Lung ventilation and introduction to the respiratory system Flashcards
Which parts of the respiratory system make up the conducting portion?
- Nasal cavity
- Pharynx
- Larynx
- Trachea
- Primary bronchi
- Secondary bronchi
- Bronchioles
- Terminal bronchioles
Which parts of the respiratory system make up the respiratory portion?
- Respiratory bronchioles
- Alveolar ducts
- Alveoli
What do we mean by anatomical dead space within the respiratory system?
- The volume of air in the conducting airways
What do we mean by alveolar dead space within the respiratory system?
- Air in alveoli (not perfused or damaged) which do not take part in gas exchange
Tidal volume =
- Anatomical dead space + alveolar ventilation
- It’s the volume of air being moved
Total pulmonary ventilation =
Tidal volume x respiratory rate
Alveolar ventilation =
(Tidal volume - dead space) x respiratory rate
What is the normal value for respiratory rate?
- 12-20 breaths per minute
Define respiration
- The exchange of oxygen and carbon dioxide across a membrane either in the lungs or at the cellular.
Define ventilation
- Ventilation is the process of inspiration and expiration
- The physical action of breathing and moving air into and out of the lung.
How do we move air into and out of the lungs?
- Air flows from an area of higher pressure to an area of lower pressure.
What happens to the lungs as we breathe in?
- Ribs move up and out due to contraction of intercostal muscles.
- Diaphragm flattens
- Intrathoracic volume increases
- Intrapulmonary pressure decreases
- Elastic tissue in alveoli is stretched
What happens to the lungs as we breathe out?
- Ribs fall due to relaxation of intercostal muscles.
- Diaphragm moves up
- Volume of thoracic cavity decreases and volume of lungs reduces.
- Pressure in chest increases until it is equal to atmospheric pressure.
- This is passive
What are the pleurae of the lungs?
- A pair of serous membranes lining the thorax and enveloping the lungs.
- Parietal pleura lines the inside of each hemi-thorax
- Visceral pleura lines the outside of the lung
What is the intrapleural space?
- Intrapleural space = space between visceral and parietal pleura - contains 15ml fluid
-Looks like a shiny member over the lung
What is the pleural seal?
- Surface tension between the pleural surfaces created by the presence of thin film of pleural fluid
- This holds the outer surface of the lung to the inner surface of the chest wall.
Outline the importance of negative intrapleural pressure in the lungs
- It remains negative throughout inspiration and expiration relative to atmosphere and intra-alveolar pressure.
- This keeps the alveoli and lungs from fully collapsing with each expiration.
What creates a negative pressure within the intrapleural space?
- Lungs have a natural inward elastic recoil while the chest wall has a natural outward elastic recoil.
What is the functional residual capacity (FRC)?
- Volume of air at resting expiratory level - i.e. the volume of air that remains in the lungs after we have breathed in and out.
Describe how the intrapulmonary pressure and intrapleural pressure changes during breathing
- Inspiration - intrapulmonary pressure negative relative to atmosphere.
- Expiration - intrapulmonary pressure positive relative to atmosphere.
- Intrapleural pressure stays negative throughout
What is transpulmonary pressure?
- Intrapulmonary pressure minus intrapleural pressure
What is lung compliance?
- Measure of distensibility - change in volume relative to change in pressure.
- Basically measures how stretchy the lungs are.
- If lungs are scarred or stiff = less stretchy
- If elasticity is lost = too stretchy
What is lung compliance related to?
- Inversely related to connective tissue surrounding alveoli - when connective tissue is low, compliance is high.
- Inversely related to alveolar fluid surface tension
How are elastic recoil and compliance in competition with each other?
- The greater the amount of elastic tissue, the greater the elastic recoil, but the lower the compliance.
What is elasticity?
- The tendency of something that has been distended to return to its original size.
- Directly related to connective tissue surrounding alveoli.
- Directly related to alveolar fluid surface tension.
Why do we need surfactant in our lungs?
- Individual alveoli all contain a highly thin inner lining of water-based fluid.
- The surface tension of this fluid exerts a collapsing force on the alveolus.
- Surfactant breaks this surface tension so the alveoli don’t collapse.
What creates resistance in the airways?
- Surface tension
- Small diameter of airways - there are many small airways though, so overall resistance is low.
Which factors can affect airway diameter?
- Mucus in airways
- Intrapulmonary pressure gradients
- Radial traction
What is the significance of the airways being connected in parallel?
- Reduces overall resistance
- Creates alternative routes through which air can pass
- Combined resistance of downstream branches is always less than higher up so it’s easier for air to flow deeper into the lungs.
- Highest resistance is in upper airways.
What do forced inspiration and expiration require?
- Lung reserve volumes
- Involvement of more muscles
What are the accessory muscles of inspiration?
- Sternocleidomastoid
- Scalene muscles
- Serratus anterior
- Pectoralis major
What are the accessory muscles of expiration?
- Internal intercostals
- Abdominal wall muscles
