Human Anatomy and Physiology

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Human Anatomy and Physiology

• Respiration Gas exchange

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Gas transfer systems
External respiration
Internal respiration

• Components
• 1. Breathing
• 2. Respiratory diffusion
• 3. Bulk transport
• 4. Cellular diffusion

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Daltons Law

• PT P1 P2 P3 etc.
• Therefore each gas has a partial pressure (pgas)
• Pgas of total mixture

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Daltons Law

• Atmospheric air

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Henrys Law

• Gases dissolve into liquid in proportion to their
  partial pressure
• Equilibrium will be reached (e.g. gases in the
  lung)

Gas state (lung)
Liquid state (blood)
100
(fast)
300
250
(slower)
150
(no movement)
200
200
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Gas solubility

• Factors effecting
• Temperature (not in humans)
• Solubility of gas
• Air CO2 gt O2(20th) gt N2 (1/2)
• Would humans survive if air had more CO2 than O2?

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Alveolar gases

• At any point in time air in alveoli contains
• Less O2, more CO2 H2O

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Why is gas composition different?

• O2 diffuses into blood, CO2 in opposite direction
• Humid air in conductive pathway
• Air in alveoli a mixture of air from more than
  one breath
• How can humans alter gas composition?
• Increase rate and depth of breathing

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Vascular circuits

• Systemic
• Coronary
• Pulmonary
• Bronchial to lungs from heart

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Gas pressure gradients
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Pressure gradients

• Oxygen
• pO2 in deoxygenated blood is 40 mmHg
• pO2 in alveoli is 104 mmHg

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Pressure gradients

• Carbon dioxide
• pCO2 in alveoli is 40 mmHg
• pCO2 in deoxygenated blood is 45 mmHg

5
64
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Pressure gradients

• Relatively the same amount of O2 and CO2 are
  exchanged. Why?
• Answer Solubility

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Surface area

• Why is surface area important?
• Surface area in a human lung is 70m2
• Factors decreasing surface area
• Emphysema (volume unchanged)
• Tumors, mucus

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Ventilation-perfusion coupling
vasoconstriction
Low ventilation Well perfused
Poor ventilation Poor perfusion
vasodilation
High ventilation Poor perfusion
High ventilation High perfusion
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Gas transport in blood

• Methods of transport
• Dissolved in plasma (3 ml per liter)Problem
  C.O. would need to be 80 l/min
• Bound to a respiratory pigment (Hb)(200 ml per
  liter)
• Solution Hb carries both O2 and CO2
  simultaneously

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Hemoglobin structure
O2
CO2
Oxy vs. deoxyhemoglobin
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Oxygen transport in blood

• The term percent saturation
• Deoxyhemoglobin Hb is 75 saturated

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Hb-O2 affinity

• Decreasing affinity
• Decrease in pH (Bohr effect)
• Binding to 2,3 diphosphoglycerate
• Elevated temperature
• Increase in pCO2

75
55
pO2
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Oxygen transport

• Hypoxia inadequate O2 to tissues
• Anemic few RBCs
• Ischemic impaired or blocked blood circulation
• Histotoxic body cells unable to use O2 even
  though enough delivered (cyanide)
• Hypoxemic reduced arterial pO2 (CO2 poisoning)

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CO2 transport

• Ways to transport
• Dissolved in plasma (7 - 10)
• Bound to Hb (20 - 30)
• Bicarbonate ion (60 - 70)

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CO2 transport from tissue
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CO2 transport into lungs