Respiratory System and Mechanics of Breathing I

Question 1

Only simple organisms can rely solely on _______exchange of O2 and CO2 with the environment.

Answer 1

diffusive

Question 2

• Problem of ________distance is overcome in larger
organisms by ________the diffusion processes with
______processes.

Answer 2

diffusion
coupling
convectional

Question 3

The tracheo-bronchial tree has volume, but no

Answer 3

gaseous exchange takes place.

Question 4

nose, pharynx, larynx, trachea, bronchi, and bronchioles make up what?

Answer 4

conducting
portion of
the resp. system

Question 5

Tidal Volume

VT ~

Answer 5

500 mL

Question 6

Total alveolar gas volume

~

Answer 6

3000 mL

Question 7

Anatomical
deadspace VD
~

Answer 7

150 mL

Question 8

PA = PB when?

Answer 8

With open airways

& no air flow:

Question 9

• The chest wall

tends to recoil _______:

Answer 9

outwards

Question 10

The lungs are

highly ________:

Answer 10

elastic

Question 11

The lungs are

highly elastic: which results in

Answer 11

– Reduces Pip (below
atmospheric pressure
(PB or Patm)
– Pulls the chest wall
inward

Question 12

Pressures that

determine lung volume:

Answer 12

PA & Pip

Question 13

Given the forces acting on the chest wall (FCW) and
the lungs (FL), why don't the lungs collapse?

Answer 13

The pleural membranes

Question 14

What do we call the the volume of air in

the lungs when PA = PB?

Answer 14

functional residual capacity

Question 15

The pleural membranes:

Answer 15

• cover the outer surface of the
lungs (visceral) and thoracic
cavities (parietal)
• are coupled together by a thin
layer of liquid (~20 µm)
This layer of liquid:
• acts as a lubricant
• allows the lungs to move
relative to the chest wall

Question 16

Intra-pleural pressure (Pip) is the pressure in

Answer 16

the sealed

space between the pleural membranes.

Question 17

Mechanics of Breathing

Answer 17

• Movement of air into and out of the lungs
• Process of “bulk flow”
• Achieved by generating pressure differences

Question 18

Thoracic movements are transmitted to the lungs by

Answer 18

pressure changes in the intra-pleural space.

Question 19

The work of breathing is done by

Answer 19

the respiratory muscles.

Question 20

To change lung volume & generate air flow (V) it is necessary to create a

Answer 20

pressure gradient

Question 21

Compliance is the reciprocol

Answer 21

of elastance

Question 22

• FRC is determined by the

Answer 22

Compliance of the Lung and Chest Wall.

Question 23

• Compliance is the inverse of

Answer 23

Elastance & is a measure

of how easy the lungs inflate.

Question 24

• Reduced outward mobility of chest wall decreases

Answer 24

compliance

e.g. Severe obesity, constrictive bandages

Question 25

• Similarly, reduced lung volumes decreasing ?

Answer 25

C

e.g. pulmonary oedema, fibrosis, intra-bdominal pressure (late pregnancy).increased

Question 26

Using a spirometer (to adjust lung volume) and a pressure transducer (to measure airway pressure) can construct a curve
showing

Answer 26

relationship when respiratory

muscles are fully relaxed (black line).

Question 27

At high lung vols recoil of both

Lungs & Chest wall is

Answer 27

+ve.

Question 28

When flow is zero:

Answer 28

Ptotal = Pelastic = V/C

Question 29

Ventilation:

Answer 29

the movement of gas

into & out of the lungs

Question 30

Ventilation Mechanism:

Answer 30

bulk flow (diffusion is too slow)
Air moves down its pressure gradient

Question 31

Respiratory muscles utilised to ?

Answer 31

(intercostals & others) are
utilized to change thoracic volume & therefore
create the pressure gradients

Question 32

Thoracic movements are transmitted to the lungs by

Answer 32

pressure changes in the intra-pleural space.

Question 33

Inspiratory muscles:

Answer 33

• Diaphragm (dome descends)
• External intercostals (raise &
enlarge ribcage)
• Accessory muscles (during
exercise)

Question 34

Expiratory muscles:

Answer 34

• Passive during quiet
breathing. •
 At other times: the muscles of
the abdominal wall & the
internal intercostals.

Question 35

open pneumothorax (“collapsed lung”)
secondary to trauma.

Answer 35

On inspiration, the negative intrathoracic
pressure generated causes air to flow into
the lungs through the airways and into the
intrapleural space through the chest wall
defect.
• Air in the pleural space will press on the
lung, which can then partially or fully
collapse, causing dyspnoea.
• If air builds up in the pleural space, it can
push against the heart or the aorta – a
tension pneumothorax à Medical
emergency!

Question 36

Minute Ventilation:

Answer 36

Volume of air
shifted in & out of the lungs per minutes
Vt x fr

Question 37

Alveolar Ventilation eqn

Answer 37

VA = fR x (VT - VD)

Question 38

This expt showed that surface
tension contributed a large part to
the _______ ______ ______of the lungs

Answer 38

static recoil force

Question 39

Saline-filled lungs: vs. Air-filled lungs

Answer 39

Saline-filled lungs:
• Lungs inflated with saline have a much larger compliance
Air-filled lungs:
• show the effects of elastic elements and surface tension
• require larger pressures during inflation (hysteresis)

Question 40

Alveoli cell types

Answer 40

• Type I cells: gaseous
exchange
• Type II cells : secrete
surfactant
• Many elastic fibres
• Many capillaries
Large volume of blood in
pulmonary circulation (entire
RV output!)

Question 41

For surfactant & water, ____areas have the surface tension reduced much more than ____areas.

Answer 41

small

large

Question 42

Transmural pressure (P) is directly proportional to

Answer 42

surface

tension (T) and inversely proportional to radius (r).

Question 43

_______law & the properties of pulmonary surfactant are

important for understanding the mechanics of the lung.

Answer 43

Laplace’s

Question 44

The opening and closing of the _____airways account for
many of the properties of whole lung mechanics that were
once attributed to opening and closing of ______ alveoli.

Answer 44

small

spherical

Question 45

dyspnoea.

Answer 45

difficult or laboured breathing