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What is the symbol for atmospheric pressure at sea level (also called barometric pressure)?  


  1. What are the two types of gauge pressures?  
  2. What are the specific examples (3)

  1. mm Hg and
    • cm H2O


If PB is 760 mmHg and PA is 755 mmHg   

  • What is the gauge pressure?  

PA  - PB 

  • -5 mmHg



the higher the altitude  what happens with atospheric pressure?

lower the atmospheric pressure


  • How does the animal produce pressure changes in the alveoli?

(what is PA at during the stages of respiration)

  1. PA low  during inspiration
  2. PA high during expiration
  3. PA  zero – during pause or no air flow


What is Boyle’s Law?   

At a constant temperature, the same amount of gas will decrease in volume with an increase in pressure


How is the animal able to change the volume in the lungs and dimensions of the thoracic cavity? (generally 3 ways) 


1. Muscles of ventilation
2. Direction of ribs/thoracic cage movement
3. Ppl (pleural pressure) and PA (alveolar pressure) pressure changes during ventilation 


Which muscles are used for inspiration


  1. Diaphragm
  2. External intercostals
  3. Abductor muscles of nares and larynx


what muscles are used for exhalation

  1. it is passive
  2. Exceptions: coughing and sneezing
    • Internal intercostals
    • Abdominal muscles- Active


fill in for inspiration


fill in for expiration


What is visceral pleura?

serous membrane covering lungs


what is Parietal pleura?

serous membrane covering the thoracic wall


Between parietal and visceral pleura is what

Very thin layer of fluid


  1. what type of pressure is in the interpleural space, positive or negative
  2. how does this happen?

  1. negative
  2. is related to the blood flow in the capillaries of the pleura and the blood-gas tensions within those capillaries


  1. what happens to pleuural pressure during inspiration?
  2. expiration?
  3. what does that change in pleural pressure allow for in the alveoli?

  1. Starts at resting level, goes more negative at inspiration, and
  2. comes back to resting level at the end of expiration
  3. The change in the pleural pressure causes the change in the alveolar pressure which in turns causes the air to flow in, resulting in the change in lung volume 


explain what happens to..... during insipration for most animals (excluding equine)

  1. lung volume
  2. air flow
  3. pleural pressure
  4. alveolar pressure

  1. lung volume- goes up
  2. air flow- goes up and then down
  3. pleural pressure- goes down
  4. alveolar pressure- down then up


what happens to .... during expiration for most animals (excluding equine)

  1. lung volume
  2. air flow
  3. pleural pressure
  4. alveolar pressure

  1. lung volume- goes down
  2. air flow- down then up
  3. pleural pressure- goes up
  4. alveolar pressure- up then down


diagram intrapleural pressure for the horse during inspiration and expiration


diagram alveolar pressure for a horse during inspiration and expiration


diagram air flow for a horse during inspiration and expiration


  1. What is Vt?
  2. IRV
  • where would each of these be on a lung capacity graph?

  1. Vt= Tidal Volume
    • Volume of each breath
  2. IRV -  Inspiratory Reserve Volume
    • Extra Volume That Can Be Inhaled After a Normal Inhalation


  1. What is ERV
  2. RV
  • where would each of these be on a lung capacity graph?

  1. ERV - Expiratory Reserve Volume
    • Extra Volume That Can Be Exhaled After a Normal Expiration
  2. RV -  Residual Volume
    • Volume in the lungs after complete exhalation


  1. What is IC
    • equation?
  2. VC?
    • equation?
  • how are they on a lung capacity graph?

  1. IC = Inspiratory Capacity
    •   IC = VT + IRV
  2. VC = Vital Capacity
    •   VC = IRV + VT + ERV


  1. What is FRC?
    • equation?
  2. TLC?
    • Equation?
  • where are they on a lung volume graph?


What is pleural fluid?

This fluid helps to lubricate parietal and visceral pleura so that there is not a lot of friction, and may act to adhere the two layers gently together. 


What factors are strong collapsing forces within the lung?  

  1. Lung elasticity- Elastic and collagen tissue
  2. Surface tension present at liquid-air interface


  1. between cattle horse and dog which animal has smallest amount of tital volume /kg
  2. middle?
  3. largest?

  1. Cattle - 8 ml / kg
  2. Horse - 12 ml / kg
  3. Dog - 15 ml / kg


Why do cattle have a small tidal volume?

have small chest cavity because of large rumen size