Session 1- Intro to the unit Flashcards
conducting portion of respiratory tract
nasal cavity to terminal brochioles
respiratory portion
respiratory bonchioles to alveoli
what is ventilation
process of inspiration and expiration not the same as respiration
movement of a volume of gas into and out the lungs. Respiration is the exchange of oxygen and Co2 across a membrane either in the lungs or at the cellular level
tidal volume
volume of air being moved during quiet inspiration and expiration
boyle’s law
inverse relationship between pressure of a gas and voume it occupies
lung mechanics in quiet inspiration
requires active expansion of thoracic cavity expands the lungs- increase in volume causes decrease in pressure relative t atmosphere- gas moves from greater to lower pressure- air is drawn in
lung mechanics in quiet expiration
air expelled from the airways passivly by relaxing muscles used in inspiration- reduces volume of thoracic cavity- reduces volume of lungs as they return to original volume, this increases pressure inside lungs relative to atmosphere and air expelled
what connects lungs to chest wall
pleura
pleura
each of a pair of serous membranes lining thorax and enveloping the lungs
Parietal pleura lines the inside of each hemi-thorax
visceral lines outside of lung
what is the pleural seal
surface tension between the pleural surfaces created by the presence of thin film of parietal fluid holds outer surface of lung to inner surface of chest wall
what creates the negative pressure between pleura
lungs have a natural inward elastic recoil, chest wall has a natural outward recoil
this 2 opposing forces create a negative pressure in the intrapleural space
What does the intrapleural pressure remain
Remains negative which prevents alveoli from fully collapsing
What does positive pressure mean
More than atmospheric pressure
What does negative pressure mean
Less than atmospheric pressure
What does 0 pressure mean
Same at atmospheric
What does trabspulmonary pressure mean
Difference between intrapulmonary pressure minus intrapleural pressure
What is compliance
A measure of distensibility change in volume relative to change i pressure
How much pressure do i have to exert to make something stretch out
volume change per unit pressure change
What is elastance
Measure of elastic recon= the tendency of something that has been distended to return to its original size
Relationship between compliance and elastance
Inversely related
what is the relationship between Lung compliance
Inversely related to connective tissue surrounding alveoli- elastic fibres including collagen and other matrix elements within the lung parenchyma
Inversely related to alveolar fluid surface tension
What is resting expiratory level
When we have just expired and before we start inspiring
What occcurs during resting expiratory level
Lungs collapse inwards- elastic recoil
Chest wall pulls out- chest elastic recoil
Forces are equal and opposite
Volume air at resting expiratory level is called FRC
What is the effect of surface tensio
Limits expansion of the alveoli
Decreases compliance making g i more difficult to expand them
Surface tension increases as alveoli increase in size
Function of surfactant
Counteracts surface tension
Acts to disrupt interaction between fluid molecules on alveolus surface…reducing surface tension
Better at this when molecules are closer together
Difference between distribution of surfactant in sizes of alveoli
Farther apart in larger less surface tension
Closer together in smaller- more surface tension
Accessory muscles of inspiration
SCM Scalene Serratus anterior Pectoral is major external intercostal muscles
Accessory muscles of expiration
Internal intercostal
Abdominal walls muscles
external oblique
Functional residual capacity
Volume of air in lungs at resting expiratory level
what percentage of chest expansion is the diaphragm responsible for during quiet respiration
80% the diaphragm is the cheif muscle for chest expansion
what is the most likely cause of reduced lung compliance
increased amount of collagen in the alveolar interstitium which makes the lungs stuiff
