Synonyms in a broader sense
Mammary gland, mammary gland, mastos, mastodynia, mastopathy, mammary carcinoma, breast cancer
Introduction
The female breast consists of glands (Glandula mammaria), fat and connective tissue. From the outside the breast can be distinguished the nipple from the surrounding atrium. It is used for milk production and nutrition of the baby.
Anatomy of the female breast
Anatomically, the breast can be divided into 10 to 12 lobes (lobi). One mammary gland lies in each of these lobes. This consists of several end pieces, which together form a lobule (lobuli).
A lobule is therefore divided into several lobules. The end pieces have a connection to a small excretory duct (terminal duct). These small terminal ducts of the end pieces in turn join together to form several somewhat larger ducts (lactiferous duct).
And the somewhat larger ducts finally lead to a main duct (Ductus lactifer colligens), which widens at the end (terminal). This extension is called a sinus. The sinuses have a connection to the nipple (Papilla mammaria).
The breast (mamma) lies directly under the skin and subcutaneous fatty tissue on the pectoral muscle (musculus pectoralis). The breast is fed with nutrients from several small vessels (arteries), which come from arteries in the intercostal spaces between the ribs (intercostal arteries =Arteriae intercostales). The lymph vessels lead to lymph nodes located in the axilla (Nodi lymphatici axillares), on and in the pectoral muscle (Nodi lymphatici pectorales et interpectorales), in the intercostal spaces (Nodi lymphatici intercostales) and on the lateral edge of the mammary gland (Nodi lymphatici paramammarii).
Development and function
The female breast begins to develop at the beginning of puberty. From the age of 10.11. onwards there is an accelerated growth of the mammary gland. According to this, there are even fewer glands in the child than in the sexually mature woman.
At the end of puberty, the woman has reached the maximum number of mammary glands. However, the mammary glands are not fully developed unless pregnancy or breastfeeding is present. The end pieces are rather small and the connective and fatty tissue predominates (dominates) proportionally.
Only when pregnancy and then breastfeeding (see Breastfeeding) are present do the lobules increase in size compared to the resting state. The end pieces widen and have large spaces filled with milk (lumens). The fat and connective tissue is greatly reduced.
This process is controlled by hormones of the pituitary gland (hypophysis). If there is no pregnancy, the hormonal influence (the hormonal stimulus) is missing and the mammary glands do not develop. In case of pregnancy, high levels of sex hormones are present, which cause the mammary gland to develop.
The hormone progesterone for the growth (proliferation) and formation (differentiation) of the end pieces. Due to the influence of the hormone estrogen, there is a growth of the excretory ducts. This hormonal influence on the breast begins directly in the first three months of pregnancy (first trimester).
Thus, the breast develops more and more during pregnancy. Nevertheless, during pregnancy no milk is produced and therefore no milk is secreted through the nipple. This is because high levels of the hormone progesterone suppress the release (secretion) of two other hormones.
These other hormones are prolactin and oxytocin, also hormones from the pituitary gland. Prolactin is responsible for the production of breast milk in the end pieces. This hormone is only released (secreted) when the woman has given birth to her child and the high prosgesterone level required to maintain the pregnancy is reduced.
Only then can prolactin be secreted at all. The necessary impulse to secrete prolactin is given by the infant itself by sucking on the breast. This tells the pituitary gland that prolactin is needed and the hormone is released.
Oxytocin is necessary for the milk to pass from the end pieces into the main excretory duct and then into the nipple and reach the infant. It is thus responsible for the expulsion (ejection) of the milk. It does nothing else but influence (stimulate) small muscles (myoepithelia) that are arranged around the cells of the end pieces and excretory ducts.This influence (stimulation) causes the muscles to contract and the milk is directed from the end pieces through the small and large ducts to the main duct and sinus where the milk can collect.
The stimulus for the release of the hormone is also the sucking of the infant at the nipple. The so-called touching stimulus (tactile stimulus) thus triggers the complete reflex for the release of breast milk (milk ejection reflex). These two hormones are secreted for as long as the infant is breastfed.
During this time, the hormone prolactin also suppresses the menstrual cycle by inhibiting the sex hormones required for this. This means that menstruation usually stops during the breastfeeding period (secondary amenorrhea). Only when the tactile stimulus is removed does the milk ejection reflex cease.
The mammary gland is then returned to its previous resting state and the hormones in the body change in such a way that menstruation resumes. As the sex hormones (estrogen, progesterone) decrease during and after the menopause (peri- and postmenopausal), the mammary gland degenerates or “shrinks” (age atrophy). The lobules become smaller (atrophic), the fat content of the breast increases.
