Topic 14: Ventilation

Question 1

Give the parts of respiratory system

Answer 1

• Nasal passages
• Pharynx
• Larynx
• Trachea
• Lungs: bronchii/bronchioles/alveoli

Question 2

What are nasal passages + pharynx + trachea made of?

Answer 2

• Cartilage

Question 3

What are the bronchi made of?

Answer 3

• Cartilage in larger branches
• Smooth muscle

Question 4

What are alveoli made of?

Answer 4

• Simple squamous epithelium

Question 5

Give the 5 functions of respiratory system

Answer 5

1) Ventilation
2) Gas exchange
3) pH regulation
4) Smell
5) Sound production

Question 6

What is the difference between ventilation and respiration?

Answer 6

• Ventilation = movement of air in/out of lungs = breathing
• Respiration = entire process of gas exchange = requires respiratory + circulatory systems

Question 7

Describe external respiration

Answer 7

• Exchange of O2 + CO2 between external environment and tissues
• O2 in = air → lungs → blood → tissue
• CO2 = tissue → blood → lungs → air

Question 8

Describe cellular respiration

Answer 8

• Metabolism of nutrients in cells using O2 + releasing CO2

Question 9

Give the steps of external respiration

Answer 9

1) Ventilation/gas exchange between atmosphere + alveoli
2) Exchange of O2 + CO2 between air in alveoli + blood in pulmonary capillaries
3) Transport of O2 + CO2 by blood between lungs + tissues
4) Exchange of O2 + CO2 between blood in systemic capillaries + tissue cells

Question 10

Explain airway conduction

Answer 10

• Air conducted from atmosphere to lung = conditioned
• Airway from nasal passage to bronchioles = moiste + warm + filter + condition air as it moves to lungs

Question 11

Define conducting zone

Answer 11

• Nasal passage to terminal bronchioles = movement of air only

Question 12

Define respiratory zone

Answer 12

• Respiratory bronchioles to alveoli = gas exchange between alveoli + blood

Question 13

Describe ventilation

Answer 13

• Inspiration: air in
• Expiration: air out
  REQUIRES:
• Coordination of muscles
• Pressure gradients

Question 14

Describe 2 types of inspiratory muscles

Answer 14

1) Resting inspiratory muscles: enlarge thoracic cavity
- Diaphragm
- External intercostal
2) Forced inspiratory muscles: raise sternum + ribs 1+2 = further enlarge thoracic cavity
- Sternocleidomastoid
- Scalenes

Question 15

Describe 2 types of expiratory muscles

Answer 15

1) Resting expiratory muscles: none = passive relaxation decreases volume of thoracic cavity due to elastic recoil of lungs
2) Forced expiratory muscles: further reduce volume
- Internal intercostal
- Rectus abdominus
- Obliques

Question 16

Decribe the pressure volume relationship

Answer 16

• Due to ventilation movement of air in + out of lungs causes changes
• Air moves along a pressure gradient from high to low pressure
  INSPIRATION:
• Expands chest + increases volume = decreases pressure in lungs
• Air sucked in from atmosphere higher pressure
  EXPIRATION:
• Recoil chest + decrease volume = increase pressure in lungs
• Air pushed out to lower pressure atmosphere

Question 17

Define Boyle’s law

Answer 17

• Pressure exerted by gas in closed container is inversely proportional to volume of gas in container
• If temp + number of molecules = constant

Question 18

Give the equations for Boyle’s law

Answer 18

P₁V₁ = P₂V₂
P ∝ 1/V
- Increasing volume = decreases pressure = air in
- Decreasing volume = increases pressure = air out

Question 19

Give the 3 main pressures for breathing

Answer 19

1) Atmospheric
2) Intra-alveolar
3) Intrapleural

Question 20

Describe atmospheric pressure

Answer 20

• Pressure on air of earth surface
• Sea level = 760mmHg
• Stays constant

Question 21

Describe intra-alveolar pressure

Answer 21

• Pressure with lungs/alveoli
• Varies as lungs expand + recoil to equilibrate with P-atm
• Determines if air enter/leave lungs
• If P-alv <760mmHg = inspire
• If P-alv >760mmHg = expire

Question 22

Describe intra-pleural pressure

Answer 22

• Pressure within pleural sac
• At rest = 756 mmHg
• Doesn’t equilibrate with atmosphere as it is a closed sac filled with fluid
• Important for keeping lungs attached to thoracic cavity as muscles move = loss of pressure leads to lung collapse

Question 23

Define transmural pressure gradient

Answer 23

• Difference between pleural cavity + atm/alveolar
• Approx = -4 mmHg

Question 24

Give the 3 ventilation factors

Answer 24

1) Pressure gradients
2) Airway resistance
3) Lung compliance

Question 25

What determines airways resistance?

Answer 25

- Radius of conducting airway = bronchiole smooth muscle contract/relax [F = ΔP/R]

Question 26

Define bronchoconstriction

Answer 26

- Decrease radius of bronchioles - Increase resistance - Reduce air flow - PNS input at rest

Question 27

Give the pathological reasons for bronchoconstriction

Answer 27

- Allergies/histamine - Inflammation - Excess mucus - Chronic lung disease

Question 28

Define bronchodilation

Answer 28

- Increase radius of bronchioles - Decrease resistance - Increase airflow - SNS input + epinephrine + increased activity

Question 29

Define lung compliance

Answer 29

- Ability of lung to stretch + distend during ventilation

Question 30

Give the 3 factors that affect lung compliance

Answer 30

1) Elastin fibers: lung connective tissue 2) Water: on surface of alveoli = surface tension = enhances coil 3) Pulmonary surfactants: fluid secreted by alveolar cells = counteracts + balances effect of water = reduces surface tension + increases compliance by softening recoil

Question 31

Give the forces keeping the alveoli open

Answer 31

1) Transmural pressure gradient 2) Pulmonary surfactant

Question 32

Give the forces promoting alveolar collapse

Answer 32

1) Elasticity of stretched pulmonary tissue fibers 2) Alveolar surface tension