Anatomy and Physiology of Breast

Anatomy and Physiology of Breast

The female reproductive system's auxiliary glands are located in the breast. They are located on the pectoralis major and serratus anterior muscles' superficial fascia in the anterior chest wall.

The breast reaches from the second to the sixth ribs vertically. It runs horizontally from the axilla to the sternum's lateral border. The term "Axillary tail of space" refers to the portion of the breast that rises into the axilla and reaches as high as the third rib.

The nipple, a central protuberance on the breast, is what gives it its name. Erectile tissue makes up the nipple. It is encircled and covered by the pigmented area known as the areola. The areola extends for a distance of 2.5 cm around the nipple. There are sebaceous glands at the edge of the area. These sebaceous glands secrete sebum to keep the nipple supple.

Microscopic structure

The 20 or more lobes that make up the breasts' complex secreting glands are primarily made of glandular tissue. Alveoli and ducts make up the lobules that separate each lobe. The myoepithelial cells that surround the acini cells in the alveoli, which generate milk, contract and force the milk out of the alveoli. Blood is abundantly supplied to the breasts. A larger duct is formed when smaller lactiferous ducts bringing milk from the alveoli combine with larger ducts carrying milk from the alveoli. One large duct exits each lobe and is wider to create a lactiferous sinus or ampulla, which serves as a temporary milk reservoir. From each sinus, a lactiferous tubule protrudes onto the nipple's surface. Each breast functions independently of the other.

Estrogen and progesterone stimulate ductal and alveolar development, as well as colostrum output, throughout pregnancy. Other hormones have a role and control a complicated series of processes that get the breast ready for lactation.

Physiological of lactation

Progesterone and estrogen stimulate the breasts during pregnancy. The breasts enlarge and begin to secrete colostrum, a fluid. They are anticipated to secrete milk, which differs from colostrum, during the puerperium. Lactation is the process by which milk is secreted or produced.

Prolactin is the hormone that starts lactation. It is anterior pituitary gland secretion. Estrogen inhibits the action of prolactin. Because of this, prolactin does not start working until the blood estrogen level is high. Within the first two days of puerperium, the level of estrogen starts to decline. This explains why lactation begins on the third day of puberty. After eight days, prolactin's effects stop becoming noticeable.

• Mammogenesis:
  • During mammogenesis, the ductal system expands and branches, connective tissue and supporting cells proliferate, and fat is distributed throughout the breast. Estrogens, growth hormone, prolactin, insulin, and adrenal corticoids all increase this.
  • Following the development of the ductal system, progesterone is implicated in the final phases of mammogenesis. Together with other hormones, it promotes the growth of the breast lobules and alveoli and modifies their ability to secrete.
• Lactogenesis
  • There are two main stages of lactogenesis:
    • Lactogenesis I:
      • The ability of the mammary glands to secrete milk from mid-pregnancy to late pregnancy.
      • Lactogenesis I starts from mid-pregnancy till 2 days after birth. It involves the differentiation of alveolar epithelial cells and the stimulation of milk synthesis by prolactin.
    • Lactogenesis II: T
      • The formation of large amounts of milk after parturition.
      • Lactogenesis II starts from day 3 postpartum to day 8. It is triggered by the reduction of progesterone. The breast becomes full and warm and produce large amounts of milk.
• Galactopoiesis
  • Around nine days after birth, galactopoiesis begins, and it ends with the start of involution. It is the hormone-controlled maintenance of milk secretion. Six to nine months after giving birth, breast size begins to decrease. Normal milk formation slows down around 7-9 months, however if the kid continues to suckle, milk production can last for years.
• Involution
  • Involution is the reduction of milk's secretory ability as a result of the buildup of inhibitory peptides. Usually, it begins 40 days after the final breastfeed. Adipocytes replace the epithelial cells through the process of apoptosis because they are no longer needed for their secretory abilities.