Lect 5-Mechanics & Gas Exchange Flashcards
conducting zone
brings air into and out of lungs
respiratory zone
where gas exchange occurs
structures comprising conducting zone
nose/mouth, pharynx, larynx, trachea, bronchi, bronchioles, terminal bronchioles
main conducting airway
trachea
innervation of what neurons/receptors leads to relaxation and dilation of the airways?
sympathetic adrenergic neurons, B2 receptors
innervation of what neurons/receptors leads to contraction and constriction of airways?
parasympathetic cholinergic; M3 receptors
area of most airway resistance
bronchioles
where are club “clara” cells and what do they do
bronchioles; secrete protective glycosaminoglycans
epithelial cell phenotype in bronchi
ciliated columnar
epithelial cell phenotype in bronchioles
ciliated columnar
epithelial cell phenotype in respiratory bronchioles
cuboidal ciliated
structures of respiratory zone
respiratory bronchioles, alveolar ducts, alveolar sacs
type I pneumocytes
gas exchange; squamous; nonreplicating
type II pneumocytes
make surfactant; columnar, can differentiate into type I
function of alveolar macrophages
keep alveoli free of debris (no cilia); found in inter-alveolar septum
pulmonary coupling=
alveoli + vasculature
blood supply to lungs
pulmonary artery + branches
when standing, where is pulmonary blood flow focused?
lower lobes (gravity)
which side of the heart is assoc w lungs
right side (deox blood travelling to lungs)
bronchial circulation is the blood flow to the…
conducting zone
does bronchial blood flow participate in gas exchange?
no… except for a few respiratory bronchioles; the blood just perfuses the lungs themselves
pulmonary function test
measure volume of gas in lungs at a given time
tidal volume
amt of air that can be inhaled/exhaled during one resp cycle (300-500mL)
inspiratory reserve volume
additional volume that can be forcibly inspired above tidal volume (3000mL)
expiratory reserve volume
additional volume that can be forcibly expired below tidal volume (1200mL)
residual volume
volume of air remaining in lungs after maximal exhalation (1000-1200mL) can only be indirectly measured
capacities contain ____ or more lung volumes
2
inspiratory capacity
tidal volume + inspiratory reserve volume (500+3000)
functional residual capacity
expiratory reserve volume + residual volume (1200+1200)
the volume remaining in lungs after a normal, passive exhale
vital capacity
inspiratory capacity + expiratory reserve (3500 + 1200)
total lung capacity
vital capacity + residual volume (4700+1200)
total average lung capacity
6L (includes theoretical amt of capacity)
how many L is a normal functional residual capacity
3L
at FRC, the airway pressure is >, =, < than atmospheric pressure?
EQUAL
dead space
volume of air that is inhaled but does not participate in gas exchange because it remains in conducting airways
anatomic dead space
volume of conducting airways (150mL)
alveolar dead space
sum of volumes of alveoli that have no blood flow; ventilated but not perfused
physiological dead space
(total dead space)
=anatomic + alveolar
in a healthy individual, what is the ratio of anatomic: physiologic dead space?
roughly equal
physio ds= anatomic ds + alveolar ds
ventilation rate
volume of air moved into and out of lungs per unit time
minute ventilation
total rate of air movement
=tidal volume x RR
alveolar ventilation
corrects for physiologic dead space and only considers am of air capable of gas exchange
=(tidal v-physio ds) x RR
in a normal person, FEV1/FVC is about…
0.8L
____% of the vital capacity can be expired in the first second of forced expiration
80%
accessory muscles for inspiration
external intercostals, sternocleidomastoid, scalenes
what happens to intrathoracic V and P when the diaphragm contracts?
increase in V, decrease in P so air flows in
accessory muscles for expiration
abdominals, internal intercostals
transmural pressure
the pressure inside a compartment relative to outside compartment (alveolus)
transpulmonary pressure
difference between intraalveolar pressure and intrapleural pressure
intra-alveolar pressure is always (greater/equal/less than) intrapleural pressure
greater than
alveolar surfactant produced by
type II pneumocytes; it acts as a soap to reduce surface tension
surfactant (incr/decr) compliance?
increase
a pneumothorax occurs when air enters the _______
intrapleural space… pressure becomes equal to atmospheric… atelectasis
airflow is __________ to resistance of the airways
inversely proportional; more resistance, less flow
the pressure gradient in the thoracic cavity is accomplished by…
contraction of inspiratory muscles
3 phases of breathing cycle
rest/pause, inspiration, expiration
at rest… alveolar pressure? intrapleural? transmural?
alveolar= equals atmospheric
intrapleural= negative
transmural= positive, keeping alveoli open (alv pressure - intrapleural)
during inspiration, alveolar pressure? intrapleural pressure?
alveolar- falls as volume increases
intrapleural- more negative
during expiration, intrapleural pressure? alveolar?
intrapleural- less negative
alveolar- becomes positive as elastic forces compress
forced expiration raises what type of pressure?
intrapleural
resistance is determined by
Poiseuille law
what part of the respiratory tract has the highest airway resistance?
medium-sized bronchi… due to their directional changes
alveolar interdependence
alveoli tend to hold each other open thru mechanical tethering
dalton’s law
total pressure is sum of partial pressures
henrys law
amount of dissolved gas in a liquid is proportional to its partial pressure above the liquid
transfer of gasses across cell membranes occurs by
simple diffusion
fick’s law states
the rate of diffusion is directly proportional to diffusion coefficient, surface area, partial pressure differences (driving force), thickness of membrane
lung diffusing capacity
measures how well the lungs move gas from air into bloodstream; uses CO
diffusing capacity of lung for CO
(DLCO), technique that helps to measure lung diffusing capacity
emphysema
destruction of alveoli, decrease in surface area; net decrease in lung diffusion capacity
pulmonary fibrosis or edema
increase in alveolar membrane thickness; net decrease in lung diffusion capacity
carbonic anhydrase
converts CO2 to HCO3-
most CO2 is carried in the blood as…
HCO3-
physiological shunt
small % of blood that bypasses the alveoli and drains directly into left ventricle
strenuous exercise (incr O2 demand) can cause periods of …
diffusion limitation
altitude effects on perfusion
pressure reduced, lower pressure, slower diffusion rate
