Introduction Lecture 1 Flashcards
Functions of the respiratory system are
Gas exchange - large surface area for diffusion
Blood pH control - important as CO2 affects acidity
Remove blood clots from the circulation - acts as a filter for stopping clots going to the heart/brain
Defence against microbes - lots of white blood cells in the lung
Heat and water loss through ventilation
Blood reservoir (pulmonary vessels) - holds quite alot of blood and can help circulation
Metabolic functions - eg Ang II, BK, PGs
What are the 2 types of circulation
Pulmonary and Bronchial (bronchial for nutritive blood supplying the lungs to allow cells to get nutrition)
Functions of various parts in the airways are
Filtering (hairs filter in nose), warming (through blood supply) , humidifying (dry air coming in, but as we breathe water is added) and distribution (airways provide distribution to the lungs).
Trachea - C shaped cartilage ring acts as a scaffold
Bronchiole - smooth muscle, can change size of airways to change air flow by bronchoconstriction/dilation.
Pulmonary artery = low oxygen entering lung
Pulmonary vein - high oxygen leaving lung
Clara cells - produce mucus
Type II cells, produces surfactant
Capillary - provides short diffusion distance to alveoli
Alveoli have huge surface area for diffusion
The generation of airways
Up to generation 16, it is the conducting zone = air conducted through to the gas exchange regions
From generation 17 to 23, is the transitional and respiratory zones where gas exchange occurs
What happens to the surface area as the number of airways go up
Surface area increases as you go down the generations due to increased number of airways.
By generation 17, velocity is less than the speed of diffusion. THe velocity is low so diffusion can occur.
FLow = velocity x area
Increase in total cross sectional area results in decreasing gas velocity
Types of gas transport in the genarations
Air to generation 16 = convection Generation 17 to alveoli = diffusion Gas exchange = diffusion Pulmonary capillaries to systemic capillaries = convection Gas exchange in tissue = diffusion
Describe convection and diffusion
Convection = Moves down fluid/gas pressure gradient, conducting airways and in blood vessels, used to move down O2 and CO2 long distances around the body, found in larger tubes, Flux = velocity x concentration
Diffusion = moves down concentration gradient, found at sites of large gas exchange, in alveoli and capillaries, used to move O2/CO2 short distances around the body only.
Ficks law
What is dead space
The volume of gas within the respiratory system where no gas exchange takes place.
Where there are no alveoli, no airflow, no blood flow.
Anatomic dead space = 150ml
Alveolar dead space = 0ml (due to there being gas exchange in alveoli)
Affected by body size, age (increase with age), head position (decreases when tilted forwards), drugs (bronchodilators/constrictors)
How to work out physiological dead space
Anatomic dead space + alveolar dead space
Tidal breathing and ventilation are
Vt = tidal volume (volume expired in each breath) = 500ml
fR = respiratory frequency (number of breaths per min) = 12
VE = minute ventilation (volume of air expired per min)
VE = Vt x fR
= 6000ml/min at rest
How to work out tidal volume
Vt = VD + VA
VD = dead space volume (no gas exchange) VA = alveolar volume has gas exchange
VE = Vt x fR VD = VD x fR VA = VA x fR
Respiratory quotient (RQ) =
VCO2 / VO2
= Rate of CO2 and O2 consumption (about 0.8 at rest)
