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Air is breathed in through the nose and the mouth. It makes its way down the trachea (windpipe) and enters into the lungs. The air enters into the small sacs of the lungs called alveoli which in a microsc...

The Loop of Henle is a 'U' shaped portion of the nephron tubule which is very important in retaining water and Na+ from urine, in the process of 'Osmoregulation'. Water leaves the descending limb of the L...

There are several different ways substances can be transported:

1) simple diffusion, i.e. substances that tend to be lipid soluble/ non-polar and can pass easily across the phospholipid bilyar of c...

Alveoli have features that speed up the rate of diffusion so that gases can be exchanged quicly. They have a thin exchange surface - the alevolar epithelium is only one cell thick, which means there's a s...

The temperature of the earth is a balance between the heat it gets from the sun and the heat it radiates back out into space. Gases in the atmosphere absorb most of the heat that would normally be radiate...