8.2 Ventilation Flashcards
What are the resting inspiratory muscles? What innervates them?
enlarge the thoracic cavity Diaphragm Phrenic Nerve (C3,C4,C5) External intercostals intercostal nerves (T1-T11), subcostal nerve (T12)
What are the forced inspiration muscles?
raise sternum and 1st 2 ribs to further enlarge thoracic cavity
Sternocleidomastoid (CN 11)
Scalenes (C1-C4)
What muscles are used for normal expiration?
NONE! Passive relaxation decreases volume of thoracic cavity due to elastic recoil of lungs
What muscles are used for forceful expiration?
further reduce volume of the thoracic cavity Internal intercostals (intercostal nerves, T1-T11, T12) Rectus abdominus, obliques (intercostal nerves T7, lumbar spinal nerve L1)
What are inspiration and expiration? What is happening in the thorax?
Inspiration: breathing air IN
Expand chest, increases volume, decreases pressure in the lungs, air is sucked in from the atmosphere
Expiration: breathing air OUT
Recoil chest, decreases volume, increases pressure in the lungs, air is pushed out to the atmosphere
What is atmospheric pressure? What is the partial pressure of the pleura?
Atm: 760mmHg
Ppleura: 756
Where is pressure lower? Pleural space or thoracic cavity? Why?
Pressure in the pleural cavity is always less than pressure in the thoracic cavity, causing a negative pressure which “sticks the pleural sac to the thoracic cavity”
What is an obstructive airway disease?
increased resistance to airflow
trachea to bronchi, bronchioles
ex: asthma, COPD, obstructive sleep apnea
What is a restrictive lung disease?
reduced expansion of lung, decreased total lung capacity
stiff, non-compliant lungs
ex: pulmonary fibrosis, bronchitis, pneumonia, musculoskeletal disorders, vertebral abnormalities (kyphosis, lordosis
What 3 factors impact ventilation?
Pressure Gradients
Airway Resistance
Lung Compliance
What helps increase pulmonary compliance?
Elastin fibers in lung connective tissue
Water on surface of alveoli, creates surface tension that enhances recoil, but opposes alveolar expansion
excess fluid (ex: pneumonia, bronchitis) = difficult to expand lungs and breathe
Pulmonary Surfactant: fluid secreted by alveolar cells (Type II) counteracts and balances effects of water to reduce alveolar surface tension, increase compliance, soften recoil
What is tidal volume?
Amount of air inhaled or exhaled with each breath under resting
conditions
What is the inspiratory reserve volume?
Amount of air that can be forcefully inhaled after a normal tidal
volume inspiration
What is the expiratory reserve volume?
Amount of air that can be forcefully exhaled after a normal tidal
volume expiration
What is the residual volume?
Amount of air remaining in the lungs after a forced expiration
