RESPIRATORY MECHANICS

Question 1

Internal respiration

Answer 1

intracellular mechanism which consumes O2 and produces CO2 (at level of body tissue)
simple diffusion due to partial p. gradient

Question 2

external respiration

Answer 2

exchange of gases betw. external env. and bloodstream

Question 3

components of extracellular respiration

Answer 3

alveolar S.A.
ventilation
perfusion matching
partial p. gradient

Question 4

partial p. gradient?

Answer 4

allows gases to flow from high to low p. areas

Question 5

what must be balanced to maintain efficient gas exchange ?

Answer 5

ventilation & perfusion in alveoli

Question 6

what are the 4 steps of external respiration?

Answer 6

1. ventilation
2. gas exchange betw. alveoli and blood
3. gas transport in blood
4. gas exchange at tissue level

Question 7

ventilation

Answer 7

gas exchange betw. atm. and alveoli

mechanical process of movement of air in & out the lungs

Question 8

gas exchange betw. alveoli and blood

Answer 8

exchange of O2 & CO2 betw.
air in alveoli
&
blood in pulmonary capillaries

Question 9

gas transport in blood

Answer 9

betw. lung and tissue

binding & transport of O2 & CO2 in circulating blood

Question 10

gas exchange at tissue level

Answer 10

exchange of O2 and CO2 betw.
blood in systemic capillaries
and body cells

Question 11

key features in ventilation

Answer 11

• air flow from high to low p. regions down the p. gradient

- Palv < Patm - for air flow into lungs during inspiration

Question 12

before inspiration

Answer 12

Palv = Patm

Question 13

during inspiration

Answer 13

thorax and lungs expand - due to contraction of inspiratory muscles

v. of gas increases
p. exerted by gas decreases

Question 14

what 2 forces links lung to thorax ?

Answer 14

1. intrapleural fluid cohesiveness

2. negative intrapleural pressure

Question 15

intrapleural fluid cohesiveness

Answer 15

• attraction of H2O M/ - resist pulling forces

- pleural membranes stick together

Question 16

negative intrapleural pressure

Answer 16

• sub-atm. intrapleural p. creates a TRANMURAL p. gradient across lung and chest wall
• lung forced to expand outwards
• chest forced to squeeze inwards

Question 17

Patm at sea level

Answer 17

760 mmHg

Question 18

across lung wall

Answer 18

Palv. = 760 mmHg - push inwards
Pip. = 756 mmHg - push outwards

Question 19

across lung wall, the 4 mmHg difference between Palv. and Pip. .

Answer 19

creates a TRANSMURAL p. gradient
push out on lung
STRETCH to fill thoracic cavity

Question 20

across thoracic wall

Answer 20

Patm. = 760 mmHg - push inwards

Pip. - 756 mmHg - push outward

Question 21

across thoracic wall, the 4 mmHg difference bet. Patm. and Pip. ..

Answer 21

creates a TRANSMURAL p. gradient
push in
COMPRESS thoracic wall

Question 22

3 imp. p. in ventilation are ..

Answer 22

1. Patm.
2. Palv.
3. Pip.

Question 23

Patm.

Answer 23

p. caused by weight of gas in atm. on earths surface

~ 760 mmHg at sea level

Question 24

Palv.

Answer 24

p. within lung alveoli

~ 760 mmHg when equilibrated w/ Pat,.

Question 25

Pip.

Answer 25

P. exerted outside lung within pleural cavity | Pip. < Patm.

Question 26

Inspiration key features

Answer 26

active process | depends on muscle contraction (external intercostal)

Question 27

what happens to the V. of thorax during inspiration?

Answer 27

increases vertically

Question 28

what happen to the diaphragm during inspiration?

Answer 28

- diaphragm contracts - flattens dome shape - which increases vertical dimension of thoracic cavity - phrenic nerve 3, 4, 5

Question 29

what happens when the external intercostal muscle contracts during inspiration?

Answer 29

- ribs are lifted - sternum moves upwards and outwards -which increases the side - side dimension of the thoracic cavity - chest wall &lungs stretch

Question 30

what happens to the Palv. during inspiration?

Answer 30

Palv. decreases - due to increase in size of lungs due to Boyle's law (air M/ contained in larger v.) air enters lung down P. gradient until Patm. = Palv.

Question 31

Expiration key features

Answer 31

passive process | relaxation of inspiratory muscles

Question 32

what happens to Palv. during expiration?

Answer 32

Palv. increases as lung recoils - bcz air M/ are contained in smaller V. air leaves lung down p. gradient until Palv. = Patm.

Question 33

pneumothorax

Answer 33

air in pleural space - enters from outside/ lungs | abolish TRANSMURAL p. gradient - - - - lung collapses (unstretched size)

Question 34

3 types of pneumothorax

Answer 34

1. spontaneous - hole in wall 2. traumatic - puncture in chest wall 3. iatrogenic

Question 35

symptoms of pneumothorax

Answer 35

shortness of breath | chest pain

Question 36

physical signs of pneumothorax

Answer 36

hyper resonant percussion note | the decrease/ absence of breath sound

Question 37

what results in lung recoil during expiration?

Answer 37

elastic connective tissue | alveolar surface tension

Question 38

alveolar surface tension

Answer 38

attraction betw. H2O M/ at the liquid air interface | produces a force the resists stretching of lungs in alveoli

Question 39

pulmonary surfactant

Answer 39

complex mixture of lipids and proteins | secreted by type II alveoli

Question 40

what does pulmonary surfactant do ?

Answer 40

decreases alveolar surface tension | by interspersing betw. H2O M/ lining the alveoli

Question 41

smaller alveoli has ..

Answer 41

smaller r | so higher tendency to collapse

Question 42

what prevents small alveoli from collapsing and emptying its contents into large alveoli?

Answer 42

decrease in surface tension in small alveoli

Question 43

Laplace's Law

Answer 43

P = 2T/ r

Question 44

alveolar interdependence

Answer 44

neighbouring alveoli recoil in resistance to being stretched by collapsing alveoli pill it open