Circulation and Gas Exchange

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Circulation and Gas Exchange

• Chapter 42

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Internal Transport

• Gastrovascular cavity makes circulatory system
  unnecessary
• Open and closed circulatory systems
• What are the limits an open circulatory system
  places on an organism?
• What is the difference between an artery and a
  vein?
• Arteries carry blood away from the heart
• Veins bring blood back to the heart

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• Why do veins have valves and arteries do not?
• Veins move blood against gravity without benefit
  of the heart contraction
• Blood flow
• Heart ? arteries ? arterioles ? capillaries ?
  venules ? veins ? heart
• Which chamber of the heart receives the blood?
• Which chamber pumps the blood?

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Vertebrate Circulatory Evolution

• Fish have 2 chambered heart, one beat circuit
• 1 atrium
• 1 ventricle
• Amphibians have 3 chambered heart
• 2 atria
• 1 ventricle
• Reptiles have 3 4 chambered heart
• Septum keeps 2 parts of ventricles separate
• Mammals and birds have 4 chambered heart!

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The Heart

• Cardiac muscle
• Atria have thin walls
• Ventricles have thick and powerful walls
• Systole ventricular contraction blood is pumped
• Diastole ventricular filling
• Lub dub heart sounds opening and closing of the
  valves
• Lub contraction of ventricles (AV closing)
• Dub blood recoiling against Semi Lunar valves
• Heart murmur valve defect

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• CO cardiac output
• Volume of blood pumped/ minute
• SV stroke volume
• Amount of blood pumped by L ventricle/contraction
• CO is effected by heart rate and SV
• Myogenic heart can regulate its own rhythm
• SA node is the pacemaker of the heart

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Arteries and Veins

• How do differences between arteries and veins
  reflect their different functions?
• Artery wall is very thick to absorb pulsation
  from heart
• Veins are wider in diameter and are not as
  muscular
• Veins have valves
• Capillaries have only single layer of endothelium

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Blood Pressure

• The force that blood exerts against vessel walls
• BP is greater in arteries than veins
• Pulse is measure of BP
• Exact BP is measured as systolic/diastolic
  pressures
• Constricted blood vessels have higher BP than
  dilated vessels
• In veins heart has little effect on BP
• How, then does blood move in veins?

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Blood Flow Velocity
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Blood Flow Through Capillary Beds
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Capillary Movement of Fluids
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Lymphatic System

• Lymphatic system returns lost blood to
  circulatory system
• Lymph nodes filter the lymph
• Help fight infection

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How can 1 heartbeat circulate blood through 2
capillary beds?
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What are the advantages and disadvantages of the
amphibian circulatory system?
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Why do endotherms have the greatest need for a 4
chambered heart?
Birds and mammals show convergent evolution of 4
chambered heart!
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