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Respiratory System 1, Revision
Trachea to terminal bronchiole (1st…
Respiratory System 1
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Alveoli
Alveolar sacs, "covered" by capillaries.
Alveolar Macrophage
- For protection against foreign particles
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Alveolar fluid with pulmonary surfactant
- Prevents alveoli from sticking together
- Allows the air to be dissolved, for diffusion of O2 or CO2 to take place
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Ventilation
Before inspiration
- Intercostal muscles relaxed
- Diaphragm relaxed
Inspiration
- Intercostal muscles contracts, increases side-to-side dimensions of thoracic cavity (transverse diameter)
- Elevation of ribs, increases front-to-back dimensions of thoracic cavity (AP diameter)
- Diaphragm contracts, increases vertical dimensions of thoracic cavity (vertical diameter)
- Active process
- Muscles
- Sternocleidomastoid
- Scalene
- Pectoralis minor
- Serratus anterior
- External intercostal
- Diaphragm
Expiration
- Everything relaxes
- Passive process
- Muscles
- Transversus Thoracis
- Internal intercostal
- Rectus abdominus
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Revision
- Trachea to terminal bronchiole (1st-16th division) > Conducting Zone. The volume of air is called the anatomic dead space.
- Respiratory bronchiole to alveoli (17th to 23rd division) > Respiratory Zone
May vary. Anything beyond the 15th can be considered the respiratory zone for our module
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Bronchiole to terminal bronchiole
Bronchi and bronchiole
- Can constrict and dilate
- Innervated by automatic nervous system
- sympathetic > brochodilation
- parasympathetic > bronchoconstriction
Protective Mechanisms
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Lungs
- Mucociliary trapping of foreign matter
- Ciliary Escalator (movement of mucous up and out of respiratory tract)
- Alveolar macrophages
- Airway reflexes eg. cough, sneeze, epiglottis closes glottis during swallowing
Clinical Requirements
- Assisted ventilation
- Treatment
- Smokers
Lungs receive 100% of the cardiac output
- Blood into lungs is not uniform
Revision
- Deoxygenated blood enters heart
- From heart, it goes into lungs via arteries
- Oxygenation of blood and removal of CO2 via alveoli
- Oxygenated blood goes back to heart via veins
- Oxygenated blood goes to system via aorta
- During inspiration, intra-alveolar pressure is less than atm pressure.
- During expiration, intra-alveolar pressure is greater than atm pressure.
- At the end of both inspiration and expiration, intra-alveolar pressure is equal to atm pressure because the alveoli are in direct communication with the atmosphere, and air continues to flow down its pressure gradient until the two pressures equilibrate.
- Throughout the respiratory cycle, intrapleural pressure is less than intra-alveolar pressure.
- Thus, a transmural pressure gradient always exists, and the lung is always stretched to some degree, even during expiration.
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0.75s for blood in capillary travel around alveoli, from artery to vein
0.25s for blood to be oxygenated. Provides enough buffer for blood to be oxygenated even with high blood flow, e.g. during exercise
During Exercise
- Stronger inspiratory efforts
- Stronger expiratory efforts
Alveolar Ventilation = (Tidal Volume - Anatomic Dead Space) x Breaths Per Minute
- Tidal Volume typically 550ml
- Anatomic dead space typically 150ml