Unit 2 - Lungs Flashcards
describe the conducting zone and its respiratory tree
no gas exchange - transfer of gases to & from alveoli/ filtration/ warming & humidifying air
trachea - generation 0/ bronchi (1)/ lobar bronchi (2/3)/ segmental bronchi (4)/ small bronchi (5-11)/ bronchioles (12-15)/ terminal bronchioles (16)
describe the cell lining the airways in conducting zone
trachea to small bronchi - pseudostratified columnar ciliated epithelium
bronchioles - simiple ciliated cuboidal epithelium
describe the walls lining the airways in conducting zone
trachea/ bronchi - C-shaped rings of hyaline cartilage
smaller bronchi - overlapping cartilage
bronchioles - no cartilage
terminal bronchioles - thick walls due to smooth muscle
describe the transitional/ respiratory zones and the respiratory trree
gas exchane - large SA respiratory bronchioles (17-19)/ alveolar ducts (20-22)/ alveolar sacs (23)
what does an alveolar sac contain?
2 or more alveoli enveloped by pulmonary capillaries
what are the two types of cell found in alveolar septa?
Type I: squamous epithelial
Tupe 2: thicker cell which synthesis and secrete pulmonary surfactant
what is found between alveolar septa and capillaries?
lung parenchyma - connective tissue containing elastic fibres & collagen linking alveoli together
(pores of Kohn interconnect neighbouring alveoli)
give the definitions of: TV/ IRV/ ERV/ RV/ FRC/ VC
tidal volume - air taken in/ out in each breath
inspiratory reserve volume = difference in lung volume between normal and maximal inspiration
expiratory reserve volume = difference in lung volume between normal and maximal expiration
residual volume - air remaining after maximal expiration
functional residual capacity - ERV + RV - volume of air left at end of normal expiration
vital capacity - difference in lung volume between maximal inspiration and expiration
what is the formula for tidal volume?
dead space + alveolar ventilation
what is dead space?
anatomical - air taken in not mixing with air in alveoli
physiological - air taken in not taking part in gas exchange
Vd= Ve (1 -Fe/ Fa) where Ve = minute volume(fVt) and F is fractional content of CO2 in e- air exhaled/ a- alveoli
how do you calculate alveolar ventilation rate?
Va = (Vt - Vd) x f Va = Ve - (Ve x Vd/ Vt)
what is the dead space: tidal volume ratio?
Vd/ Vt = (PaCO2 - PeCO2)/ PaCO2
why is ventilation uneven?
progressive decrease in intrapleural pressure from apex to base
transpulmonary pressure decreased in lower regions at rest since Patm=Palv so increase more in volume during inspiration
- also lower ribs more curved
- descent of diaphragm expand lower lobes more than upright ones
- peripheral tissue more compliant than deeper tissue
describe perfusion at apex, middle and base of lungs
apex - Palv = Pa - high vascular resistance no blood flow
middle - Pa> Palv - blood flow increases down the zones
base - Pa» Palv - arterial pressure exceeds alveolar pressure considerably so increased blood flow
what do the dots mean on top of V and Q?
flow in litres per minute
what does it mean when Va: Q =1 = 0 < 1 > 1
Va: Q - ventilation: perfusion ratio
=1 optimum matching/ optimum gas exchange
= 0 right to left shunt - blood passes through lung without coming into contact with alveolar air
< 1 poorly ventilated alveoli - well perfused
> 1 well ventilated alveoli - poorly perfused
what happens in hypoventilation?
ventilation does not meet metabolic demands - increased PCO2/ decreased O2 - chest wall damage -increased dead space
what happens in hyperventilation?
ventilation exceeds metabolic demands - decreased PCO2/ increased O2 - asthma attack
what are the formulas for work?
mechanical work - force x distance moved
work done by gas - pressure x volume = Nm = J
what is the formula for transpulmonary pressure?
Pl= Pa - Ppl (alveolar - intrapleural pressure)
what is the behaviour of the curves in pressure-volume loop?
hysteresis - greater pressure change to inhale than to exhale due to static compliance of chest and non-elastic resistances of airways and tissue
difference between curves - cost of ventilation of lung during single respiratory cycle
what is compliance?
change in volume / change in pressure
higher compliance = lower resistance = greater elasticity and stretch - reduced work of breathing
what two properties determine the elasticity of the lungs?
- elastic fibres of parenchyma
- surface tension of liquid film lining alveoli
what is laplace’s law? describe the relevance
P = 2T/r - when lungs inflated with air surface tension and elasticity of parenchyma opposes expansion - this would suggest a higher pressure of 3 kPa to inflate lung when in reality maximum inflation occurs at <2 kPa
