Lung Mechanics

Question 1

What is respiration in biochemical and physiological terms

Answer 1

Biochemical - Energy producing chemical reactions(converting lactic acid to CO2 and H2O)
Physiological - An interchange of gases between an organism and its environment

Question 2

What is ventilation

Answer 2

The movement of air into and out of the lungs (breathing)

Question 3

What do the muscles in the lungs do

Answer 3

They control the diameter of the airways

Question 4

What generates pressure differences for breathing

Answer 4

Respiratory muscles

Question 5

What is the active part of breathing

Answer 5

inspiration

Question 6

What allows expiration to be mostly passive

Answer 6

The elastic recoil of the lungs that pulls the lungs and diaphragm back to the resting position

Question 7

What is the main respiratory muscle

Answer 7

Diaphragm

Note: not essential for life as other muscles can take over mostly

Question 8

What effect does activity in the PHRENIC nerves cause in the diaphragm

Answer 8

Diaphragm flattens and descends in the chest, causing air to be drawn into the chest

Question 9

What are the 3 flat muscles that are found in each intercostal space

Answer 9

External
Internal
Innermost

Question 10

What are the roles of the intercostal muscles

Answer 10

• Increase the diameter of the chest to reduce pressure and draw air in.
• ## Stiffens chest during inspiration preventing it from being sucked in

Question 11

When are the external intercostals most active and what motion do they control

Answer 11

Most active = inspiration

Moves ribs superiorly

Question 12

When are the internal intercostals most active and what motion do they control

Answer 12

Most active = expiration

Moves ribs inferiorly

Question 13

What is the role of the innermost internals

Answer 13

They just act with the internal intercostal muscles

Question 14

What nerves innervate the intercostal muscles

Answer 14

Intercostal nerves

Question 15

What two types of movement happen during inspiration

Answer 15

Pump-handle

Bucket-handle

Question 16

Describe Pump handle and Bucket handle movements

Answer 16

Pump handle - anterior end of each rib is elevated

Bucket handle - diameter of chest increases by rib on either side raised from horizontal position

Question 17

When can expiratory muscles actively contract

Answer 17

During high levels of breathing or if airways obstructed by disease

Question 18

What are the most important expiratory muscles

Answer 18

Abdominal muscles

Question 19

How do the abdominal muscles help expiration

Answer 19

They squeeze the contents of the abdomen up against the diaphragm and force it up into the chest to expel air

Question 20

What is the intrapleural pressure (Ppl)

Answer 20

The pressure in the small amount of fluid between the visceral and parietal pleruae

Question 21

Is the intrapleural pressure usually negative or positive with respect to the atmosphere and what effect does this ha ve on the lungs

Answer 21

Negative this means the lungs are firmly pressed to the chest wall as the space is airtight

Question 22

What would happen if a puncture wound is made through the thorax

Answer 22

Air enters the pleural space, as the pleural pressure is less than the atmosphere, causing pneumothorax. The pressure around the lungs will increase and the lungs may collapse

Question 23

What happens to intrapleural pressure during inspiration and expiration

Answer 23

Intrapleural pressure = more negative in inspiration, less negative for expiration
Can become positive in forced expiration

Question 24

What are the elastic properties of the lungs caused by

Answer 24

elastic and collagen fibres

surface tension in the alveolar-liquid interface

Question 25

What is lung compliance an expression of

Answer 25

the elasticity of the lungs or how easily they can be stretched

Question 26

What is the main thing that affects lung compliance

Answer 26

Lung diseases

Question 27

How is lung compliance defined

Answer 27

The change in volume produced by a change in pressure across the wall of the structure being investigated - lungs (Cl), chest wall (Cw) or lungs and chest wall (Total compliance Ctot)

Question 28

What is the equation for compliance

Answer 28

Change in Volume/Change in Pressure

Question 29

How would emphysema and fibrosis affect compliance

Answer 29

Emphysema = increased
Fibrosis = decreased

Question 30

Why does emphysema increase lung compliance

Answer 30

It causes destruction of the normal lung architecture, including elastic and collagen fibres, so lungs are mode easily distended and the compliance increases

Question 31

Why does fibrosis decrease compliance

Answer 31

Scar tissue replaces normal interstitial tissue so the lungs become stiffer and compliance decreases

Question 32

How is airway resistance (Raw) defined

Answer 32

This is the resistance to the flow of has within the airways of the lung

Question 33

What is COPD

Answer 33

Chronic Obstructive Pulmonary Disease

Question 34

What is bronchitis

Answer 34

Blocking of airways by secretions

Question 35

What are the 2 types of airway flow

Answer 35

Laminar and Turbulent

Question 36

Describe laminar and turbulent flow

Answer 36

Movement is orderly and streamlined whereas in turbulent flow movement is chaotic

Question 37

What is Poiseuille’s Law

Answer 37

Laminar flow is described by this law and is the relationship between driving pressure and flow

Question 38

How is airflow affected by tube radius

Answer 38

Wider tube = less resistance
Not directly proportional to change in resistance. radius in equation is r^4. so if radius is halved and everything else is constant, flow is reduced to 1/16.