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Mammary Gland

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What are Mammary Glands in Mammals?

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The mammary glands are specialised organs that are found in pairs on either side of the anterior chest wall. The principal purpose of the organ is to secrete milk. Though both sexes have it, it is more developed in females and primitive in males. It's also an important part of the female reproductive system's accessory organs. The mammary gland is located in the superficial fascia of the pectoral area. The axillary tail, on the other hand, pierces the deep fascia and lies in the axilla. It's a sort of apocrine gland. 

The apical region of the cells and a portion of the cytoplasm are lost in secretion in these glands.

Mammary Gland Anatomy 

The mammary glands are located in the breasts. They emerge in pairs from sweat glands that have been modified. Regardless of gender, all people have mammary glands when they are born. However, only those who experience an increase in oestrogen levels during puberty will have fully formed mammary glands and breasts. Those who have a spike in testosterone during puberty will have undeveloped mammary glands and no breast development.

The external breast has an elevated nipple, and the dark area surrounding it is known as the areola. The breast contains 15-20 lobes of glandular tissue that spread out in a circle from the nipple on the inside. Milk ducts gather milk from lobules, which are tiny portions of tissue found inside the lobes. The milk ducts widen at the nipple to collect milk, then narrow again, with each duct opening separately on the nipple. Refer to the mammary gland diagram for a better understanding.

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Structure of Mammary Gland 

The skin, parenchyma, and stroma are the three sections of the mammary gland structure.

Skin: It consists of a nipple and areola.

  • Nipple: The fourth intercostal space has a conical prominence. The nipple is pierced by 15–20 lactiferous canals. The nerve supply is abundant in the nipple, which contains circular and longitudinal smooth muscle fibres. When the nipple is stimulated, these smooth muscles help in erecting it. Sweat glands, fat, and hairs are all absent from the nipple.

  • Areola: The areola is the dark pigmented region around the nipple. It has a lot of modified sebaceous glands in it (called tubercles of Montgomery in pregnancy and lactation). These glands produce an oily fluid that prevents the nipple and areola from cracking. The areola is notable for its lack of fat and hair.

Parenchyma: Branching ducts and terminal secretory lobules make up the glandular tissue of the mammary gland. Each of the 15 to 20 lobes has a lactiferous duct that drains them. Before opening separately into the nipple, these ducts expand to form the lactiferous sinus. The milk is gathered in the lactiferous sinuses. The lactiferous ducts in the nipple are organized radially.

Stroma: This is the breast's supporting framework that surrounds the parenchyma.

  • Fibrous Stroma: The suspensory ligaments of Cooper, which separate lobes and suspend the mammary gland from the pectoral fascia, are formed as a result of this. Shortening and tugging of these ligaments produce stiffness of the organ and puckering of the skin above it in individuals with breast cancer. The shortening of ligaments in conjunction with cutaneous edoema results in a characteristic appearance that resembles an orange peel. As a result, it's known as Peau d'orange.

  • Fatty Stroma: Despite the absence of fat in the nipple and areola, the mammary gland's major mass is filled with varying levels of fat.

What are Mammary Glands Functions?

Hormones are critical in supporting the mammary glands' primary function, milk production. Oestrogen causes milk ducts to branch out and contains more milk by causing them to enlarge. Oestrogen and growth hormones stimulate the mammary glands to expand and enlarge during puberty. The milk ducts expand and the breasts enlarge when oestrogen and progesterone levels rise during pregnancy.

Prolactin plays a role in the development of mammary glands and milk production. Progesterone promotes the growth of lobules in the breast in preparation for breastfeeding, as well as the enlargement of blood vessels in the breast following ovulation, which adds to breast swelling and soreness. Oxytocin induces the glands to release milk.

Mammary Glands Atrophy: When oestrogen production decreases around menopause, breasts appear softer and less plump with age.

Associated Conditions 

Breast Cancer

Breast cancer in women is one of the most frequent malignancies, affecting one out of every eight women. Cisgender women have a lower risk than women who have had their breasts removed for any reason (including top surgery or preventive mastectomy).

Hormone therapy has the potential to reduce the risk of breast cancer. Breast cancer in non-hormone-treated cisgender men and transfeminine people is extremely rare, although it does happen. Transmasculine people who took puberty blockers had the same risk of breast cancer as cisgender men and transfeminine people who did not use gender-affirming hormone therapy.

Breast cancer can begin in several places in the breast, including the mammary glands, milk ducts, and other soft tissues. Breast cancer can spread to other organs through the blood and lymph node system if it goes unnoticed.


Ectasia of the mammary duct is most frequent near or after menopause. Ectasia is a swelling of the milk ducts that are not malignant. It doesn't always cause symptoms, although it can cause breast soreness and swelling, nipple discharge, or a nipple that pushes inward in some cases. Ectasia does not necessarily require treatment, however, antibiotics or surgical duct removal may be necessary in some cases.


Breast cysts that are filled with fluid are usually benign. Breast cysts form in the milk ducts and are rather prevalent in women who are past childbearing age. Cysts account for about 1 in every 4 breast masses. Cysts have no known cause, but they may develop as a result of hormonal changes.

Fibrocystic Breast Changes

Lumps in the breast, in addition to tumours and cysts, can signify fibrocystic breast alterations. Fibrocystic breast change is a common, harmless disorder that typically affects women prior to menopause. Breast tissue that is lumpy is a symptom of this condition. This disorder was previously known as fibrocystic breast disease, however, most clinicians now refer to it as "changes" rather than "disease" because it is not a disease.


Mastitis is a type of infection that affects the tissue of the breast. Breastfeeding mothers are the ones who are most likely to be affected. Bacteria enter the breast through a milk duct or a breach in the skin, causing mastitis. Breast swelling, pain, redness, fever, and flu-like muscular aches are all symptoms of mastitis. Mastitis is normally treated at home, however, antibiotics may be required in some situations.

Breast Pain

Breast pain can be caused by a variety of factors, including cysts, hormonal changes, pregnancy, infection, lactation, and cancer. Breast pain can often be handled at home, depending on the cause. However, chronic or severe discomfort, as well as all lumps, should be checked by a healthcare specialist.

Why is Breastmilk called Liquid Gold? And What's So Special About “Liquid Gold”? 

Colostrum is a thick golden-coloured substance that serves an important purpose. It delivers precisely the proper amount of nutrition to provide a good start for a newborn. Colostrum is generated during pregnancy and for a few days following childbirth, according to La Leche League International. It has a higher concentration of antibodies than mature milk and is high in carbs and protein but low in fat. Colostrum also contains a high quantity of leukocytes (white blood cells), which aid in the destruction of disease-causing germs and viruses.

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FAQs on Mammary Gland

1. How do mammary glands produce milk?

Lactation takes place within the mammary gland after delivery, and it involves the release of milk by the luminal cells in the alveoli. Milk is discharged via the ducts and into the nipple for the nursing newborn when the myoepithelial cells surrounding the alveoli contract.

2. What does the mammary gland produce?

The mammary glands function as milk producers and are physically similar to sweat glands. Mammary glands, which are found in the breast above the pectoralis major muscles, are found in both sexes but are usually exclusively functioning in women.

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