Respiratory System Lecture 1

Question 1

What are the 3 main components of the Respiratory System?

Answer 1

Ventilation:

Gas exchange:

Gas transport:

Question 2

What is Ventilation?

Answer 2

Air exchange between the atmosphere and alveoli.

Question 3

What is Gas Exchange?

Answer 3

• External respiration: gas exchange between alveoli and pulmonary capillaries.
• Internal respiration: gas exchange between tissue capillaries and interstitial fluid/tissue cells.

Question 4

What is Gas Transport?

Answer 4

Gas movement by pulmonary and
systemic circulations.

Question 5

sea level atmospheric pressure

Answer 5

typically ~760 mmHg

Question 6

reporting pressure changes

Answer 6

Question 7

How does Inspiration Work?
(in regards to pressure)

Answer 7

Breath in – inspiration:
atmosphere (high pressure) to lungs (low pressure)

Question 8

How does Expiration Work?
(in regards to pressure)

Answer 8

Breath out – expiration:
lungs (high pressure) to atmosphere (low pressure)

Question 9

What happens to pressure between breaths?

Answer 9

Between breaths –
pressures equalize between lungs and atmosphere;
no pressure gradient so no air movement for a moment

Question 10

How do we create a pressure gradient for ventilation?

Answer 10

To get pressure gradient for ventilation:
Since Atmospheric pressure is variable, we are not usually in control of it.

We Need to manipulate pressure at lung level to get pressure gradients no matter what atmospheric pressure is doing.

Question 11

Boyle’s Law

Answer 11

Question 12

3 Pressures of Interest:

Answer 12

1. Atmospheric Pressure (P-atm):
   AKA air pressure or barometric pressure.
   Surrounding environmental conditions.
2. Alveolar Pressure (P-alv):
   Within alveoli.
3. Intrapleural Pressure (P-ip)
   Inside intrapleural space

Question 13

What is Intrapleural Pressure?
How does it create a pressure gradient?

Answer 13

Variable but always subatmospheric (lower than P-atm)

Creates a pressure gradient:
Pulls lung out – opposes natural lung elastic recoil.
Pulls chest wall in – opposes natural chest wall elastic recoil.

Allows the lung and chest wall to move together as a unit.
Without this pressure gradient, the lungs collapse and chest wall springs out

Question 14

What would happen if intrapleural pressure were to equalize with atmospheric pressure?

Answer 14

If the intrapleural pressure were to equalize with atmospheric pressure or become positive (higher than atmospheric pressure), the lung’s elastic recoil would dominate, and the lung would tend to collapse

Question 15

What Muscles are being used during Inspiration at rest?

Answer 15

Resting breathing:

75% Diaphragm
Contraction – downward flattening (~ 2cm).

25% External intercostals
Contraction – outward and upward movement of the chest wall.

Question 16

How Does Inspiration Work? (6)

Answer 16

1. Diaphragm/external intercostals contract
2. Thoracic cavity volume increases
3. P-ip becomes more subatmospheric
4. Lung Volume increases
5. P-alv becomes subatmospheric
6. AIr Flows into Lungs

Question 17

How do muscles act when breathing in (inspiration) becomes more forceful? (3)

What does this Result in? (3)

Answer 17

Diaphragm
Stronger Contraction; more downward flattening (up to 10 cm).

External intercostals
Stronger Contraction; more outward and upward movement of the chest wall.

Accessory muscles of inspiration recruited
(scalenes, sternocleidomastoid, pectoralis minor).

Result
- Greater increase in lung volume.
- P-ip becomes more subatomic (larger pressure gradient).
- Even more air flows into the lungs

Question 18

What Muscles are being used during Expiration at rest? (3)

Answer 18

Resting breathing:
Recoil to pre-inspiration positions.

Diaphragm
Contraction ends – recoil back to dome shape.

External intercostals
Contraction ends – inward and downward recoil of the chest wall.

Question 19

How Does Expiration Work? (6)

Answer 19

1. Diaphragm/external intercostals stop contracting
2. Recoil – thoracic cavity volume decreases
3. P-ip returns to pre-inspiration level
4. Lung volume decreases returning to pre-
   inspiration size (compresses alveoli)
5. P-alv becomes greater than P-atm
6. Air flows out of lungs

Question 20

How do muscles act when breathing out (expiration) becomes more forceful? (3)

What does this Result in? (3)

Answer 20

Diaphragm
Contraction ends – recoil back to dome shape.

External intercostals
Contraction ends – inward and downward recoil of the chest wall.

Accessory muscles of expiration recruited
(internal intercostals, abdominals).

Result
- Greater decrease in lung volume; more compression of alveoli.
- P-alv increases beyond P-atm (larger pressure gradient).
- Even more air flows out of the lungs.