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In Depth: Mammary Glands and Ducts

The word “mammary” is similar to “mammal” because our classification in the animal kingdom is named after our glands. The presence of sweat glands is a distinguishing characteristic for mammals.  The glands and ducts of the female breast are similar to sweat glands.

Although every human has sweat glands, only females have glands and ducts capable of producing milk. Specifically, only women who have given birth have functioning mammary glands.

The mammary glands located in the breast are responsible for producing milk for a suckling baby following childbirth. Each gland consists of a series of lobules, glands that produce milk. They connect to ductal lobes, which connect to the lactiferous ducts.

The lactiferous ducts are responsible for delivering the milk to the surface of the skin and out of the mother through tiny pores in the nipple. These ducts form a tree-branch-like network that converges at the nipple. Lactiferous ducts are known by many names, including milk ducts, mammary ducts, and galactophores.

When women have not given birth and aren’t lactating, a plug blocks the ducts to prevent bacteria from entering and causing an infection. The plug is made of keratin, a structural protein that is the key component to skin, hair, and nails.

Hormonal changes during pregnancy signal the mammary ducts to begin producing milk. This can continue for years, as long as there is regular suckling or pumping of the milk.

Mammary glands and ducts are also important in gauging the stage of a woman’s breast cancer. Staging depends on where the cancer is located and what areas are affected.  

  • Ductal carcinoma refers to cancer in the milk ducts. It is the most common form of breast cancer.
  • Lobular carcinoma refers to cancer in the lobules.

Both types of breast cancer have subgroups:

  • In situ: The cancer remains in the area it originated.
  • Invasive: The cancer cells have spread to neighboring regions from where they began. 

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