Natalie - Compliance and Elastic Recoil Flashcards
What are two other names for the alveolar region of the lung?
Acinar region
Parenchymal region
What are the main functions of the alveolar region?
Gas exchange
Support
What is the name given to a support tissue?
Parenchymal tissue
Give an example of a disease brought on by the lack of alveoli and closed airways
Emphysema
What are the alveolar walls also called?
The respiratory membrane
Write a note on the alveolar walls
(5)
Simple squamous epithelium
Endothelial cells line the capillaries
Fused basal laminae -> alveoli share walls for efficient gas diffusion
Septal cells
Alveolar macrophages - patrol epithelium and engulf foreign particles
Write a note on the simple squamous epithelium found in the alveoli.
(5)
Type 1 alveolar cell/type 1 septal cell/type 1 pneumocyte
Provide structure to the wall
Have energy-dependent membrane associated pumps
Important in removal of fluid which could potentially prevent gas exchange
These cells cannot divide when they are damaged or dying
Write a note on type 2 pneumocytes
(5)
Pneumocytes
Type 2 alveolar/septal cells
Scattered in respiratory membrane, more rounded than type 1
Produce surfactant - keep alveoli open during breathing and reduce surface tension
Twice as abundant as type 1
Can replace type 1 when they die
What type of cells produce surfactant?
Type 2 septal cells/pneumocytes
What are alveolar macrophages also called?
Dust cells
What determines the rate at which air flows into and out of the lungs?
(2)
The pressure gradient between the atmosphere and alveoli
The airway resistance
Define lung compliance
(2)
A measure of the ease at which our lungs can stretch
The change in lunge volume that results from a given change in transpulmonary pressure
What is the equation for lung compliance?
Change in lung volume/change in transpulmonary pressure
Why is a large lung compliance advantageous?
(2)
Because a smaller change in transpulmonary pressure is needed to bring a given volume of air
Therefore less work/muscle contraction is required
Describe the chest wall in infants
Very soft cartilaginous chest wall = very compliant
Describe the chest wall in the elderly
(2)
They develop arthritis and chest muscle wasting
This can affect stiffness of chest wall which decreases compliance
Describe the chest wall in the diseased
Altered compliance because of the effects on the chest wall -> restrictive conditions such as muscular dystrophy can decrease compliance
How is compliancy affected by fibrosis?
Stiffer lung = less compliant = harder to inhale
How is compliancy affected by emphysema?
(3)
Alveoli are lost
Lung more compliant on inhalation because the spaces fill quickly
Air can’t get out on exhalation
How does elastic recoil compare to lung compliancy?
(2)
Compliant = lung can stretch out
Elastic recoil = lung can recoil in and can resist being overstretched
Define elastic recoil
Lungs ability to return to its resting volume after distension
What is responsible for the lungs elastic nature?
Elastin nature of tissues (elastin and collagen)
Surface tension in alveoli
What gives rise to the surface tension in the alveoli?
It arises from liquid molecules lining alveoli (surfactant) having a stronger attraction to each other than to air (made by type 2 pneumocytes)
In relation to elastic recoil, how does the alveolus work?
(3)
It resists stretching
It recoils back into shape after stretching
It favours reduced surface area
The lung and chest wall system is in dynamic equilibrium, what does this mean?
(3)
The chest wall expands OUT, the lung recoils IN
The two forces are of equal magnitude but in opposite directions
Therefore they are in dynamic equilibrium
What type of disorder is emphysema?
Obstructive
What happens in emphysema?
(4)
Loss of alveoli from lung
Airways become narrowed because alveoli around them collapse - can’t hold airways open (loss of radial traction)
Initially increases compliance but overall leads to reduced compliance because air becomes trapped (cant exhale)
Less alveolar wall = less gas diffusion
What is radial traction?
How the alveoli hold the airways open
