Breast
The scientific term breast is used to designate the anterosuperior lateral region of the human female trunk, other primates and other mammals such as elephants, and the anterocaudal region overexposed to the pelvis for other species of mammals. It includes as content the mammary gland and lactiferous ducts, connective tissue and perilobular fat.
In human anatomy, the breasts develop in a pair, correlative to the area described above for humans, while in other mammals the number is doubled in the region described above. Their structure is generally asymmetrical, the left one is larger than the right in most cases —the opposite is very rare— and they are located under the skin in the thorax of all individuals of the human species.
It is very common to use the euphemism and pseudocultism «breasts» as a synonym for breasts; however, the term is imprecise: the word "breast", applied to the breast, actually corresponds to the space between the breasts. In colloquial Spanish, human breasts are usually called "tetas", "pechos", "bubis", "chichis" or "lolas" among many other names. In the case of other mammals, some terms more specifically referring to humans are not used, such as "breasts", but other denominations are added, such as "udders" (this last term, although considered correct by some in its application to humans, It is normally only used, in these cases, in a vulgar and even derogatory way, to refer to large breasts).
Male mammals also have breasts, although these are not fully developed. They do tend to develop, however, as a consequence of different congenital diseases, such as pseudohermaphroditism.
Features
Each breast, whose external appearance is a prominence of variable size and turgor, has certain structures, both external and internal, beginning with those on the outside where the nipple and areola can be seen. Internally, the breast has a large amount of adipose tissue, which constitutes it by 90%, giving it a bulky shape. In addition, the lactiferous ducts and the mammary gland are integrated into the tissue, both responsible for the production and secretion of breast milk. The mammary glands are distributed throughout the breast, although two-thirds of the glandular tissue is found in the 30 mm closest to the base of the nipple.
These glands drain into the nipple through ducts, each of which has its own opening, or pore. The intricate network formed by the ducts is ordered radially and converges on the nipple. However, the ducts closest to it do not act as milk reservoirs.
Histology
The mammary gland consists of two fundamental elements: the glandular acini, where the milk-producing cells are found, and the ducts, a set of tubular and hollow structures, branched in the shape of a tree, whose lumens progressively converge into more and more canaliculi. thicker to terminate at one of twelve to eighteen vertices called galactophores. Lactophores are reservoir-like ductal dilations immediately posterior to the nipple, formed of non-kerantinized squamous epithelium.
The myoepithelial cells are located at the base of the areola-nipple complex, with the particularity that they are capable of contracting like smooth muscle cells. A set of smooth muscle fibers in a radial shape, cause the erection of the nipple before stimuli such as suction, rubbing, touch and cold, producing the output of milk stored in the galactophores.
The rest of the breast is made up of connective tissue -collagen and elastin-, adipose tissue (fat) and an aponeurosis called Cooper's ligament. The ratio of gland to adipose tissue ranges from 1:1 in non-lactating women to 2:1 in lactating women.
Lymphatic drainage
About 75% of the lymph from the breast travels to the lymph nodes in the armpit on the same side. The rest travel to the parasternal nodes, to the breast on the opposite side, and finally to the abdominal lymph nodes. The axillary nodes include the inferior or pectoral group —which drains the deep and transmuscular part—, the internal or subscapular group —which drains the internal part of the mammary gland— and the external or humeral group —which drains the external edge of the breast. —.
The lymphatic drainage from the breasts drains into the lymph nodes in the armpit.
This drainage is of particular importance in oncology, since the breasts are a frequent site of cancer development. If malignant cells detach from the breast tissue, they could spread to other parts of the body through the lymphatic system, producing metastasis. The fact that the lymphatic vessels run through the transmuscular tissue of the pectoralis major justifies its removal in the surgical treatment of breast cancer —the so-called Halsted radical mastectomy.
Form and support
Breasts vary in size and shape. Your external appearance does not predict your internal anatomy or your lactation potential. The shape of the breast depends to a large extent on its support, which comes mainly from Cooper's ligaments and the underlying thoracic tissue on which it rests. Each breast is attached at its base to the thoracic wall by a deep fascia that covers the pectoral muscles. In the upper part of the chest it receives some support from the skin that covers them. That combination of anatomical support is what determines the shape of the breasts. In a small group of women, the ducts and galactophores are visible because they do not fuse with the surrounding tissue.
The location of the nipple in relation to the inframammary fold defines the term ptosis, in which the breast hangs so low on the chest that the nipple extends beyond the inframammary fold. In some cases, the nipple-areola assembly may eventually hang down to the level of the navel. The distance between the nipple and the upper base of the sternum in a young breast averages 21 cm and is an anthropometric measurement used to determine breast symmetry and ptosis. The breasts exist in a range of ratios between length and diameter of the base, varying from 1:2 to 1:1.
Anatomy
1. chest box
2. Músculo pectoral mayor
3. Lobes
4. Pezón
5. Areola mamaria
6. Gallophoric conduct
7. Tejido adiposo
8. Piel
The breasts lie over the pectoralis major muscle and generally extend vertically from the level of the second rib to the sixth or seventh rib. Horizontally, it extends from the edge of the sternum bone to a midline, imaginary, from the armpit. At the level of the most distal anterior end of the thorax, at the level of the third intercostal space, the skin specializes to form the areola and the nipple.
Each breast is bordered on its posterior face by the aponeurosis or fascia of the pectoral muscle and contains abundant fatty tissue where there is no glandular tissue. The fat and connective tissue, together with Cooper's ligaments (which attach the gland to the skin) constitute a true ligament that gives shape and supports it, allowing the normal sliding of the breast on the underlying muscular planes. The breast also contains arterial, venous and lymphatic vessels, as well as nervous elements. There is nothing within the breast that resembles a continuous capsule that surrounds the breast. In fact, it is very common for there to be tissue called aberrant or ectopic (literally 'out of place') in areas quite distant from the breast.
The upper lateral quadrant (farthest from the sternum) runs diagonally toward the axilla and is known as the tail of Spence. A thin layer of breast tissue extends from the clavicle above, to the seventh or eighth rib below, and from the midline to the edge of the latissimus dorsi muscle. It is not uncommon to find breast tissue in the hollow of the armpit or under the skin, on the front side of the abdomen.
The arterial blood supply to the breasts comes from the internal thoracic artery (previously called the internal mammary artery), which is derived from the subclavian artery; from the lateral thoracic artery, from the thoracoacromial artery (both arise from the axillary artery) and from the posterior intercostal arteries. The venous drainage of the sinuses is carried out mainly by the axillary vein, although the internal thoracic and intercostal veins may also participate. Both men and women have a high concentration of blood vessels and nerves in the nipples.
In both sexes, the nipples are erectile in response to both sexual stimuli and cold. The innervation of the breasts is given by stimuli from the anterior and lateral branches of intercostal nerves four to six, coming from the spinal nerves. The nipple is innervated by the dermatomal distribution of the T4 thoracic nerve.
Embryology
Embryologically, the glandular tissue of the breast is nothing but the product of the excessive development—from the morphological and functional point of view—of modified sweat glands of the skin, adapted for the production of milk.[ citation required] Breast milk is a type of secretion of high nutritional value, adequately adapted to the needs of newborns and the only source of food and antibodies during the first months of life.
Breast development during puberty is stimulated by ovarian hormones, mainly estrogen and progesterone. Estrogen stimulates the development of the excretory portion of the mammary gland—mainly the galactophores—and progesterone is responsible for the development of the secretory portion—the lobules. These hormones drive the development of female characteristics, producing the same effect in males. with hormonal imbalances or in those who wish to modify their sexual identity.
Development
The breast undergoes changes throughout the development of the individual. Except for specific, more or less pathological cases, the male breast atrophies completely, although the nipple-areola complex never disappears and always retains its particular sensitivity and the ability to pucker the areola and erect the nipple to stimuli. Men undergoing treatment with estrogens or who abuse certain drugs can develop accumulations of fat that take the form of breasts (pseudogynecomastia) and can secrete fluids spontaneously, although without milk content. The development of true breasts in men, made up of glands and other structures, is called gynecomastia. Obese males also often develop pseudogynecomastia, but without the female anatomical components.
In isolated cases there are people with more than two glands, which is known as polymastia. Each "extra" is called the "supernumerary breast" and has an abnormal situation, although it will almost always be located within an imaginary line located on each side of the body, from the apex of the armpit to the lateral aspect of the labia majora of the vulva (base of the scrotum in the male) on the same side. The presence of supernumerary nipples, of different proportions and composition, is known as polythelia.
Changes During Puberty
In young individuals, under normal conditions, the breast remains in an embryonic state and does not develop until puberty. Girls typically develop the breasts non-simultaneously, noting the appearance of a firm breast bud directly retroareolar, below the center of the areola, often somewhat eccentric. The button soon develops on the other side, although they can develop simultaneously, and in a short time the two breasts acquire their usual developed appearance, under the stimulation of the female sex hormones. The development of adipose and connective tissue increases under the influence of other hormones such as progesterone, prolactin, corticosteroids and growth hormone.
Changes During Pregnancy
During pregnancy, increased levels of estrogen and progesterone stimulate glandular development. The breasts tend to become spherical due to the increase in adipose tissue.
In this period the breasts become turgid and increase in size. The pigmentation of the skin of the areola and the nipple increases very markedly and small granular eminences appear on the edges of the areolas known as areolar glands (also called Montogomery's tubercles), corresponding to the development of sebaceous glands. The circulation of the breast increases and superficial veins become prominent.
Changes during lactation
Breastfeeding tends to maintain the changes that occurred during pregnancy. At the beginning of it and during the first hours, the repeated sucking attempts by the neonate end up causing the output of a thick, yellowish secretion, rich in cholesterol, called colostrum.
Functions of the breast
Breastfeeding
The production of milk in the breasts begins before childbirth, due to which, during childbirth, the breasts or, what is the same, the mammary sinuses, of the parturients tend to dilate or "swell" When producing milk, the mammary glands (glands that in the mammary sinuses or breasts of a woman once nubility has been overcome, together with the adipose tissue, occupy a large part of the volume of the breasts). However, fluid output does not usually occur until then, due to the decrease in progesterone concentrations and the production of prolactin and oxytocin. From that moment (in some women even before) the breast secretes colostrum, a thick liquid with mild laxative properties (it has a high content of chlorine, sodium, potassium and protein) that facilitates the evacuation of meconium from the intestine of the newborn. The colostrum is secreted for three days, an intermediate milk for the next fifteen to give way to mature milk later.
Breast milk contains more than 300 components, including high proportions of water (up to 85%). Although it might seem that this circumstance limits the supply of nutrients to the neonate, it is important to consider that a high osmolarity is not easy for the infant's kidney to balance, which, in its first months, must extract the water it needs from the milk and without inputs. additional. The composition of breast milk varies according to the age of the newborn, the climate and the specific needs of the newborn.
In milk there are numerous nutrients, as well as proteins, amino acids, vitamins, and essential minerals, in addition to finding a powerful type of IgA immunoglobulins that act as antibodies, providing the newborn with important protection against potential infections. Dairy formulas made from bovine milk lack this component, and although some laboratories, such as Bayer, have recently indicated that IgA gammaglobulin (or immunoglobulin) is preserved in microfragments within the formula, it is uselessly not beneficial. for humans due to its molecular structure linked to certain amino acid links that the human organism cannot recognize and that can even be rejected in certain individuals. This is one of the reasons why breastfeeding is recommended for at least the first year of life. Even the World Health Organization suggests breastfeeding six months with exclusive breastfeeding (only breast milk, without water, teas or bovine or caprine milk formulas) and continue breastfeeding for at least two years, supplementing the newborn's diet with solids.
Psychiatry studies the way in which breastfeeding reinforces in a particular way the emotional bond in the mother-child relationship in a way that is as solid as primary, which provides particular satisfaction to both, developing in the newborn the semblance of human affection. In fact, some mothers continue to breastfeed their child for two years or more, even though the child is already eating a very varied and complete diet. In theory, prolonged lactation also has another consequence: during lactation, blood prolactin levels remain high, which prevents adequate secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), thereby inhibits ovulation. This delay in the return of fertility has given rise to a method of contraception called LAM, which could be used during the first six months of the baby's life. However, breastfeeding as such is not effective as a contraceptive method.
Lactation can be induced in a woman who has not been pregnant. No nutritional differences between induced breast milk or that resulting from pregnancy have been reported.
Surgical risks
Any operation performed on the breasts, including cosmetic surgery, carries the potential to interfere with future lactation, causing alterations in nipple sensation and difficulties in interpreting a mammogram. Some studies have shown comparable lactation ability among women with macromastia (breast enlargement) compared to control groups in which the breast reduction operation was performed using a modern surgical technique called "upper pedicle". Some plastic surgery agencies advise postponing elective breast reductions in young adolescents because breast volume may continue to grow considerably as young women mature and the long-term risks of these cosmetic procedures are still unknown. Most surgeons evaluate each case individually, before subjecting a young patient to a significant breast reduction, to correct hypoplasia or severe asymmetry.
Sexual function
The breasts play a physiological and cultural role in human male and female sexual function. As an erogenous zone, your participation in sexual intercourse is very important. There are numerous sexual practices centered on the breasts (see, for example, masturbation with the breasts and breast fetishism), in women sexual arousal is usually manifested in a vegetative way by three phenomena: the erection of the clitoris (at the entrance of the vagina), usually some swelling of the breasts that is accompanied by an "erection" or stiffness of the nipples called thelotism. In technologically developed western societies, many men are attracted, above all, by large breasts. Others, however, prefer them to be smaller, although turgid and firm. In reality, size and shape, as well as consistency, do not at all predict the ability of the breast to efficiently produce milk. In fact, much of the breast is adipose tissue, which, in part, has structural and support functions and contributes to providing sexual attractiveness to women, but not at all to lactation.
Female sexual function of the breast, after diagnosis and treatment of breast cancer, does not tend to decrease or differ, especially in women undergoing cosmetic reconstruction surgery (mammoplasty). However, in women who have had a total mastectomy, a decrease in sexual interest has been noted. Chemotherapy tends to cause problems in the sexual function of the treated woman.
Pathologies
Cancer
Breast cancer consists of the accelerated and uncontrolled proliferation of cells of the glandular epithelium between the thin ducts that connect, like branches of a tree, the clusters of lobules and lobules that make up the mammary gland. As in other malignant tumors, these cells are characterized by their own peculiarities of embryonic cells: they are differentiated cells that have greatly increased their reproductive capacities and have become immortal, that is, they cannot age. The diagnosis of breast cancer requires microscopic examination of a biopsy of suspicious breast tissue. Physical examination, mammography, and other routine tests are effective in early diagnosis of the disease.
The most common types of cancer that develop are ductal cancer, if it occurs in the ducts, and lobular carcinoma, if it occurs in the lobules. Breast cancer is rare in males. More than 99% of cases occur in women.
Several studies have shown that black women in the United States have a higher mortality from breast cancer, although white women have a higher incidence. After being diagnosed, black women are less likely to receive treatment compared to white women. Other studies have focused on these disparities, and theories revolve around less accessibility to early screening, diagnostic and treatment techniques -medical and surgical- and even some biological characteristics in the black population of the United States.
About 50% of women with breast and gynecologic cancer, whether treated or not, have long-term sexual dysfunction. Often, patients treated for cancer feel that the disease was caused by their sexual activity and that new sexual relations could contribute to its reappearance. Although they are misconceptions, they are real concerns and feelings that should be shared with the health professional. Decreased libido and other sexual problems in breast cancer patients are common symptoms of depression, and treating the depression usually improves the patient's sexual function.
Others
Infection or inflammation of the breast is known as mastitis and can be caused by bacteria, paralysis of glandular flow (ductal ectasia), abscesses, syphilis, fungi (actinomycosis), etc.
Other benign conditions include inverted nipples or congenital conditions such as polymastia. Cysts (such as fibrocystic breast disease) and other fibrotic changes, adenomas, fistulas, galactorrhea, and papillomas are also common. Any abnormality in the breast should be consulted with a health professional.
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