Pulmonary Respiration — Chapter 10 Flashcards
Function of the pulmonary respiratory system
- Provides a means of gas exchange between the environment and the body.
- Regulation of acid-base balance during exercise.
Definitions – ventilation and diffusion
Ventilation – the mechanical process of moving air into and out of lungs.
Diffusion – Process by which O2 moves out of lungs into the blood, and CO2 moves from blood into lungs.
Purpose of the different zones of the respiratory system
Divided into 2 functional zones
Conducting Zone:
- Conducts (moves) air through the trachea, bronchi, bronchioles, and terminal bronchioles to the respiratory zone.
- Humidifies, warms, and filters the air (via mucus and macrophages)
No exchange of gases b/t lungs and blood here
Respiratory Zone:
- Exchange of gases between lungs and blood occurs in alveoli of respiratory bronchioles and in alveolar sacs.
How many alveoli are estimated to exist in the lungs?
About 300 million alveoli
Importance of the diaphragm for ventilation
Diaphragm initiates the pressure change inside lungs. It stimulates contraction several times per minute.
Active vs. passive phases of ventilation
Inspiration (Active)
o Lowering the diaphragm expands the volume of the chest cavity, intrapulmonary pressure is decreased (2-3 mmHg below atmospheric pressure of 760 mmHg or 757 mmHg)
o Create a “vacuum”, allows air to flow into the bronchial passages.
Expiration (Passive)
o Diaphragm relaxes, elastic recoil of the alveoli raises the intrapulmonary pressure (about 763 mmHg)
o Air is forced out of lungs
Average tidal volume and breathing frequency for healthy adult
0.5 L x 15 = 7.5 L/min
Alveolar vs. dead-space ventilation
- Alveolar ventilation (Va) (about 0.35 L out of 0.5 L)
o Volume of “fresh air” that reaches the respiratory zone each minute. - Dead Space ventilation (Vd) (about 0.15 L out of 0.5 L)
o Not all air that passes the lips reaches the respiratory zone (remains in conducting zone); this unused ventilation is called dead space ventilation.
Inflammation = increases Vd
Dalton’s law of partial pressures
The total pressure of a gas mixture is = to the sum of the pressure that each gas would exert independently.
o O2 = 20.93 159 mmHg
o CO2 = 0.03 0.3 mmHg
o N2 = 79.04 600.7 mmHg
Total = 100 760 mmHg
Definition of diffusion
Random movement of molecules from high to low concentration.
o Gases diffuse from high to low partial pressure
Definition of diffusion
Random movement of molecules from high to low concentration.
o Gases diffuse from high to low partial pressure
Fick’s law of diffusion – factors that influence gas movement in the body
Rate of gas transfer across tissues depends on :
o Vgas = rate of diffusion
o A = tissue area
o T = tissue thickness
o D = diffusion coefficient of gas
o P1-P2 = difference in partial pressure of the gas on the 2 sides of the tissue