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Flashcards in Lung Microanatomy Deck (40):
1

Inspiration carried out by ___

contraction of the inspiratory muscles

2

what is the mechanism of inspriation

1) contraction of inspiratory muscles

force abdominal contents down and forward

upper ribs inward

lower ribs elev and rotate

3

what is most important inspiratory muscle

what innervates it

diaphragm

innerv by phrenic nerve

4

function of diaphragm

contracts during inspiration and diaphragm descend

5

muscles of respiration

1) diaphragm

2) external intercostals

3) sternocleidomastoids

4) scalenes

6

what happens to external intercostals with inspiration

pulls rib forward and outward

7

role of sternomastoids and scalenes in respiration

silent during normal breathing

elevate rib cage with ventilation and incr respiratory load

8

mechanism of expiration

abdominal muscles contract

push diaphragm up

9

when does active expiration become necessary

volumes >40 L/min

or significant expiratory resistance

10

most important expiratory muscles

when are they active

abdominal wall muscles

active in upright position
silent during supine position

push diaphragm down during active expiration

11

during active expiration, the abdominal muscles ___

push diaphragm down

12

function of internal intercostals

pull ribs inward and down

decr thoracic volume

13

during active expiration, the intenral intercostals ___

pull ribs in and down

14

force generated by muscle is a function of its ___

length

15

___ generated by muscle is a function of its length

force

16

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

130% of resting length

17

mechanical disadvantages of diaphragm

1) diaphragm is more contracted, reduced length

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

18

diseases assoc with diaphragm being more contracted

1) asthma

2) chronic bronchitis

3) emphysema

19

define intrapleural pressure (P IP)

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

20

what is source of P IP

intrinsic elastic properties of lung + chest wall

lung and chest wall deviate from equilibrium

21

lung is more __ than its intrinsic equilibrium position

this causes

more inflated

--> force to make lung DEFLATE

22

chest wall is more ___ than its intrinsic equilibrium position

this causes

more deflated

--> force to make chest expand

23

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

negative P IP (vacuum)

to glue lung to chest cavity

24

how does negative P IP affect during inspiration

expanding chest cavity pulls lung open to expand volume

25

what happens when expansion of chest cavity fails?

what disease

chest wall spring out

lung collapse

--> pneumothorax

26

define transpulmonary pressure

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

27

how do you measure P IP

needle into pleural cavity and connect to water manometer

(difference in atmospheric pressure (cm H2O))

28

how does P IP vary during breathing cycle

-5 cm H2O at end of expiration

-30 cm H2O at end of inspiration

29

why is P IP greater at end of inspiration

tendency of lung to recoil toward equilibrium position

30

a

a

31

a

a

32

what happens to pressures during inspiration

P L (lung)

33

what happens to pressure during expiration

P L (lung) > P (mouth)

34

what happens after expiration and before inspiration

no air flow because lung pressure = 0

35

function of P TP

driving force for changing lung volume during breathing

36

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

P L = P TP + P IP

both P TP and P IP become more negative
PIP more quickly negative than P TP

37

why does P L achieve negative values during inspiration

increase in negativity of P IP due to lung inflating

38

what happens to chest wall and lungs during expiration

chest wall contract

releases lung from more inflated state

lungs recoil back to intrinsic equilibrium --> push air out

39

what happens to pressure when lungs recoil back to intrinsic equilibrium

transient positive pressure inside lung (elastic recoil pressure)

40

define compliance equation

compliance = change in volume