5A

Question 1

How is the negative intrapleural pressure established?

Answer 1

Two forces act to pull the lungs away from the chest wall and cause lung collapse: 1) lungs have a natural tendency to recoil 2) The surface tension of the alveolar fluid constantly acts to draw the alveoli to their smallest possible dimension

Question 2

What are the lung-collapsing forces opposed by?

Answer 2

WThe natural elasticity of the chest wall - a force that tends to pull the thorax outward and to enlarge the lungs

Question 3

Which force wins - the lung collapsing force or the natural elasticity of the chest wall?

Answer 3

Neither, in a healthy person b/c of the strong adhesive force b/w the parietal and visceral pleura

Question 4

How does pleural fluid secure the pleurae together?

Answer 4

In the same way that a drop of water holds two glass slides together. The pleurae can slide from side to side easily, but separating them requires extreme force.

Question 5

What is the net result of the dynamic interplay between the forces in the lungs?

Answer 5

Negative P_ip (intrapleural pressure)

Question 6

What would happen if the negative p_ip was equalized with intrapulmonary or atmospheric pressure?

Answer 6

lung collapse

Question 7

What pressure keeps the air space of the lungs open (keeps the lungs from collapsing)?

Answer 7

Transpulmonary pressure

Question 8

What is transpulmonary pressure?

Answer 8

The difference b/w the intrapulmonary and intrapleural pressures (P_pul - P_ip)

Question 9

What pressure determines that size of the lungs at any given time?

Answer 9

Transpulmonary pressure - the greater this pressure the larger the lungs