Mechanics of Breathing

Question 1

Conducting zone

Answer 1

transports gases

Question 2

Respiratory zone

Answer 2

takes part in gas exchange

Question 3

Airway resistance is greater in the conducting airways because:

Answer 3

they are arranged in series

Question 4

Lungs synthesize

Answer 4

surfactant, prostaglandins, histamine

Question 5

Lungs activate

Answer 5

Angiotensin I to Angiotensin II

Question 6

“air-blood” barrier includes:

Answer 6

Surfactant
Alveolar epithelium
Interstitial fluid
Capillary endothelium

Question 7

Alveolar 3 cell types of epithelium

Answer 7

1. Type I alveolar cells:
   •form a part of the thin gas diffusion barrier
2. Type II alveolar cells:
   •produce surfactant
   • differentiate into type 1 epithelial cells (when the pulmonary membrane is damaged )
3. Club (Clara) cells:
   • Secrete component of surfactant, degrade toxins, act as reserve cells.

Question 8

Primary muscles of respiration

Answer 8

diaphragm
external intercostal

(also produce a quiet inspiration)

Question 9

Accessory muscles of inspiration

Answer 9

sternocleomastoid
scalene
pectoralis minor
serratus anterior

(also produce forced inspiration)

Question 10

Accessory muscles of exhalation

Answer 10

internal intercostal
transversus thoracis
external oblique
rectus abdominis 
internal oblique

also produce forced exhalation)

Question 11

Inspiration

Answer 11

thoracic volume to increase
lung volume to increase
lung pressure to decrease

Question 12

*** A premature newborn infant is noted to have a deficiency of pulmonary surfactant. Which of the following muscles will the infant likely require to use to accomplish adequate inspiration?

Answer 12

Diaphragm, external intercostals, scalene, sternomastoids

Question 13

Pressures:

• at rest
• during inspiration
• end of inspiration
• during exhalation

Answer 13

at rest

• Patm = 0
• Alv. press. = 0
• Intrapleural = -5

during inspiration

• Patm = 0
• Alv. press. = -1
• Intrapleural = -6.5

end of inspiration

• Patm = 0
• Alv. press. = 0
• Intrapleural = -8

during exhalation

• Patm = 0
• Alv. press. = +1
• Intrapleural = -6.5

Question 14

transmural pressure

Answer 14

alveolar pressure - intrapleural pressure

Question 15

*** The intrapleural pressure of a 37-year-old man is -4.5 cm H2O, immediately before the inspiration. What is the transpulmonary pressure at rest?

Answer 15

+4.5 cm H2O

Question 16

*** The airway tree is divided into two zones, the conducting zone and respiratory zone. Which of the following is not part of the conducting zone?

Answer 16

both respiratory bronchioles and alveoli

Question 17

*** A 58-year-old factory worker, who has worked in the insulation industry for over 30 years, develops progressive shortness of breath. His wife has tried to get him to go to the doctor, and he finally relents with the appearance of hemoptysis. A chest x-ray is consistent with an alveolitis from asbestos inhalation. Which of the following is the major route for removal of small particles from the alveoli?

Answer 17

Phagocytosis

Question 18

*** Which of the following is true during inspiration?

Answer 18

Intrapleural pressure is more negative than it is during expiration

Question 19

Compliance

Answer 19

ΔV / ΔP

• inversely related to Elastance
• inversely related to stiffness

Question 20

pulmonary fibrosis

Answer 20

elastic tissue is replaced by fibrous tissue

↓ Compliance
↓ resting lung volume
↑ resistance
↑ work of breathing

Question 21

pneumonia

Answer 21

↓ Compliance

Question 22

pulmonary edema

Answer 22

↓ Compliance

Question 23

emphysema

Answer 23

↑ Compliance (due to loss of elastic recoil)

↓lung elastance

Question 24

asthma

Answer 24

↓ Compliance

Question 25

asbestosis

Answer 25

↓ Compliance

Question 26

respiratory distress syndrome (RDS)

Answer 26

alveoli do not remain open due to a lack of surfactant

↓ Compliance

Question 27

chronic bronchitis

Answer 27

↓ Compliance

Question 28

used to induce bronchodilation and reduce airway resistance in patients with asthma

Answer 28

β2-receptor agonists

Question 29

Turbulent gas flow

Answer 29

increases airway resistance

a wheezing sound

Question 30

Compliance curve

Answer 30

intrapleural pressure is negative→ the lungs expand → lung volume↑

intrapleural pressure is positive → the lungs collapse → lung volume↓

The difference between the inspiration curve and the expiration curve is called HYSTERESIS

*** Compliance is highest at MODERATE lung volumes

Question 31

Surfactant

Answer 31

Secreted by Type II alveolar cells

decreases surface tension

Question 32

In Fetus

Answer 32

L/S ratio ≥2 = normal

L/S ratio <2 = RDS

Question 33

*** If surfactant is absent from the alveoli, the lungs’

Answer 33

Compliance will decrease

Question 34

*** During inspiration (as compared to expiration)

Answer 34

lung recoil is increasing

Question 35

*** Based on a pressure-volume curve of the lungs, which of the following is the most likely diagnosis for the patient with a curve above normal?

Answer 35

Emphysema