Lung Microanatomy Flashcards
Inspiration carried out by ___
contraction of the inspiratory muscles
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
what is most important inspiratory muscle
what innervates it
diaphragm
innerv by phrenic nerve
function of diaphragm
contracts during inspiration and diaphragm descend
muscles of respiration
1) diaphragm
2) external intercostals
3) sternocleidomastoids
4) scalenes
what happens to external intercostals with inspiration
pulls rib forward and outward
role of sternomastoids and scalenes in respiration
silent during normal breathing
elevate rib cage with ventilation and incr respiratory load
mechanism of expiration
abdominal muscles contract
push diaphragm up
when does active expiration become necessary
volumes >40 L/min
or significant expiratory resistance
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
during active expiration, the abdominal muscles ___
push diaphragm down
function of internal intercostals
pull ribs inward and down
decr thoracic volume
during active expiration, the intenral intercostals ___
pull ribs in and down
force generated by muscle is a function of its ___
length
___ generated by muscle is a function of its length
force
maximal tension (force) for diaphragm achieved at ___ of resting length
130% of resting length
mechanical disadvantages of diaphragm
1) diaphragm is more contracted, reduced length
2) @ high lung volumes, greater radius of curvature (decr pressure generated by muscle)
diseases assoc with diaphragm being more contracted
1) asthma
2) chronic bronchitis
3) emphysema
define intrapleural pressure (P IP)
movement of thoracic cavity into expansion of lung based on pressure outsdie of lung
what is source of P IP
intrinsic elastic properties of lung + chest wall
lung and chest wall deviate from equilibrium
lung is more __ than its intrinsic equilibrium position
this causes
more inflated
–> force to make lung DEFLATE
chest wall is more ___ than its intrinsic equilibrium position
this causes
more deflated
–> force to make chest expand
two opposing forces from lung and chest wall make —> ___
negative P IP (vacuum)
to glue lung to chest cavity
how does negative P IP affect during inspiration
expanding chest cavity pulls lung open to expand volume
what happens when expansion of chest cavity fails?
what disease
chest wall spring out
lung collapse
–> pneumothorax
define transpulmonary pressure
P TP = P L(lung) - P IP (intrapleural
how do you measure P IP
needle into pleural cavity and connect to water manometer
difference in atmospheric pressure (cm H2O)
how does P IP vary during breathing cycle
- 5 cm H2O at end of expiration
- 30 cm H2O at end of inspiration
why is P IP greater at end of inspiration
tendency of lung to recoil toward equilibrium position
a
a
a
a
what happens to pressures during inspiration
P L (lung)
what happens to pressure during expiration
P L (lung) > P (mouth)
what happens after expiration and before inspiration
no air flow because lung pressure = 0
function of P TP
driving force for changing lung volume during breathing
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
why does P L achieve negative values during inspiration
increase in negativity of P IP due to lung inflating
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
what happens to pressure when lungs recoil back to intrinsic equilibrium
transient positive pressure inside lung (elastic recoil pressure)
define compliance equation
compliance = change in volume
