Exchange Surfaces Flashcards
Tidal Volume
Volume of air that moves in OR out each resting breath, usually around 500cm³
Vital Capacity
The volume of air that can be breathed in when the strongest possible exhalation is followed by the deepest breath in (eg, force out as much air as possible. This is the start point, then breathe in as deep as possible = the vital capacity)
Inspiratory reserve volume
Maximum volume breathed in over and above normal tidal
Expiratory reserve volume
The extra air that can be forced out of the lungs over and above normal volume breathed out
Residual volume
Volume of air left in the lungs when you have exhaled as hard as possible. Cannot be directly measured
Breathing rate
Number of breaths per minute
Ventilation rate
Tidal volume * breathing rate (min⁻¹)
Oxygen uptake
The volume of oxygen absorbed by the blood. It is assumed that this is equal to the volume of carbon dioxide absorbed by the soda lime
Features of a good exchange surface and reason why
Large surface area: greater area over which to exchange substances
Thin layers: shorter distance over which to diffuse, makes it faster
Good blood supply: constantly taking away diffused substances to maintain a concentration gradient
Ventilation (gases): maintains concentration gradient
What happens to the SA:V area as the organism gets larger
The ratio decreases as size increases
What is the function of the trachea and what tissues are related to it?
Function: Tube that carries air into the lungs, branches into bronchi
Tissues: C Shapes rings of cartilage, ciliated epithelium and goblet cells, smooth muscle, elastic fibres
What is the function of the bronchi and what tissues are related to it?
Function: Two tubes, carry air into left and right lung, branches into bronchioles
Tissues: Cartilage in full rings, ciliated epithelium and goblet cells, smooth muscle and elastic fibres
What is the function of the bronchioles and what tissues are related to it?
Function: many tubules carrying air, the smallest tubules terminate in alveoli
Tissues: Larger ones may have cartilage. Smooth muscle, elastic fibres, lined with goblet cells and ciliated epithelium
What is the function of the alveoli and what tissues are related to it?
Function: Air sacs, site of gaseous exchange
Tissues: Squamous epithelium, elastic fibres
How does breathing in/inhalation work?
External intercostal muscles contract moving the ribcage upwards and outwards
The diaphragm muscles contract and moves downwards
The volume of the thorax is increased by these two actions
The pressure in the chest therefore decreases. The pressure in the thorax is now lower than the pressure outside so air is drawn into the lungs
How does breathing out/exhalation work?
The external intercostal muscles relax and the ribcage falls under its own weight
The diaphragm muscle relaxes and moves upwards
The volume of the chest cavity or thorax is decreased by these two actions
The pressure inside the chest therefore increases. The air pressure inside the thorax is now greater than outside so air is forced out of the lungs
Explain how the lungs are adapted for gas exchange
-Pulmonary vein continually removes oxygenated blood
-Pulmonary artery brings deoxygenated blood to the lungs
-Maintains concentration gradient
-Squamous epithelium, flattened, short diffusion path
-RBC carry O2 in haemoglobin
-O2 moves into blood via diffusion down concentration gradient
-CO2 moves out of blood into alveoli down concentration gradient
-Frequent ventilation keeps oxygen high and CO2 low
How does a spirometer work?
-Breathing out makes the trace go up
-Breathing in makes the trace go down
-Chamber is filled with oxygen or air and floats on a tank of water
-The air breathed out passes through soda lime to remove CO2
-Total volume goes down as patient breathes in oxygen
-Decrease in volume = amount of oxygen used
-Volume goes down because CO2 is taken out
What precautions should be taken when using a spirometer?
-Make sure patient is healthy, no asthma
-No air leaks as this invalidates results
-Sterilised mouth piece
-Soda lime and functioning
