Biology - Exchanging gases

The lungs exchange oxygen and carbon dioxide with atmosphere. They have a very large surface area provided with millions of air sacks. The surfaces of the lungs are moist and thin so that diffusion takes place quickly. The alveoli also has a good blood supply that maintains a concentration gradient for diffusion by removing oxygen and bringing lots of carbon dioxide.

Oxygen diffuses into many capillaries surrounding the alveoli and carbon dioxide diffuses back into the lungs. 

All living organisms need to exchange gases. They need oxygen (for respiration) and to get rid of carbon dioxide. When organisms becomes multi cellular (made of more than one cell) It will need to have a respiratory system.

• Fish exchange oxygen through gills 
• Frogs exchange oxygen through their skin
• Insects exchange oxygen through holes in their sides (spiracles) leading to a series of tubes called trachea

These gas exchange systems have a number of features in common

• They have a large surface area
• They are moist
• The gases are transported away quickly to maintain a high concentration gradient
• The membranes that the gas diffuses through are thin

• It is not illegal to smoke over the age of 18
• The nicotine in tobacco smoke is addictive 
• Tobacco smoke contains all sorts of cancerous causing chemicals
• The carbon monoxide in tobacco smoke reduces the amount of oxygen your blood can carry
• Pregnant women who smoke have babies with lower birth weights, as the babies do not get enough oxygen to release the energy from food that they need to grow properly 

The lungs are in the thorax (the upper part of your body)

It's separated from the lower part of the body by the diaphragm. The lungs are like big pink sponges protected by the ribcage. The air that you breathe goes through the trachea, they split into two tubes called bronchi. The bronchi split into progressively smaller tubes called bronchioles. Bronchioles finally end at small bags called alveoli this is where the gas exchange takes place.

Breathing in....... The intercostal muscles and diaphragm contract, the thorax muscle volume increases, this decreases the pressure, drawing air in.

Breathing out........Intercostal muscles and diaphragm relax, Thorax volume decreases and the air is forced out

Diffusion actually happens in the tiny little air sacks called alveoli. where they diffuse into capillaries.

Gases diffuse in & out of leaves through tiny holes called stomata.

Oxygen diffuses out of leaves during respiration and carbon dioxide in. 

The stomata also allow water to leave the plant which is not good for it, therefore plants only have stomata on the underside of the leaf and can close them too prevent too much water being lost.