Gas exchange Flashcards
What is the broad composition of gases in air?
79% N2
21% O2
What is the air pressure at sea level?
101 kPa
What is Dalton’s Law?
Each gas in a mixture contributes to the pressure in direct proportion to its percentage
What are the broad partial pressures of gases in air?
N2 79 kPa
O2 21 kPa
What is anoxia?
No oxygen
What is hypoxia?
Low oxygen levels
What is normoxia?
Normal oxygen levels
What is hyperoxia?
High oxygen levels
What is Fick’s Law?
Q=ΔP x A x D/ΔX
How have respiratory organs in animals been enhanced to increase the efficiency of diffusion?
High diffusion coefficient Low diffusion distance Large surface area Vascularisation Conversion of gas to non-diffusable substance
How is the diffusion distance lowered?
Thin epithelia
How is the surface area increased?
Invaginations
How is gas converted to a non-diffusible substance?
Using respiratory proteins such as haemoglobin and haemocyanin
Is the viscosity and density of water high or low?
High
Why don’t aquatic organisms use tidal flow?
Too much energy is required to accelerate and decelerate a bulk of water
What do aquatic organisms use instead of tidal flow?
Flow-through system and a countercurrent
Describe an octopuses ventilation system
Water enters through the slit and exits through the siphon
The pressure in the upper mantle is higher than in the lower mantle
This gives a constant one-way ventilation
Describe a fishes ventilation system
One way water flow is achieved by the sequential opening of the mouth and operculum
This sets up an almost continuous pressure difference between the 2 cavities
This ensures the water will flow through the dense sieve-like arrangement of lamellae
How do animals keep their respiratory systems moist?
They themselves remain in moist areas
Have covered/ internal structures
Describe the insect tracheal system
Discontinuous ventilation where the valves of the trachea open and close allowing gas to enter the tracheal system and the frequency of opening is varied depending on the oxygen requirement
What is discontinuous ventilation?
The trachea are not ventilated constantly
Describe the first step in aerial gas exchange in lungfish
The mouth opens, the buccal cavity expands and air enters the buccal cavity
Describe the second step in aerial gas exchange in lungfish
The mouth closes, the buccal cavity compresses and air enters the anterior chamber of the air-breathing organ
Describe the third step of aerial gas exchange in lungfish
The mouth is closed, the anterior chamber is closed and the posterior chamber contracts, and the spent air is exhaled from the posterior chamber through the operculum
Describe the fourth step in aerial gas exchange in lungfish
The mouth is closed, the anterior chamber opens, the posterior chamber contracts and air flows into the posterior chamber, and gas exchange occurs
What is the name for how frogs respire?
Buccopharyngeal pump
Describe the mammalian respiratory system
Air enters the lungs from the oral cavity or nasal passages via the trachea and bronchi
The air then enters the alveoli
In the alveolus, the air is very close to the blood flowing through the capillary network surrounding them
The alveolar walls and capillary walls are very thin thus the diffusion distance is lowered to ~2mm
Describe the process of inhalation
The diaphragm contracts The thoracic cavity expands The intrapleural pressure becomes negative The lungs expand Air enters the lungs
Describe the process of exhalation
The diaphragm relaxes The thoracic cavity contracts The intrapleural pressure becomes less negative The lungs contract Gas is expelled from the lungs
What method of gas exchange do mammals use?
Tidal ventilation
Describe bird lungs
Small
Rigid
No alveoli
Connected to air sacs
What do birds use instead of alveoli?
Vascularised tubes called parabronchi
What do air sacs do?
Penetrate viscera and many bones (pneumatisation)
They are poorly vascularised and play no role in air exchange
Describe unidirectional flow in birds
Air travels through the lungs in one direction from the posterior to anterior air sacs
How many cycles of inhalation/exhalation is required for the air to travel all of the way through a bird’s respiratory system?
2 but in reality, these 2 breaths happen simultaneously
What system of gas exchange do fish gills use?
Countercurrent system
What system of gas exchange do mammalian lungs use?
Tidal flow
What system of gas exchange do bird lungs use?
Crosscurrent system
What system of gas exchange does amphibian skin use?
Cocurrent system
Describe the cocurrent system
Blood and medium flow in the same direction and gradually approach equilibrium with each other
Describe the countercurrent system
Blood and medium flow in opposite directions so oxygen always diffuses from the medium into the blood
Describe the tidal flow system
Fresh medium mixes with the stale medium in the lung so the partial pressure of oxygen at the exchange surface is lower than the environmental medium
Oxygen diffuses into the blood so the partial pressure increases in the blood but remains lower than the exhaled medium do won’t diffuse backward
