Anatomy of chest wall, mechanics of breathing

Question 1

What’s at the hilum of the lungs?

Answer 1

• Pulmonary arteries, veins and main bronchi

Question 2

What’s the pleural cavity between?

Answer 2

Ribs and lung tissue

Question 3

What are the two membranes of the pleural cavity?

Answer 3

• Visceral

- Parietal

Question 4

Where does the parietal membrane go in the lungs?

Answer 4

Around the ribs

Question 5

Where does the visceral membrane go in the lungs?

Answer 5

Around the lungs

Question 6

Are the parietal and visceral membranes continuous or separate?

Answer 6

Continuous with eachother, at the hilux of the lung

Question 7

What does the pleural fluid do?

Answer 7

• Reduces friction

- Allows two membranes to glide over each other -> lubrication and prevents them from separating

Question 8

How much pleural fluid is there?

Answer 8

3ml

Question 9

Why are the parietal and visceral pleura so important in relation to lung inflation?

Answer 9

The lungs are effective stuck to the rib cage through the relationship of the pleural membranes

Question 10

Which muscles are involved in respiration?

Answer 10

External intercostal muscles, diaphragm, sternocleidomastoids, scalenes

Question 11

What do the muscles involved in respiration do?

Answer 11

Help lift the rib cage
Increase the thoracic cavity volume -> lung volume increases -> pressure inside lungs decreases -> air flows in from higher pressure

Question 12

Describe the motion of rib cage in respiration

Answer 12

• Bucket handle motion -> increases lateral dimension of the rib cage -> ribs increase anterior-posterior dimension of rib cage like pump handle

Question 13

With a normal breathing load, which muscles contract during expiration

Answer 13

None, the muscles STOP contracting.

They are assisted by the elastic fibre in alveoli

Question 14

During severe expiratory load, which muscles are used in expiration

Answer 14

Internal intercostal muscles

Abdominal muscles

Question 15

What is the motion of the internal intercostal muscles in expiration in exercise?

Answer 15

Downwards and inwards

Question 16

What is the motion of the abdominal muscles in expiration in exercise?

Answer 16

Up into the diaphragm

Question 17

Step by step process of breathing in relation to the diaphragm

Answer 17

• Breathing in -> diaphragm contracts and moves down
• Breathing out -> diaphragm relaxes and moves upwards into chest cavity -> in exercise abdominal muscles contract and push diaphragm against lungs more

Question 18

What’s Boyle’s Law?

Answer 18

• Pressure exerted by a gas is inversely proportional to its volume
• Gases will move from areas of high pressure to low pressure

Question 19

What’s the relationship between Boyle’s Law and the lungs?

Answer 19

• Change in volume of thoracic cavity
• Increase the volume, decrease the pressure
• Decrease the volume, increase the pressure

Question 20

What’s Charles’s law?

Answer 20

Total pressure of a gas mixture is the sum of the pressures of the individual gases

Question 21

What’s respiratory minute volume and why is it relevant?

Answer 21

Volume of gas inhaled or exhaled from a person’s lungs per minute

Question 22

What mechanical factors affect the respiratory minute volume?

Answer 22

Intra-thoracic pressure
Intrapleural pressure
Transpulmonary pressure

Question 23

What’s intrathoracic pressure?

Answer 23

P_A
Pressure inside lungs, inside thoracic cavity
Positive as long as alveolar pressure is greater than atmospheric pressure -> expiration
Negative as long as alveolar pressure is less than atmospheric pressure -> inspiration

Question 24

What’s intra-pleural pressure?

Answer 24

P_IP
Always negative
Pressure inside pleural cavity

Question 25

What’s transpulmonary pressure?

Answer 25

P_T
Difference between alveoli pressure and intrapleural pressure
Always positive
P_T = P_A - P_IP

Question 26

Why is intrapleural pressure always less than alveolar pressure?

Answer 26

IP has to be negative so inspiration can take place

Keeps the lungs inflated