respiratory system Flashcards
Explain general principles of gas exchange across an interface(ficks law)
Q=DA (Pe-Pi)/L
Q=rate of diffusion
D=diffusion coefficient
P=partial pressure difference
L=thickness of interface
A=surface area
Describe general anatomical features of respiratory organs
specialised body surfaces for gas exchange
mechanisms to ventilate the env. fave of this surface
mechanisms to perfuse the internal face of this surface
some organisms
O2 obtained by simple diffusion
requires thin, moist integument
Discuss respiratory adaptations to life in air and water
aqueous:
gills-highly branched/folded extension of body surface(evaginations)
max. SA
thin tissue, minimises diffusion path length
new medium flows continuously over surfaces
gaseous:
invagination-protects respiratory surface(alveoli)
increase internal SA
thin tissue-minimise diffusion path length
lungs are elastic-increase capacity
Describe the functional anatomy of the human respiratory system
- nasal cavity
- pharynx
- larynx
- trachea
- primary bronchus(conducting zone-“dead space”-transfer gas, warm/humidify air, filtering)
- lungs(transsitional/resp. zones-gas exch. -O2 delivery/CO2 removal)
Compare tidal breathing with unidirectional air flow
consequences of tidal:
incoming air mixes with “used” gas
provides reservoir of O2
“dead space” does not participate in exch.
+:warming/humidifying and protection(mucus, cilia)
unidirectional flow(birds):
incoming air doesn’t mix with “used” gas=more efficient
Describe the mechanical events of breathing in humans, including the sequence of pressure and volume changes during the breathing cycle
(at rest)
pressure is lower than atmospheric
TF constant P gradient - holding alveoli open
lungs are expanded to fill thoracic cavity bc intrapleural P is negative
ventilation only occurs when active muscle force is applied to relaxed resp. system
Describe the mechanical events of breathing in humans, including the sequence of pressure and volume changes during the breathing cycle
(inspiration)
active process-vol. of thorax increased as:
diaphragm moves down
ext. intercostal muscles contract(up+out)
as V of thorax increases:
intrapleural P falls
alveoli expand
alveolar P<atmospheric P
air flows in lungs until alveolar P=atmospheric P
change in lung vol=change in air movement
air moves passively down P gradient
Describe the mechanical events of breathing in humans, including the sequence of pressure and volume changes during the breathing cycle
(expiration)
largely passive
elastic recoil of lungs+chest wall = decreased vol of thorax
intrapleural P rises
alveoli recoil
P in alveoli > amtospheric P
air expelled from lungs
Discuss the forces which assist / oppose airflow
oppose:
airway resistance-resistance to movement of air
pulmonary tissue resistance-friction between lungs+chest wall
inertia of air and tissues
assist:
elastic recoil of lungs in chest wall
surface tension-alveoli
expiration=more active when forced(muscles used)
Describe and compare ventilation in birds, frogs and insects
birds:
small lung vol change
air moves through lungs from interconnected air sacs
sacs dont participate in gas exchange
lamina flow
lungs act as reservoir of air
negative P pump
frogs:
air forced into lungs
lungs emptied via abdominal contraction
positive pressure pump
insects:
airways penetrate each body segment allowing diffusion
abdominal muscles ‘pump’ air through trachea
Describe water flow through fish gills
energy required to ‘pump’ water across gills
water ‘pulled’ across gills when opercular cavity expands and flaps open(active)
water ‘pushed’ over gills when fish closes mouth
Outline the principles of airflow through tubes
laminar flow:
slow flow rate
parallel stream lines
shorter/slower on outside
turbulent flow:
high flow rate
disorganised stream lines
transitional flow:
intermediate flow rate
eddy currents
Define airway resistance and explain how anatomical and physiological factors affect RAW
AR: majority of resistance to inhale air is resistance to air movement through conducting airways
Raw: (airway resistance) decreases with increasing lung volume
radial traction-bronchiole diameter inc. as lungs expand TF Raw falls
dynamic compression-forced expiration at low lung volume
bronchiole smooth muscle tone-caused by nervous activity, hormones or ext. force
bronchioconstriction-inc. Raw
bronchiodilation-lowered Raw
inflammation/mucus-increase Raw
Explain the anatomical and physiological factors which influence lung compliance and the functional consequences of altered compliance
compliance of lungs is linear -reduced when surface tension inc. or elasticity is impaired eg.
elastic tissue in lungs:
elastin/collagen fibres in alveolar wall/vessels/bronchi-allows distension but recovers when released(lungs collapse)
surface tension in alveoli:(problems)
air-fluid(vape) liquid has attractive forces-oppose expansion by inspired air
transduction of fluid from capillaries
lung collapse
(problems minimised with surfactant)
pulmonary surfactant:
lowers surface tension in liquid layer
prevents alveolar collapse at low P
present in air breathing animals
Describe the anatomical and physiological features of the human pulmonary circulation.
Gas composition of blood in pulmonary arteries and veins is 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.
