Do men have mammary glands?
Mammary gland
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.
Male accessory gland
The male accessory glands are the ampullary gland, seminal vesicles, prostate, bulbourethral gland, and urethral glands.
Sweat gland
Non-primate mammals have eccrine sweat glands only on the palms and soles. Apocrine glands cover the rest of the body, though they are not as effective as humans' in temperature regulation (with the exception of horses'). Prosimians have a 1:20 ratio of follicles with apocrine glands versus follicles without. They have eccrine glands between hairs over most of their body (while humans have them between the hairs on their scalp).
House mouse
Newborn males and females can be distinguished on close examination as the anogenital distance in males is about double that of the female. From the age of about 10 days, females have five pairs of mammary glands and nipples; males have no nipples. When sexually mature, the most striking and obvious difference is the presence of testicles on the males. These are large compared to the rest of the body and can be retracted into the body.
Body odor
Sebaceous and apocrine glands become active at puberty. This, as well as many apocrine glands being close to the sex organs, points to a role related to mating. Compared to other primates, humans have extensive axillary hair and have many odor producing sources, in particular many apocrine glands. In women, the sense of olfaction is strongest around the time of ovulation, significantly stronger than during other phases of the menstrual cycle and also stronger than the sense in males.
Vulva
Organs in the male and female with a shared common ancestry are said to be homologous. The clitoral glans is homologous to the male glans penis, and the clitoral body and the clitoral crura are homologous to the corpora cavernosa of the penis. The labia majora is homologous to the scrotum; the clitoral hood is homologous to the foreskin, and the labia minora is homologous to the spongy urethra. The vestibular bulbs beneath the skin of the labia minora are homologous to the corpus spongiosum, the tissue of the penis surrounding the urethra, and to the bulb of the penis. Bartholin's glands are homologous to the bulbourethral glands in males.
Adrenal gland
Cells in zona reticularis of the adrenal glands produce male sex hormones, or androgens, the most important of which is DHEA. In general, these hormones do not have an overall effect in the male body, and are converted to more potent androgens such as testosterone and DHT or to estrogens (female sex hormones) in the gonads, acting in this way as a metabolic intermediate.
Maternal physiological changes in pregnancy
The pituitary gland grows by about one-third as a result of hyperplasia of the lactrotrophs in response to the high plasma estrogen. Prolactin, which is produced by the lactrotrophs increases progressively throughout pregnancy. Prolactin mediates a change in the structure of the breast mammary glands from ductal to lobular-alveolar and stimulates milk production.
Glans penis
The glans penis is a structure at the distal end of the penis in male mammals. It is the sensitive bulbous structure at the end of the human penis, and is anatomically homologous to the clitoral glans of the human female. The glans penis may be smooth, spiny, elongated, or divided in other mammals.
Mammary gland
Mammary gland development is characterized by the unique process by which the epithelium invades the stroma. The development of the mammary gland occurs mainly after birth. During puberty, tubule formation is coupled with branching morphogenesis which establishes the basic arboreal network of ducts emanating from the nipple.
Binturong
Both sexes have scent glands; in females on either side of the vulva, in males between the scrotum and penis. Their musk glands emit an odor reminiscent of popcorn or corn chips, likely due to the volatile compound 2-acetyl-1-pyrroline, found in their urine, which is also produced in the Maillard reaction at high temperatures.
Preorbital gland
Other than during the rut (mating season) and for the first six months after giving birth, the adult Indian muntjac ("Muntiacus muntjac") is a solitary animal. Adult males in particular are well spaced and marking grass and bushes with secretions from their preorbital glands appears to be involved in the acquisition and maintenance of territory.
Sexual differentiation in humans
Most mammals, including humans, have an XY sex-determination system: the Y chromosome carries factors responsible for triggering male development. The "default sex," in the absence of a Y chromosome, is female-like. This is because of the presence of the sex-determining region of the Y chromosome, also known as the SRY gene. Thus, male mammals typically have an X and a Y chromosome (XY), while female mammals typically have two X chromosomes (XX). In humans, biological sex is determined by five factors present at birth: the presence or absence of a Y chromosome, the type of gonads, the sex hormones, the internal genitalia (such as the uterus in females), and the external genitalia.
Male menstruation
Male menstruation is a term used colloquially for a type of bleeding in the urine or faeces, reported in some tropical countries. It is actually caused by parasite infestation of the urinary tract or intestines by "Schistosoma haematobium", and cases of it are actually schistosomiasis, formerly known as bilharziasis. In some tropical peoples that work in wet places such as rice fields, most boys pick up "Schistosoma", and start the bleeding, about puberty when they start working in the rice fields, and uneducated locals think that it is normal and refer to it as the male equivalent of female menstruation, and call it by their native language word for "menstruation".
Bulbourethral gland
A bulbourethral gland, also called a Cowper's gland for English anatomist William Cowper, is one of two small exocrine glands in the reproductive system of many male mammals (of all domesticated animals, they are only absent in the dog). They are homologous to Bartholin's glands in females.
Skin
Sweat glands and sebaceous glands are both unique to mammals, but other types of skin gland are found in other vertebrates. Fish typically have a numerous individual mucus-secreting skin cells that aid in insulation and protection, but may also have poison glands, photophores, or cells that produce a more watery, serous fluid. In amphibians, the mucus cells are gathered together to form sac-like glands. Most living amphibians also possess "granular glands" in the skin, that secrete irritating or toxic compounds.
Human sexuality
The prostate gland and the seminal vesicles produce seminal fluid that is mixed with sperm to create semen. The prostate gland lies under the bladder and in front of the rectum. It consists of two main zones: the inner zone that produces secretions to keep the lining of the male urethra moist and the outer zone that produces seminal fluids to facilitate the passage of semen. The seminal vesicles secrete fructose for sperm activation and mobilization, prostaglandins to cause uterine contractions that aid movement through the uterus, and bases that help neutralize the acidity of the vagina. The Cowper's glands, or bulbourethral glands, are two pea sized structures beneath the prostate.
Breast
The breast is one of two prominences located on the upper ventral region of the torso of primates. In females, it serves as the mammary gland, which produces and secretes milk to feed infants. Both females and males develop breasts from the same embryological tissues. At puberty, estrogens, in conjunction with growth hormone, cause breast development in female humans and to a much lesser extent in other primates. Breast development in other primate females generally only occurs with pregnancy.
Testicle
During mammalian development, the gonads are at first capable of becoming either ovaries or testes. In humans, starting at about week 4 the gonadal rudiments are present within the intermediate mesoderm adjacent to the developing kidneys. At about week 6, sex cords develop within the forming testes. These are made up of early Sertoli cells that surround and nurture the germ cells that migrate into the gonads shortly before sex determination begins. In males, the sex-specific gene SRY that is found on the Y-chromosome initiates sex determination by downstream regulation of sex-determining factors, (such as GATA4, SOX9 and AMH), which leads to development of the male phenotype, including directing development of the early bipotential gonad down the male path of development.
Seminal vesicle
The seminal vesicles (), vesicular glands, or seminal glands, are a pair of simple tubular glands posteroinferior to the urinary bladder of some male mammals. Seminal vesicles are located within the pelvis. They secrete fluid that partly composes the semen.
Male accessory gland
In some species, branched tubular mucous glands are found along the length of the urethra, especially dorsal to the lumen of the urethra. The exact function of their product is not clear.
Urethral gland
The urethral or periurethral glands (also Littre glands after Alexis Littré) are glands that branch off the wall of the urethra of male mammals. The glands secrete mucus and are most numerous in the section of the urethra that runs through the penis. Urethral glands produce a colloid secretion containing glycosaminoglycans; this secretion protects the epithelium against urine.
Endocrine system
The human endocrine system consists of several systems that operate via feedback loops. Several important feedback systems are mediated via the hypothalamus and pituitary.Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into interstitial spaces and then absorbed into blood rather than through a duct. The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus and adrenal glands. The hypothalamus and pituitary gland are neuroendocrine organs.
Mammary gland
Embryonic mammary gland development can be divided into a series of specific stages. Initially, the formation of the milk lines that run between the fore and hind limbs bilaterally on each side of the midline occurs around embryonic day 10.5 (E10.5). The second stage occurs at E11.5 when placode formation begins along the mammary milk line. This will eventually give rise to the nipple. Lastly, the third stage occurs at E12.5 and involves the invagination of cells within the placode into the mesenchyme, leading to a mammary anlage (biology).
Mammary gland
The evolution of the mammary gland is difficult to explain; this is because mammary glands are typically required by mammals to feed their young. There are many theories on how mammary glands evolved. For example, it is thought that the mammary gland is a transformed sweat gland, more closely related to apocrine sweat glands. Because mammary glands do not fossilize well, supporting such theories with fossil evidence is difficult. Many of the current theories are based on comparisons between lines of living mammals—monotremes, marsupials, and eutherians. One theory proposes that mammary glands evolved from glands that were used to keep the eggs of early mammals moist and free from infection (monotremes still lay eggs). Other theories suggest that early secretions were used directly by hatched young, or that the secretions were used by young to help them orient to their mothers.
Testicle
The testicle or testis is the male reproductive gland in all animals, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testosterone. Testosterone release is controlled by the anterior pituitary luteinizing hormone; whereas sperm production is controlled both by the anterior pituitary follicle-stimulating hormone and gonadal testosterone.
Development of the reproductive system
The bulbourethral glands in the male, and Bartholin's gland in the female, also arise as diverticula from the epithelial lining of the urogenital sinus.
Areolar gland
Areolar glands or Glands of Montgomery are sebaceous glands in the areola surrounding the nipple. The glands make oily secretions (lipoid fluid) to keep the areola and the nipple lubricated and protected. Volatile compounds in these secretions may also serve as an olfactory stimulus for newborn appetite.
Scent gland
Scent glands are exocrine glands found in most mammals. They produce semi-viscous secretions which contain pheromones and other semiochemical compounds. These odor-messengers indicate information such as status, territorial marking, mood, and . The odor may be subliminal—not consciously detectable. Though it is not their primary function, the salivary glands may also function as scent glands in some animals.
Preputial gland
Some, including Satya Parkash, dispute their existence. While humans may not have true anatomical equivalents, the term may sometimes be used for tiny whitish yellow bumps occasionally found on the corona of the glans penis. The proper name for these structures is pearly penile papules (or hirsutoid papillomas). According to detractors, they are not glands, but mere thickenings of the skin and are not involved in the formation of smegma.
Endocrine gland
The testes of the male begin to produce testosterone at puberty in response to LH. Testosterone promotes maturation of the male reproductive organs, development of secondary sex characteristics such as beard, hoarse voice, etc. and production of sperm by the testes.
Stallion
The internal genitalia comprise the accessory sex glands, which include the vesicular glands, the prostate gland and the bulbourethral glands. These contribute fluid to the semen at ejaculation, but are not strictly necessary for fertility.
Hormonal breast enhancement
Systemic administration of GH or IGF-1 causes mammary hyperplasia (enlargement of the mammary glands) in animals. For example, in a study of aged female rhesus macaques, treatment with GH alone, IGF-1 alone, and the combination of GH and IGF-1, were found to produce mammary gland hyperplasia and increased mammary gland size and epithelial proliferation by 2-fold, 3- to 4-fold, and 4- to 5-fold, respectively, changes that were directly correlated with serum concentrations of GH and IGF-1. Accordingly, research has found that girls with growth hormone deficiency (GHD) who are treated with GH experience accelerated breast growth and that boys with growth hormone deficiency treated with GH sometimes experience gynecomastia. Moreover, IGF-1 levels and activity have been found to be correlated with breast volume in the female general population.
Human digestive system
There are three pairs of main salivary glands and between 800 and 1,000 minor salivary glands, all of which mainly serve the digestive process, and also play an important role in the maintenance of dental health and general mouth lubrication, without which speech would be impossible. The main glands are all exocrine glands, secreting via ducts. All of these glands terminate in the mouth. The largest of these are the parotid glands—their secretion is mainly serous. The next pair are underneath the jaw, the submandibular glands, these produce both serous fluid and mucus. The serous fluid is produced by serous glands in these salivary glands which also produce lingual lipase. They produce about 70% of the oral cavity saliva. The third pair are the sublingual glands located underneath the tongue and their secretion is mainly mucous with a small percentage of saliva.
Teat
The number and positioning of mammary glands and teats varies widely among 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
The basic components of a mature mammary gland are the "alveoli" (hollow cavities, a few millimeters large) lined with milk-secreting cuboidal cells and surrounded by myoepithelial cells. These alveoli join to form groups known as "lobules". Each lobule has a "lactiferous duct" that drains into openings in the nipple. The myoepithelial cells contract under the stimulation of oxytocin, excreting the milk secreted by alveolar units into the lobule lumen toward the nipple. As the infant begins to suck, the oxytocin-mediated "let down reflex" ensues and the mother's milk is secreted — not sucked from the gland — into the baby's mouth.
Male accessory gland
The products of these glands serve to nourish and activate the spermatozoa, to clear the urethral tract prior to ejaculation, serve as the vehicle of transport of the spermatozoa in the female tract, and to plug the female tract after placement of spermatozoa to help ensure fertilization. Although the glands are usually described as being branched tubular or branched tubuloalveolar, they vary in their organization and in their distribution in different species.
Clitoris
The clitoris ( or ) is a female sex organ present in mammals, ostriches and a limited number of other animals. In humans, the visible portion - the glans - is at the front junction of the labia minora (inner lips), above the opening of the urethra. Unlike the penis, the male homologue (equivalent) to the clitoris, it usually does not contain the distal portion (or opening) of the urethra and is therefore not used for urination. The clitoris also usually lacks a reproductive function. While few animals urinate through the clitoris or use it reproductively, the spotted hyena, which has an especially large clitoris, urinates, mates, and gives birth via the organ. Some other mammals, such as lemurs and spider monkeys, also have a large clitoris.
Excretory system
Like sweat glands, eccrine glands allow excess water to leave the body. The majority of eccrine glands are located mainly on the forehead, the bottoms of the feet, and the palms, although the glands are everywhere throughout the body. They help the body to maintain temperature control. Eccrine glands in the skin are unique to mammals.
Prostate
Skene's gland is found in both female humans and rodents. Historically it was thought to be a vestigial organ, but recently it has been discovered that it produces the same protein markers, PSA and PAB, as the male prostate. This means Skene's gland functions as a female prostate, a histologic homolog to the male prostate gland.
Mammary gland
Androgens such as testosterone inhibit estrogen-mediated mammary gland development (e.g., by reducing local ER expression) through activation of androgen receptors expressed in mammary gland tissue, and in conjunction with relatively low estrogen levels, are the cause of the lack of developed mammary glands in males.
Amazia
Amazia refers to a condition where one or both of the mammary glands is absent (the nipple and areola remain present). This may occur either congenitally or iatrogenically (typically the result of surgical removal and/or radiation therapy). Amazia can be treated with breast implants.
Male accessory gland
Grossly the prostate gland can be divided into two parts: the body and the disseminate part. Low cuboidal to low columnar epithelium provides the lining for this compound, tubuloalveolar gland which consists primarily of serous secretory end pieces. The secretion of this gland is more serous in dogs and more mucous in bulls. It serves to promote the movement of spermatozoa and to form a vaginal plug. Additionally, in bulls, the secretion contains high amounts of fructose and citric acid. Concretions may be present in the secretory end pieces as well as parts of the duct system.
Hypothalamic–pituitary–prolactin axis
The hypothalamic–pituitary–prolactin axis (HPP axis), also known as the hypothalamic–pituitary–mammary axis or hypothalamic–pituitary–breast axis, is a hypothalamic–pituitary axis which includes the secretion of prolactin (PRL; luteotropin) from the lactotrophs of the pituitary gland into the circulation and the subsequent action of prolactin on tissues such as, particularly, the mammary glands or breasts. It is involved in lobuloalveolar maturation of the mammary glands during pregnancy and the induction and maintenance of lactation following parturition. Hormones that control the secretion of prolactin from the pituitary gland include dopamine ("prolactin-inhibiting factor", or "PIF"), estradiol, progesterone, thyrotropin-releasing hormone (TRH), and vasoactive intestinal peptide (VIP).
Mammary ridge
The mammary ridge is primordial for the mammary gland on the breast in humans, and is associated with mammary gland and breast development.
Reproductive biology
The male reproductive system includes sex accessory glands, sex accessory ducts, testes, and external genitalia.
Bartholin's gland
The Bartholin's glands (also called Bartholin glands or greater vestibular glands) are two pea sized compound racemose glands located slightly posterior and to the left and right of the opening of the vagina. They secrete mucus to lubricate the vagina and are homologous to bulbourethral glands in males. However, while Bartholin's glands are located in the superficial perineal pouch in females, bulbourethral glands are located in the deep perineal pouch in males. Their duct length is 1.5 to 2.0 cm and open into navicular fossa. The ducts are paired and they open on the surface of the vulva.
Mammary gland
Estrogen and growth hormone (GH) are essential for the ductal component of mammary gland development, and act synergistically to mediate it. Neither estrogen nor GH are capable of inducing ductal development without the other. The role of GH in ductal development has been found to be mostly mediated by its induction of the secretion of insulin-like growth factor 1 (IGF-1), which occurs both systemically (mainly originating from the liver) and locally in the mammary fat pad through activation of the growth hormone receptor (GHR). However, GH itself also acts independently of IGF-1 to stimulate ductal development by upregulating estrogen receptor (ER) expression in mammary gland tissue, which is a downstream effect of mammary gland GHR activation. In any case, unlike IGF-1, GH itself is not essential for mammary gland development, and IGF-1 in conjunction with estrogen can induce normal mammary gland development without the presence of GH. In addition to IGF-1, other paracrine growth factors such as epidermal growth factor (EGF), transforming growth factor beta (TGF-β), amphiregulin, fibroblast growth factor (FGF), and hepatocyte growth factor (HGF) are involved in breast development as mediators downstream to sex hormones and GH/IGF-1.
Dromedary
The skin is black; the epidermis is thick and the dermis is thick. The hump is composed of fat bound together by fibrous tissue. There are no glands on the face; males have glands that appear to be modified apocrine sweat glands that secrete pungent, coffee-coloured fluid during the rut, located on either side of the neck midline. The glands generally grow heavier during the rut, and range from . Each cover hair is associated with an arrector pilli muscle, a hair follicle, a ring of sebaceous glands and a sweat gland. Females have cone-shaped, four-chambered mammary glands that are long with a base diameter of . These glands can produce milk with up to 90% water content even if the mother is at risk of dehydration.
Mammary gland
Lactiferous duct development occurs in females in response to circulating hormones. First development is frequently seen during pre- and postnatal stages, and later during puberty. Estrogen promotes branching differentiation, whereas in males testosterone inhibits it. A mature duct tree reaching the limit of the fat pad of the mammary gland comes into being by bifurcation of duct terminal end buds (TEB), secondary branches sprouting from primary ducts and proper duct lumen formation. These processes are tightly modulated by components of mammary epithelial ECM interacting with systemic hormones and local secreting factors. However, for each mechanism the epithelial cells' "niche" can be delicately unique with different membrane receptor profiles and basement membrane thickness from specific branching area to area, so as to regulate cell growth or differentiation sub-locally. Important players include beta-1 integrin, epidermal growth factor receptor (EGFR), laminin-1/5, collagen-IV, matrix metalloproteinase(MMPs), heparan sulfate proteoglycans, and others. Elevated circulating level of growth hormone and estrogen get to multipotent cap cells on TEB tips through a thin, leaky layer of basement membrane. These hormones promote specific gene expression. Hence cap cells can differentiate into myoepithelial and luminal (duct) epithelial cells, and the increased amount of activated MMPs can degrade surrounding ECM helping duct buds to reach further in the fat pads. On the other hand, basement membrane along the mature mammary ducts is thicker, with strong adhesion to epithelial cells via binding to integrin and non-integrin receptors. When side branches develop, it is a much more “pushing-forward” working process including extending through myoepithelial cells, degrading basement membrane and then invading into a periductal layer of fibrous stromal tissue. Degraded basement membrane fragments (laminin-5) roles to lead the way of mammary epithelial cells migration. Whereas, laminin-1 interacts with non-integrin receptor dystroglycan negatively regulates this side branching process in case of cancer. These complex "Yin-yang" balancing crosstalks between mammary ECM and epithelial cells "instruct" healthy mammary gland development until adult.
Cetacea
The male genitals and mammary glands of females are sunken into the body.
Mammary gland
During embryonic development, IGF-1 levels are low, and gradually increase from birth to puberty. At puberty, the levels of GH and IGF-1 reach their highest levels in life and estrogen begins to be secreted in high amounts in females, which is when ductal development mostly takes place. Under the influence of estrogen, stromal and fat tissue surrounding the ductal system in the mammary glands also grows. After puberty, GH and IGF-1 levels progressively decrease, which limits further development until pregnancy, if it occurs. During pregnancy, progesterone and prolactin are essential for mediating lobuloalveolar development in estrogen-primed mammary gland tissue, which occurs in preparation of lactation and nursing.
Neuroscience of sex differences
In a 2013 meta-analysis, researchers found on average males had larger grey matter (GM) volume in bilateral amygdalae, hippocampi, anterior parahippocampal gyri, posterior cingulate gyri, precuneus, putamen and temporal poles, areas in the left posterior and anterior cingulate gyri, and areas in the cerebellum bilateral VIIb, VIIIa and Crus I lobes, left VI and right Crus II lobes. On the other hand, females on average had larger grey matter volume at the right frontal pole, inferior and middle frontal gyri, pars triangularis, planum temporale/parietal operculum, anterior cingulate gyrus, insular cortex, and Heschl's gyrus; bilateral thalami and precuneus; the left parahippocampal gyrus and lateral occipital cortex (superior division). The meta-analysis found larger volumes in females were most pronounced in areas in the right hemisphere related to language in addition to several limbic structures such as the right insular cortex and anterior cingulate gyrus.
Human vestigiality
Human vestigial structures also include leftover embryological remnants that once served a function during development, such as the belly button, and analogous structures between biological sexes. For example, men are also born with two nipples, which are not known to serve a function compared to women. In regards to genitourinary development, both internal and external genitalia of male and female fetuses have the ability to fully or partially form their analogous phenotype of the opposite biological sex if exposed to a lack/overabundance of androgens or the SRY gene during fetal development. Examples of vestigial remnants of genitourinary development include the hymen, which is a membrane that surrounds or partially covers the external vaginal opening that derives from the sinus tubercle during fetal development and is homologous to the male seminal colliculus. Some researchers have hypothesized that the persistence of the hymen may be to provide temporary protection from infection, as it separates the vaginal lumen from the urogenital sinus cavity during development. Other examples include the glans penis and the clitoris, the labia minora and the ventral penis, and the ovarian follicles and the seminiferous tubules.
Urinary bladder
In men, the prostate gland lies outside the opening for the urethra. The middle lobe of the prostate causes an elevation in the mucous membrane behind the internal urethral orifice called the uvula of urinary bladder. The uvula can enlarge when the prostate becomes enlarged.
Complete androgen insensitivity syndrome
All human fetuses, whether genetic males or females, begin fetal development looking similar, with both the Müllerian duct system (female) and the Wolffian duct system (male) developing. It is at the seventh week of gestation that the bodies of unaffected genetic males begin their masculinization: i.e, the Wolffian duct system is promoted and the Müllerian duct system is suppressed (the reverse happens with normal females). This process is triggered by androgens produced by the gonads, which in genetic females had earlier become ovaries, but in genetic males had become testicles due to the presence of the Y Chromosome. The cells of unaffected genetic males then masculinize by, among other things, enlarging the genital tubercle into a penis but in females it becomes the clitoris, while what in females becomes the labia fuses to become the scrotum of males (where the testicles will later descend).
Androgen
During mammalian development, the gonads are at first capable of becoming either ovaries or testes. In humans, starting at about week 4, the gonadal rudiments are present within the intermediate mesoderm adjacent to the developing kidneys. At about week 6, epithelial sex cords develop within the forming testes and incorporate the germ cells as they migrate into the gonads. In males, certain Y chromosome genes, particularly SRY, control development of the male phenotype, including conversion of the early bipotential gonad into testes. In males, the sex cords fully invade the developing gonads.
Preputial gland
Preputial glands are exocrine glands that are located in the folds of skin front of the genitals of some mammals. They occur in several species, including mice, ferrets, rhinoceroses, and even-toed ungulates and produce pheromones. The glands play a role in the urine-marking behavior of canids such as gray wolves and African wild dogs. The preputial glands of female animals are sometimes called clitoral glands.
Paternal care
Male mammals may invest heavily in reproduction through efforts to enhance reproductive success (e.g., courtship displays, intrasexual combat) or to provide paternal care. However, the costs of paternal care have rarely been studied in mammals, in large part because only 5-10% of mammals exhibit such care. Nonetheless, in those species in which males do provide extensive care for their offspring (i.e., biparental species, including humans), indirect evidence suggests that its costs can be substantial. For example, mammalian fathers that care for their young may undergo systematic changes in body mass and in circulating or excreted concentrations of a number of hormones (e.g., androgens, glucocorticoids, leptin) as a function of reproductive status, and several of these hormones have important effects on body composition, metabolism, and organismal performance. Nonetheless, the energetic and performance consequences of male parental investment have rarely been investigated directly in mammals.
Male reproductive system
The structures are masculinized by secretions of the testes:
The prostate gland derives from the urogenital sinus, and the other embryonic structures differentiate into the external genitalia. In the absence of testicular secretions, the female genitalia are formed.
Colostrum
Notably in humans a lack of colostrum production is linked to a mutation in the ABCC11 gene that occurs in most people of East Asian descent. This gene is also one the determining factors in wet or dry type earwax, as the mammary glands are a form of apocrine gland.
Male accessory gland
The secretory endpieces of these glands are lined with simple columnar epithelium; the main ducts are lined with stratified columnar epithelium. These glands do not occur in carnivores, but are present in some form in horses, ruminants and swine. Seminal fluid, the product of this gland, serves as a vehicle for the transport of spermatozoa.
Vaginal epithelium
The vagina itself does not contain mucous glands. Though mucous is not produced by the vaginal epithelium, mucous originates from the cervix. The cervical mucous that is located inside the vagina can be used to assess fertility in ovulating women. The Bartholin's glands and Skene's glands located at the entrance of the vagina do produce mucous.
Body shape
Females have enlarged breasts due to functional mammary glands, which develop from puberty onward due to the effects of estrogen. Mammary glands do not contain muscle tissue. The shape of female breasts is affected by age, genetic factors, and body weight.
Mammary gland
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.
Bulbourethral gland
According to one preliminary study, the bulbourethral gland fluid does not contain any sperm, whereas another study showed some men did leak sperm in potentially significant quantities (in a range from low counts up to 50 million sperm per ml) into the pre-ejaculatory fluid, potentially leading to conception from the introduction of pre-ejaculate. However, the sperm source is a residual or pre-ejaculatory leak from the testicles into the vas deferens, rather than from the bulbourethral gland itself.
Male lactation
Human male breastfeeding is possible, but production of the hormone prolactin is necessary to induce lactation, so male lactation does not occur under normal conditions. Domperidone is a drug that can be used to increase lactation. Male lactation has also been seen during recovery from starvation. This may be because glands that produce hormones recover faster than the liver, which absorbs hormones, leading to high hormone levels.
Lactotropic cell
Prolactin is involved in the maturation of mammary glands and their secretion of milk in association with oxytocin, estrogen, progesterone, glucocorticoids, and others. Prolactin has numerous other effects in both sexes.
Mammary tumor
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.
Cytoplasmic male sterility
Cytoplasmic male sterility, as the name indicates, is under extranuclear genetic control (under control of the mitochondrial or plastid genomes). It shows non-Mendelian inheritance
, with male sterility inherited maternally. In general, there are two types of cytoplasm: N (normal) and aberrant S (sterile) cytoplasms. These types exhibit reciprocal differences.
Salt gland
Some theories suggest mammalian tear ducts and sweat glands may be evolutionarily related to salt glands. While human tears are high in potassium, most phylogeneticists disagree with the association.
Woman
In terms of biology, the female sex organs are involved in the reproductive system, whereas the secondary sex characteristics are involved in nurturing children or, in some cultures, attracting a mate. The ovaries, in addition to their regulatory function producing hormones, produce female gametes called eggs which, when fertilized by male gametes (sperm), form new genetic individuals. The uterus is an organ with tissue to protect and nurture the developing fetus and muscle to expel it when giving birth. The vagina is used in copulation and birthing, although the term vagina is often colloquially and incorrectly used in the English language for the vulva or external female genitalia, which consists of (in addition to the vagina) the labia, the clitoris, and the female urethra. The breast evolved from the sweat gland to produce milk, a nutritious secretion that is the most distinctive characteristic of mammals, along with live birth. In mature women, the breast is generally more prominent than in most other mammals; this prominence, not necessary for milk production, is probably at least partially the result of sexual selection. (For other ways in which men commonly differ physically from women, see man.)
Sebaceous gland
The preputial glands of mice and rats are large modified sebaceous glands that produce pheromones used for territorial marking. These and the scent glands in the flanks of hamsters have a similar composition to human sebaceous glands, are androgen responsive, and have been used as a basis for study. Some species of bat, including the Mexican free-tailed, have a specialized sebaceous gland occurring on the throat called a "gular gland". This gland is present more frequently in males than females, and it is hypothesized that the secretions of the gland are used for scent-marking.
Mammal
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.
Female
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.
Preputial gland
There is debate about whether humans have functional homologues to preputial glands. Preputial glands were first noted by Edward Tyson and in 1694 fully described by William Cowper who named them Tyson's glands after Tyson. They are described as modified sebaceous glands located around the corona and inner surface of the prepuce of the human penis. They are believed to be most frequently found in the balanopreputial sulcus. Their secretion may be one of the components of smegma.
Endocrine gland
Many body organs not normally considered endocrine organs contain isolated cell clusters that secrete hormones. Examples include the heart (atrial natriuretic peptide); gastrointestinal tract organs (gastrin, secretin, and others); the placenta (hormones of pregnancy—estrogen, progesterone, and others); the kidneys (erythropoietin and renin); the thymus; skin (cholecalciferol); and adipose tissue (leptin and resistin).
Man
The male sex organs are part of the reproductive system, consisting of the penis, testicles, vas deferens, and the prostate gland. The male reproductive system's function is to produce semen which carries sperm and thus genetic information that can unite with an egg within a woman. Since sperm that enters a woman's uterus and then fallopian tubes goes on to fertilize an egg which develops into a fetus or child, the male reproductive system plays no necessary role during the gestation. The concept of fatherhood and family exists in human societies. The study of male reproduction and associated organs is called andrology.
Gastric glands
The gastric glands are located in different regions of the stomach. These are the fundic glands, the cardiac glands, and the pyloric glands. The glands and gastric pits are located in the stomach lining. The glands themselves are in the lamina propria of the mucous membrane and they open into the bases of the gastric pits formed by the epithelium. The various cells of the glands secrete mucus, pepsinogen, hydrochloric acid, intrinsic factor, gastrin, and bicarbonate.
Glandulocaudinae
Many of the genera also have a gland situated in the gill cavity called a "gill gland", a secondary sex characteristic found in sexually mature male glandulocaudines that is apparently suited to release chemical signals. No genus contains species that have glands and other species without glands. This gill gland is derived from anterior gill filaments of the first gill arch. Gland size and degree of gill modification varies with species. Though the true function of the gill glands has yet to be determined, they are probably used to release chemical signals into the gill current.
Transgender hormone therapy (male-to-female)
Though the role of progestogens in visible breast development is uncertain, progestogens are essential for lobuloalveolar maturation of the mammary glands, and hence are required for any transgender woman who wishes to lactate or breastfeed. A study found full lobuloalveolar maturation of the mammary glands on histological examination in transgender women treated with an estrogen and high-dose cyproterone acetate. However, the lobuloalveolar development reversed with discontinuation of cyproterone acetate, indicating that continued progestogen exposure is necessary to maintain the tissue.
Salivary gland
The salivary glands in mammals are exocrine glands that produce saliva through a system of ducts. Humans have three paired major salivary glands (parotid, submandibular, and sublingual) as well as hundreds of minor salivary glands. Salivary glands can be classified as serous, mucous or seromucous (mixed).
Marsh rice rat
Some features of the accessory glands in the male genital region vary among oryzomyines. In the marsh rice rat, a single pair of preputial glands is present at the penis. As is usual for sigmodontines, two pairs of ventral prostate glands and a single pair of anterior and dorsal prostate glands exist. Part of the end of the vesicular gland is irregularly folded, not smooth as in most oryzomyines.
Prostate cancer
The prostate is a part of the male reproductive system that helps make and store seminal fluid. In adult men, a typical prostate is about 3 centimeters long and weighs about 20 grams. It is located in the pelvis, under the urinary bladder and in front of the rectum. The prostate surrounds part of the urethra, the tube that carries urine from the bladder during urination and semen during ejaculation. Because of its location, prostate diseases often affect urination, ejaculation, and rarely defecation. The prostate contains many small glands which make about 20% of the fluid constituting semen. In prostate cancer, the cells of these prostate glands mutate into cancer cells. The prostate glands require male hormones, known as androgens, to work properly. Androgens include testosterone, which is made in the testes; dehydroepiandrosterone, made in the adrenal glands; and dihydrotestosterone, which is converted from testosterone within the prostate itself. Androgens are also responsible for secondary sex characteristics such as facial hair and increased muscle mass.
Sweat gland
Specialized sweat glands, including the ceruminous glands, mammary glands, ciliary glands of the eyelids, and sweat glands of the nasal vestibulum, are modified apocrine glands. Ceruminous glands are near the ear canals, and produce cerumen (earwax) that mixes with the oil secreted from sebaceous glands. Mammary glands use apocrine secretion to produce milk.
Reproductive system
Most mammal reproductive systems are similar, however, there are some notable differences between the non-human mammals and humans. For instance, most male mammals have a penis which is stored internally until erect, and most have a penis bone or baculum. Additionally, males of most species do not remain continually sexually fertile as humans do. Like humans, most groups of mammals have descended testicles found within a scrotum, however, others have descended testicles that rest on the ventral body wall, and a few groups of mammals, such as elephants, have undescended testicles found deep within their body cavities near their kidneys.
Udder
An udder is an organ formed of the mammary glands of dairy breeds of cattle and female four-legged mammals, particularly ruminants such as goats, sheep and deer. It is equivalent to the breast in primates. The udder is a single mass hanging beneath the animal, consisting of pairs of mammary glands with protruding teats. In cattle there are normally two pairs, in sheep, goats and deer there is one pair, and in some animals such as pigs there are many pairs. In animals with udders, the mammary glands develop on the milk line near the groin, and mammary glands that develop on the chest (such as in humans and apes) are generally referred to as breasts.
Mammary gland
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
Tumorigenesis in mammary glands can be induced biochemically by abnormal expression level of circulating hormones or local ECM components, or from a mechanical change in the tension of mammary stroma. Under either of the two circumstances, mammary epithelial cells would grow out of control and eventually result in cancer. Almost all instances of breast cancer originate in the lobules or ducts of the mammary glands.
Sex differences in psychology
Women are known to have anatomically differently shaped tear glands than men as well as having more of the hormone prolactin, which is present in tear glands, as adults. While girls and boys cry at roughly the same amount at age 12, by age 18, women generally cry four times more than men, which could be explained by higher levels of prolactin.
Male accessory gland
The lining of these paired, compound, tubuloalveloar glands is simple columnar epithelium. A capsule of dense connective tissue contains some smooth muscle as well as skeletal muscle of the bulbospongiosus and urethral muscles. All domestic species have these glands except the dog, and their mucus secretion serves to clear the urethra of urine and to lubricate it and the vagina. The product may also serve as an energy source for the spermatozoa.
Perianal gland tumor
A perianal gland tumor is a type of tumor found near the anus in dogs that arises from specialized glandular tissue found in the perineum. Perianal glands do not exist in cats. It is also known as a hepatoid tumor because of the similarity in cell shape to hepatocytes (liver cells). It is most commonly seen in intact (not neutered) dogs and is the third most common tumor type in intact male dogs. There are two types of perianal gland tumors, perianal gland adenomas, which are benign, and perianal gland adenocarcinomas, which are malignant. Both have receptors for testosterone. Perianal gland adenomas are three times more likely to be found in intact male dogs than females, and perianal gland adenocarcinomas are ten times more common in male dogs than females. The most commonly affected breeds for adenomas are the Siberian Husky, Cocker Spaniel, Pekingese, and Samoyed; for adenocarcinomas the most commonly affected breeds are the Siberian Husky, Bulldog, and Alaskan Malamute.
Flank gland
The flank gland is located laterally on each side of the abdomen. It is often present in both males and females, though this varies by species, and is usually larger in males. In some species, self-scratching of the flank gland, typically with a hind foot, causes secretion of an oily substance that leaves the surrounding hair visibly matted and emits a chemical odor. These chemicals vary in composition within the same species as well as within an individual as it progresses through sexual maturity. Scent marking via secretions of the flank gland has been observed: for example, some male microtene rodents will perform “drum-marking,” in which they repeatedly scratch their flank gland with their foot and proceed to stomp the ground several times.
Transandinomys talamancae
Some features of the accessory glands in the male genital region vary among oryzomyines. In "Transandinomys talamancae", a single pair of preputial glands is present at the penis. As is usual for sigmodontines, there are two pairs of ventral prostate glands and a single pair of anterior and dorsal prostate glands. Part of the end of the vesicular gland is irregularly folded, not smooth as in most oryzomyines.
Anti-Müllerian hormone
In mammals, AMH prevents the development of the Müllerian ducts into the uterus and other Müllerian structures. The effect is ipsilateral, that is each testis suppresses Müllerian development only on its own side. In humans, this action takes place during the first 8 weeks of gestation. If no hormone is produced from the gonads, the Müllerian ducts automatically develop, while the Wolffian ducts, which are responsible for male reproductive parts, automatically die. Amounts of AMH that are measurable in the blood vary by age and sex. AMH works by interacting with specific receptors on the surfaces of the cells of target tissues (anti-Müllerian hormone receptors). The best-known and most specific effect, mediated through the AMH type II receptors, includes programmed cell death (apoptosis) of the target tissue (the fetal Müllerian ducts).
Human placental lactogen
hPL has been found to bind to the prolactin receptor with equal affinity to that of prolactin in rabbit milk fat gobule membrane, and hPL and prolactin have been found to possess very similar lactogenic activity "in vitro" in mouse and rat mammary gland explants. In addition, hPL has been found to stimulate DNA synthesis in human mammary fibroadenoma cells transplanted into mice, which suggests that hPL promotes the growth of the human mammary gland similarly to prolactin. As hPL circulates at concentrations that are 100-fold higher than those of prolactin during pregnancy, these findings suggest that hPL may play an important role in human mammogenesis during this time. However, the relative affinities of hPL and prolactin for the human prolactin receptor have yet to be published and the effects of hPL on normal human mammary epithelial tissue have not yet been investigated, and so a definitive role of hPL in human mammary gland development during pregnancy has not been established at present.
Glans
The glans (, plural "glandes" ; from the Latin word for "acorn") is a vascular structure located at the tip of the penis in male mammals or a homologous genital structure of the clitoris in female mammals.
Gastric glands
Cells found in the gastric glands include foveolar cells, chief cells, parietal cells, G cells and enterochromaffin-like cells (ECLs). The first cells of all of the glands are foveolar cells in the neck region–also called "mucous neck cells" that produce mucus. This is thought to be different from the mucus produced by the gastric mucosa.
Elliot Abravanel
The Body Type program asserts that there are four major glands in the human body (pituitary, thyroid, adrenal, and gonadal) and that each individual has one "dominant gland." Ann Louise Gittleman stated that Abravanel developed these ideas as an expansion of speculations by Henry G. Bieler and noted that this was done, "Without directly monitoring the behavior of any gland..." According to Abravanel, men can be P-types, T-types, or A-types, based on the dominant gland, and women can be P-types, T-types, A-types or G-types (only women can be G-types due to the purported overall influence that a woman's sexual glands can have on her body). An individual's dominant gland is claimed to influence his or her body shape, and the glandular secretions that purportedly influence personality, sleeping schedule, metabolic activity, and other characteristics. Certain foods and exercises are claimed promote or inhibit activity among one or more glands, and Abravanel asserts that, people tend to feed their dominant gland first and foremost.
Anovulation
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.
Mammary gland
By the pubertal stage, the mammary ducts have invaded to the end of the mammary fat pad. At this point, the terminal end buds become less proliferative and decrease in size. Side branches form from the primary ducts and begin to fill the mammary fat pad. Ductal development decreases with the arrival of sexual maturity and undergoes estrous cycles (proestrus, estrus, metestrus, and diestrus). As a result of estrous cycling, the mammary gland undergoes dynamic changes where cells proliferate and then regress in an ordered fashion.