Most women have them to some degree or another. How we feel about them often depends on our upbringing, our circumstances and the amount of pressure, expectations and acceptance we received when we sprouted them. I'm talking about our breasts, those often maligned, revered or misunderstood glands that women just can't get away from. One way or another, we deal with them. We push them up, flatten them out, support them, add to them, take away from them and sometimes even pierce them, but often we don't understand them and the changes they go through during a woman's life cycle.

Christa Miller of Southern Maine doesn't always understand the changes her breasts go through. They always became tender and sore before her period, but that changed after her son was born. "I noticed only a drop in milk supply from month to month – but no soreness," Miller says. "I assumed that the symptoms would return after my son weaned himself at 13 months, but they never did."

Like other women, Miller noticed a change in her breasts directly related to her monthly cycle. More changes can come with puberty, child birth, breastfeeding and menopause, but before we can understand why our breasts change, it is important to understand what they are.

The breast, or mammary gland, is one of our bodies' most complex and efficient organs, says Jan Buchanan, a registered nurse and certified nurse midwife at the William Beaumont Hospital in Royal Oak, Mich.

Buchanan says the breast is composed of the following parts:

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