pulmonary ventilation

Question 1

what is pulmonary ventilation needed for

Answer 1

-maintain oxygen and co2 gradients between alveolar air and arterial blood
-allows sufficient level of gas exchange
-adequate blood supply

Question 2

what is ventilation dependant on and what is the equation for ventilation

Answer 2

depth and rate of breath

ventilation = tidal volume x frequency

Question 3

how much of the dead space volume is left in the respiratiry system

Answer 3

150mL

Question 4

equation for alveolar air

Answer 4

Va= (Vt-Vd) x f

Vt = tidal volume
Vd= dead space volume ( volume of air remaining in respiratory system at the end of expiration )

Vt-Vd= the volume of fresh air entering each breath

Question 5

brief overview of what happens in inspiration

Answer 5

-diaphragm contracts
-thoracic cavity expands
-alveolar pressure decreases

Question 6

brief overview of what happens in expiration

Answer 6

-diaphragm relaxes
-lungs recoil
-thoracic cavity volume decreases
-alveolar pressure increases

Question 7

at the end of expiration

Answer 7

P alveoli=P atmostphere

there is no movement of air

Question 8

describe pressure changes in atmostphere and alveoli during inspiration

Answer 8

-higher atmostpheric pressure
-lower alveolar pressure
-air flows into alveoli
-outer surfaces of lungs are pulled outwards

Question 9

describe pressure changes in alveoli and atmosphere during expiration

Answer 9

-lower pressure in atmosphere
-higher pressure in alveoli
-air flows out
-air within lungs is compressed

Question 10

what is the pleural cavity

Answer 10

fluid filled space between membranes that line the chest wall and each lung

Question 11

use of the pleural cavity

Answer 11

-reduces friction between lungs and chest during breathing

Question 12

what are the properties of the pleural cavity

Answer 12

-sealed
-fluid filled
-sub atmospheric

Question 13

what causes the pleural cavity to be sub atmospheric

Answer 13

the opposing elastic recoil of the chest wall (outwards) and the lungs (inwards ) makes the pressure in the pleural cavity sub atmospheric

Question 14

what is negative pressure

Answer 14

lower number of molecules per volume which generates a collapsing force

Question 15

what is positive pressure

Answer 15

increased number of molcules per volume which generates expanding force

Question 16

outline inspiration

Answer 16

-respiratory muscles eg diaphragm, contract
-volume of thoracic cavity increases
-interpleural pressure becomes negative
-lungs expand, increasing volume
-p alv decreases below p atm
-air moves down pressure gradient , through airways into alveoli , expanding lungs

Question 17

outline expiration

Answer 17

-respiratory muscles relax eg diaphragm
-volume of thoracic cavity decreases
-interpleural pressure increases
-lungs compressed , volume decreases
-p alv increases above p atm
-air moves down pressure gradient into atmosphere

Question 18

what happens in forced expiration

Answer 18

compression of lungs due to increased interpleural pressure

Question 19

what happens in quiet breathing

Answer 19

elastic recoil is sufficient to decrease lung volume

Question 20

what happens if either pleura is ruptured

Answer 20

-air will enter pleural space because its sub atmospheric
-lung will recoil and collapse
-pneumothorax

-pressure gradient in pleural cavity and surrounding environment causes air to enter (pneumothorax) until intrapleural pressure = atmospheric pressure