The Circulatory System

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The Circulatory System
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Idea that blood circulates in the body dates back
to the 1620s and English physician William
HarveyBlood vessels form closed delivery
system that begins and ends with the heart
transporting blood 60,000 miles (the Earth has a
circumference of 24,902 miles) Includes
50,000,000,000 capillaries
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Functions of the Peripheral Circulatory System

• Carries blood from heart to tissues to heart
• Exchange nutrients, waste products and gases
  w/tissues
• Transports substances (hormones, components of
  immune system, coag. Agents, NZs, nutrients,
  gases, waste products, etc.
• Helps regulate blood pressure
• Directs blood flow to tissues when required to
  maintain homeostasis

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Vessels In Sequence

• ELASTIC ARTERIES
• MUSCULAR ARTERIES
• ARTERIOLES
• CAPILLARIES
• VENULES
• SMALL VEINS
• MEDIUM/LARGE VEINS

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General Features of Blood Vessels
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Tunics- the details

• Tunica Intima
• innermost layer smooth surface of endothelium
  enables ease of blood flow
• Tunica Media
• middle layer of smooth muscle cells arranged
  circularly with variable amounts elastic and
  collagen fibers elastic connective tissue in
  muscular arteries
• Tunica Externa or Adventitia
• outer layer of connective tissue

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Action of Smooth Muscle

• Long, narrow, tapered muscle cells arranged
  circularly that contract and relax slowly so not
  to affect heart action but control size of blood
  vessel lumen
• Vasoconstriction- narrows lumen
• Vasodilation- enlarges lumen
• WHY?

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Specialized Features of Blood Vessels

• Arteries- conduct blood under high pressure have
  thick strong walls
• a. elastic arteries-
• b. muscular arteries-
• c. arterioles-

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• 2. Capillaries- allow greater surface area and
  slows speed of blood so exchange can take place

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• 3. Veins- return blood to heart under low
  pressure

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• YouTube - Mechanism of Vein

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Physiology of Circulation

• Pulse- wave of pressure that begins in the
  ventricles and travels through the arteries
• PULSE RATE HEART RATE
• Can be measured in any artery close to body
  surface compress artery against firm tissue

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• Assess
• Rate
• Regularity
• Strength
• Normal- 70-76 bpm in resting person
• Factors Influencing Pulse-
• activity
• postural changes
• emotions

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Blood Pressure

• The pressure the blood exerts against the inner
  walls of blood vessels
• It is the force that keeps the blood circulating
  between heartbeats

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• In other words

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• Any system equipped with a pump that forces fluid
  through a network of closed tubes operates under
  pressure.
• The closer you get to the pump, the higher the
  pressure.
• Blood pressure understood to mean the pressure
  within the large systemic arteries near the heart

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Principles that determine pressure and flow
include

1. The heart-
   
2. Size of the vessel-
3. Speed vs. Pressure-
4. Constriction-

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• YouTube - Blood Pressure