Respiratory system Flashcards
Steps in gas exchange
1) ventilation
2) diffusion
3) perfusion
carina
point of bifurcation of trachea
- sensitive → anything touch and instantly triggers cough reflex
pleura
parietal → surrounds lung tissues
visceral pleura → connects to parietal pleura
pleural space → serous fluid to dec friction and adhesion
-ve pressure b/w pleura
exists to help keep lungs open
- space becomes more -ve with inspiration
diaphragm
pulls down → pull lungs down → visceral layer stuck to the viscera → creates -ve pressure
larynx
ciliated epithelium → filters dust particles
- protects against entrance of substances
- organ for voice production (vocal cords)
trachea
- cartilaginous rings ANT
- trachealis POS → prevents collapse
- cartilage weak in children → prone to bronchoconstriction → asthma significant
composition of alveoli
squeamish tissues
- type 2 → secretes surfactant (dec surface tension → prevent aveoli collapse)
- lung infection → disturbs surface tension → shortness of breath
inspiration
- dia + ex IC contract
- chest walls and lungs expand
- accessory muscles (SCM and pec minor) contracts
expiration
- passive elastic recoil
- accessory muscles (int IC and abs) contract for active expiration
conc of gases (PaCO2, PaO2…)
conc of HCO3 and pH level
PaCO2 → 35-40
PvCO2 → 46
PaO2 → 80-100
PvO2 → 40
HCO3 → 22-26mmol/L
pH → 7.35-7.45
what is the aim of respiration
to maintain normal levels of O2, CO2, HCO3
effects of humidifying gases
gas enter lungs → humidified → dec PO2 to 100mmHg (from atmospheric pressure)
3 neurochemical control of vent
1) central chemoR → bathed by CSF close to resp center
2) peripheral chemoR → in carotid A and aorta
3) lung stretch R
H+ cannot diffuse through BBB, but CO2 can
central chemoR
- sensitive to changes in small pH
- change by PaCO2 stimulates both peripheral and central chemoR
equation for CO2 into HCO3
CO2 + H2O → H2CO3 → H + HCO3
- ↑PaCO2 → ↑diffusion of CO2 into CSF → ↑H+ in CSF → ↑signals to central chemoR → ↑ventilation
peripheral chemoR
- near baroR
- primary response to changes in O2 blood levels
- not as sensitive to changes in central chemoR (only when O2
neural innervation of lungs
- SNS b2 → bronchial SM relax
- PNS m3 → bronchial SM contract
external resp
ex gas exchange
- b/w alveoli and blood
int gas exchange
- exchange of O2 and CO2 b/w blood and tissues
internal (cellular) resp
aerobic & anaerobic
resp membrane permeability
membrane more permeable to CO2 than O2
boyle’s law
p inversely proportional to V at constant temp
*i.e. if can’t change vol → can’t breath)
dalton’s law
total pressure exerted by mixture of gases = sum of pressure of each individual gas
(p1+p2+p3=Ptot)
fick’s law
rate of diffusion → directly proportional to:
- SA membrane
- pressure gradient
- gas solubility
indirectly proportional to
- thickness of membrane
how is O2 transported
binds to hb
~1000ml/min O2 delivered to cell
how is CO2 transported
~200ml/min prod by tissues
1) dissolved in plasma (PCO2) - 10% (20x more soluble than O2)
2) as a carbaminohaemoglobin - 20% (hb-co2 complex)
3) as a bicarbonate - 70% (as hco3 dissolved in plasma)
factors affecting oxyhaemoglobin dissociation curve
CO → takes up Hb subunit → remaining subunits ↑affinity for O2 → BUT saturation of Hb with O2 is lowered
- temp/2,3DPG/CO2 (dec pH) → all shifts curve right
tidal vol
normal in out (500ml)
inspiratory reserve vol
max vol breathed in over normal insp (~3.3L)
expiratory reserve vol
max vol breathed out over normal exp (~1L)
vital capacity
max in out (4.8L)
residual vol
vol remaining in lungs at the end of exp (~1.2L)
functional residual capacity
vol remaining at the end of normal in and out
total lung capacity
total vol air lung can hold
ageing and resp system
premature
inadequate surfact → may lead to resp distress
given steroids
ageing and resp system
elderly
- dec collagen prod → dec lung compliance & airway diameter
- dec # cilia → inc infection rate
- changes in parenchyma → lowers diffusion capacity (dec oxygenation of lungs)
ageing and resp system
changes in resp rate throughout ages
newborn: 40-80
5yo: 25
adult: 12-18
elderly: inc
