Lung ventilation and introduction to the respiratory system

Question 1

Which parts of the respiratory system make up the conducting portion?

Answer 1

• Nasal cavity
• Pharynx
• Larynx
• Trachea
• Primary bronchi
• Secondary bronchi
• Bronchioles
• Terminal bronchioles

Question 2

Which parts of the respiratory system make up the respiratory portion?

Answer 2

• Respiratory bronchioles
• Alveolar ducts
• Alveoli

Question 3

What do we mean by anatomical dead space within the respiratory system?

Answer 3

• The volume of air in the conducting airways

Question 4

What do we mean by alveolar dead space within the respiratory system?

Answer 4

• Air in alveoli (not perfused or damaged) which do not take part in gas exchange

Question 5

Tidal volume =

Answer 5

• Anatomical dead space + alveolar ventilation
• It’s the volume of air being moved

Question 6

Total pulmonary ventilation =

Answer 6

Tidal volume x respiratory rate

Question 7

Alveolar ventilation =

Answer 7

(Tidal volume - dead space) x respiratory rate

Question 8

What is the normal value for respiratory rate?

Answer 8

• 12-20 breaths per minute

Question 9

Define respiration

Answer 9

• The exchange of oxygen and carbon dioxide across a membrane either in the lungs or at the cellular.

Question 10

Define ventilation

Answer 10

• Ventilation is the process of inspiration and expiration
• The physical action of breathing and moving air into and out of the lung.

Question 11

How do we move air into and out of the lungs?

Answer 11

• Air flows from an area of higher pressure to an area of lower pressure.

Question 12

What happens to the lungs as we breathe in?

Answer 12

• Ribs move up and out due to contraction of intercostal muscles.
• Diaphragm flattens
• Intrathoracic volume increases
• Intrapulmonary pressure decreases
• Elastic tissue in alveoli is stretched

Question 13

What happens to the lungs as we breathe out?

Answer 13

• Ribs fall due to relaxation of intercostal muscles.
• Diaphragm moves up
• Volume of thoracic cavity decreases and volume of lungs reduces.
• Pressure in chest increases until it is equal to atmospheric pressure.
• This is passive

Question 14

What are the pleurae of the lungs?

Answer 14

• A pair of serous membranes lining the thorax and enveloping the lungs.
• Parietal pleura lines the inside of each hemi-thorax
• Visceral pleura lines the outside of the lung

Question 15

What is the intrapleural space?

Answer 15

• Intrapleural space = space between visceral and parietal pleura - contains 15ml fluid

-Looks like a shiny member over the lung

Question 16

What is the pleural seal?

Answer 16

• Surface tension between the pleural surfaces created by the presence of thin film of pleural fluid
• This holds the outer surface of the lung to the inner surface of the chest wall.

Question 17

Outline the importance of negative intrapleural pressure in the lungs

Answer 17

• It remains negative throughout inspiration and expiration relative to atmosphere and intra-alveolar pressure.
• This keeps the alveoli and lungs from fully collapsing with each expiration.

Question 18

What creates a negative pressure within the intrapleural space?

Answer 18

• Lungs have a natural inward elastic recoil while the chest wall has a natural outward elastic recoil.

Question 19

What is the functional residual capacity (FRC)?

Answer 19

• Volume of air at resting expiratory level - i.e. the volume of air that remains in the lungs after we have breathed in and out.

Question 20

Describe how the intrapulmonary pressure and intrapleural pressure changes during breathing

Answer 20

• Inspiration - intrapulmonary pressure negative relative to atmosphere.
• Expiration - intrapulmonary pressure positive relative to atmosphere.
• Intrapleural pressure stays negative throughout

Question 21

What is transpulmonary pressure?

Answer 21

• Intrapulmonary pressure minus intrapleural pressure

Question 22

What is lung compliance?

Answer 22

• Measure of distensibility - change in volume relative to change in pressure.
• Basically measures how stretchy the lungs are.
• If lungs are scarred or stiff = less stretchy
• If elasticity is lost = too stretchy

Question 23

What is lung compliance related to?

Answer 23

• Inversely related to connective tissue surrounding alveoli - when connective tissue is low, compliance is high.
• Inversely related to alveolar fluid surface tension

Question 24

How are elastic recoil and compliance in competition with each other?

Answer 24

• The greater the amount of elastic tissue, the greater the elastic recoil, but the lower the compliance.

Question 25

What is elasticity?

Answer 25

• The tendency of something that has been distended to return to its original size.
• Directly related to connective tissue surrounding alveoli.
• Directly related to alveolar fluid surface tension.

Question 26

Why do we need surfactant in our lungs?

Answer 26

• Individual alveoli all contain a highly thin inner lining of water-based fluid.
• The surface tension of this fluid exerts a collapsing force on the alveolus.
• Surfactant breaks this surface tension so the alveoli don’t collapse.

Question 27

What creates resistance in the airways?

Answer 27

• Surface tension
• Small diameter of airways - there are many small airways though, so overall resistance is low.

Question 28

Which factors can affect airway diameter?

Answer 28

• Mucus in airways
• Intrapulmonary pressure gradients
• Radial traction

Question 29

What is the significance of the airways being connected in parallel?

Answer 29

• Reduces overall resistance
• Creates alternative routes through which air can pass
• Combined resistance of downstream branches is always less than higher up so it’s easier for air to flow deeper into the lungs.
• Highest resistance is in upper airways.

Question 30

What do forced inspiration and expiration require?

Answer 30

• Lung reserve volumes
• Involvement of more muscles

Question 31

What are the accessory muscles of inspiration?

Answer 31

• Sternocleidomastoid
• Scalene muscles
• Serratus anterior
• Pectoralis major

Question 32

What are the accessory muscles of expiration?

Answer 32

• Internal intercostals
• Abdominal wall muscles