37'2: The Circulatory System

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37.2 The Circulatory System

• Section Objectives
• Distinguish among the various components of blood
  
• Trace the route blood takes through the body and
  heart.
• Explain how heart rate is controlled.

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Your Blood Fluid Transport

• It transports O2 and nutrients to cells
• It takes away CO2 and other wastes
• Aids in fighting disease
• Helps maintain body temp.
• Blood composition
• Plasma 55 (liquid part)
• Blood cells 45 (red, white, platelets

• Blood smear

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Red blood cells Oxygen carriers

• Bioconcave disc shaped, most numerous
• No nucleus when mature, last 120 days
• Produced in red marrow of long bones
• contain hemoglobin
• Hemoglobin enables the transport of O2

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White blood cells Infection fighters

• Largest blood cell
• play a major role in protecting your body from
  foreign substances.

White Blood Cells
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Platelets Blood clotting

• Smallest (fragments)
• help blood clot after an injury.
• Short-lived

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Your Blood Vessels Pathways of Circulation
Artery and vein, cross-section

• Arteries carry blood away from heart, thick
  walled elastic, under great pressure
• Veins carry blood toward heart
• Valves in veins prevent the backflow of blood
• Capillaries microscopic, site of exchange
  between blood and body tissue

Capillary
Redbloodcell
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Your Heart The Vital Pump

• Atria upper chamber which receive blood that
  pump blood to
• Ventricles muscular walled chambers which pump
  blood from heart

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Bloods path through the heart

• 1. vena cavae
• 2. right atrium
• 3. valve
• 4. right ventricle
• 5. valve
• 6. pulmonary artery (to lungs)
• 7. pulmonary veins
• 8. left atrium
• 9. valve
• 10. left ventricle
• 11. valve
• 12. aorta largest blood vessel in the body.

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Heartbeat regulation

• surge of blood through an artery is called a
  pulse.
• Pacemaker initiates heartbeat generates an
  electrical impulse that spreads over both atria.

Sinoatrial node (Pacemaker
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Blood pressure

• the force that the blood exerts on the blood
  vessels.
• Blood pressure is measured as systolic
  (ventricles contract) and diastolic (ventricles
  relax) pressures

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Control of the heart

• A portion of the brain called the medulla
  oblongata regulates the rate of the pacemaker,
  speeding or slowing its nerve impulses.
• If the heart beats too fast, the medulla
  oblongata, sends signals that slow the pacemaker.
• If the heart slows down the medulla oblongata
  sends signals to speed up the pacemaker and
  increase the heart rate.

Medulla oblongata