2.2 - ventilation of the lungs (workbook)

Question 1

how is air drain into the lungs?

Answer 1

by expanding thoracic cavity

Question 2

what is done during breathing?

Answer 2

work is done to move structures of the lung and thorax and to overcome the resistance to the flow of air through the airways

Question 3

what type of structures are the lungs?

Answer 3

elastic structures and if removed from the chest cavity the inward elastic recoil of the lungs causes the lungs to totally collapse

Question 4

how is the chest wall like?

Answer 4

recoils outwards, from its usual position when the thoracic cavity is open to the atmosphere e.g. thoracic surgery

Question 5

what are the lungs like within the living respiratory system?

Answer 5

lungs are sealed within the chest by the pleural seal
the elastic forces of lung and chest walls are balanced in equal and opposite directions at the end of quiet expiration (respiratory muscles are at rest)

Question 6

what happens when there is an absence of muscular activity?

Answer 6

(when the respiratory muscles are relaxed)
there is an equilibrium position, when the inward force of the elastic recoil of the lungs is balanced by the outward recoil of the chest wall - same state as the end of normal quiet expiration

Question 7

what is the equilibrium position known as?

Answer 7

resting expiratory level

Question 8

what are the lungs sealed within the chest by?

Answer 8

pleural seal

Question 9

what forms the pleural seal?

Answer 9

the pleural space (filled with few ml of pleural fluid) forms a seal, holding outer surface of the lungs (visceral) to the inner surface of the chest wall (parietal)

Question 10

what does the pleural seal ensure?

Answer 10

that the chest wall and lungs move together

when the chest expands increasing the volume of the thorax cage, the lungs also expand

Question 11

what is the functional residual capacity (FRC)?

Answer 11

the lung volume that exists at the end of expiration (at resting expiratory level)

Question 12

what is significant at FRC (functional residual capacity)?

Answer 12

the elastic forces of the lung and chest walls are balanced

Question 13

what disrupts the FRC (functional residual capacity)?

Answer 13

the muscles involved in breathing apply force to disturb this equilibrium in an inspiratory and expiratory direction

Question 14

what does breathing in from the equilibrium position involve?

Answer 14

contraction of the diaphragm (contract down) and the external intercostal muscles (pull up - increase AP length) - all increase volume of thorax

Question 15

what does breathing out during quiet expiration involve?

Answer 15

only passive recoil of the lungs

Question 16

what does breathing out during forced expiration require?

Answer 16

contraction of the abdominal muscles (push in and up) and the internal intercostal muscles (inferior posterior fibres)

Question 17

what happens when muscle contraction stops?

Answer 17

the lungs and thorax will return to the equilibrium position by passive recoil

Question 18

in inspiration, what happens (in terms of volume)?

Answer 18

the volume of thorax increases, so will volume of lungs (pleural seal)

Question 19

what happens as lung volume increases?

Answer 19

Boyle’s law: pressure falls below atmospheric pressure, air flow into lungs

Question 20

what happens as air flow into lungs?

Answer 20

alveolar pressure gradually rise back to atmospheric pressure, when inspiration ceases

Question 21

what happens in quiet expiration?

Answer 21

muscle contraction ceases, elastic recoil of lung results in a decrease in volume of the thorax and lung
decrease in lung volume causes pressure in terminal and respiratory bronchioles to rise above atmospheric pressure, so air flows back out again (until alveolar pressure = atmospheric pressure)

Question 22

where does fresh atmospheric air reach?

Answer 22

only a far as the terminal & respiratory bronchioles

Question 23

how does exchange of oxygen and CO2 occur?

Answer 23

by diffusion between atmospheric air in the terminal and respiratory bronchioles and alveolar gas (maintains normal composition of alveolar gas)

Question 24

describe how the pleural pressure is like

Answer 24

since lungs and chest wall recoil in opposing directions, pressure within the pleural cavity is slightly less than atmospheric pressure (negative in relation to atmospheric pressure - due to opposing forces)

Question 25

in quiet respiration, what happens to the pressure in the pleural cavity?

Answer 25

increases, but still remains negative relative to atmospheric pressure, throughout the respiratory cycle

Question 26

in inspiration, what happens to pleural pressure?

Answer 26

the chest wall expands out (increase vol.), pleural pressure becomes more negative (than normal), and returns to original negative pressure as the lung returns to the resting expiratory level in quiet expiration

Question 27

what happens to the muscles in quiet breathing?

Answer 27

diaphragm (major muscle of inspiration), moves down to increase vertical dimensions
external intercostal muscles (inferior anterior fibres) move ‘bucket handle’ movement to increase AP & transverse diameters of thorax

Question 28

in forced inspiration what happens? when does forced inspiration occur?

Answer 28

(when ventilation is increased - exercise / resistance to respiration is present - COPD)
accessory muscles of inspiration are used

Question 29

what are the accessory muscles of INspiration used?

Answer 29

exercise: serratus anterior & pec major
COPD: sternocleidomastoid & scalene muscles

Question 30

how does quiet breathing occur?

Answer 30

elastic recoil of lungs

Question 31

what happens in forced EXpiration? when does this occur?

Answer 31

accessory muscles of expiration are used e.g. exercise

Question 32

what are the accessory muscles of expiration?

Answer 32

internal intercostal muscles

abdominal wall muscles (external & internal oblique muscles & rectus abdominis muscles)

Question 33

which muscle is the major muscle of inspiration? what does it do?

Answer 33

diaphragm
major work against forces required to stretch the lungs - stretch the elastic tissue of the lung & to stretch the film of fluid lining the alveoli (against surface tension pulling it in & VdW forces)