Anatomy of Chest Wall and Mechanics of breathing

Question 1

How much pleural fluid is between the pleural membranes and what does it do?

Answer 1

3ml - lubricates them and keeps them stuck together.

Question 2

Where do the pleural membranes become continuous?

Answer 2

the hilux of the lung - where all the stuff goes in

Question 3

whats the membrane on the surface of the lungs called?

Answer 3

visceral

Question 4

whats the membrane on the inside of the ribs called?

Answer 4

pariental

Question 5

why is the relationship between the visceral and parietal pleura important for the inflation of the lung?

Answer 5

They are held together due to the pleural fluid, and attach the lungs to the inside of the rib cage. So when the ribcage expands, they expand too (although they want to recoil)

Question 6

Which muscles are involved in inspiration?

Answer 6

Diaphragm and external intercostals (aided by scalene and sternocleidomastoid)

Question 7

What muscles can be used for forced expiration?

Answer 7

internal intercostals and abdominal muscles.

Question 8

What does forced expiration do?

Answer 8

It reduces thoracic dimensions and reduces the duration of breathing cycle and allows more breaths per min..

Question 9

What type of motion increases the anterior - posterior dimensions of the rib cage?

Answer 9

‘Pump handle’

Question 10

What type of motion increases the lateral dimensions of the rib cage?

Answer 10

‘Bucket handle’

Question 11

What is Boyle’s law?

Answer 11

‘The pressure exerted by a gas is inversely proportional to its volume’ P a 1/V).

Question 12

In terms of boyles law, why would air go into the lungs during inspiration?

Answer 12

Increase in thoracic volume > decrease in pressure > gas goes from high pressure to low > gas goes into the lungs

Question 13

What is respiratory minute volume?

Answer 13

The volume of gas inhaled or exhaled per minute

Question 14

What creates a sub atmospheric pressure in the intrapleura, that leads to a transpulmonary pressure that opposes the force of elastic recoil?

Answer 14

The opposite forces of the lungs and the chest wall

Question 15

inspiration causes intrapleural pressure to become more negative. Explain?

Answer 15

Breath in, increase space, pulls pleural down, increases volume and decreases pressure.

Question 16

What does the amount of air flow during ventilation depend on ?

Answer 16

the difference between the atmospheric pressure and then alveolar pressure. It is inversely proportional to air way resistance.

Question 17

What is inter thoracic pressure?

Answer 17

alveolar pressure - pressure inside the thoracic cavity.

Can be negative or positive compared to atmospheric pressure.

Question 18

What is intra-pleural pressure?

Answer 18

pressure inside the pleural cavity. Always negative, suction to keep lungs inflated.

Question 19

What is transpulmonary pressure?

Answer 19

difference between alveolar pressure and inter pleural pressure. Always positive cos pip is always negative.
PT = Palv - Pip

Question 20

What is pleurisy?

Answer 20

Inflammation of the pleural membranes - so they do not slide across each other smoothly

Question 21

Does asthma make inspiration of expiration difficult? Why?

Answer 21

Expiration - as its passive. Since asthma is over- reactive constriction of bronchioles, the air cannot get back out well

Question 22

explain pneumothorax.

Answer 22

the pleural cavity is sitting at a lower pressure than the atmosphere. If the sealed pleural cavity is opened to the atmosphere, air rushes in until the intraplureal pressure and atmospheric pressure are equal. Lungs collapse to unstretched size.