Normal Breast Structure
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When a girl reaches puberty, her breasts enlarge if her brain and glands are all working in concert – hypothalamus, anterior pituitary, ovaries, pancreas and hyroid. A normal female breast weighs between 50 to 500 grams (1.76 to 17.63 ounces). Here’s a simplified explanation of how the breast is formed and operates, so you can easily understand your particular problem and treatment options:
- Each breast is divided into 15 to 20 lobes
- Lobes divide into smaller lobules
- Lobules end in milk-producing bulbs, also called terminal ductal lobular units (TDLU)
- Lobes, lobules and bulbs are connected by ducts
- Ducts lead to the nipple, where milk is expressed Normal Breast Structure
- Fat fills the space between lobules and ducts
- The areola is the pink or dark ring around the nipple, which has oil glands to lubricate the breast for nursing
- No muscle is within the breast, just underneath it, riding atop the ribs
- Lymph nodes in the armpits, skin and chest wall drain the breasts of excess fluid and potential disease organisms
Your breasts change five times throughout the course of your menstrual cycle. Three or four days before menstruation, they retain water and the cells proliferate under the influence of estrogen and progesterone. Day 1 of your menstrual cycle is the first day you bleed. During the first two weeks of your cycle, estrogen causes the ducts in your breasts to grow. During the last two weeks of your cycle, progesterone causes the lobes to grow.
If you conceive, progesterone lays the foundation for milk production and breastfeeding (lactation) by the fifth or sixth month of pregnancy. The hormones required for breastfeeding are follicle stimulating hormone (FSH), luteinizing hormone (LH), prolactin, oxytocin (for “let-down” reflex), and human placental lactogen (HPL).
Breasts enlarge and the areola darkens for breastfeeding.
Breasts lose volume (involute) during menopause. If you are thin, breastfeeding, or have small breasts, then the fat, lobes, and underlying muscle can make your breasts seem lumpy, when they are really quite normal.