Week 3 - Airway Resistance Flashcards
Where is the highest resistance and why?
Larger airways (first and second bronchi). Due to non-laminar flow (turbulent).
Where is the lowest resistance and why?
Despite bronchioles being narrow (high resistance), their extensive branching results in a low resistance pathway overall.
Explain the silent zone and difference between diseases in this area to the rest of the lung
Lower respiratory is classified as the silent zone. Diseases in the lower respiratory are often not felt until later as the disease progresses. Upper respiratory infections are felt a lot sooner.
Why do patients with airway resistance problems take deeper breathes?
People with Asthma or COPD tend to have airway constriction. Breathing deeper further expands lungs to allow proper ventilation. Normal breathing depth will have lower ventilation due to constriction.
Expiration and Emphysema
Normal alveoli are tethered to lung tissue with elastin, allowing expansion and recoil back to shape during inspiration and expiration. This tether is lost with Emphysema and the alveoli tend to collapse when expiring.
Expiration and Asthma
Normal alveoli are tethered to lung tissue with elastin, allowing expansion and recoil back to shape during inspiration and expiration. Smooth muscle around alveoli constricts when Asthma exacerbates which can collapse alveoli.
How do individuals with Emphysema prevent their alveoli from collapsing?
Pursed lip breathing creates pressure within the airways starting from the mouth and this prevents alveoli from collapsing.
Parasympathetic stimulation of lungs
- Parasympathetic fibers (vagus nerve) secrete acetylcholine, stimulating M3 receptors and causing bronchoconstriction.
Sympathetic stimulation of lungs
- Direct sympathetic control is weak, but the bronchial tree is responsive to norepinephrine and epinephrine (from adrenal gland), which stimulate β2 receptors, causing bronchodilation.
