lecture 15 - respiratory system 2 Flashcards
what is elasticity?
ability of tissue to return to its original state when stretched
what influences the overall effectiveness of pulmonary ventilation?
airway resistance
alveolar surface tension
lung compliance
what is airway resistance?
defined as anything that impedes air flow through the respiratory tract
what is alveolar surface tension?
alveoli are converted with thin film of liquid composed mainly of water creating gas-water boundaries
what is lung compliance?
refers to the ability of lungs and chest wall to stretch
which part of the respiratory tract has the highest resistance?
bronchi
as generation increases
• resistance decreases
• SA increases
when does resistance increase?
inflammation of airways
increased mucus secretion
presence of tumour
what is the diameter of bronchioles controlled by?
ANS - parasympathetic
• bronchoconstriction increases resistance
how does alveolar surface tension change?
greatest when alveoli are at their smallest diameter - during expiration
increases surface tension resists the ability of the alveolus to inflate
law of LaPlace in alveoli
smaller radius = higher pressure
more difficult to inflate - need to have a higher pressure
small alveolar are more difficult to inflate than larger ones
surfactant reduces surface tension
how does surfactant reduce surface tension?
without surfactant, H bonds pull the water molecules together and the alveolus collapses
with surfactant, the H bonds are disrupted and the alveolus remain inflated
what is surfactant produced by?
type 2 alveolar cells
what is surfactant?
mixture containing proteins and phospholipids
polar and non-polar end
disrupts cohesive force of H bonds in water
more concentrated in small alveoli - increase stability
what is compliance?
defined as a change in volume produced by a change in pressure
low compliance = hard to stretch
high compliance = easy to stretch
what is compliance affected by?
alveolar surface tension - surfactant increases compliance
distensability of elastic tissue of lung
ability of chests all to move or stretch in inspiration
as you increase pressure, volume in the lungs increase
what is tidal volume (TV)?
volume inspired or expired with each normal breath
500 ml
what is expiratory reserve volume (ERV)?
maximal volume that can be expired after tidal volume
1200 ml
what is inspiratory reserve volume (IRV)?
maximal volume that can be inspired after tidal volume
3100 ml
what is residual volume (RV)?
volume that remains in the lungs after maximal expiration
1200 ml
what is inspiratory capacity (IC)?
volume of maximal inspiration
TV + IRV
3600 ml
what is functional residual capacity (FRC)?
volume of gas remaining in the lung after normal expiration
ERV + EV
2400 ml
what is vital capacity (VC)?
volume of maximal inspiration and expiration
IRV+ TV + ERV = IC + ERV
4800 ml
what is total lung capacity (TLC)?
the volume of the lung after maximal inspiration
the sum of all 4 lung volumes
what is forced vital capacity (FVC)?
amount of air you can get in your lungs
what is FEV1?
forced expiratory volume in 1 second
how do changes in FVC and FEV1 indicate disease?
a healthy person should exhale about 80% of vital capacity in 1 second
what indicates an obstructive lung disease?
FVC close to normal
FEV1 reduces
asthma
bronchitis
what indicates a restrictive lung disease?
FVC reduces
FEV1 close to normal
pulmonary fibrosis
what are non-respiratory movements not intended for ventilation?
sigh
yawn
sneeze
cough
sigh
slow, deep expiration held and followed by slow expiration
reopens local groups of collapsed alveoli
stimulates release of surfactant
yawn
large sigh
takes lung volume ti inspiratory capacity
when tired, minuses alveolar collapse during sleep
after sleep, opens alveoli that collapsed during sleep
sneeze
deep inspiration followed by large forceful expiration through nose
clears foreign or irritating substances
velocity of 100mph
cough
similar to sneeze but initial inspiration is small or absent
clears larnynx, trachea or lower airways
velocity can be up to 500mph
what is dead space?
areas that don’t contribute to gas exchange
anatomical dead space
volume of the conducting airways
alveolar dead space
in unhealthy or elderly people not all alveoli function properly
physiologic dead space
anatomic dead space + alveolar dead space
what is total pulmonary ventilation?
ventilation rate x tidal volume (TV)
greater than alveolar ventilation due to dead space
why is alveolar ventilation a better measure?
better indication of how much fresh air reaches the alveoli
= ventilation rate x (TV - dead space volume)
