Lung Microanatomy

Question 1

Inspiration carried out by ___

Answer 1

contraction of the inspiratory muscles

Question 2

what is the mechanism of inspriation

Answer 2

1) contraction of inspiratory muscles

force abdominal contents down and forward

upper ribs inward

lower ribs elev and rotate

Question 3

what is most important inspiratory muscle

what innervates it

Answer 3

diaphragm

innerv by phrenic nerve

Question 4

function of diaphragm

Answer 4

contracts during inspiration and diaphragm descend

Question 5

muscles of respiration

Answer 5

1) diaphragm
2) external intercostals
3) sternocleidomastoids
4) scalenes

Question 6

what happens to external intercostals with inspiration

Answer 6

pulls rib forward and outward

Question 7

role of sternomastoids and scalenes in respiration

Answer 7

silent during normal breathing

elevate rib cage with ventilation and incr respiratory load

Question 8

mechanism of expiration

Answer 8

abdominal muscles contract

push diaphragm up

Question 9

when does active expiration become necessary

Answer 9

volumes >40 L/min

or significant expiratory resistance

Question 10

most important expiratory muscles

when are they active

Answer 10

abdominal wall muscles

active in upright position
silent during supine position

push diaphragm down during active expiration

Question 11

during active expiration, the abdominal muscles ___

Answer 11

push diaphragm down

Question 12

function of internal intercostals

Answer 12

pull ribs inward and down

decr thoracic volume

Question 13

during active expiration, the intenral intercostals ___

Answer 13

pull ribs in and down

Question 14

force generated by muscle is a function of its ___

Answer 14

length

Question 15

___ generated by muscle is a function of its length

Answer 15

force

Question 16

maximal tension (force) for diaphragm achieved at ___ of resting length

Answer 16

130% of resting length

Question 17

mechanical disadvantages of diaphragm

Answer 17

1) diaphragm is more contracted, reduced length

2) @ high lung volumes, greater radius of curvature (decr pressure generated by muscle)

Question 18

diseases assoc with diaphragm being more contracted

Answer 18

1) asthma
2) chronic bronchitis
3) emphysema

Question 19

define intrapleural pressure (P IP)

Answer 19

movement of thoracic cavity into expansion of lung based on pressure outsdie of lung

Question 20

what is source of P IP

Answer 20

intrinsic elastic properties of lung + chest wall

lung and chest wall deviate from equilibrium

Question 21

lung is more __ than its intrinsic equilibrium position

this causes

Answer 21

more inflated

–> force to make lung DEFLATE

Question 22

chest wall is more ___ than its intrinsic equilibrium position

this causes

Answer 22

more deflated

–> force to make chest expand

Question 23

two opposing forces from lung and chest wall make —> ___

Answer 23

negative P IP (vacuum)

to glue lung to chest cavity

Question 24

how does negative P IP affect during inspiration

Answer 24

expanding chest cavity pulls lung open to expand volume

Question 25

what happens when expansion of chest cavity fails? what disease

Answer 25

chest wall spring out lung collapse --> pneumothorax

Question 26

define transpulmonary pressure

Answer 26

P TP = P L(lung) - P IP (intrapleural

Question 27

how do you measure P IP

Answer 27

needle into pleural cavity and connect to water manometer | difference in atmospheric pressure (cm H2O)

Question 28

how does P IP vary during breathing cycle

Answer 28

- 5 cm H2O at end of expiration | - 30 cm H2O at end of inspiration

Question 29

why is P IP greater at end of inspiration

Answer 29

tendency of lung to recoil toward equilibrium position

Question 30

a

Answer 30

a

Question 31

a

Answer 31

a

Question 32

what happens to pressures during inspiration

Answer 32

P L (lung)

Question 33

what happens to pressure during expiration

Answer 33

P L (lung) > P (mouth)

Question 34

what happens after expiration and before inspiration

Answer 34

no air flow because lung pressure = 0

Question 35

function of P TP

Answer 35

driving force for changing lung volume during breathing

Question 36

based on P TP why does P L get more negative with inspiration

Answer 36

P L = P TP + P IP both P TP and P IP become more negative PIP more quickly negative than P TP

Question 37

why does P L achieve negative values during inspiration

Answer 37

increase in negativity of P IP due to lung inflating

Question 38

what happens to chest wall and lungs during expiration

Answer 38

chest wall contract releases lung from more inflated state lungs recoil back to intrinsic equilibrium --> push air out

Question 39

what happens to pressure when lungs recoil back to intrinsic equilibrium

Answer 39

transient positive pressure inside lung (elastic recoil pressure)

Question 40

define compliance equation

Answer 40

compliance = change in volume