Anatomy of Chest Wall and Mechanics of Breathing

Question 1

State Boyle’s Law

Answer 1

Pressure exerted by a gas is directly proportional to its volume

Question 2

What are the two membranes of the pleural cavity

Answer 2

pariteral - sits inside the rib

Viscera - coats outer surface

Question 3

What is the importance of the pleural fluid

Answer 3

allows gliding of the membranes

stops separation of thoracic cavity and the lungs

Question 4

define pleurisy

Answer 4

inflammation of the lungs

Question 5

What simple mechanism allows us to breath and why

Answer 5

thoracic cavity increases in volume, following Boyles law this means there is a decrease in pressure, causing air move from high pressure in the atmosphere to the low pressure in the lungs

Question 6

What muscle are used for Inspiration?

Answer 6

Intercostal muscle
Diaphragm - contracts, flattening out
(both result in an increase in thoracic volume)
Scalene + sternomastoid - (help intercostal)

Question 7

How is pneumothorax caused?

Answer 7

Break in the pleural membrane, allowing air in changing intrapleural pressure
While the recoil equilibrium created between thorasic cavity and lungs by the pleural membrane means the lung recoils and collapses

Question 8

What is intrapleural pressure

Answer 8

pressure inside the pleural cavity

always negative

Question 9

What muscles are used for expiration when you are respiring quickly e.g. through exercise and how?

Answer 9

internal intercostal muscles and abdominal muscles

abdominal muscles actively decreases thoracic dimensions this reduces duration of breathing cycle and allows more breaths/min.

Question 10

How is asthma caused

Answer 10

Over reactive constriction of bronchial smooth muscle, increase resistance, expiration difficult

Question 11

Define Intra-thoracic (Alveolar) Pressure

Answer 11

pressure inside the thoracic cavity, (essentially pressure inside the lungs).

Question 12

How do you calculate transpulmonary pressure

Answer 12

difference between alveolar pressure and intra-pleural pressure

Question 13

Why is transpulmonary pressure always positive

Answer 13

Intrapleural is always negative
and although alveolar pressure is negative during inspiration, Intrapleual pressure is always gonnna be more negative so transpulmonary pressure WILL always be POSITIVE

Question 14

Why does intrapleural pressure need to be negative

Answer 14

As needs to be less that atmospheric pressure to allows oxygen into the lungs
and must oppose the pressure of the chest wall recoiling out while lungs recoil in

Question 15

what is the major determinant in airway resistance

Answer 15

the radii of the airways

Question 16

How do you calculate the bulk flow of air between the atmosphere and alveoli

Answer 16

the difference between atmospheric pressure and alveoli pressure
divided by airway reisitance

Question 17

When does atmospheric pressure equal alveoli pressure

Answer 17

Between breaths at the end of an unforced expiration

Question 18

What are the opposing elastic forces present in the lungs and thoracic cage

Answer 18

The lungs are stretched and are attempting to recoil, whereas the chest wall is compressed and attempting to move outward

Question 19

What opposes the force of elastic recoil

Answer 19

transpulmonary pressure

Question 20

what does the opposing elastic recoils create

Answer 20

a subatmospheric intrapleural pressure (keeping it negative and below atmospheric pressure) as allow the lungs to expand and pressure to decrease so air can move in

Question 21

What two basic things does the lungs volume depend on?

Answer 21

transpulmonary pressure and how stretchable the lungs are

Question 22

What occurs during expiration

Answer 22

Inspiratory muscles stop causing elastic recoil, therefore chest size returns to normal and compresses the alveolar air, raising alveolar pressure above atmospheric pressure and driving air out of the lungs