Deck 45: Mechanics of Breathing

Question 1

Most of the work of breathing is overcoming

A) Surface tension in the lungs
B) Recoil from elastic fibers in the lungs C Airway resistance in the lungs
D Internal resistance from m uscles
E) None of these pathetic distractors

Answer 1

A

Question 2

The La w o f La Pla ce for a th in- wa lled sp he re is

A) ç = dG /dA
B) P = 2 T / r
C) P = T / r
D) T = ç
E) P = 2T r

Answer 2

B

Question 3

The Law of LaPlace predicts that alveoli at constant wall tension are unstable because

A) Small alveoli will have greater pressures tha n larg er alv eo li
B) Sm all a lve oli w ill ha ve sm alle r pr es su re s th an larg er alv eo li
C) It predicts pressures greater than atmospheric during inspiration
D) It predicts pressures smaller than atmospheric during expiration
E) The Law of LaPlace is not applicable here because it applies only to cylinders

Answer 3

A

Question 4

The m ajor muscle used during quiet resting inspiration is the

A) Diaphragm
B) Inte rn al in ter co sta ls
C) Ex ter na l inte rc os tals
D) Ste rn oc leid om as toid
E) None of the above

Question 5

The m ovement of the "mucus escalator" is provided by

A) Flagella in the trachea
B) Ciliated cells lining the airw ays
C) Sm oo th m us cle co ntr ac tion s o f th e a irw ays
D) Secretory movement of the mucus
E) Move m ent of m ucus by wave s of air pressure

Question 6

Inspiratory muscles include

A) Diaphragm and external intercostal muscles
B) Diaphragm and internal intercostal muscles
C) Diaphragm and abdom inal muscles
D) Abdominal muscles and external intercostal muscles
E) Abdominal muscles and sternocleidomastoid muscles

Question 7

Com pliance of the lungs is due to

A) Elastic fibers in the lungs
B) M us cle ten sio n o n th e c he st w all
C) Su rfac e ten sion of th e alv eo li
D) Stif f air wa ys
E) Both A and C are correct

Question 8

Surface tension has the units of

A) N m -2
B) Pa s
C) N m -1
D) N m -3
E) m Pa -1

Question 9

The m ajor muscle used during quiet resting expiration is the

A) Diaphragm
B) Inte rn al in ter co sta ls
C) Ex ter na l inte rc os tals
D) Ab do m ina ls
E) None of the above

Question 10

The pn eu m oth or ax is

A) A dire ct p ath w ay b etw een the intra pleu ral sp ace and the am bien t air
B) Negative pressure in the intrapleural space
C) Po sitiv e p re ss ur e w ithin the alv eo li
D) N eg ativ e p re ss ur e w ithin the alv eo li
E) Negative pressure in the intrapleural space

Question 11

In the relaxation volume-pressure curves, the respiratory muscles are relaxed and the requirement for muscular involvement is shown by a positive pressure. In these curves, expansion of the chest wall alone requires a positive pressure Pchest wall = Ppl - PB (Ppl is the intrapleural pressure and PB is the b arom etric o r am bien t air pre ssu re ou tside o f the b ody).

A) Over the entire range of chest and lung volumes
B) Only for volumes > FRC
C) Only for volumes < FRC
D) Only for large volumes greater than the volume at normal end inspiration
E) Only for small volumes less than the volume at normal end inspiration

Question 12

Compliance is defined as (Q is airflow)

A) 6 P / 6 V
B) 6 P / Q
C) dG / dA
D) 6 V / 6 P
E) 6 V / Q

Question 13

The intrapleural pressure is always less than the alveolar pressure because

A) Airway resistance slows down air movem ent into and out of the lungs
B) The chest wall always tends to expand at all lung volumes
C) The lungs tend to pull away from the chest wall at all lung volum es
D) The respiratory muscles tug on the chest at all times
E) Otherw ise we wouldn't have these c ool sucking gu n shot wou nds in the m ovies where on ly the ba d g uys die ins tan tly an d th e h er os ge t to s ay g oo db ye

Question 14

Expansion of the lungs requires a positive pressure Plung = PA - Ppl

A) Over its entire range of volumes
B) Only for volumes > FRC
C) Only for volumes < FRC
D) Only for volumes greater than the volume at normal end inspiration
E) Only for volumes less than the volume at normal end inspiration

Question 15

Air moves into the lungs during inspiration

A) Be cau se th e pr ess ure in th e lun gs is less tha n th e pr ess ure in th e am bien t air
B) Because humidification of the air in the lung dilutes the air molecules
C) Because oxygen depletion of alveolar air has lowered the pressure in the lungs
D) Be cau se a ir m olec ules diffus e do wn th eir co nce ntration grad ients
E) Due to contraction of smooth muscle in the trachea

Question 16

The m ain fu nction of the lungs is to

A) Sup ply O 2 to the blood
B) Provide inspiration
C) Remove CO₂ from the blood
D) Remove CH 4, H₂ and other gasses from the blood
E) Both A and C are correct

Question 17

During quiet inspiration

A) The lung expands from elastic forces
B) The intrapleural pressure is pos itive
C) Alveo lar pres sure is less th an a tm osp heric p ressu re
D) The lung volume is less than the FRC
E) Surfactant is conce ntrated m ore

Question 18

The ple ur al flu id

A) Is the same as the ISF of the lungs
B) Lies between the p arietal pleura and the p ulmo nary pleura
C) H as a p re ss ur e w hic h is alw ays m or e p os itive tha n a lve ola r air
D) Allow s th e lun gs to s lide w hile a dh erin g th e lun g to the che st w all
E) Lin es the airw ays