Breathing & Airways Flashcards
what are the jobs of the lungs
to bring in fresh air rich in oxygen needed to feul the body + expel the waste gas (CO2) produced from cells in body
movement of air in/out of the lungs (breathing) must be coupled to cellular respiration
how is the respiratory system divided
upper and lower
what does the upper resp system comprised of
nares (nostrils)
nasal passages
pharynx
larynx
what is the function of upper resp system (3)
- conduct air to and from the lungs
- filter out particles
- warm the air
what is the lower resp tract comprised
trachea
bronchi
bronchioles
alveoli (site for gas exchange)
what filters air coming into resp tract
trachea lined by pseudo-stratified ciliated columnar epithelium
inhaled particles stick to mucus –> mucus moved towards mouth by beating cilia
what occurs at the alveoli
gas exchange
O2 moves from air to capillaries
CO2 moves from capillaries to air
move by diffusion
what processes are involved in gas exchange
O2 consumption and CO2 production vary with metabolic rate (variable across species/lifestyle/body size)
when does O2 consumption vary
when animals exercise their muscles need more O2
what is maximal O2 consumption (VO2max) directly related to
directly related to total mass of mitochondira witihin the skeletal muscles
what is TLC
total volume of air lungs can hold
what is RV
total volume of air remaining after forced expiration
what is VC
total volume of air that can be moved
what is FRC
amount of air remaining after quite resting exhalation
what is TV
total volume of air moved in/out during quiet breathing
what is VE
total volume of air breathed per minute (minute ventilation, VE)
how is VE determined by
volume of each breath (VT) and breathing frequency (breaths per minute)
what is anatomic dead space
regions where air flows through conducting airways (not involved in gas exchange)
how does dead space occur in the wall of alveoli
ventilated alveoli are not perfused with blood
what is physiologic dead space
sum of both (anatomic) and determines portion of each breath not available for gas exchange
what is the formula for dead space
VT = VA + VD
VT = volume of each breath
VA = air that enters perfused alveoli
VD = volume that remains in physiologic dead space
what is the dead space/tidal volume ratio (VD/VT)
the fraction of each breath ventilating the physiological dead space
how does the dead space/tidal volume ration vary among species
33% in small species (dogs)
50-70% in larger species such as cattle and dogs
how does panting affect VT and f
small VT and high f
more air ventilates the dead space = increased water evaporation and heat loss
cold stress –> increases VT and decreases f –> retain heat
what is equipment dead space
excessively long endotracheal tubes or overly large face masks create a large amount of equipment dead space
animals must increase its VT to obtain adequate alveolar ventilation
what occurs during inspiration
active
diaphragm contracts downwards pushing abdominal contents outwards
external intercostals pull ribs outwards and upwards
what occurs during expiration
passive
elastic recoil (except horses which have active phase to exhalation)
what are the muscles of inspiration
diaphragm major inspiratory –> dome-shaped skeletal muscle
other resp skeletal muscles active during more strenous breathing
what are the muscles of inspiration and expiration
what are the volume and pressure changes during inspiration and expiration (14)
- beginning of inspiration, no flow –> PA=0, PB=0
- inspiratory muscles contract –> increases thoracic volume
- pleural pressure becomes more negative
- increase in transpulmonary pressure
- lungs expand and alveolar volume increases
- PA becomes negative (below PB)
- air flows into alveoli (from higher to lower pressure)
- end inspiration –> muscles stop contracting, thorax and alveoli stop expanding PA = PB (no flow)
- beginning expiration: thoracic volume decreases
- Ppl & PL return to pre-inspiration values
- thorax and lungs recoil (elastic recoil pressure)
- air in alveoli compressed
- PA becomes greater than PB
- air flows out of lungs
what is compliance and how is it calculated
measure of distensibility of an elastic structure
for the lung –> calculated as the change in lung volume that occurs for a given change in transpulmonary pressure
(C= V/P)
how compliant is the lung
very compliant –> readily increases in volume with modest changes in transpulmonary pressure
what is elasticity
materials that recoil
elastance relates to the work required to inflate and deflate the lungs and is the reciprocal of compliance
E = P/V
what are the alveoli lined with
thin layer of aqueous fluid –> surfactant
where is the surfactant produced in the lungs
type II alveolar epithelial cells
what does surfactant contain and what is its function
lipid dipalmitoyl phosphatidylcholine and proteins
displaces water at the fluid/air interface
1. reduces surface tension (cohesive forces where liquid meets air)
2. increases lung compliance
what are these cells
what are these structures
what is airway resistance (R)
force that impedes airflow along the respiratory passage
what is a source of airway resistance
upper airways are the major source of R –> large flow of air through a modest tube
what occurs to airway resistance as lung volume increases
airway resistance decreases
what are the blood supply to the lung
- pulmonary circulation (low pressure)
- bronchial circulation
what is the pulmonary circulation
arteries: brings deoxygenated blood from heart to pulmonary capillaries around alveoli and
veins: oxygenated blood from lung to heart (reservoir of blood for increase cardiac output)
what is bronchial circulation
brings oxygenated blood to lung parenchyma
what are the structures
what is extra alveolar
pulmonary arteries/veins
what are alveolar
alveolar capillaries
thin walled –> perfuse alveolar septa
what is the direction of pulmonary circulation in quadruped animals
caudodorsal flow –> increased by exercise
what is alveolar hypoxia
potent constrictor of small pulmonary arteries (beneficial for localized alveolar hypoxia)
what is bronchial circulation
part of systemic circulation
venous drainage is unique –> returns to the heart by both system and pulmonary circulations
where does deoxygenated bronchial venous blood drain
drains into the pulmonary veins and left ventricle –> deoxygenated blood leaving from the bronchial veins mixing with oxygenated blood leaving the lungs in pulmonary veins
one form of anatomic shunt because deoxygenated blood leaving bronchial circulation does not pass alveoli but is shunted to left side of heart
what must occur for adequate gas exchange
ventilation (V) and perfusion (Q) must match
what is the V/Q ratio
ratio of ventilation to blood flow
ratio can be defined for single alveolus, a group of alveoli or entire lung
what occurs when ventilation exceeds perfusion
V/Q > 1
what occurs when perfusion exceeds ventilation
V/Q < 1
what occurs when pulmonary blood flow and ventilation are mismatched
impaired O2 and CO2 transfer
what are lung zones
V/Q at apex = 3 (wasted ventilation)
V/Q at base = 0.6 (wasted perfusion)
both ventilation and perfusion are greater at the base of the lung than the apex of the lung
what is V/Q = O
airway obstruction (shunt) ex. foreign body aspiration
what is V/Q = ∞
blood flow obstruction (physiological dead space) ex. pulmonary embolus
when does optimal gas exchange occur
brings together air and blood in the alveolus ex. the matching of ventilation and blood flow (perfusion)
when can gas exchange not occur
if an alveolus receives blood but no ventilation and vice versa
ideally each part of the lung would receive equal amounts of ventilation however uneven ventilation mostly becomes apparent in disease
when does uneven ventilation occur
decreased compliance (pneumonia) or local airway obstruction (mucus, bronchoconstriction, foreign body)
important for recumbent animals becuase lowermost part of lung compressed –> anesthetized large animals
