Intro to Respiratory Physiology - Trachte Flashcards
What are the four basic components of Respiratory Physiology?
- Ventilation
- Perfusion
- Diffusion
- Exchange
How do gasses move across the blood-gas interface?
Diffusion
(high pressure → low pressure)
What is the driving force of oxygen in diffusion?
- Partial pressure air > Partial pressure blood
- Air = 150 mmHg (humidified)
- Venous blood = 40 mmHg
- Moves from AIR → BLOOD via diffusion
What is the driving force of carbon dioxide in diffusion?
- Partial pressure blood > Partial pressure air
- Venous Blood = 46 mmHg
- Air = 0 mmHg
- Moves from BLOOD → AIR by diffusion
Gases move across the capillary/alveolar barrier depending on what?
- Cross-sectional area of the barrier (50-100 m2)
- tons of blood vessels surrounding alveoli
- greater surface area → greater potential for diffusion
- more vasculature → more efficient exchange
- Inversely proportional to the thickness of barrier
- thicker barrier → less diffusion
- thinner barrier → more permeable
- CO2 is more permeable than O2
What are conducting airways?
- Branched tubes that conduct air but are not involved in gas exchange
- They comprise anatomic “dead space”
- have gas concentrations similar to atmosphere, except that air is humidified
What are the conducting airways composed of?
- Trachea
- Right & Left bronchi
- Lobar bronchi
- Segmental bronchi
- Eventually → Terminal bronchioles
- smallest airways without alveoli
What is the typical volume of air that the conducting airways hold?
150 mL
What is the volume of a normal breath?
500 mL
Can you think of clinical examples that are the equivalent of a longer neck?
Intubated patient
tube → increases dead space
What is the respiratory zone?
- Acinus
- terminal bronchioles divide into → respiratory bronchioles
- occasional alveoli
- respiratory bronchioles lead to → alveolar ducts
- completely lined with alveoli
- terminal bronchioles divide into → respiratory bronchioles
What is airflow initiated by?
- Expansion of thoracic cavity
- Diaphragm contracts (moves downward)
- Intercostals contract (raises ribs)
Where does dust settle in the respiratory tract if inhaled?
Terminal bronchioles
(not alveoli)
Why is the lung so easy to expand?
Very compliant!
- Lungs are balanced between chest wall
- helps with compliance to volume change
- Compliance = change in volume/change in pressure)
How much of the body’s total metabolic work is spent on breathing?
15%
(this is why COPD patients get so tired)
What is the path of blood flow in the lungs?
- Pulmonary artery (O2 poor) →
- Capillaries →
- Pulmonary Vein (O2 rich)
Because the capillaries in the lungs have extremely thin walls, they are at increased susceptibility to damage from what processes?
- Increasing capillary pressure
- e.g. pulmonary HTN
- Increasing alveolar pressure
- e.g. tension pneumothorax
***The capillaries have the same amount of flow through them as the pulmonary artery/vein, but with much less resistance!
How long do RBCs spend in the pulmonary capillaries?
less than a second
Alveoli are 500 million bubbles and surface tension should make them want to collapse when they are small, but a really important mechanism keeps them from doing so. What is it?
Lung surfactant
- reduces surface tension and prevents alveolar collapse
- Surfactant = nonpolar tail + polar head
- prevents water molecules from attracting each other → decreases Tension
- develops at 7 months gestation
- Surfactant = nonpolar tail + polar head
What are the three mechanisms to eliminate unwanted inhaled particles?
- Can be filtered (nose)
- Can be moved toward the mouth by a mucous-ciliary elevator (inhibited by cigarrete smoke)
- Can be engulfed by macrophages (typically in alveoli)
