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Flashcards in 5 Overview of the Respiratory System Deck (13)
1

Chest wall

  • Respiratory system consists of...
  • Chest wall includes...

  • Respiratory system consists of...
    • Lungs
    • Chest wall
  • Chest wall includes...
    • Rib cage
    • Thoracic spine
    • All structures attached to the rib cage & thoracic spine
      • Respiratory muscles (including the diaphragm)
      • Other skeletal muscles
      • Fat

2

Parenchyma:
Lungs

  • Divided into lobes, segments, and lobules

3

Airways

  • Upper airways
  • Lower airways
  • Terminal bronchioles
  • Respiratory bronchioles

  • Upper airways
    • Above the vocal cords
    • Nose, mouth, pharynx, larynx
  • Lower airways
    • Below the vocal cords
    • Conducting airways, respiratory airways
  • Terminal bronchioles
    • Each terminal bronchiole provides gas to a separate pulmonary lobule
  • Respiratory bronchioles
    • Each respiratory bronchiole provides gas to a lung acinus

4

Respiratory system

  • Function of the respiratory system
  • This depends on...

  • Function of the respiratory system: "gas exchange"
    • Maintain a normal partial pressure of oxygen (PaO2) & carbon dioxide (PaCO2) in the arterial blood
    • Remove CO2 from and add O2 to the mixed venous blood
  • This depends on...
    • Ventilation: movement of air into and out of lungs
    • Perfusion: movement of blood into and out of lungs
    • Matching of ventilation & perfusion
    • Gas diffusion: movement of molecules along their pressure gradients

5

Ventilation

  • Definition
  • Functions
  • Regulated by...

  • Definition
    • Repetitive movement of gas into and out of the lungs (i.e. breathing)
    • Ventilation = breathing
  • Functions
    • Delivers oxygen to and removes carbon dioxide from the alveoli
    • Controls CO2 excretion by the lungs and therefore regulates the PaCO2
  • Regulated by...
    • Neurons in the medulla, which receive input from the cerebral cortex and from peripheral receptors

6

Ventilation

  • Inspiration
  • Expiration

  • Inspiration
    • Occurs when the respiratory muscles increase the volume of the respiratory system
    • Active proces
  • Expiration
    • Occurs when the elastic recoil of the respiratory system decreases its volume
    • Passive process

7

Perfusion

  • The flow of mixed venous blood from the right ventricle through the pulmonary arteries and the alveolar capillaries
  • Delivers CO2 and removes O2 from the alveoli

8

Ventilation-perfusion relationships

  • Each alveolus receives...
  • The relationship between ventilation and perfusion
  • Ideally, all alveoli should receive...
  • In reality...
  • Ventilation-perfusion relationships are important because...

  • Each alveolus receives...
    • A certain volume of gas (ventilation; V) and blood flow (perfusion; Q) each minute
  • The relationship between ventilation and perfusion
    • The V/Q ratio
  • Ideally, all alveoli should receive...
    • The same amount of ventilation and perfusion
    • I.e. V/Q should be 1.0
  • In reality...
    • There is a range or distribution of V/Q ratios in the lungs
  • Ventilation-perfusion relationships are important because...
    • The V/Q ratio of each alveolus determines the PO2 and PCO2 of the alveolar gas (PAO2, PACO2) in each alveolus
  • Normal vs. lung disease
    • Normally, ventilation and perfusion are well-matched
    • Lung disease produces mismatching between ventilation and perfusion
      • This causes the PaO2 to fall and the PaCO2 to rise as the range or distribution of V/Q ratios increases

9

Diffusion

  • Definition
  • Affected by...
  • O2 & CO2
  • O2
  • CO2

  • The movement of molecules from a region of high to low partial pressure
  • Affected by...
    • Partial pressure gradients
    • Area of contact between alveolar gas and capillary blood
    • Distance for gas diffusion
  • O2 and CO2 move between the alveoli and the pulmonary capillary blood along partial pressure gradients
  • O2 dissolves in and diffuses through the alveolar epithelium, the capillary endothelium, the plasma (where some remains dissolved) and the erythrocyte, where it combines with hemoglobin
  • CO2 diffuses in the opposite direction

10

Diffusion

  • The rate of gas diffusion varies directly with...
  • The rate of gas diffusion varies inversely with...

  • The rate of gas diffusion varies directly with...
    • The contact area between alveolar gas and capillary blood
    • The partial pressure gradient
  • The rate of gas diffusion varies inversely with...
    • Diffusion distance

11

Diffusion

  • Normally,...
  • Lung disease...

  • Normally,...
    • Complete equilibration occurs, so that the alveolar gas and the capillary blood leaving the alveoli have the same PO2 and PCO2
  • Lung disease...
    • Can cause incomplete equilibration, which causes the PaO2 to fall and the PaCO2 to increase

12

Diffusion: O2

  • Once O2 has been added to the arterial blood, it must be transported to the tissues and organs of the body
  • Almost all O2 is carried combined with hemoglobin and a very small amount is dissolved in the plasma
  • In the systemic capillaries, O2 enters cells by diffusing along its partial pressure gradient

13

Diffusion: CO2

  • CO2 is a byproduct of cellular metabolism
  • It diffuses out of cells and into the systemic capillary blood and is then transported back to the lungs
  • Most of the CO2 combines with hemoglobin or is converted to bicarbonate (HCO3), and a small amount dissolves in the plasma
  • In the pulmonary capillaries, CO2 diffuses into the alveolar gas

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