Respiration Lecture 1

Question 1

Basic Function

Answer 1

Homeostasis of CO2, O2, and blood pH
- Generation of speech
- Warm, humidify and clean inspired air
- The nose serves as an olfactory organ
- Activates some hormones
(AngiotensinII)
- Inactivates other hormones
(Prostaglandins)

Question 2

Steps of external respiration

Answer 2

1. Ventilation or gas exchange between the atmosphere and air sacs (alveoli) in the lungs
2. Exchange of O2 and CO2 between air in the alveoli and the blood CO2
3. Transport of O2 and Co2 between lungs and the tissues
4. Exchange of O2 and CO2 between the blood and the tissues

Question 3

Fick’s Law of Diffusion

Answer 3

 The shorter the distance through which diffusion must take place, the greater the rate of diffusion
 The greater the surface area across which diffusion can take place, the greater the rate of diffusion

Question 4

Branching results in:

Answer 4

 Up to airway generation 19:
Increase of number of airways with decreasing diameter.
 Above airway generation 19:
Increase of total cross section area

Question 5

An alveolus

Answer 5

At an air-water interface, the
H2O molecules are attracted to
each other. In a bubble like an
alveolus, it results in alveolar
surface tension that causes an
inward pressure. Thus an
alveolus resists being
stretched, tends to
collapse/reduce in size, and
tends to recoil after being
stretched.

Question 6

Law of LaPlace

Answer 6

Magnitude of inward-directed pressure (P) in a bubble (alveolus)

2 x Surface tension (T)/
Radius (r) of bubble (alveolus)

-According to the Law of LaPlace, small alveoli would collapse and empty their air into neighbouring larger alveoli.

Question 7

Pulmonary Surfactant

Answer 7

 reduces the lung’s tendency to recoil
 increases pulmonary compliance
 helps maintaining lung stability by preventing small alveoli to collapse into larger ones

Question 8

Pulmonary Surfactant

Answer 8

 Pulmonary surfactant molecules scatter
between H2O molecules reducing the alveolar
surface tension.
- Pulmonary surfactant reduces
alveolar surface tension more in small alveoli than
in large ones, because the surfactant molecules
are closer together in small alveoli.
- Pulmonary surfactant therefore helps maintaining lung stability by preventing small alveoli to collapse
into larger ones.

Question 9

Alveolar Interdependance

Answer 9

stabilizes alveoli by interconnectedness
if alveolus in center begins to collapse –> increases in wall stress of adjacent alveoli, which then tend to hold the collapsing one open