Lecture 24 - Mechanics Of Breathing

Question 1

What is lung mechanics

Answer 1

The physical forces that influence breathing

Question 2

What are the two categories of lung mechanics

Answer 2

Static and dynamic

Question 3

Definition of static properties

Answer 3

Mechanical properties of the lung that influence gas flow but which are independent of volume change

Question 4

What are the static properties

Answer 4

Elasticity, compliance and surface tension

Question 5

Define dynamic properties

Answer 5

Mechanical properties affecting the flow of air into and out of the lung as volume changes with time

Question 6

What are the dynamic properties

Answer 6

Flow, resistance and turbulence

Question 7

What does the pleural sac link

Answer 7

The elastic forces in the chest with the lung wall

Question 8

What does the fluid in the pleural cavity do

Answer 8

It transduces the changes in pressure/movement from the rib cage into the lung

Question 9

What type of force do the lungs possess

Answer 9

Inwards recoil force

Question 10

What type of force does the rib cage have

Answer 10

An outwards recoil force

Question 11

What is holding the lungs open

Answer 11

The outwards recoil force of the rib cage

Question 12

What do the elastic forces link

Answer 12

The pleural pressure to alveolar pressure

Question 13

What does elastin in the alveoli act as

Answer 13

An inwards recoil force

Question 14

What does the balance of the inwards and outwards forces of the lungs result in

Answer 14

Sub-atmospheric intrapleural pressure

Question 15

During quiet breathing what is the intrapleural pressure

Answer 15

Sub-atmospheric

Question 16

What does elastin retraction allow

Answer 16

Alveolar pressure to go above atmospheric pressure

Question 17

What is compliance

Answer 17

A measure of how readily distended the lung is

Question 18

What is the equation for compliance

Answer 18

Compliance = change in volume / change in pressure

Question 19

If a lung has a high compliance what effect does this have on its ability to distend

Answer 19

A living with high compliance is easily distended

Question 20

What is the relationship between lung compliance and lung elasticity

Answer 20

Compliance varies inversely with lung elasticity

Question 21

Under what conditions is static compliance measured

Answer 21

Conditions of no gas flow

Question 22

What do emphysema and COPD cause

Answer 22

Mucus in the bronchiole, enlargement of the alveoli and cause fewer capillaries to surround the alveoli

Question 23

Disadvantages of the surface molecules

Answer 23

They can only interact in two dimensions which causes an energy loss in forming more surface with a set amount of material

Question 24

Why does rain fall as drops rather than flat sheets

Answer 24

Spheres minimise the surface area

Question 25

Characteristics of the surface tension within an alveolus

Answer 25

It resists stretch, tends to become smaller and tends to recoil after stretch

Question 26

What is the law of Laplace

Answer 26

The smaller diameter bubbles have a higher surface tension than large diameter ones

Question 27

Equation for pressure (Lapace law)

Answer 27

Pressure = 2(surface tension) / radius

Question 28

What does pulmonary surfactant do

Answer 28

It stabilises alveolar structure by reducing surface tension

Question 29

What effect does pulmonary surfactant have on the density of water

Answer 29

It decreases the density of water at the air-water interface

Question 30

What is pulmonary surfactant composed of

Answer 30

Dipalmityol phosphatidyl chlorine (DPPC) Packard around surfactant molecules (A-D)

Question 31

What cells secrete pulmonary surfactant

Answer 31

Type II alveolar epithelial cells

Question 32

What does pulmonary surfactant prevent

Answer 32

The collapse of the alveoli during lung expansion/contraction and reduces the pressure required to inflate the lung

Question 33

What occurs as r falls in relation to lung pressure

Answer 33

As r falls, surfactant molecules crowd together, so surface tension is reduced and smaller alveoli are stabilised

Question 34

Other than pulmonary surfactant what else stabilises alveoli

Answer 34

Mechanical interactions between neighbouring alveoli

Question 35

What happens if pulmonary surfactant is lost

Answer 35

Alveolar collapse