Term
| the elastic properties of the lung are important in expiration. name the 2 components in the elastic behaviour of the lungs |
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Definition
Elasticity of lung tissue - Collagen and elastin are naturally elastic
surface tension - a thin layer of fluid lining the alveoli
Lungs have a huge surface area 70m2 |
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Term
what is the name of the pressure required to inflate the lungs? what is pressure opposed by?
is it easier to inflate lungs in aqueous solution or in air? explain why |
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Definition
Translung pressure is needed to inflate the lungs
this pressure is opposed by air-liquid surface tension which tries to deflate the lungs
it is easier to inflate lungs in aq solutions because in air you need to apply a larger pressure to ovcome the surface tension in lungs |
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Term
| as .............. pressure inflates the alveolus, it is opposed by air-liquid .............. tension that tries to deflate it |
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Definition
translung, surface
translung distending pressure is worked out using Laplace's law.
P= 2 x T/r |
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Term
| what is laplaces law used to work out? break down the equation. |
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Definition
law used to work out translung distending pressure
P= 2 x T/r
P = translung distending pressure
T = wall surface tension
r = radius |
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Term
| which product lowers the surface tension of the fluid lining the alveoli to prevent its collapse? |
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Definition
Lung surfactant
the normal ST for water is 70nM/m and in lungs it can drop to less than 2nM/m thus, surfactant considerably < surface tension in lungs |
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Term
| lung surfactant is 35-40% made from this lipid with other lipids and proteins. which lipid is this |
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Definition
dipalmitoylphosphatidylcholine (DPPC)
lung surfactant important at birth and premature babies can lack it. this makes it difficult to inflate the lungs. |
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Term
| name the condition caused by surfactant deficiency in premature babies |
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Definition
respiratory distress syndrome
without surfactant lungs cannot inflate properly. this occurs in approx 50% premature babies and the likelihood increases the more premature the babies are. |
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Term
how can respiratory distress syndrome be treated?
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Definition
use of mechanical respirators and administration of artificial surfactant in form of a spray.
severe respiratory distress syndrome can be treated by the administration of a special oxygenated liquid to the lungs.
RDS can result from a genetic problem with surfactant associated proteins |
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Term
| dipalmitoyl phosphatidylcholine has the formula C40H80NO8P. it is described to have a detergent structure. what does this mean? |
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Definition
| it has a polar tail and long hydrophobic tail like detergent micelle where polar groups are exposed to water and the hydrophobic tails are hidden within the core |
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Term
| describe the relation between surfactant and alveolus size |
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Definition
the smaller the alveolus the more surfactant you need. the bigger the alveolus the less you need.
the lung automatically adjusts surfactant levels so smaller alveoli have more than larger ones. |
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Term
| from .... law, small alveoli require a greater ........ force to counteract effects of surface tension than ..... ones BUT .......... in the lungs ....... surface tension more in ....... alveoli than in larger ones, and so adjusts surface ......... to correspond to .............. size |
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Definition
Laplace's, distending, larger, sufactant, reduces, smaller, tension, alveolar
from laplace's law, small alveoli require a greater distending force to counteract effects of surface tension that larger ones BUT surfactant in the lungs reduces surface tension more in small alveoli than in larger ones, and so adjusts surface tension to correspond alveolar size |
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Term
what is the air pressure at sea level?
what is the air pressure at 6000m?
how much oxygen does water contain? |
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Definition
sea level = 760 mm Hg = 1 atmosphere
6000m = 380 mm Hg = 0.5 atomospheres
water contains 5-10ml oxygen/litre |
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Term
| work out the partial pressure of o2 |
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Definition
PO2 = 760 x 20.95 = 159.2 mm Hg
760 is the air pressure at sea level = 1 atmosphere
20.95 is the amount of oxygen making the compostion of air |
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Term
| which type of lung cells does oxygen diffuse across? |
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Definition
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Term
| what is fick's law of diffusion? |
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Definition
R = D x A x Δp/d
R = rate of diffusion
D = diffusion constant
A = area over which diffusion takes place
ΔP = differences in partial pressures
d = distance
here the area (A) is very large as human lungs have 70m2 surface areas and the distance to diffuse is small (0.5-1.5 uM in human lung) |
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Term
| differences in PP of O2 and CO2 allow diffusion to take place. what are the solubilities of Oxygen, Nitrogen and CO2 in water at 15C and 1 atosphere pressure? |
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Definition
O2 - 34.1 ml per litre of water
N2 - 16.9 ml per litre of water
CO2 - 1019 ml per litre of water
1 litre of blood plasma can hold 3 mls oxygen at PP = 100 mm Hg |
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Term
true or false?
H20 is better at dissolving co2 than it is at dissolving o2 |
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Definition
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Term
o2 is transported in combination with Hb inside RBC in the form of?
how many molecules of o2 does each Hb molecule carry? |
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Definition
oxyHb
Hb has 4 polypeptide chains 2 alpha and 2 beta each with a haem group and central Fe 2(II) which binds o2.
each haem binds four molecules of o2 |
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Term
roughly how many molecules of Hb in each RBC?
how much O2 can 1 g of Hb combine? |
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Definition
~280 million molecules of Hb
1 g Hb can combine 1.34 mls of O2 |
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Term
| how many grams of Hb in 1 litre saturated blood? how many mls of O2 in 1 litre saturated blood? |
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Definition
in 1 litre there are 150 g of Hb and 200 mls of Oxygen
at rest, 250mls O2 are carried per minute between the lungs and tissues |
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Term
how many layers of cell between the diffusion path between alveolar air and blood?
how long do rbc spend in alveolar capillaries? |
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Definition
two layers - alveolar and capillary walls
an individual RBC spends only 0.3 - 1 second in an alveolar capillary. this is normally sufficient for full oxygenation except for high altitude or in diseased lungs |
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Term
| what is the difference between the haem groups in Mb and Hb? what are the HbO2 and MbO2 dissociation curves like? |
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Definition
Hb has 4 haem groups /Mb has only one haem group
Hb has a sigmoidal curve = positive cooperativity. when O2 is bound to a haem, remaining haems have > affinity for O2 due to conformational change on binding
Mb has hyperbolic curve. it stores O2 temporarily in skeletal muscles |
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Term
| in co2 transport, how many percent co2 is bound with amine groups on Hb to form carbaminoHb? (Hb-NHCOOH) |
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Definition
20%
oxyHb is a weaker CO2 binding agent but blood plasma is better at dissolving CO2 than O2.
8% CO2 dissolved in blood plasma and 72% reacts with water |
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Term
| 72% CO2 diffuses into the cytoplasm of RBC and reacts with water. what is the equation for this reaction? |
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Definition
CO2 + H20 ---> H2CO3 ---> HCO3- + H+
co2 reacts with water to form carbonic anhydrase. the more co2 there is, the more acidic the environment will be |
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Term
| in relation to the bohr effect the curve shifts to the right causing the realease of more oxygen to the tissues that require it. what causes the curve to shift to the right? |
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Definition
| in exercise we respire more and produce more co2 which lowers pH and increases temperature. 2,3 BPG is a product of glycolysis and combined these shift the curve to the right meaning more O2 is realeased in the tissue during periods of exercise and metabollic activity |
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