The female breasts in humans, referred to as mammary glands in medicine, usually start developing between the ages of 9 to 14 years due to hormonal changes associated with puberty. The mammary glands are exocrine glands present in humans and other mammals that produce and secrete milk to feed the newborn.

Breasts are more prominent in females because the female sex hormones (mainly estrogen), which are present in females are responsible for breast development.

The word mammary comes from the Greek and Latin word “mama”, which is the first word uttered by the infant calling upon its mother to breastfeed it.

In men, this does not happen because of the higher level of the male sex hormone testosterone. This is the reason why women have more developed and prominent breasts and to fulfill the primary function of feeding the newborn baby.

What tissues make up the female breast?

There are three types of tissues that make up the normal female breast. They include

  1. glandular tissue, which is responsible for making milk
  2. fatty tissue, which gives the breast its size
  3. connective tissue, which holds the above two tissues firmly in place

Parts of breast anatomy

The breast is made of different parts:

  • Lobes and lobules. The breasts also referred to as the mammary glands, are the milk-producing glands that are situated between the pectoralis muscle of the chest below and the skin. They are made up of round areas called lobes. About 15 to 20 lobes exist in each breast. Each lobe is again made up of small lobules. These lobules are made up of glandular tissue, which produces the milk. The lobes and the lobules are linked by thin tubes called ducts.
  • Nipple. The ducts carry milk from the lobules to the main duct, which empties into the nipple. The nipple is the most anterior portion of the breast and is instrumental in allowing the baby to suck the milk from its mother’s breasts. Small muscles open and close the nipple.
  • Nerves. Many nerves that enhance sexual arousal innervate the nipples of both males and females. The breast is innervated by the anterior and lateral cutaneous branches of the 4th to 6th intercostal nerves. They contain both sensory and autonomic nerve fibers.
  • Areola. The areola is the dark-colored circle, which surrounds the nipple. It may be dark brown or pink. The areola has sebaceous glands called Montgomery glands, which lubricate and clean the nipple and the areola.
  • Fatty tissue. Fat fills the spaces between lobules and ducts and it gives bulk to the breasts.
  • Blood vessels. Blood vessels circulate blood to every part of the breast and chest.
  • Lymph vessels. Lymph vessels transport lymph, a fluid that helps your body’s immune system fight infection. They drain into the lymph nodes (or lymph glands) found under the armpits, in the chest, and other places such as the axillary nodes, parasternal nodes, and posterior intercostal nodes.
  • Cooper’s ligament. Cooper’s ligament acts as a natural bra holding the breast up and not allowing them to sag.
  • Tail of Spence. The upper and outer quadrant of the breast extends diagonally outwards towards the axilla and form the tail of Spence.
  • Muscle. The breasts do not contain any muscles but they rest on the pectoralis major muscle, which is the muscle of the chest wall. However, it is not part of the breast anatomy.

Physiology of breastfeeding

When the baby sucks the mother’s nipple, the nipple is stimulated and becomes erect. This is brought about by the muscular tissue that surrounds the nipple.

At this time, the pituitary gland in the brain is stimulated to secrete the hormone prolactin. This triggers the milk glands in the breasts to increase and initiate milk production. All this happens only after the baby and the placenta are delivered.

When the newborn baby touches its mouth to the nipples, the nerves in the breasts signal the brain to release the hormone oxytocin.

Oxytocin contracts the muscles around the milk-producing glands to push the milk out of the glands through the nipple into the newborn’s mouth.

This is called the letdown milk or milk ejection reflex. This may take several minutes if the mother is tensed or tired. However, oxytocin also helps the mother to relax

Male breast

In males, the male hormone testosterone stops the breast from developing like in females. Externally, the males do have a nipple and the areola, but internally the milk ducts are undeveloped and the glandular tissue is absent.

The two common male breast conditions include:

  • Gynecomastia is a common condition that causes boys’ and men’s breasts to swell and become larger than normal.
  • Breast cancer in men is very rare. Less than 1% of all breast cancers occur in men.

Functions of the Breasts

In females, breasts perform the function to breastfeed the newborn and they also play an important role in bringing sexual pleasure. Male breasts, however, do not have a function.

Besides adding feminism to the woman, the primary function of the breasts is to provide human milk, which the mother breastfeeds the newborn till it is able to start on outside foods.

The breasts produce human milk, which is the most nutritious food that Providence has created for the newborn.

WHO recommends breastfeeding till the child is six months old. It is then gradually started on liquid and then semisolid foods.

Variations seen in woman’s breasts

  • There is a variation in the size, shape, and position of the breasts from woman to woman. There is a variation in the size of the two breasts in the same woman. According to statistics, the left one is usually bigger than the right breast, and this normal. A perfectly symmetrical set of breasts is only imaginary.
  • The size of the breasts does not reflect upon the lactating potential of the woman.
  • Certain normal events like menstruation, menopause, and virginal breast hypertrophy can alter the size and shape of the breasts.
  • During pregnancy, there is a rapid growth of the breasts.
  • Rarely one breast may be absent. This is called amastia and occurs due to the absence of the pectoral muscles.
  • Rarely there may be bilateral amastia (both breasts absent) which is due to congenital reasons.

Changes in the breasts during the menstrual cycle

Breasts are very responsive to hormones during the menstrual cycle.

Estrogens increase before a period, causing milk ducts and glands to swell. The ducts develop side branches to carry more milk.

Prolactin levels change during the course of the menstrual cycle with the levels being highest during the ovulatory period or the luteal phase. Prolactin stimulates the secretion of progesterone and prepares glands for milk production.

Progesterone is secreted by the corpus luteum during the second half of the menstrual cycle. It increases the number and size of lobules for breastfeeding and enlarges blood vessels and breast cells. The breasts become swollen and tender.


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