Respiratory System Flashcards
Why do we breathe?
It brings air (oxygen) into the body which is used for metabolism to produce ATP as it is stored in limited quantities and is essential for cells to function. A product of metabolism is CO2 which needs to be removed from the body through exhaling.
What is the structure of the respiratory system?
We breathe in through the mouth and the air goes down the trachea which branches into 2 parts, the right and left bronchus which goes into each lung. The bronchus split into many bronchioles which disperses throughout the lung. at the end of each bronchiole there is alveoli which are like bunches of grapes. These are where the gas exchange takes place.
How are the alveoli adapted for gas exchange?
There are over 600 million, creating more surface area to increase gas exchange. They have a very thin cell wall for efficiency of gas exchange and they are also moist to lubricate the gas exchange. they are surrounded by many capillaries for a huge blood supply. Oxygen diffuses out of the alveoli and into the blood. CO2 diffuses from the blood into the alveoli.
What are the 2 sections of the respiratory tract?
The conducting zone (dead space) - no gas exchange occurs. The air is vaporised, warmed and moistened to help with diffusion.
The respiratory zone - site of gas exchange (includes respiratory bronchioles, alveolar ducts and alveolar sacs).
What is Boyles law?
States that decreasing volume will increase pressure. p1v1 = p2v2.
What is atmospheric and intrapulmonary pressure normally?
760mmHg
How does pressure move along the pressure gradient?
During inhalation, lungs expand and volume increases, reducing pressure to 759mmHg and causing air to be sucked in. During exhalation, lung volume decreases, increasing the pressure to 761mmHg and causing air to be pushed out. This pressure is moving along a gradient, when atmospheric and intrapulmonary pressure is equal, there is no movement of air.
Changes in lung volume are due to the diaphragm - when it moves down the lungs can expand into the space and thus volume increases.
What is the equation for airflow in litres/minute?
airflow = pressure difference / airway resistance.
What is the amount of oxygen present in the atmosphere and how does this translate to pressure?
Air is made up of 20.98% oxygen (78% is nitrogen) - in terms of pressure, oxygen makes up 159mmHg out of the 760mmHg. When air is vapourised in the trachea, total pressure goes from 760mmHg to 713mmHg, therefore oxygen reduces to 140mmHg.
Oxygen has a pressure gradient of 60, CO2 has a pressure gradient of only 6. However diffusion of both gasses is relatively equal due to the increased solubility of CO2.
What are the four effects on the rate of diffusion?
Pressure gradient - The higher the pressure on the air side and liquid side, the quicker the rate of diffusion.
Solubility - the more soluble the gas is, the quicker it will diffuse. Oxygen will diffuse 2.26ml per 100ml of fluid, whereas CO2 will diffuse 57.03ml.
Surface area - larger the SA, more diffusion as diffusion can take place in more areas.
Resistance - The alveolar membrane is 1 cell thin therefore has very little resistance on the diffusion gradient.
What is Fick’s law of diffusion?
Rate of diffusion = diffusion constant (solubility) x area for gas exchange x((pressure 2 - pressure 1) / thickness of barrier)
What is minute ventilation?
volume of air moved per breath x number of breaths per minute
What is the equation for alveolar ventilation and what does it mean?
AV = minute ventilation - dead space ventilation (dead space volume and breath frequency).
Not all the air we inhale reaches the alveoli as some will stay in the dead space which can be 150-200ml (around 30% TV). So, in normal breathing of around 500ml, only 350ml ‘fresh’ air will reach the alveoli.
So, alveolar ventilation will always be lower than minute ventilation.
What is residual volume?
When we expire as much as possible, there will still be an amount of air left in the lungs, allowing gas exchange to continually take place.
What is total lung volume?
TLV is the maximum lung volume after maximum inspiration. The adequacy of pulmanory ventilation depends on how well an individual can sustain this high airflow.
