respiration 3

Question 1

Compliance

Answer 1

• Refers to how much effort is required to
  stretch or distend the lungs
• How much Δ in lung volume results from a Δ in
  transmural pressure

Question 2

The less _______ the lungs are, the more work is required to produce a given degree of inflation

Answer 2

compliant

Question 3

poor compliance =

Answer 3

stiff lung

Question 4

compliance is decreased by factors such as

Answer 4

pulmonary fibrosis

Question 5

Elastic Recoil

Answer 5

• Refers to how readily the lungs rebound after
  having been stretched
• Responsible for lungs returning to their pre-
  inspiratory volume when inspiratory muscles
  relax at end of inspiration

Question 6

Elastic Recoil depends on 2 factors

Answer 6

• Highly elastic connective tissue in the lungs

- Alveolar surface tension

Question 7

Alveolar surface tension

Answer 7

• Thin liquid film lines each alveolus
• Reduces tendency of alveoli to recoil
• Helps maintain lung stability
  > Newborn respiratory distress syndrome

Question 8

Surface tension

Answer 8

Unequal attraction of water molecules to each other at water air interface

Question 9

The _______ the surface tension, the less compliant (stiffer)

Answer 9

greater

Question 10

Emphysema:

Answer 10

loss of elastic

• fibers - decrease in elastic
• recoil - expiration dysfunctional

Question 11

2 factors opposing alveoli collapse

Answer 11

• Surfactant (surface active agent)

- LaPlace

Question 12

Surfactant

Answer 12

(surface active agent)
- lipids/proteins by pneumocytes II
> increases complicance, reduces recoil

Question 13

LaPlace:

Answer 13

collapsing pressure ~ surface tension
collapsing pressure~ 1/radius
P=2T/r

Question 14

Role of pulmonary surfactant in counteracting the tendency for small alveoli to collapse into larger alveoli.

Answer 14

1. According to the law of LaPlace, if two alveoli
   of unequal size - but the same surface tension
   are connected by the same terminal airway,
   the smaller alveolus—because it generates a
   larger inward-directed collapsing pressure—
   has a tendency (without pulmonary surfactant)
   to collapse and empty its air into the larger
   alveolus.
2. Pulmonary surfactant reduces the surface
   tension of a smaller alveolus more than that
   of a larger alveolus. This reduction in surface
   tension offsets the effect of the smaller radius
   in determining the inward-directed pressure.
   Consequently, the collapsing pressures of
   the small and large alveoli are comparable.
   Therefore, in the presence of pulmonary
   surfactant a small alveolus does not collapse and empty its air into the larger alveolus.

Question 15

Alveolar interdependence

Answer 15

1. When an alveolus in a group of interconnected alveoli starts to collapse, the surrounding alveoli are stretched by the collapsing alveolus.
2. As the neighbouring alveoli recoil in resistance to being stretched, they pull outward on the collapsing alveolus.
3. This expanding force pulls the collapsing alveolus open.

Question 16

Forces keeping the alveoli open

Answer 16

• transmural pressure gradient
• pulmonary surfactant
  (opposes alveolar surface tension)
• alveolar interdependence

Question 17

Forces promoting alveolar collapse

Answer 17

• Elasticity of stretched pulmonary connective
  tissue fibres
• Alveolar surface tension

Question 18

Work of Breathing

Answer 18

• Normally requires 3% of total energy
  expenditure for quiet breathing
• Lungs normally operate at about “half full”

Question 19

Work of breathing is increased in the following situations

Answer 19

• When pulmonary compliance is decreased
• When airway resistance is increased
• When elastic recoil is decreased
• When there is a need for increased ventilation

Question 20

Decrease in radius, increase resistance to airflow (airway).
Caused by:
- allergy-induced spasm
- excess mucus
- edema of the walls
- airway collapse

Answer 20

Bronchoconstriction

Question 21

Increase in radius of airway, decreased resistance to airflow
Hormone control:
Epinephrine

Answer 21

Bronchodilation

Question 22

a device that measures the volume of air breathed in and out; it consists of an air-filled drum floating in a water-filled chamber. As a person breathes air in and out of the drum through a connecting tube, the resultant rise and fall of the drum are recorded as a spirogram, which is calibrated to the magnitude of the volume change.

Answer 22

A spirometer.

Question 23

Variations in lung volume in a healthy young adult male.
Values for females are somewhat lower.
(Note that residual volume cannot be measured with a spirometer but must be determined by another means.)

Answer 23

Question 24

vital capacity

Answer 24

The difference between the maximum volume of the lungs at maximum inspiration and the minimum volume of the lungs at maximum expiration

[the maximum volume of air that can be moved out during a single breath following a maximum inspiration.]

Question 25

Pulmonary Ventilation

Answer 25

• Minute ventilation
• Volume of air breathed in and out in one
  minute

Question 26

Alveolar Ventilation

Answer 26

[More important than pulmonary ventilation]
- Volume of air exchanged between the
atmosphere and the alveoli per minute
=> functional respiration
- Less than pulmonary ventilation due to
anatomic dead space
- Volume of air in conducting airways that is
useless for exchange
Averages about 150 ml in adults

Question 27

Alveolar ventilation=

Answer 27

(tidal volume – dead space) x respiratory rate

Question 28

Effect of dead space volume on the exchange of tidal volume between the atmosphere and the alveoli.

Answer 28

• Even though 500 ml of air move in and out
  between the atmosphere and the respiratory
  system and 500 ml move in and out of the
  alveoli with each breath,
• only 350 ml are actually exchanged between the atmosphere and the alveoli because of the anatomic dead space
  (the volume of air in the respiratory airways).

Question 29

effect of a local change in O2 on pulmonary and systematic arterioles

Answer 29

Decreased O2 Increased O2
Pulmonary Vasoconstriction Vasodilation
arterioles

Systematic Vasodilation Vasoconstriction
arterioles

Question 30

Local control matches ventilation and perfusion

Answer 30

1. Ventilation in alveoli is matched to perfusion through pulmonary capillaries
2. [ Ventilation-perfusion mismatch]
   If ventilation decreases in a group of alveoli, PCO2 increases, and PO2 decreases. Blood flowing past those alveoli doesn’t get oxygenated
3. [Local control mechanisms try to keep ventilation and perfusion matched]
   Decreased tissue PO2 around underventilated alveoli constricts their arterioles, diverting blood to better ventilated alveoli

Question 31

Local controls to match airflow and blood flow to an area of the lung.

Answer 31

• CO2 acts locally on bronchiolar smooth muscle
• O2 acts locally on arteriolar smooth muscle
  to adjust ventilation and perfusion, respectively, to match airflow and blood flow to an area of the lung.

(and vice versa-for the picture)

Question 32

Differences in ventilation, perfusion, and ventilation-perfusion ratios at the top and bottom of the lungs as a result of

Answer 32

• gravitational effects.

Note that the top of the lungs receives less air and blood than the bottom of the lungs, but the top of the lungs receives relatively more air than blood and the bottom of the lungs receives relatively less air than blood.

Question 33

match perfusion with ventilation - make respiration functional

Answer 33

O2 via capillary radius control

and Co2 via bronchial radius control