Respiration - Gas Exchange Flashcards
Where does gas move?
from a high to low pressure
How do gases move across concentration gradients?
via diffusion
What is barometric pressure at sea level?
760mmHg
What is partial pressure?
the pressure an individual gas exerts within a mixture. The total pressure of a gas is the sum of all the partial pressures in the mixture.
How can the partial pressure be found?
fraction of gas in mixture x barometric pressure
Pgas = Fgas x Pb
What is the partial pressure of 21% of oxygen in air?
PO2 =0.21 x 760 = 159mmHg
What happens to air in airways?
becomes humidified and warmed with water vapour
What is water vapour partial pressure at body temperature?
47mmHg
How is the partial pressure of oxygen found in the trachea and what is it?
by subtracting the water vapour PP
in Trachea 760-47 (water vapour) therefore 150mmHg
What is the anatomic dead space?
conducting airways
- trachea, bronchi, non-respiratory bronchioles
What happens with each divisions of the respiratory tree?
increase in number
decrease in diameter
increase in surface area
What volume do the conducting airways hold?
150ml
What is a respiratory unit?
a gas exchange unit
respiratory bronchioles, alveolar ducts and alveoli
How many alveolar sacs are present in adults?
300-400 million
What shape is an alveolar sac and what size is it’s diameter?
polygonal, 250 micrometers
What are the cells present in alveoli?
type 1 epithelia (pneumocytesl cells
type 2 epithelial (pneumocytes) cells
macrophages
Describe type 1 epithelial cells
occupy 97% of surface area
primary site of gas exchange
Describe type 2 epithelial (septal) cells
occupy 3% of surface area
produce pulmonary surfactant to reduce surface tension
What makes alveoli perfect for gas exchange?
large surface area 100m2
thin walls 0.5 micrometers
good diffusion
What are the types of circulation found in lungs?
pulmonary
systemic (bronchial)
lymphatic
What is the total blood volume in pulmonary circulation?
500ml
What is the difference in arteries of the pulmonary and systemic?
pulmonary has thinner walls
less resistance
higher compliance
larger diameter
What is the distance between alveoli and red blood cells?
1-2 micrometres
In a pulmonary capillary what are the values of exchange from alveolar air to venous blood?
PO2 100 > 40
PCO2 40 < 46
In a systemic capillary what are the values of exchange from tissues to arterial blood?
PO2 <40 < 100
PCO2 >46 > 40
Why is the pressure gradient for PO2 higher?
O2 is less diffusible than CO2
