Biology - The Lung As An Organ Of Exchange

Front 1

what is the definition of gaseous exchange ?

Back 1

the movement of gases by diffusion between an organism and its environment across a barrier such as the alveolus wall.

Front 2

how does the air pass into the lungs ?

Back 2

through the nose, trachea ,bronchi ,bronchioles, alveoli.

Front 3

Where exactly does gaseous exchange take place ?

Back 3

the walls of the alveoli.

Front 4

what gases are involved in gaseous exchange ?

Back 4

oxygen and carbon dioxide

Front 5

movement of the ribs and diaphragm help with what ?

Back 5

ventilation ( breathing)

Front 6

how thick are the alveoli and capalliries walls ? what is good about this ?

Back 6

1 cell thick , it reduces diffusion distance.

Front 7

how are the lungs adapted for gaseous exchange ? how do these adaptions help ?

Back 7

it has a large surface area- provides more space for molecules to pass trhough.
the plasma membrane is a semi perameable - allows diffusion of oxygen and carbon dioxide.

Front 8

what is the total surface area of alveoli ?

Back 8

70m2

Front 9

what factors adaptations reduce diffusion distance?

Back 9

-alveolus wall and capillary wall one cell thick
-both walls consist of squamous cells
-capillaries are in close contact with the alveolus wall
-the capillaries are narrow so that the red blood cells are squeezed agaisnt the capillary wall, making them closer to air in alveoli and reducing rate of blood flow.
-total barrier of diffusion is two cells thick less than 1 micro metre thick.

Front 10

what is surfactant ?

Back 10

a substance that the lungs produce to reduce the cohesive forces between water molecules.

Front 11

why do the lungs need surfactant ?

Back 11

to prevent the alveolus from collapsing due to the cohesive forces between the water water molecules lining the air sac.

Front 12

why do we need to maintain a steep diffusion gradient in our lungs ?

Back 12

so diffusion is rapid.

Front 13

how do we maintain a steep diffusion gradient ?

Back 13

- a high concentration on the supply side of the exchange surface and a low concentration on the demand side.
-a fresh supply to provided to keep concentration high.
-removal of molecules to keep concentration low.
-this is achieved by the blood transport system and ventilation movements

Front 14

what casues inspiration ?

Back 14

the diaphragm contracts and moves downwards. external intercoastalmuslces contract casuing the ribs to move up and outwards,this increases the volume in the lungs , decreasing pressure in the lungs below atmospheric pressure.This then causes are to flow into the lungs.

Front 15

what causes expiration ?

Back 15

diaphragm relaxes and is pushed up by displaced organs underneath. The external intercoastal muscles relax and ribs fall.This causes volume of the chest cavity to decrease, increasing air pressure above atmospheric pressure. Which, causes air pressure air of to move out of the lungs.