Gaseous exchange surfaces
Structure of Gaseous Exchange Surfaces in Humans, Fish, Insects and Frogs
Gaseous Exchange is a biological process where oxygen diffuses into the body or bloodstream and carbon dioxide diffuses out of the body or blood stream. This process is different for Humans, Fish. Frogs and Insects.
Humans:
In humans the gas exchange system is known as the Respiratory system. The respiratory surface is the Alveoli located on Bronchial tubes inside of the lungs. The average human adult has about 600 million alveoli which comes together to form a surface area of over 100 metres squared. There is only 2 thin walls of epithelial cells on the alveoli so things can diffuse quite easily. Water diffuses into the alveoli to keep it moist. Oxygen dissolves in this blood before diffusing into the blood stream. The steep concentration gradient across the respiratory surface is maintained in two ways: by blood flow on one side and by air flow on the other side. This means oxygen can always diffuse down its concentration gradient from the air to the blood, while at the same time carbon dioxide can diffuse down its concentration gradient from the blood to the air. The sheer number of alveoli inside the lungs means that the surface area for diffusion to take place is huge. In humans, carbon dioxide waste is breathed out through the lungs. Ammonia produced from cells is converted to urea as it is much less toxic and is excreted through the kidneys.
Fish:
Gas exchange is more difficult for fish than for other animals because the concentration of dissolved oxygen in water is less than 1%, compared to 20% in air. Fish have developed specialised gas-exchange organs called gills, which are composed of thousands of filaments. The filaments in turn are covered in feathery lamellae which are only a few cells thick and contain blood capillaries. The gills are so thin that they cannot support themselves without water, so if a fish is taken out of water after a while the gills will
Gaseous Exchange is a biological process where oxygen diffuses into the body or bloodstream and carbon dioxide diffuses out of the body or blood stream. This process is different for Humans, Fish. Frogs and Insects.
Humans:
In humans the gas exchange system is known as the Respiratory system. The respiratory surface is the Alveoli located on Bronchial tubes inside of the lungs. The average human adult has about 600 million alveoli which comes together to form a surface area of over 100 metres squared. There is only 2 thin walls of epithelial cells on the alveoli so things can diffuse quite easily. Water diffuses into the alveoli to keep it moist. Oxygen dissolves in this blood before diffusing into the blood stream. The steep concentration gradient across the respiratory surface is maintained in two ways: by blood flow on one side and by air flow on the other side. This means oxygen can always diffuse down its concentration gradient from the air to the blood, while at the same time carbon dioxide can diffuse down its concentration gradient from the blood to the air. The sheer number of alveoli inside the lungs means that the surface area for diffusion to take place is huge. In humans, carbon dioxide waste is breathed out through the lungs. Ammonia produced from cells is converted to urea as it is much less toxic and is excreted through the kidneys.
Fish:
Gas exchange is more difficult for fish than for other animals because the concentration of dissolved oxygen in water is less than 1%, compared to 20% in air. Fish have developed specialised gas-exchange organs called gills, which are composed of thousands of filaments. The filaments in turn are covered in feathery lamellae which are only a few cells thick and contain blood capillaries. The gills are so thin that they cannot support themselves without water, so if a fish is taken out of water after a while the gills will
References: http://www.s-cool.co.uk/a-level/biology/gas-exchange/remember-it/s-cool-revision-summary http://www.brown.edu/Departments/Engineering/Courses/En123/MuscleExp/Frog%20Respiration.htm http://www.biologymad.com/resources/M6GasExchange.pdf http://new.freshwaterlife.org/gills-and-respiration http://www.mrothery.co.uk/exchange/exchange.htm http://yr11-biology-revision.wikispaces.com/Gaseous+exchange