breathing when diving.

Question
hi there! im doin biology at university and we have been asked two questions. Why shoul you breathe out on your way up from diving and why should you not take extra deep breaths before heading down. I would really apreciate it if you can help me.


Answer
Lynsey--
The reason for exhaling on the way up is two-fold.  The first is to equalize the pressure in your ears.  The second is to keep the bends(nitrogen buildup) from occuring.
The reason you don't take real deep breaths before heading down is that the pressure is greater as you go deeper and if you take an extra deep breath the extra pressure with the extra air in your lungs can possibly cause damage to your lungs.
Sorry this took so long and I hope it is some help
George