Download The Respiratory Membrane

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2 fissures (horizontal and oblique)
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1 primary bronchi
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3 secondary bronchi
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Can sometimes appear shorter due to liver being directed underneath it
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Pushes the lung superiorly
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Lobes are separated by fissures and supplied by secondary (lobar) bronchi
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Hilum (triangular depression) is on medial surface (can see when lungs are separated) – the
entry point for blood and nervous supply, lymphatic vessels and bronchi
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Can distinguish between the brochus and blood vessels as bronchus have cartilage
plates in their walls, so it would feel hard
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Visceral pleura attaches to the outer surface of the lung
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If air is introduced into the pleural cavity, the lung would collapse because of the pressure
on the surface of the lung
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Called a pneumothorax
The Respiratory Membrane
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Factors affecting gas exchange
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Thickness of membrane
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Surface area
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Higher SA = more area for gas to diffuse across = faster
Diffusion coefficient: how easily a gas can diffuse in and out of a liquid or tissue (a
higher number means a faster rate of diffusion)
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Thin = faster diffusion
It’s a relative number
Partial pressure
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When partial pressure (Pp) is greater of one side of the membrane than the
other, gas will move from the higher side to the lower
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ie. down the concentration gradient
Thin interstitial space: gas has to travel less far – faster transport
Gas Transport
Oxygen
Carbon Dioxide
- Moves from body tissues into blood vessels
- Moves from alveoli in lungs to blood vessels
- Moves from blood vessels into alveoli in
lungs
- Moves from blood vessels into body tissues
- Transported as:
- Transported as:
- Red blood cells - haemoglobin (98.5%)
- HCO3- (bicarbonate ions) dissolved in
plasma (70%)
- Dissolved in blood plasma (1.5%)
- Bound to haemoglobin (23%)
- CO2 dissolved in plasma (7%)
Respiration and Breathing
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Involves organs and tissues like:
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Diaphragm
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External and internal intercostals
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Lungs
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Ribcage
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Sternum
Can control the contractions of the diaphragm in order to adjust depth of breathing
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But also is under involuntary control
Inspiration
Expiration
- Diaphragm contracts (moves inferiorly and
flattens)
- Diaphragm relaxes and moves superiorly
and back into its regular dome shape
- External intercostals lift rib cage up and out
- External intercostals relax – helps depress
rib cage
- Sternum moves out (pump handle) –
elevated
- Internal intercostals help depress rib cags
- Ribs move outwards (bucket handle) –
elevated
- Sternum moves down (depresses)
- Lungs volume increases and pressure
decreases
- Lung volume decreases and pressure
increase
- Air enters
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- Ribs move down and in (depresses)
- Air exits
Boyle’s Law stated that volume is inversely proportional to pressure
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Higher pressure, lower volume
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Air moves from areas of high pressure to low pressure
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Barometric pressure (PB) is the atmospheric pressure outside the lungs
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Assigned a value of 0 for simplicity – every other value relates to this
At the end of expiration
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PB = Palv
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Therefor Palv = 0
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No flow of air
During inspiration
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PB > Palv
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Therefor Palv = -1
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Inflow of air
End of inspiration
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PB = Palv
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Therefor Palv = 0