什么是正常的乳房发育?

乳房 development is a vital part of a woman’s reproduction. 乳房 development happens in certain stages during a woman's life: first before birth, 在青春期, 然后是生育年龄. Changes also happen to the breasts during the menstrual cycle and when a woman reaches menopause.

乳房什么时候开始发育?

乳房s begin to form while the unborn baby is still growing in the mother’s uterus. This starts with a thickening in the chest area called the mammary ridge or milk line. By the time a baby girl is born, nipples and the beginnings of the milk-duct system have formed.

乳房的变化在女性的一生中不断发生. The first thing to develop are lobes, or small subdivisions of breast tissue. Mammary glands develop next and consist of 15 to 24 lobes. Mammary glands are influenced by hormones activated in puberty. Shrinkage (involution) of the milk ducts is the final major change that happens in the breast tissue. 乳腺开始慢慢萎缩. 这通常从35岁左右开始.

青春期乳房会发生怎样的变化啊?

As a girl approaches her teen years, the first visible signs of breast development begin. When the ovaries start to produce and release (secrete) estrogen, 结缔组织中的脂肪开始聚集. 这会导致乳房增大. 管道系统也开始生长. Often these breast changes happen at the same that pubic hair and armpit hair appear.

一旦排卵和月经开始, the maturing of the breasts begins with the formation of secretory glands at the end of the milk ducts. The breasts and duct system continue to grow and mature, 随着许多腺体和小叶的发育. The rate at which breasts grow is different for each young woman.

What cyclical changes happen to the breasts during the menstrual cycle?

Each month, women go through changes in the hormones that make up the normal menstrual cycle. The hormone estrogen is produced by the ovaries in the first half of the menstrual cycle. 它会刺激乳房中乳管的生长. The increasing level of estrogen leads to ovulation halfway through the cycle. Next, the hormone progesterone takes over in the second half of the cycle. 它能刺激乳腺的形成. These hormones are believed to be responsible for the cyclical changes that many women feel in their breasts just before menstruation. 这些症状包括肿胀、疼痛和酸痛.

During menstruation, many women also have changes in breast texture. 他们的乳房可能感觉很肿块. This is because the glands in the breast are enlarging to get ready for a possible pregnancy. If pregnancy does not happen, the breasts go back to normal size. 一旦月经开始，周期又开始了.

What happens to the breasts during pregnancy and milk production?

Many healthcare providers believe the breasts are not fully mature until a woman has given birth and made milk. 乳房 changes are one of the earliest signs of pregnancy. 这是黄体酮激素的结果. In addition, the dark areas of skin around the nipples (the areolas) begin to swell. This is followed by the rapid swelling of the breasts themselves. Most pregnant women feel soreness down the sides of the breasts, and nipple tingling or soreness. This is because of the growth of the milk duct system and the formation of many more lobules.

By the fifth or sixth month of pregnancy, the breasts are fully capable of producing milk. 就像青春期一样, 雌激素控制导管的生长, and progesterone controls the growth of the glandular buds. Many other hormones also play vital roles in milk production. 其中包括促卵泡激素(FSH), 黄体生成素, 催乳激素, 催产素, 和人胎盘乳原(HPL).

其他的生理变化也会发生. These include the blood vessels in the breast becoming more visible and the areola getting larger and darker. All of these changes are in preparation for breastfeeding the baby after birth.

更年期的乳房会发生什么变化?

By the time a woman reaches her late 40s and early 50s, 围绝经期已经开始或正在进行中. At this time, the levels of estrogen and progesterone begin to change. 雌激素水平急剧下降. This leads to many of the symptoms commonly linked to menopause. Without estrogen, the breast’s connective tissue becomes dehydrated and is no longer elastic. The breast tissue, which was prepared to make milk, shrinks and loses shape. This leads to the "saggy" breasts associated with women of this age.

Women who are taking hormone therapy may have some of the premenstrual breast symptoms that they had while they were still menstruating, 比如疼痛和肿胀. But if a woman’s breasts were saggy before menopause, this will not change with hormone therapy.