The Lungs & Respiration (Lec 3) Flashcards
Respiratory Structure
- Trachea
- Bronchi
- Bronchioles
- Terminal Bronchioles
- Respiratory Bronchioles
- Alveolar Ducts
- Alveolar Sacs
Conduction Zone
Consists of everything from the trachea to the terminal bronchioles. Function: to transfer air from the outside environment to the alveoli for gas exchange.
Respiratory Zone
Major function is gas exchange. Occurs in the alveoli
Airway Resistance
Airflow= (P1-P2)/Resistance
P1-P2 is the pressure difference between 2 ends of an airway
Pulmonary Ventilation
Definition: Movement of gas into and out of the lungs
• V (with the dot) = volume per unit time (1 min)
• V (dot) = VT x f
Adding subscripts to V (dot): T (Tidal), D (Dead Space), A (Alveolar), I (Inspired), E (Expired)
Anatomical Dead Space
Space occupied by the volume of air not participating in gaseous exchange.
• Dead space = VD
Alveolar Ventilation
Air that reaches the respiratory zone (VA)
• Therefore V = VA + VD
Respiration Subdivisions
- Pulmonary respiration: refers to ventilation (breathing) and exchange of gases (O2 and CO2) in the lungs.
- Cellular respiration: relates to O2 utilisation and CO2 production by the cellular tissues.
Tension/Partial Pressure
Tension Definition = Partial Pressure (the pressure of a specific gas in mixture of gasses)
Diffusion
Random movement of molecules from a high to low area of concentration
The diffusion of gases is dependant upon:
- The partial pressure gradient.
- Inversely proportional to the membrane thickness
- The solubility of gases
Occurs rapidly in the lungs d/t
- Large SA
- Short diffusion distance
- O2 and CO2 tensions in blood leaving the lung is almost in complete equilibrium with O2 and CO2 tension in the lung.
The Respiratory Cycle: Inhalation
Occurs due to the pressure in the lungs being reduced below atmospheric pressure (Boyle’s Law). At rest the diaphragm performs most of the work (75%) for inspiration
The Respiratory Cycle: Exhalation
Expiration =Boyles’ law in reverse. During rest or normal quiet breathing, elastic properties of the lungs and chest wall tend to return to an equilibrium position without necessity for the diaphragm to receive stimulus for relaxation.
– Responsible for 25% of air movement at rest
Factors Affecting Pulmonary Ventilation
Surface tension of alveolar fluid:
– Surface tension must be overcome to expand the lungs during inhalation. Surfactant reduces the surface tension so the lungs don’t collapse at the end of exhalation
Compliance of the lungs:
– How much effort is required to stretch the lungs and chest wall. High compliance = easy
Airway resistance:
– Diameter of the airway (regulated by smooth muscle)
– Walls of bronchioles expand and contract like the lungs
Dalton’s Law
“The total pressure of a gas mixture is equal to the sum of the partial pressures”
• Ptotal = P1 + P2 + P3 + . . .
Fick’s Law of Diffusion
“The rate of gas transfer is proportional to the tissue area, the diffusion coefficient of the gas and the difference in the partial pressure of the gas on the two sides of the tissue and inversely proportional to the thickness”
