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Lecture 18

BIO310H5 Lecture Notes - Lecture 18: Respiratory Epithelium, Gas Exchange, Cellular RespirationPremium

5 pages80 viewsFall 2018

Department
Biology
Course Code
BIO310H5
Professor
Nagham Abdalahad
Lecture
18

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BIO310 Lecture 18 - Respiratory System and Gas Exchange
Gas-Transport System in Vertebrates
Animals obtain O2 from the environment and use it for cellular respiration producing
CO2 and water
O2 is the most abundant element in the Earth’s crust and it is 20.93% of the atmosphere
The amount of O2 dissolved in water is smaller than in the atmosphere ( Vs CO2) • Less
O2 dissolve in water at higher temp.
O2 is added to the atmosphere and water by photosynthesis
water under ice is hypoxic , why ?
O2 and CO2 are transferred passively through body surfaces ( depends on the size of
the animals) -------The respiratory epithelium in larger animals
To maximize diffusion, respiratory surfaces are typically thin, with a large surface area
The thinner the respiratory surfaces the easily oxygen will follow from high to low oxygen
pressures
Thin, composed of 1-2 cells
Wider the respiratory surface area, the greater chance for gas exchange
The physics of respiratory systems-Boyle’s Law
Boyle’s Law: gases move from areas of high pressure to areas of low pressure
Graham’s Law : the rate of diffusion of a substance down a given gradient is inversely
proportional to the square root of its MW.
As O2 and CO2 have similar MW , they diffuse at similar rate
From respiratory media, oxygen will pass through an oxygen gradient towards the
circulation
Then it will be distributed to tissue with low oxygen pressure, since oxygen has been
absorbed by the tissue
Same thing applies to CO2 on the other side
Co2 is a lot in tissues, circulatory will carry the c02 with be exchanged with
oxygen
Three types of specialized breathing structures
Two types of convective transport
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Unidirectional flow
Tidal flow
Respiratory system is to maintain an area for gas exchange
Gas exchange = o2-co2 (each will follow conc gradient)
The thinner respiratory the easier the exchange of gas
The wider the more change that can occur
Respiratory surface - Tissue
Movement of respiratory can be air or media
Flow can be unidirectional and tidal
B) Tidal
Respiratory organ is sac like structure with one opening
Air enters into the respiratory organ
Fills sac
Gas exchange occurs
Another process where there is respiratory media exiting the sac
Active respiration
mechanism where respiratory organ can inspiration (neg pressure)
expiration (compression) to make the sac empty and ready for
next inspiration
lungs are inside body
gills are outside body
both exposed to respiratory medium
some animals have gills but extract oxygen from air
some gills are covered by operculum, and requires opening
Tidal gas exchange: O2 transfer from the environmental medium to the blood in a tidally
ventilated lung
Because a tidally ventilated lung is never fully emptied, fresh medium mixes in the lung
with stale medium. Numbers are O2 partial pressures in arbitrary units: The blood
arriving at the breathing organ is arbitrarily assigned a value of 0, whereas the
atmosphere is arbitrarily assigned a value of 100
Close to respiratory surface is the blood capillary
Introduction of respiratory media, and gas exchange between blood and
respiratory
Blood carried to respiratory surface by blood capillaries
Capillaries have single layer of endothelial cells
Respiratory is a single layer of epithelial cells
Medium is air filling alveolus (resp organ)
Partial pressure is less in organ then outside before it diffuses to blood capillary
There is still air (CO2) in the organ which is why we have 60 (less than atmos
pressure)
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