Respiratory Systems Flashcards
Write an equation for the rate of diffusion.
Q = D A (Pe - Pi) / L
Describe the features of gills.
- highly branched and folded extensions (evaginations) to maximise surface area
- thin tissue, minimises diffusion path length
- new medium flows continuously over surfaces
What is the role of ‘dead space’ in mammalian airways?
- transfer of gases to/from alveoli
- warming and humidifying inspired air
- filtration and removal of foreign material
Describe the pathway of oxygen through the lungs.
- trachea
- bronchi
- bronchioles
- terminal bronchioles
- respiratory bronchioles
- alveolar
- alveolar sacs
What are the consequences of tidal ventilation.
- incoming air mixes with ‘used’ gas
- alveoli provide reservoir of oxygen
- ‘dead space’ does not participate in gas exchange
- benefits of dead space: warming/humidifying and protection
Write an equation for the minute ventilation of the entire lung.
Ve = Vd + Va
What is Boyle’s Law?
P1V1 = P2V2
Describe the mechanisms that occur during inspiration.
- the volume of the thorax increases
- intrapleural pressure falls
- alveoli expand
- alveolar pressure < atmospheric pressure
- air flows into the lungs until alveolar pressure = atmospheric pressure
Describe the mechanisms that occur during expiration
- elastic recoil of lungs and chest wall reduces volume of the thorax
- intrapleural pressure rises
- alveoli recoil
- Palv > Patmos
- air is expelled from lungs
Write an equation for ‘compliance’
C = change in V/ change in P
Describe and explain the difference in V against P graphs for both inspiration and expiration
- in inspiration, the curve deviates to the right due to resistive forces which oppose airflow (airway resistance, pulmonary tissue resistance)
- in expiration, the curve deviates to the left because resistive forces assist airflow (elastic recoil of lungs and chest wall, surface tension in alveoli)
Briefly describe the ventilation process in birds
- bird lung volume changes less than in mammals
- air moves through lungs from interconnected air sacs
- sacs do not participate in gas exchange
Briefly describe the ventilation process in frogs
- air forced into lungs
- lungs emptied by abdominal canal
Briefly describe the ventilation process in insects
- airways penetrate each body segment, allowing diffusion
- abdominal muscle pumps air through tracheae
What is partial pressure?
the pressure of a single gas in a gas mixture
Which factors influence the rate of diffusion?
- partial pressure gradient
- diameter of gas molecules
- temperature
- solubility of the gas in liquid
- thickness of gas exchange liquid
surface area of the gas exchange surface
How is pulmonary circulation specialised?
- gas composition of blood in pulmonary arteries and veins opposite to those in systemic circulation
- pressures in the pulmonary circulation are very low
- pulmonary arterial walls are thin and contain little smooth muscle
- pulmonary vascular resistance is low
Write an equation for vascular resistance
vascular resistance = (input pressure - output pressure) / blood flow
Describe the differences between laminar flow, turbulent flow and transitional flow.
laminar flow - slow flow rate, parallel stream lines
turbulent flow - high flow rate, disorganised stream lines
transitional flow - intermediate flow rate, eddy currents
What is radial traction?
Refers to the force exerted by elastic fibers in healthy lung tissue that helps keep small airways open - generated by surrounding alveoli and connective tissue
What is bronchioconstriction?
- increased airway resistance
- irritants cause reflex constriction
- parasympathetic stimulation
- fall in PCO2
- asthma
What is bronchiodilation
- lowered airway resistance
- autonomic stimulation - circulating catecholamines
- sympathomimetic agents
How can infection increase airway resistance
- inflammation of the tissue lining the upper airways
- overproduction/accumulation of mucus
How can the presence of air-fluid interface cause potential problems?
- attractive forces in liquid (surface tension) oppose expansion by inspired air
- promotes collapse of smaller alveoli
- causes transudation of fluid from capillaries
- these problems minimised by surfactant
