Human Physiology Lesson 13- Heart Dissection

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Human Physiology Lesson 13- Heart Dissection
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Heart Dissection
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The human mass transport system

• In human mass transport, materials are carried
  mainly by blood through the circulatory system
• The heart forces blood through blood vessels
• Substances are exchanged between the blood and
  the tissues

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Introduction to the heart

• The heart is the organ that supplies blood and
  oxygen to all parts of the body
• It is the size of a clenched fist, weighs about
  10.5 ounces and is shaped like a cone
• The heart is located in the chest cavity, behind
  the breast bone, between the lungs and above the
  diaphragm

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Intact Heart

• This shows the pig heart from the front, with the
  portion on the right of the picture being the
  left side of the heart and vice versa.
• The aorta is clearly visible at the top, with an
  atrium on either side, while the ventricles are
  in the bottom left.

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Dissection

1. Find the 4 holes in the heart
2. Place your finger in them to enlarge them
3. With the 4 holes facing away from you, place the
   heart on the dissecting plate.
4. Have the two larger holes facing the back
5. Sketch the heart as you see it now
6. Place your fingers in the two large holes, what
   do you feel?
7. You should see a line moving from bottom left to
   top right in on the front. CUT DEEPLY INTO THIS
8. Open up the two halves
9. What do you see? Sketch the valves
10. About a third of the way up, where you see the
    valves, cut shallowly across the heart from the
    middle outwards

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• The left and right sides of the heart are
  separated by the inter-ventricular septum
• Walls of right ventricle are 3x thinner than the
  left and it produces less force and pressure in
  the blood
• WHY?
• The blood has less far to travel and the lower
  pressure in the pulmonary circulation means that
  less fluid passes from the capillaries to the
  alveoli

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The first incision

• is along the right ventricle.
• The right ventricle can be identified by
  squeezing the heart, since the myocardium on the
  right side is much less rigid than that of the
  left ventricle.
• This allows us to see the tricuspid valve and the
  right ventricular outflow tract which includes
  the pulmonary valve.

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Longitudinal Cut

• The right ventricle has been cut open from the
  bottom towards the top.
• In this picture, the myocardium is being held
  back. My finger is stuck underneath one leaflet
  of the tricuspid valve, which leads to the
  pulmonary valve.

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The Tricuspid Valve up close

• The tricuspid valve allows blood to flow from the
  right atrium into the right ventricle.

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Pulmonary Valve

• When the heart is contracting, the pulmonary
  valve is open because the blood pushes the cusps
  out of the way.
• After contracting, the ventricles begin to relax
  and the pulmonary valve closes and prevents
  back-flow (called regurgitation) of blood into
  the ventricle.

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The Left Ventricle

• This longitudinal incision extends from the
  bottom to the top of the left ventricle, then
  continues up into the atrium to allow us to view
  the entire left heart.

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The Mitral (bicuspid) valve

• The mitral valve prevents blood from flowing back
  into the left atrium
• The mitral valve is positioned between the atrium
  (at top) and ventricle (at bottom).

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Left Ventricular Outflow

• Blood flows into the ventricles by passing
  through the mitral valve, but can you see where
  it flows out? This is a bit of a trick question
  because the outflow tract is hidden behind the
  mitral valves

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The Human Heart