Mechanics of breathing Flashcards
What are the four primary functions of the respiratory system?
Describe external respiration and its four step process
What are the structures and their components that are involved in ventilation and gas exchange?
Describe the anatomy of the lungs and the function of the pleural sac
The pleural sac creates a moist slippery surface and holds lungs tight to thoracic wall
Describe the branching of the airways
Larger total cross sectional area = decreased velocity of flow
What are the roles of the upper airways and bronchi?
Explain how air is filtered in the trachea and bronchi (mucocilliary escalator)
Why is saline necessary for mucocilliary escalator function? How is it produced?
- basolateral membrane, potassium leaks out and sodium is pumped out (NaK-ATPase)
- CFTR channel is chloride transporter moving Cl down concentration gradient
- Due to Cl in lumen
- Osmotic gradient
What is cystic fibrosis?
Describe alveolar structure
Explain flow and pressure in pulmonary circulation
What is daltons law?
Describe gas pressures during inspiration and expiration
What is Boyles Law?
Increased alveolar volume results in a drop in pressure below atmoshperic pressure resulting in air flow from the atmosphere into our alveoli and vise versa
What is ventilation? (eupnea/quiet breathing)
-The bulk flow exchange of air between the atmosphere and the alveoli
-A single respiratory cycle consists of a singe inspiration followed by an expiration
-Lung volumes change during ventilation (spirometer)
Explain lung volumes
Four primary volumes that do no overlap
- Tidal volume (TV) -about 500ml:
-The amount of air that enters or exits the lungs during quiet respiration (resting respiration)
-Total pulmonary ventilation:
-Total ventilation during rest represents the product of tidal volume and frequency of breaths
-TV x frequency of breaths = 500ml x (12 breaths/min) = 6L/min - Inspiratory reserve volume (IRV): about 3000 ml
-The additional air that could still be inspired after quiet inspiration - Expiratory reserve volume (ERV): about 1100ml
-At the end of quiet expiration, the volume of air that still remains within the lungs that can be expired - Residual volume: about 1200ml (cannot be measured with spirometer)
-Even with maximal expiratory effort air always remains in the lungs
-Two important functions:
-Prevents airway collapse, after a collapse it takes an unusually large pressure to re-inflate it
-It allows continous exhange of gases
Explain lung capacities
- Total lung capacity:
-The sum of all 4 volumes - Functional residual capacity:
-The capacity of air remaining in the lungs after quiet expiration, the sum of ERV and RV - Inspiratory capacity:
-The sum of IRV and TV respresenting the maximal amount of air that one can inspire after quiet expiration - Vital capacity:
-The sum of IRV, TV and ERV representing the maximal achievable air moved with a single breath
Describe a pulmonary function test
Explain the activity of skeletal muscle during inspiration
-65 to 75% of increased inspiratory volume change is due to diaphragm (results in decreased pressure)
-Diaphragm contracts and flattens, pulling lungs down due to attachment to parietal pleura that subsequently pulls visceral pleura
-External intercostals = inspiration
Describe skeletal muscle activity in quiet expiration (passive)
-Relaxation of the inspiratory muscles, hence passive
-Diaphragm, external intercostals and scalene muscle relax, thoracic volume decreases
-Pressure inside increases above atmospheric pressure
What muscles are involved in forced inspiration?
What muscles are involved in forced expiration?
Pulls ribcage dowm, pushes visceral organs against diaphragm moving it further up
Describe the change in alveolar and interpleural pressure during inspiration/expiration
-Intrapleural pressure is about -3mmHg and is important for holding air in the lungs
-Lungs are drawn to more negative intrapleural pressure and expand
Explain the cause of pneumothorax (collapsed lung)
Describe lung compliance
-Increased compliance makes inspiration easy but expiration much more difficult (low lung elastance/elastic recoil)
-Decreased compliance makes inspiration very difficult
-Both are bad
Explain pulmonary fibrosis
Explain emphysema
What are the effects of surface tension on compliance and lung elastic recoil?
Increased surface tension decreases compliance and increases elastic recoil
How can you calculate surface tension using Laplace’s equation?
What is surfactant?
What are the effects of surfactant on alveoli?
What is Infant Respiratory Distress Syndrome?
Describe airway resistance
Explain bronchoconstriction/dilation
Describe asthma
How can you measure efficiency of breathing?
Dead space represents air remaining in upper airways (trachea, bronchi, bronchioles) and is called fresh air since there has been no gas exchange
-Stale air represents air that has been through gas exchange in the alveoli
What are the normal ventilation values in pulmonary medicine?
Describe gas composition in the alveoli
When perfusion (blood flow) remains constant, increase/decrease in ventilation causes alteration in partial pressures of O2 and CO2 (wasted perfusion)
Describe the relationship between ventilation and alveolar blood flow (perfusion)
Explain local control of ventilation and perfusion
-Very little autonomic innervation of the pulmonary arterioles
Pulmonary arterioles primarily influenced by decreasing O2 levels around them:
-Decreases in O2 cause constriction, opposite of systemic CV system (presence of O2 sensitive K+ channels)
-Low O2 -> K+ channel closure -> depolarization (action potential resulting in contraction)
-Bronchioles are sensitive to CO2 levels, increases (dilates) or decreases (constricts)
