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breast anatomy

Anatomy of a lactating breast, excerpt from Clinician’s Guide to Breastfeeding, L. Dahl, 2015

Internal anatomy

Your breast is composed of fatty and glandular tissues. The glandular tissue is what produces milk. When lactating, your breast contains about twice as much glandular tissue as fatty tissue, although the percentage can vary greatly between women. Most of the glandular tissue is in the front of the breasts, directly underneath your areola, and therefore easily accessible to your baby.

The glandular tissue is comprised of:

  1. Alveoli – where milk is made and stored. Alveoli are arranged into lobules. A group of lobules is called a lobe.
  2. Milk (lactiferous) ducts – how the milk travels from the alveoli to the nipple and out of the breast.

External anatomy

On the exterior of the breast are the areola, nipple, and Montgomery glands.

  1. Areola – circular, pigmented area of the breast.
  2. Nipple – centered in the areola, it carries the openings of the milk ducts. There are 6 to 10 such openings in each nipple, corresponding to the 6 to 10 lobes in each breast.
  3. Montgomery glands – surrounding the nipple, within the areola, they secrete an oily liquid that creates a seal to prevent nipple damage and affects newborn behavior.


You can insert almost any adjective in the sentence: “Your baby can’t latch on because your breasts or nipples are are too   (fill in the blank)  . The truth is, the size and shape of your breast and nipples are not an absolute determinate of their “appropropriateness” for nursing. It is all about FIT. While certain breast and nipple shapes may be more challenging than others, if your baby has an appropriately wide gape, she can nurse on almost any breast.

Breast size and shape

Lactating breasts come in every shape and size, and they aren’t necessarily symmetric. Believe it or not,  breast size does not determine the amount of milk your breasts can make. Large breasts may contain more fat than milk-making tissue, and vice versa. Large areolas or breasts may, however, require your baby have a wider gape. And most importantly, when you firs start to nurse, when your breasts are engorged and “rounder” your baby has to stretch a little wider to fit all the way around them.

Nipple size and shape

Nipples also come in all shapes and sizes, some very large, so small. About one-third of mothers have flat or inverted nipples during pregnancy. This shape makes it a little more challenging for your baby to gape around all the tissue, but different holds can help.

  • Flat nipples are not necessarily inverted. One way to differentiate the two is by performing a pinch test:  Pinch the areolar tissue an inch behind the nipple. If the nipple protrudes it is simply flat and not inverted.
  • Inversions occur when the nipple adheres to the underlying tissue at the base. They are rare and usually congenital, but can also happen from previous nursing, surgery, breast cancer, infection, or breast drooping. In most cases, drawing out the nipple eventually resolves the problem.


Breast hypoplasia, or insufficient glandular tissue (IGT), is well known to plastic surgeons because they often see these women for implants. Simply put, IGT means your breasts do not contain enough milk making or glandular tissue. This gives them a particular look and shape. They tend to be widely spaced across your chest, with larger areola for your breast size, and they are asymmetric. They may also have stretch marks that developed during puberty, even though your breasts are not large.

If you have hypoplastic breasts, it is not surprising that you will have a tendency to make less milk. One study found that about 85% of mothers with hypoplastic breasts produced less than half of the milk requirement their baby needed during the first week. Even if you can’t make everything your baby needs, you can definitely give him what you have. Nursing more frequently and taking supplements that promote your supply can also help.