To understand the structure and origin of the mammary glands, anatomy will help. The mammary gland is a modified sweat apocrine glands developed from the ectoderm. In humans, the development of mammary glands occurs at the sixth week of fetal life. In the area of the mammary glands, the skin is thin, delicate, contains hair follicles, sweat and sebaceous glands. In the mammary gland there are many nerve fibers from the brachial and cervical plexuses and intercostal nerves. The body of the gland has a disc-shaped convex shape, the color is usually pale pink, dense texture, the average diameter at the base is 10-13 cm. The mammary glands in girls have an average weight of 150-200 g, and during lactation - 400-900 g. In most healthy young women, the glands are hemispherical and resilient. The breast structure, size, shape and position have individual characteristics and characteristics.
The structure of the mammary gland and its anatomy
Female mammary glands are composed of many cells that produce milk, which are collected in lobules. A milky stream departs from each individual lobule, and all lobules are combined into segments having an excretory duct, in which all terminal small ducts are combined.
The lobes are located relative to the nipple radially and are separated from each other by adipose tissue. Each lobe of the gland has the shape of a cone with an apex at the nipple, where the excretory duct opens. The ducts in front of the nipple expand, forming milky sinuses. The formed area around the nipple is called the areola, and the small elevations on it are sweat glands. The structure of the mammary gland in women differs from the structure of the male gland.
The growth of the mammary glands is due to prolactin (the hormone of the anterior pituitary gland) and ovarian hormones. Thanks to prolactin, lactation occurs. In the first half of pregnancy, the breast increases in size, and in the second half there is an increase in the secretory activity of epithelial lobular cells, which are composed of alveoli. At the end of pregnancy and within a few days after giving birth, secretion increases and a yellowish, thick nutrient fluid called colostrum is produced. Then there is a change in the composition of the secret, it acquires a more fluid consistency and secretes milk. By the end of the feeding period, milk production decreases and stops until the next pregnancy.
The development of mammary glands in girls occurs during puberty at the age of 10-15 years. The process begins with the growth of the nipple and paranasal areola, then the growth of the mammary gland as a whole begins. The breast in women grows for a long time and the breast size is finally fixed only after feeding the baby. The penultimate stage of breast growth reaches the age of 15-17 years.
The mammary gland is a labile organ, as well as the uterus, subject to cyclic modifications. Before the onset of menstruation, proliferation of the glands occurs, the tissues swell, the gland becomes swollen and loose. After the end of menstruation, these manifestations disappear. In accordance with age periods, the mammary gland is divided into 4 types.
- Iron girls or women 20-25 years old. The mammary gland has a homogeneous structure, the milky ducts are invisible, the width of the premammary space is not more than 5 mm.
- Iron in women aged 25 to 40 years is functionally active. Its milky passages are lined with epithelium, constantly grow, branches with terminal secretory vesicles appear on the walls. The structure of the glands changes due to cyclical changes.
- The mammary gland during menopause. In premenopausal glandular tissue is scattered in the form of small islands in the glandular triangle, which are separated by fields of adipose tissue. With age, the number of glandular parenchyma decreases, the mammary gland becomes wide-looped. Fibrous tissue atrophies.
- The mammary gland of a woman in the postmenopausal period. During menopause, changes in the mammary gland become irreversible, glandular tissue completely disappears, it is replaced by adipose tissue.
As mentioned above, the structure of the mammary gland directly depends on age, the level of development of the genitals, on the phase of the woman’s menstrual cycle , hormonal status, gestational age and lactation. Age is the main factor that determines the structural type of glands. But, nevertheless, there is individual variability in the reduction and development of glandular elements, which are determined by nutritional, endocrine and other factors.