L16 Flashcards
What are five mechanical descriptions of breathing?
- Movement of air into and out of the lungs is caused by a pressure gradient
- ATM pressure remains constant during breathing cycle
- Alveolar pressure changes affect gradient
- Boyles Law= pressure is inversely related to volume
- Resistance to airflow is related to airway radius and mucus
What is the formula for flow?
Patm-Palv/R
At rest, diaphragm is _____
At inspiration, thoracic volume _____, diaphragm _____ and ________
At expiration, diaphragm ______, thoracic volume ______
Relaxed
increases, contracts, flattens
relaxes, decreases
Describe characteristics of inspiration
- Pressure in lungs < ATM pressure
- occurs when alveolar pressure decreases
- involves contractions of skeletal muscles of rib cage and diaphragm
Describe characteristics of expiration
- Pressure in lungs > ATM pressure
- occurs when alveolar pressure increases
- involves passive relaxation, elastic recoil returns rib cage and diaphragm to original relaxed position
What is intrapleural pressure?
This is pressure inside the pleural sac, the surface tension of intrpleural sac/fluid prevents chest walls from pulling apart
Subatompheric pressure keeps lungs inflated, what is the Normal intrapleural pressure of it? What happens during inspiration and expiration of the pressure?
3 mm Hg
Inspiration: pressure drops
Expiration: increases to normal pressure
Explain what happens to the following during quiet breathing
Alveolar pressure
Intrapleural pressure
Volume of air moved
Alveolar pressure= decreases during inspiration, increases in expiration
Intrapleural pressure= decreases during inspiration, increases in expiration
Volume of air moved= increases during inspiration, decreases during expiration
Explain what Pnemothroax is and what happens
If the sealed pleural cavity is opened to the atmosphere, air flows in. The bond holding the lungs to the chest wall is broken and lungs collapse. This creates Pnemothroax (air in thorax)
What is compliance, what happens during high compliance, what happens during low compliance?
Compliance= this is the ability to stretch
High compliance mean stretches easily
Low compliance means it requires more force and restrictive to lung diseases. Fibrotic lung diseases is inadequate for surfactant production
What does elastance mean?
This is the ability to return to resting volume when stretching forces is released (force exerted by elastic fibres)
What is surface tension? What are surfactants?
Surface tension is the thin layer of fluid that lines alveoli, the surface tension arises due to attraction between water molecules
Surfactants are surface active agents that disrupt cohesive forces of water and are mixtures containing proteins and phospholipids. More [ ] in smaller alveoli. More surfactants you have, the less surface tension you have.
what is the law of Laplace? What does the Law of Laplace state? Give examples with bubbles and surface tension.
- 2T/r
- if two bubbles had the same surface tension, the smaller bubble will have higher pressure
- in lungs, smaller alveoli have more surfactants which equalize pressure between large and small alveoli
- smaller radius means an increase in surfactants and more surfactants means a reduced surface tension
What is the primary determinant of airway resistance?
Wider airways have _______ resistance
Airway diameter
Less resistance
What is bronchocosntriction?
What is broncodialation
Bronchoconstriction:
- This is an increase in resistance.
- caused by parasympathetic and histamines
Bronchodialation:
- this is a decrease in resistance
- sympathetic, epinephrine (beta 2 receptors and Co2)
What are the five factors that impact the airway?
- Length of system (constant, not really a factor)
- Viscosity of air (usually constant, but humidity and altitude may affect)
- Diameter of airway
- Upper airways (physical obstruction is and effector, mediated by mucus)
- bronchioles (bronchodialation and constriction)