How many mammary glands do human women have?
311440#2
All the milk-secreting tissue leading to a single lactiferous duct is called a "simple mammary gland"; in a "complex mammary gland" all the simple mammary glands serve one nipple. Humans normally have two complex mammary glands, one in each breast, and each complex mammary gland consists of 10–20 simple glands. The presence of more than two nipples is known as polythelia and the presence of more than two complex mammary glands as polymastia.
Mammary gland
20913864#5
A distinguishing characteristic of the class "Mammalia" is the presence of mammary glands. The mammary glands are modified sweat glands that produce milk, which is used to feed the young for some time after birth. Only mammals produce milk. Mammary glands are most obvious in humans, as the female human body stores large amounts of fatty tissue near the nipples, resulting in prominent breasts. Mammary glands are present in all mammals, although they are seldom used by the males of the species.
Female
311440#23
Male mammals typically have rudimentary mammary glands and nipples, with a few exceptions: male mice do not have nipples, and male horses lack nipples and mammary glands. The male Dayak fruit bat has lactating mammary glands. Male lactation occurs infrequently in some species, including humans.
Mammary gland
311440#22
The breasts of the adult human female vary from most other mammals that tend to have less conspicuous mammary glands. The number and positioning of mammary glands varies widely in different mammals. The protruding teats and accompanying glands can be located anywhere along the two milk lines. In general most mammals develop mammary glands in pairs along these lines, with a number approximating the number of young typically birthed at a time. The number of teats varies from 2 (in most primates) to 18 (in pigs). The Virginia opossum has 13, one of the few mammals with an odd number. The following table lists the number and position of teats and glands found in a range of mammals:
Mammary gland
311440#0
A mammary gland is an exocrine gland in mammals that produces milk to feed young offspring. Mammals get their name from the Latin word "mamma", "breast". The mammary glands are arranged in organs such as the breasts in primates (for example, humans and chimpanzees), the udder in ruminants (for example, cows, goats, and deer), and the dugs of other animals (for example, dogs and cats). Lactorrhea, the occasional production of milk by the glands, can occur in any mammal, but in most mammals, lactation, the production of enough milk for nursing, occurs only in phenotypic females who have gestated in recent months or years. It is directed by hormonal guidance from sex steroids. In a few mammalian species, male lactation can occur.
Mammary gland
4065055#0
A mammary tumor is a neoplasm originating in the mammary gland. It is a common finding in older female dogs and cats that are not spayed, but they are found in other animals as well. The mammary glands in dogs and cats are associated with their nipples and extend from the underside of the chest to the groin on both sides of the midline. There are many differences between mammary tumors in animals and breast cancer in humans, including tumor type, malignancy, and treatment options. The prevalence in dogs is about three times that of women. In dogs, mammary tumors are the second most common tumor (after skin tumors) over all and the most common tumor in female dogs with a reported incidence of 3.4%. Multiple studies have documented that spaying female dogs when young greatly decreases their risk of developing mammary neoplasia when aged. Compared with female dogs left intact, those spayed before puberty have 0.5% of the risk, those spayed after one estrous cycle have 8.0% of the risk, and dogs spayed after two estrous cycles have 26.0% of the risk of developing mammary neoplasia later in life. Overall, unspayed female dogs have a seven times greater risk of developing mammary neoplasia than do those that are spayed. While the benefit of spaying decreases with each estrous cycle, some benefit has been demonstrated in female dogs even up to 9 years of age. There is a much lower risk (about 1 percent) in male dogs and a risk in cats about half that of dogs.
Mammary tumor
464545#38
Most primates have two mammary glands, but the number and positions vary between species within strepsirrhines. Lorises have two pairs, while others, like the ring-tailed lemur, have one pair on the chest (pectoral). The aye-aye also has two mammary glands, but they are located near the groin (inguinal). In females, the clitoris is sometimes enlarged and pendulous, resembling the male penis, which can make sex identification difficult for human observers. The clitoris may also have a bony structure in it, similar to the baculum (penis bone) in males. Most male primates have a baculum, but it is typically larger in strepsirrhines and usually forked at the tip.
Strepsirrhini
18838#52
The mammary glands of mammals are specialized to produce milk, the primary source of nutrition for newborns. The monotremes branched early from other mammals and do not have the nipples seen in most mammals, but they do have mammary glands. The young lick the milk from a mammary patch on the mother's belly.
Mammal
692141#6
This is the most common cause of anovulation and is thought to account for about 70% of all cases. About half the women with hormonal imbalances do not produce enough follicles to ensure the development of an ovule, possibly due to poor hormonal secretions from the pituitary gland or the hypothalamus. The pituitary gland controls most other hormonal glands in the human body. Therefore, any pituitary malfunctioning affects other glands under its influence, including the ovaries. This occurs in around 10% of cases. The mammary glands are also controlled by the pituitary gland, so lactation can also be affected. The pituitary gland is controlled by the hypothalamus. In 10% of cases, alterations in the chemical signals from the hypothalamus can easily seriously affect the ovaries.
Anovulation
311440#20
During weaning, decreased prolactin, missing mechanical stimulation (baby suckling), and changes in osmotic balance caused by milk stasis and leaking of tight junctions cause cessation of milk production. It is the (passive) process of a child or animal ceasing to be dependent on the mother for nourishment. In some species there is complete or partial involution of alveolar structures after weaning, in humans there is only partial involution and the level of involution in humans appears to be highly individual. The glands in the breast do secrete fluid also in nonlactating women. In some other species (such as cows), all alveoli and secretory duct structures collapse by programmed cell death (apoptosis) and autophagy for lack of growth promoting factors either from the ECM or circulating hormones. At the same time, apoptosis of blood capillary endothelial cells speeds up the regression of lactation ductal beds. Shrinkage of the mammary duct tree and ECM remodeling by various proteinase is under the control of somatostatin and other growth inhibiting hormones and local factors. This major structural change leads loose fat tissue to fill the empty space afterward. But a functional lactiferous duct tree can be formed again when a female is pregnant again.
Mammary gland