Organisation of the respiratory system Flashcards
Respiration rate of a healthy adult at rest
4L of blood enters and leaves alveoli per minute
5L of blood flows through pulmonary capillaries (cardiac output)
Respiration during exercise
airflow can increase 20 fold
blood flow 5-6 fold
airflow structures
nose/mouth, external and internal nares, naso, oro and laryngopharynx, larynx, past vocal cords, trachea, r and l bronchi, lobar bronchi, segmental bronchi, sub-segmental bronchi, conduncing bronchioles, terminal bronchioles, respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli
division of airways beyond the larynx
conducting and respiratory zones
conducting zone
top of trachea to beginning of respiratory bronchioles. no alveoli, no gas exchange
respiratory zone
respiratory bronchioles to alveoli. gas exchange
airborne particles
trapped in nasal hairs and mucus
mucus escalator - structures, contents, function
epithelial surfaces of airways, down to respiratory bronchioles, contain cilia beating upwards towards pharynx. glands and individual cells secrete mucus and macrophages. particulate matter sticks to mucus and is moved to pharynx, then swallowed. keeps particulate matter and bacteria out of lungs
effects on cilia
ciliary activity and number can be decreased by noxious agents, e.g. smoking - smokers cough up mucus that would usually be swallowed
substance secreted by airway for mucus
airway epithelium secretes watery fluid for mucus to ride freely on
cystic fibrosis
impaired production of watery fluid. mucous layer becomes thick and dehydrated, and obstructs airways.
caused by autosomal recessive mutation in epithelial chloride channel - CF transmembrane conductance regulator (CFTR). leads to problems in salt and water movement across membranes, thickened secretions and higher chance of lung infection
responses to infection/irritation
constriction of bronchioles - prevents particulates and irritants from entering
macrophages engulf and destroy particles and bacteria
pulmonary circulation - resistance (consequences)
vessels accompany airways and branch down into networks of capillaries supplying alveoli
low resistance compared to systemic circulation
low pressure
minimises accumulation of fluid in interstitial spaces of lungs
changes in intrapleural pressure
cause lungs to move in and out during breathing
ventilation
exchange of air between the atmosphere and the alveoli
bulk flow description and equation
like blood, air moves from a region of high pressure to low pressure
flow = alveolar pressure - atmospheric pressure / resistance
atmospheric pressure
at nose and mouth (surrounding the body)
atmospheric pressure at sea level
760mmHg, decreases in proportion to an increase in altitude
pressures during inspiration
alveolar pressure is less than atmospheric pressure - negative pressure gradient
pressures during expiration
alveolar pressure is greater than atmospheric pressure - positive pressure gradient
boyle’s law definition and explanation
in a closed system, pressure of a gas and the volume of its container are inversely proportional
increasing volume of container decreases pressure, vice versa
P1V1 = P2V2
transpulmonary pressure
difference in pressure between the inside and outside of the lung
factors affecting volume of lung
transpulmonary pressure
stretchability of lungs - determines how much they expand for a given change in transpulmonary pressure
transmural pressure
pressure in the inside of a structure - pressure outside the structure
pressure outside of lungs
intrapleural fluid pressure
transmural pressure acting on the lungs
alveolar pressure - intrapleural fluid pressure
transmural pressure acting on chest wall
intrapleural fluid pressure - atmospheric pressure
muscle contraction during inspiration and its consequences
intercostal muscles contract and cause chest wall to expand, diaphragm contracts downwards
volume of thoracic cavity increases
intrapleural pressure decreases
transpulmonary pressure becomes more positive
alveolar pressure becomes more negative compared w/ atmospheric pressure
pressure when there is no airflow
intrapleural pressure is negative
transpulmonary pressure is always positive
forces causing intrapleural pressure to be negative
elastic recoil
how are the lungs held open?
positive transpulmonary pressure - exactly opposes elastic recoil
transpulmonary pressure at rest
4mmHg opposes inward elastic recoil of the lung
chest wall pressure at rest
-4mmHg opposes outward elastic recoil of the lung
what keeps lungs partially expanded between breaths?
subatmospheric negative intrapleural pressure
why is the intrapleural pressure subatmospheric/negative?
as lungs tend to collapse and thoracic wall tends to expand, they move away from eachother
causes an infinitesimal enlargement of fluid-filled intrapleural space between them
because fluid can’t expand like air, the ip is decreased
pneumothorax
atmospheric air entering the intrapleural space through thoracic wall or from inside of lung.
elastic recoil and surface tension cause collapse of lung
intrapleural pressure increases to 0mmHg - same as atmospheric. this eliminates traspulmonary pressure
why is transpulmonary pressure in the lung eliminated in pneumothorax?
the intrapleural pressure is equal to the atmospheric pressure
why does the chest wall move outwards during pneumothorax?
elastic recoil is no longer opposed
when can a pneumothorax be caused by air leaking from inside of the lung to the pleural space?
high airway pressure is applied during artificial ventilation of a premature infant with high lung surface tension and fragility
why are pneumothoraces unilateral?
the thoracic cavity is divided into left and right sides by mediastinum
