Week 9 Flashcards
Conducting Zone
Anatomical Dead Space
- No gas exchange
- Reinforced with cartilage
- Smooth Muscle regulates diameter
Respiratory Zone
- Gas Exchange
- little cartilage or smooth muscle
Regions in the conducting zone
Larynx, Trachea, primary bronchi, secondary bronchi, tertiary bronchi, bronchioles and terminal bronchioles
Regions in the respiratory zone
Respiratory bronchioles, alveolar sacs
tidal volume
Volume of single breath
Vital Capacity
Limit for inhalation/exhalation
Residual Volume
Conducting zone (about 150 mL) plus minimum volume in alveoli (1L)
Total lung capacity
Vital Capacity + residual volume
Functional Residual Capacity
Volume of conducting zone and alveoli after normal exhalation
How is the fresh air that enters the lungs with each breath determined
tidal volume - dead space volume = about 350 mL at rest
How does functional residual capacity impact the PO2 and PCO2 relative to the outside air
- FRC (about 2000mL at rest) is old air that already underwent gas exchange
- only small fraction of alveolar air is being replaced with each breath because FRC»_space; Vt-Vd
- Causes lower O2 pressure and higher CO2 pressure compared to outside
Calculating total ventillation
Total volume of air flow into the lungs and airways per minute
= tidal volume x breathing frequency
In humans, about 6L/min = 500 mL x 12 / minutes
Calculating Alveolar Ventilation
Total air flow into the alveoli per minute (anatomical dead space doesn’t participate in gas exchange)
= (Vt-Vd) x fR
In humans, 4.2 L/min = (500mL-150mL) x 12/min
How does alveolar ventilation determine gas exchange
- Determines alveolar partial pressures, and thus diffusion rates
- Increasing AV increases the rate at which fresh air enters the FRC in alveoli
Does tidal volume or breathing frequency lead to a greater improvement in gas exchange
Increasing tidal volume produces a greater increase in gas exchange
What muscles are involved in breathing
Diaphragm, intercostal and abdominal muscles
What muscles are involved in inspiration
- Diaphragm contracts, expanding the thoracic cavity downwards
- External intercostal rotate ribs outward and upward
What muscles are involved in expiration
- Passive respiration relies on recoil force
- Active expiration involves the internal intercostals contracting, rotating the ribs in and downward, abdominals push organs against diaphragm to compress thoracic cavity upward
Pleural sac
- Pleural membranes encase the lungs and lines the inside of the thoracic cavity
- The intrapleural space is fully enclosed and fluid filled, creating a flexible lubricated connection between the lungs and chest wall, held together by negative pressure
- connection between thorax and lungs ensuring lungs follow size changes
What creates the negative force in the intrapleural space
the opposing elastic recoil forces of the lungs and the chest walls
Def: elasticity
The tendency of a structure to resume its normal shape after being stretched
Why are there opposing recoil forces between the chest wall and lungs
- Pleura holds structures together
- The lungs are larger than they would normally be
- Chest wall is smaller than normal
- causes recoil forces proportional to the magnitude of stretch applied to these structures
- Fluid in intrapleural space prevents recoiling (hard to compress/expand)
Pneumothroax
Conditions in which air accumulates within the intrapleural space
how will pneumothorax affect intrapleural pressure, lung volume, ventilation and the chest wall?
- Intrapleural pressure = 0 relative to atmosphere
- Decrease in lung volume
- Increase in chest wall
- Intrapleural space increase in size
- Ventilation would stop - no mechanism to increase lung volume
