Blood Flow continued.

• Systemic Circulation carries oxygenated blood
  away from the heart, to the body, and returns
  deoxygenated blood back to the heart

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Heart Valves

• Allow blood to flow in only one direction
• Four valves
• -- Atrioventricular valves between atria
  ventricles
• Bicuspid valve or Mitral valve (left)
• Tricuspid valve (right)
• -- Semilunar valves between ventricle and
  artery
• Pulmonary semilunar valve
• Aortic semilunar valve

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Chordae Tendineae

• The chordae tendineae, or heart strings, are
  cord-like tendons that connect the muscles to the
  tricuspid valve and the mitral valve in the
  heart.
• When the right ventricle of the heart contracts,
  the blood pressure pushes the tricuspid valve
  closed and prevents a backflow of blood into the
  right atrium.

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Chordae Tendineae (aka heart strings
heart strings
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The Heart Conduction System

• The heart pumps blood through the body
• This is accomplished by systematic contraction
  and relaxation of the cardiac muscle in the
  myocardium
• Intercalated discs allow impulses to travel
  rapidly between adjacent cells so they function
  as one rather than individual cells

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Cardiac Muscle Tissue
intercalated disc
intercalated disc
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Conduction System Continued.

• Cardiac conduction system The electrical
  conduction system that controls the heart rate
• This system generates electrical impulses and
  conducts them throughout the muscle of the heart,
  stimulating the heart to contract and pump blood.

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Heart Contraction
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Components of the Conduction System

• Sinoatrial Node (Part I)
• located in posterior wall of right atrium near
  entrance of vena cava
• initiates impulses 70-80 times per minute without
  any nerve stimulation
• establishes basic rhythm of the heartbeat
• called the pacemaker of the heart
• impulses move through atria causing the two atria
  to contract .
• at the same time, impulses reach the second part
  of the conduction system

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Components of the Conduction System Continued .

• Atrioventricular Node (Part II)
• located in the floor of the right atrium near the
  septum
• cells in the AV node conduct impulses more
  slowly, so there is a delay as impulse travels
  through the node
• this allows time for atria to finish contraction
  before ventricles begin contracting

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Atrioventricular Bundle

• A.K.A. Bundle of His
• From the AV node, impulses travel through to the
  right and left bundle branches
• These branches extend to the right and left sides
  of the septum and apex of the heart.

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Atrioventricular Bundle Continued.

• These branch a lot to form the Purkinje fibers
  that transmit the impulses to the myocardium
• The bundle of His, bundle branches and Purkinje
  fibers transmit quickly and cause both ventricles
  to contract at the same time

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Atrioventricular Bundle Continued.

• As the ventricles contract, blood is forced out
  through the semilunar valves into the pulmonary
  trunk and the aorta.
• After the ventricles complete their contraction
  phase, they relax and the SA node initiates
  another impulse to start another cardiac cycle.

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1 - Sinoatrial node (SA node) 2 -
Atrioventricular node (AV node) 3 - Common AV
Bundle 4 - Right Left Bundle Branches
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Cardiac Cycle

• The two atria contract at the same time, then
  they relax while the two ventricles
  simultaneously contract.
• The contraction phase of the chambers is called
  systole.
• The relaxation phase is called diastole.
• At a normal heart rate, one cardiac cycle last
  for 0.8 seconds!

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Cardiac Cycle Continued.

• Cardiac Cycle events of one complete heart
  beat
• Mid-to-late diastole (relaxation) blood flows
  into ventricles
• Ventricular systole (contraction) blood
  pressure builds before ventricles contract
  pushing blood out
• Early diastole atria finish re-filling
  ventricular pressure is low

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