Natalie - Compliance and Elastic Recoil

Question 1

What are two other names for the alveolar region of the lung?

Answer 1

Acinar region

Parenchymal region

Question 2

What are the main functions of the alveolar region?

Answer 2

Gas exchange

Support

Question 3

What is the name given to a support tissue?

Answer 3

Parenchymal tissue

Question 4

Give an example of a disease brought on by the lack of alveoli and closed airways

Answer 4

Emphysema

Question 5

What are the alveolar walls also called?

Answer 5

The respiratory membrane

Question 6

Write a note on the alveolar walls
(5)

Answer 6

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

Question 7

Write a note on the simple squamous epithelium found in the alveoli.
(5)

Answer 7

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

Question 8

Write a note on type 2 pneumocytes
(5)

Answer 8

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

Question 9

What type of cells produce surfactant?

Answer 9

Type 2 septal cells/pneumocytes

Question 10

What are alveolar macrophages also called?

Answer 10

Dust cells

Question 11

What determines the rate at which air flows into and out of the lungs?
(2)

Answer 11

The pressure gradient between the atmosphere and alveoli

The airway resistance

Question 12

Define lung compliance
(2)

Answer 12

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

Question 13

What is the equation for lung compliance?

Answer 13

Change in lung volume/change in transpulmonary pressure

Question 14

Why is a large lung compliance advantageous?
(2)

Answer 14

Because a smaller change in transpulmonary pressure is needed to bring a given volume of air

Therefore less work/muscle contraction is required

Question 15

Describe the chest wall in infants

Answer 15

Very soft cartilaginous chest wall = very compliant

Question 16

Describe the chest wall in the elderly
(2)

Answer 16

They develop arthritis and chest muscle wasting

This can affect stiffness of chest wall which decreases compliance

Question 17

Describe the chest wall in the diseased

Answer 17

Altered compliance because of the effects on the chest wall -> restrictive conditions such as muscular dystrophy can decrease compliance

Question 18

How is compliancy affected by fibrosis?

Answer 18

Stiffer lung = less compliant = harder to inhale

Question 19

How is compliancy affected by emphysema?
(3)

Answer 19

Alveoli are lost

Lung more compliant on inhalation because the spaces fill quickly

Air can’t get out on exhalation

Question 20

How does elastic recoil compare to lung compliancy?
(2)

Answer 20

Compliant = lung can stretch out

Elastic recoil = lung can recoil in and can resist being overstretched

Question 21

Define elastic recoil

Answer 21

Lungs ability to return to its resting volume after distension

Question 22

What is responsible for the lungs elastic nature?

Answer 22

Elastin nature of tissues (elastin and collagen)

Surface tension in alveoli

Question 23

What gives rise to the surface tension in the alveoli?

Answer 23

It arises from liquid molecules lining alveoli (surfactant) having a stronger attraction to each other than to air (made by type 2 pneumocytes)

Question 24

In relation to elastic recoil, how does the alveolus work?
(3)

Answer 24

It resists stretching

It recoils back into shape after stretching

It favours reduced surface area

Question 25

The lung and chest wall system is in dynamic equilibrium, what does this mean?
(3)

Answer 25

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

Question 26

What type of disorder is emphysema?

Answer 26

Obstructive

Question 27

What happens in emphysema?
(4)

Answer 27

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

Question 28

What is radial traction?

Answer 28

How the alveoli hold the airways open