Breast appearance
The breast is located in the chest, on the surface of pectoralis major and thoracic fascia, from the 2nd to 3rd ribs to the 6th to 7th ribs, from the inside to the parasternal line, and from the outside to the axillary midline. The nipple is flush with the fourth intercostal space or the fifth intercostal space. From the appearance, there are prominent areola and nipple on the breast. The surface of nipple is covered with a layer of scaly cuticular epithelium, and the epithelial layer is very thin. The nipple is composed of dense connective tissue and smooth muscle. Smooth muscles are arranged in a ring or radial pattern. When there is mechanical stimulation, the smooth muscle contracts, which can make the nipple erect and squeeze the catheter and feeding sinus to discharge its contents. There are hairs and glands on the skin of areola. Glands are sweat glands, sebaceous glands and mammary glands. Its sebaceous gland, also known as areola gland, is large and superficial, and its secretion has the functions of protecting skin, lubricating nipple and baby's lips.
Internal structure of breast
The internal structure of the breast is like a small tree growing upside down. The "root" is the nipple and the "crown" is the milk leaf with many branches arranged radially. It is mainly composed of glands, ducts, adipose tissue and fibrous tissue.
Mammary gland: The mammary gland is the main structure of the breast and consists of 15 ~ 20 glandular lobes. Its structure is similar to sebaceous glands and its function is similar to sweat glands. Each glandular lobe is divided into several glandular lobules, which are arranged radially around the nipple. Each lobule consists of 10 ~ 100 acinus. These acinus are closely arranged around the small mammary duct, and the openings of acinus are connected with the small mammary duct. A plurality of small mammary ducts are combined into interlobular mammary ducts, and the interlobular mammary ducts are combined into a whole glandular lobe mammary duct, which is also called milk conveying duct. Breast tissue is closely related to breast health. Breast tissue is responsible for lactation function, controlled by hormones, which gradually increases with each menstrual cycle and then recovers.
Mammary duct: There are 15 ~ 20 mammary ducts in the breast, which are radially arranged around the nipple, gather in the areola and open at the nipple, and are called mammary ducts. The ductus lactis narrows at the nipple and then expands into ampulla, which is called ductus lactis sinus and has the function of storing milk. There are stratified squamous epithelial cells at the opening of mammary duct, transitional epithelium at the stricture, double-layer columnar epithelium or single-layer columnar epithelium at all levels below ampulla, and cubic epithelium near acinus at the terminal duct, which is lined with acinus.
Adipose tissue: Adipose tissue is the tissue with the most fat in breast, and its main function is to control the size of breast. The adipose tissue in the breast is wrapped around the breast to form a hemispherical whole. This layer of adipose tissue is called the adipose capsule. Due to age, fertility and other reasons, the thickness of fat sac may vary greatly among individuals. Gland tissue and connective tissue float in fat, and the amount of fat determines the size of the breast. Why not go on a diet? This is also the reason. The result of dieting is a general loss of body fat, including breasts. Of course, the reduction of breasts will also affect the overall aesthetic effect of girls, so excessive dieting is not desirable.
Connective tissue: Connective tissue is the tissue in the breast to prevent breast sagging. Connective tissue combines with pectoral muscle, which is the tissue that hangs the breast. It has no elasticity at all, and once it is stretched excessively, it is difficult to recover from tissue breakage, thus causing breast sagging. Therefore, it is very important to wear a bra that plays a good supporting role during breast development, so girls should choose a bra that suits them at ordinary times and should not be too tight or too loose.
Breast tissue: keep the breast healthy. Breast tissue is responsible for lactation function. It is controlled by hormones, gradually increasing in each menstrual cycle, and then recovering. Why can't breasts bear much sadness? Staying up late, overeating and emotional excitement directly affect hormone levels. The fluctuation of hormone level in the body will stimulate breast tissue and easily lead to pathological changes.
Pectoral muscle: determines the shape of the breast. The breast is hung on the pectoral muscle through connective tissue, and the support of the pectoral muscle determines the direction of the breast. Why can exercise breast enhancement? Through exercise, you can grow your chest muscles and hold out your chest, while exercising ligaments can make your chest more upright. The increase of your chest muscles will make your breasts more prominent and your chest look fuller.
In addition to the structures listed above, there are abundant blood vessels, lymphatic vessels and nerves in the breast, which play a nutritional role in maintaining metabolism. The arterial supply of breast mainly comes from axillary artery branch, intercostal branch of internal thoracic artery and intercostal vascular perforating branch of descending aorta. The venous reflux of breast can be divided into deep and shallow types: superficial veins are distributed under the skin of breast, and most of them converge in internal mammary vein and anterior jugular vein; Deep veins are injected into branches of internal thoracic vein, intercostal vein and axillary vein respectively, and then into innominate vein, azygos vein, semi-azygos vein and axillary vein. When blood metastasis of breast cancer occurs, cancer cells or tumor thrombi entering the blood can enter the superior vena cava through the above channels, leading to metastasis of lung or other parts; It can also enter vertebral venous plexus through intercostal vein, and bone or central nervous system metastasis occurs. There are several ways of lymphatic drainage of breast: axillary lymph nodes, intramammary lymph nodes, subclavian/supraclavicular lymph nodes, abdominal lymphatic vessels and the communication of subcutaneous lymphatic network of both sides of breast. The nerve endings in nipple and areola are rich and sensitive. When the nipple is chapped, the pain is severe.
Perhaps, you will find this knowledge too profound, even if you don't know it. In fact, understanding these internal structures of the breast is helpful to deepen the understanding of the physiological process and pathological changes of the breast and better prevent and treat breast diseases. Therefore, we should keep this knowledge in mind.