test 4 part 2

Question 1

Steps of external respiration

Answer 1

1. ventilation or gas exchange between the atmosphere and air sacs (alveoli) in the lung
2. exchange of O2 and CO2 between air in the alveoli and the blood in the pulmonary capillaries
3. Transport of O2 and CO2 by the blood between the lungs and the tissues
4. exchange of O2 and CO2 between the body in the systemic capillaries and tissue cells
   - cellular respiration

Question 2

Each lung enclosed in separate double-layered serous membrane called the

Answer 2

• pleural membrane

Question 3

Parietal pleura

Answer 3

• outer layer (superficial) is attached to the wall of

the thoracic cavity

Question 4

Visceral pleura

Answer 4

-inner layer covers the surface of the lungs

Question 5

Pleural cavity

Answer 5

• space between parietal and visceral – filled with

fluid

Question 6

what drives the movement of gas in and out of the lung

Answer 6

• P inside of the pleural cavity

Question 7

average diameter of alveoli

Answer 7

• 100 um

- HUGE surgace area

Question 8

two ways of expanding and contracting the lungs

Answer 8

 Movement of diaphragm

 Raising and lowering the ribs

Question 9

Movement of diaphragm

Answer 9

 Contraction (inspiration) & relaxation (expiration)

• contracted= diaphram drops and enlarges the thoracic area (decreases pleural pressure)
• relaxed= Diaphragm relaxes (returns to normal positions) allowing elastic recoil of lungs, chest wall, & abdominal structures to compress lungs(increases pleural pressure)

Question 10

Raising and lowering the ribs

Answer 10

 Contraction (inspiration) & relaxation (expiration) of external and internal intercostal muscles
 Changes anteroposterior diameter of chest cavity
-moves ribs from front to back

Question 11

as volume increases, the pressure inside of the cavity does what

Answer 11

-pressure goes down

Question 12

process of insipration

Answer 12

• diaphram contracts downward which greatly increases the volume inside of the thoracic cage
• so the P in the thoracic cage goes down
• P in the atmosphere is higher than the P in the thoracic cage so gas moves down the trachea and into alveoli

Question 13

what is the natural state of the alveoli

Answer 13

-collapsed

Question 14

when we need to increase the amount of gas moving and the elastic forces are not enough to rapidly expel gas from the lungs, what does the body do

Answer 14

 Add contraction of abdominal muscles

 Pushes abdominal organs up against the diaphragm adding to compression of the lungs

Question 15

Raising the rib cages moves them

Answer 15

• up and forward

 Increases anteroposterior thickness by 20%

Question 16

How does the rib cage raise during inspiration

Answer 16

 External intercostal muscles contract (inspiratory muscles)
 Internal intercostal muscles relaxed

Question 17

How does the rib cage lower during expiration

Answer 17

 Abdominal recti & internal intercostal muscles contract (expiratory muscles)
 External intercostal muscles relax

Question 18

Accessory muscles of inspiration

Answer 18

• sternocleidomastoid and scalenus

- contract only during forceful inspiration

Question 19

Lungs

Answer 19

 Lungs very elastic
 Their natural tendency is to collapse (forcing air out of lungs) when no force is applied to keep the lungs inflated
 Minimal physical/anatomical attachment of lungs to the chest wall

Question 20

effect of pleural cavity on lungs

Answer 20

 Surface tension of pleural fluid and drainage of pleural cavity by lymphatic channels creates suction (negative pressure in cavity) between
visceral pleura and parietal pleura
 Negative pressure/suction holds visceral surface of lungs close to the chest wall creating natural expansion of lungs
-it is the P in the pleural cavity that keeps the lungs expanded

Question 21

normal pleural pressure

Answer 21

• P of -5 cm H2O

- holds lungs open to normal resting level

Question 22

pleural pressure and lung volume during inspiration

Answer 22

 Expansion of chest cavity results in further decrease in pressure (-7.5 cmH2O)
 Decrease in pressure associated with increased lung volume (500 mls)

Question 23

pleural pressure and lung volume during expiration

Answer 23

 Recoil of chest cavity returns pressure back to resting level
 Increase in pressure associated with decreased lung volume (500 mls)

Question 24

normal P in alveoli is close to

Answer 24

-0 cm H2O (atmospheric pressure)

Question 25

At start of inspiration, glottis is open, no air is flowing so pressure in all parts of respiratory tree (including alveoli)

Answer 25

- equals atmospheric pressure

Question 26

in order to move air into the alveoli

Answer 26

-pressure in alveoli MUST be lower than atmospheric pressure, i.e. alveolar pressure MUST be negative

Question 27

why does alveoli pressure begin to go back up

Answer 27

-because the alveoli are being filled with gas

Question 28

what P gradient needs to be larger (alveoli vs pleural OR alveoli vs atmospheric)

Answer 28

- Alveoli vs pleural cavity must be larger

Question 29

alveoli pressure during inspiration

Answer 29

 Expansion of chest cavity results in decrease in plural pressure which causes alveolar pressure to drop  Alveolar pressure drops to -1cmH2O which draws 500 mls of air into the alveoli  Takes 2 seconds to inspire the 500 mls of air

Question 30

alveoli pressure during expiration

Answer 30

 Recoil of chest cavity returns pleural pressure back to resting level and alveolar pressure increases to +1 cmH2O pushing 500 mls of air out of the alveoli  Takes 2 to 3 seconds to expire the 500 mls of air -takes longer during expiration because it is not an active process and its working against a positive pressure