HUBS192 Lecture 18 - Oxygen and Carbon Dioxide Exchange Flashcards
what is the equation for how much air we breathe in and out?
- Vf = Vt x f
- respiratory minute volume = tidal volume (breathing strength) x respiratory rate (breathing speed)
- (L/min) = (L/breath) x (breaths/min)
what is respiratory minute volume?
volume of air respired (breathed in and out) per minute in L/min
what is the dead space (Vd)?
air in conducting portion of the respiratory system (anatomic dead space)
-volume of air trapped in the bronchial tree that does not interact with the alveoli
what is alveolar ventilation?
the amount of air that is getting in the alveoli that can be used in gas exchange per time
what is the equation for alveolar ventilation?
- Va = (Vt - Vd) x f
- Alveolar ventilation = (tidal volume (breathing strength) - dead space (the air that can’t be used) x respiratory rate (breathing speed)
- (L/min) = ((L/breath) - L/breath)) x (breaths/min)
what is not helpful to increasing alveolar ventilation?
tiny rapid breaths are not helpful
why are tiny rapid breaths not helpful in increasing alveolar ventilation?
because tidal volume is small its not much more than the dead space therefore trapping the fresh air within the dead space and not coming in contact with the alveoli
-respiratory rate is increased
how do you increase alveolar ventilation?
- increase tidal volume
- keep respiratory rate highly constant
- results in a negligable dead space
what is daltons law?
the pressure of a mixture of gases is the sum total of the pressures of each individual gas
what is the largest component of air?
nitrogen
what is the ratio of gases when inhaling air?
- mostly nitrogen (nitrogen content in the alveoli is relatively the same)
- quite a lot of oxygen (oxygen content in the alveoli is very low)
- almost no carbon dioxide or water vapour
what is the ratio of gases when exhaling air?
- mostly nitrogen
- oxygen is decreased
- carbon dioxide is increased
what is the goal of moving gas across the membranes?
the goal is to move gas back and forth between the alveoli and the capillaries (CO2 and O2)
where is inhaled oxygen transported?
transports inhaled oxygen into the capillaries
where is carbon dioxide (CO2) transported?
transports carbon dioxide into the alveoli to be exhaled
how do gases move across the membranes?
gases move across the membranes between the alveoli and the capillaries by diffusion
what 3 things determine the rate of diffusion of gases?
1) surface area of the membranes
2) thickness of the membranes
3) pressure difference between the two sides
what creates the high surface area for gas exchange?
bulbous structure of alveoli and the high density of capillaries
- creates lots of air pockets
- surface area as large as a tennis court
what is emphysema?
disease characterised by diction of the alveolar spaces and destruction of the alveolar walls
what is the result of emphysema?
reduction in surface area means less contact between the air and capillaries, oxygen exchange is greatly reduced
what is the blood air barrier mostly composed of?
mostly composed of the alveolar and capillary walls
what is the relationship between the distance between of the alveolar air and the blood?
small distance between the alveolar air and the blood
-affects diffusion
what are the 3 key determinants of how much alveolar oxygen we have at any given moment?
1) atmospheric oxygen
2) alveolar ventilation
3) blood oxygen (amount of exchange that Is occurring)
what is the relationship between exercise and blood oxygen?
exercise depletes blood oxygen
what is happening in the body at low activity in terms of oxygen consumption and oxygen in venous blood?
- reduced oxygen consumption
- higher levels of oxygen in the venous blood
what is happening in the body at high activity in terms of oxygen consumption and oxygen in venous blood?
- increased oxygen consumption
- lower levels of oxygen in the venous blood
what are the things that 3 determine how much alveolar carbon dioxide we have at any given moment?
1) atmospheric CO2
2) alveolar ventilation
3) blood CO2
how do gases diffuse in terms of their pressure gradient?
gases diffuse down their pressure gradient
