Wk1: Pulmonary Structure and Function Flashcards
What is the definition of pulmonary ventilation?
the process of moving and exchanging ambient air with air in the lungs.
What do the lungs do?
provide a gas exchange surface that separates blood from the surrounding alveolar gaseous environment. §
What is external respiration?
- VC02 to clear metabolically produced CO2, C02 from buffering acids and maintenance of arterial pH.
- V02 to provide O2 for transport by blood and utilisation by tissues (generate ATP).
What is internal respiration?
- O2 consumption by tissues for ATP production in mitochondria
- CO2 production from breakdown of carbon chains e.e. in the TCA cycle
- blood vessels to cells in tissues
What is the respiratory function?
- alveolarise the blood
- take up O2 from the alveolar gas into pulmonary capillary blood
- reduce amount of CO2 from blood by moving it into the alveoli
other functions:
- filter unwanted material from circulation
- water and heat loss
- metabolism
- acid base balance
What do the pores of kohn do?
- within the alveolus they evenly disperse surfactant over the respiratory membranes to reduce surface tension for easier inflation. They allow for interchange between adjacent alveoli.
- this allows indirect ventilation of damaged or blocked alveoli from lung disease.
What happens to CO2 and O2 in the alveoli/blood each minute at rest?
- 250ml of O2 leave the alveoli to blood
- 200ml of CO2 diffuses from the blood to the alveoli
What happens to CO2 and O2 in the alveoli/blood when endurance athletes exercise intensely?
- 10x this quantity of O2 and CO2 transfers across the membrane.
What is the definition of ventilation?
mechanical process of moving gas in and out of the lungs
What are the two parts ventilation is subdivided into?
Conducting zone for transport of gas between atmosphere and alveoli (anatomical dead space; ~150 ml) - includes trachea and terminal bronchioles
Respiratory zone is the alveolated region where gas exchange occurs (also includes the transitional zone) - includes bronchioles, alveolar ducts and alveoli
Outline the conducting zone
- 1-16
- trachea and terminal bronchioles
- no alveoli (anatomical deadspace)
- transports gas between atmosphere and alveoli
- other functions: air transport, humidification, warming, particle filtration, vocalisation, immunoglobulin secretion.
Outline the respiratory zone
- zones 17-23
- bronchioles, alveolar ducts, alveoli
- site of GE
- occupies 2.5 to 3L and constitutes the biggest portion of lung volume
- functions: encompass surfactant production (in alveolar endothelium), molecule activation and inactivation (in capillary endothelium), blood clotting regulation and endocrine function.
What is the relationship between lung CSA and air movement?
- shows the relationship between airway generation (forward velocity) and total cross sectional area of the conducting passages of various lung segments.
- airway cross section increases considerably (and velocity shows) as air moves through the conducting zone to the terminal bronchioles.
- at this stage diffusion provides the primary means of gas movement and distribution.
- in the alveoli, gas pressure rapidly equilibrates on each side of the alveolar capillary membrane.
What is Fick’s Law?
- Ficks law of diffusion governs the diffusion of a gas across a fluid membrane
- this law states that a gas diffuses through a sheet of a tissue at a rate:
1) directly proportional to: the tissue area, a diffusion constant and the pressure differential of the gas on each side of the membrane.
2) inversely proportional to: the tissue thickness - the diffusion constant (D) relates to the gas solubility (S) and inversely to the square root of the molecular weight (MV) of the gas.
What does P, Q, V and F stand for? (primary symbols)
P = pressure or partial pressure Q = volume of blood V = volume of gas F = fractional concentration
What does A, B, E, I, T stand for? (gas phase)
- A = alveolar
- B = barometric
- E = expired
- I = inspired
- T = tidal
What does a, c, v stand for? (blood phase)?
- a = arterial
- c = capillary
v = venous
What is the definition of total ventilation (VE)?
the total amount of air that flows out of the respiratory system in a minute?
What is the total ventilation equation?
VE = tidal volume (VT) x respiratory rate (fr)
What is the physiological dead space volume (VD)?
- includes the conducting zone and any other lung volume that does not undergo gas exchange.
What is the equation for alveolar ventilation (VA)?
VA = VE - (VD x fr) VA = 6000 - (150 X 12) VA = 4200 ml/min VA = 4.2 L/min
what do these symbols stand for:
VA VD VT VE fr
VA = alveolar ventilation VD = dead space volume VT = tidal volume VE = total Ventilation fr = respiratory rate
What is tachypnoea?
rapid, shallow breathing
What is the definition of alveolar ventilation (VA)?
- the amount of fresh inspired air available for gas exchange..
because:
- All CO2 comes from alveolar gas
- (Essentially) no CO2 in inspired air, and therefore
- (Essentially) no CO2 in the deadspace
The volume of CO2 expired per unit time (VCO2)
VCO2 = VA x FACO2
VA = VCO2 / FACO2 -> VCO2/PCO2 x k
at a given level of CO2 output….
VA is low - hypoventilation - PaCO2 will rise
VA is high - hyperventilation - PaCO2 will fall
What is the definition of hyperventilation?
- breathing more than required to clear metabolically produced CO2, i.e. PaCO2 falls
What is the definition of hypoventilation?
-breathing less than required to clear metabolically produced CO2. i.e. CO2 rises.
During moderate exercise PaCO2 is normally well maintained, suggesting VA…
very closely matches VCO2.
What is the definition of hyperpnoea?
- the appropriate increase in ventilation in response to exercise.
