Puberty is the process of physical changes by which a child Biologically, a child is generally a human between the stages of birth and puberty. The legal definition of "child" generally refers to a minor, otherwise known as a person younger than the age of majority. "Child" may also describe a relationship with a parent or authority figure, or signify group membership in a clan, tribe,'s body With regard to living things, a body is the physical body of an individual. "Body" often is used in connection with appearance, health issues and death. The study of the workings of the body is physiology becomes an adult An adult is a human being or living organism that is of relatively mature age, typically associated with sexual maturity and the attainment of reproductive age. In human context, the term has other subordinate meanings associated to social and legal concepts, for example a legal adult is a legal concept for a person who has attained the age of body capable of reproduction Reproduction is the biological process by which new "offspring" individual organisms are produced from their "parents". Reproduction is a fundamental feature of all known life; each individual organism exists as the result of reproduction. The known methods of reproduction are broadly grouped into two main types: sexual and. Puberty is initiated by hormone A hormone is a chemical released by a cell in one part of the body, that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. It is essentially a chemical messenger that transports a signal from one cell to another. All multicellular organisms produce hormones; signals from the brain to the gonads (the ovaries The ovary is an ovum-producing reproductive organ, often found in pairs as part of the vertebrate female reproductive system. Ovaries in females are homologous to testes in males, in that they are both gonads and endocrine glands and testes The testicle is the male generative gland in animals). In response, the gonads produce a variety of hormones that stimulate the growth, function, or transformation of brain The brain is the center of the nervous system in all vertebrate, and most invertebrate, animals. Some primitive animals such as jellyfish and starfish have a decentralized nervous system without a brain, while sponges lack any nervous system at all. In vertebrates, the brain is located in the head, protected by the skull and close to the primary, bones Bones are rigid organs that form part of the endoskeleton of vertebrates. They function to move, support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue. Because bones come in a variety of shapes and have a complex internal and external structure, muscle Muscle is the contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to produce force and cause motion. Muscles can cause, skin The skin is a soft outer covering of an animal, in particular a vertebrate. Other animal coverings such the arthropod exoskeleton or the seashell have different developmental origin, structure and chemical composition. The adjective cutaneous literally means "of the skin" . In mammals, the skin is the largest organ of the integumentary, breasts, and reproductive organs A sex organ, or primary sexual characteristic, as narrowly defined, is any of the anatomical parts of the body which are involved in sexual reproduction and constitute the reproductive system in a complex organism; flowers are the reproductive organs of flowering plants, cones are the reproductive organs of coniferous plants, whereas mosses, ferns,. Growth Human development is the process of growing to maturity. In biological terms, this entails growth from a one-celled zygote to an adult human being accelerates in the first half of puberty and stops at the completion of puberty. Before puberty, body differences between boys and girls are almost entirely restricted to the genitalia. During puberty, major differences of size, shape, composition, and function develop in many body structures and systems. The most obvious of these are referred to as secondary sex characteristics.

In a strict sense, the term puberty (derived from the Latin word puberatum (age of maturity, manhood)) refers to the bodily changes of sexual maturation rather than the psychosocial Psychosocial refers to one's psychological development in and interaction with a social environment. The individual is not necessarily fully aware of this relationship with his or her environment. It was first commonly used by psychologist Erik Erikson in his stages of social development. Contrasted with social psychology, which attempts to and cultural aspects of adolescent development. Adolescence Adolescence is a transitional stage of physical and mental human development generally occurring between puberty and legal adulthood (age of majority), but largely characterized as beginning and ending with the teenage stage. According to Erik Erikson's stages of human development, for example, a young adult is generally a person between the ages is the period of psychological and social transition between childhood and adulthood An adult is a human being or living organism that is of relatively mature age, typically associated with sexual maturity and the attainment of reproductive age. In human context, the term has other subordinate meanings associated to social and legal concepts, for example a legal adult is a legal concept for a person who has attained the age of. Adolescence largely overlaps the period of puberty, but its boundaries are less precisely defined and it refers as much to the psychosocial and cultural characteristics of development during the teen years as to the physical changes of puberty.

Differences between male and female puberty

Two of the most significant differences between puberty in girls and puberty in boys are the age at which it begins, and the major sex steroids involved.

Although there is a wide range of normal ages, girls typically begin the process of puberty at age 10, boys at age 12.^[1][2] Girls usually complete puberty by ages 15-17,^[2][3][4] while boys usually complete puberty by ages 16-18.^[2][3][5] Any increase in height beyond these ages is uncommon. Girls attain reproductive maturity about 4 years after the first physical changes of puberty appear.^[4] In contrast, boys accelerate more slowly but continue to grow for about 6 years after the first visible pubertal changes.^[6]

For boys, an androgen Androgen, also called androgenic hormones or testoids, is the generic term for any natural or synthetic compound, usually a steroid hormone, that stimulates or controls the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This includes the activity of the accessory male sex organs and development called testosterone Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands. It is the principal male sex hormone and an anabolic steroid is the principal sex hormone. While testosterone produces all boys' changes characterized as virilization In biology and medicine, virilization refers to the biological development of sex differences, changes that make a male body different from a female body. Most of the changes of virilization are produced by androgens. Virilization is most commonly used in three medical and biology of gender contexts: prenatal sexual differentiation, the postnatal, a substantial product of testosterone metabolism in males is estradiol, though levels rise later and more slowly than in girls. The male "growth spurt" also begins later, accelerates more slowly, and lasts longer before the epiphyses The epiphysis is the rounded end of a long bone, at its joint with adjacent bone. Between the epiphysis and diaphysis (the long midsection of the long bone) lies the metaphysis, including the epiphyseal plate (growth plate). At the joint, the epiphysis is covered with articular cartilage; below that covering is a zone similar to the epiphyseal fuse. Although boys are on average 2 cm shorter than girls before puberty begins, adult men are on average about 13 cm (5.2 inches) taller than women. Most of this sex difference in adult heights is attributable to a later onset of the growth spurt and a slower progression to completion, a direct result of the later rise and lower adult male levels of estradiol.^[7]

The hormone that dominates female development is an estrogen Estrogens , oestrogens (BE), or œstrogens, are a group of steroid compounds, named for their importance in the estrous cycle, and functioning as the primary female sex hormone, their name comes from estrus/oistros (period of fertility for female mammals) + gen/gonos = to generate called estradiol Estradiol (also oestradiol) is a sex hormone. Estradiol is the predominant sex hormone present in females. It is also present in males, being produced as an active metabolic product of testosterone. It represents the major estrogen in humans. Estradiol has not only a critical impact on reproductive and sexual functioning, but also affects other. While estradiol promotes growth of breasts and uterus The uterus (from Latin "uterus" , plural uteruses or uteri) or womb is a major female hormone-responsive reproductive sex organ of most mammals including humans. One end, the cervix, opens into the vagina, while the other is connected to one or both fallopian tubes, depending on the species. It is within the uterus that the fetus, it is also the principal hormone driving the pubertal growth spurt and epiphyseal The epiphysis is the rounded end of a long bone, at its joint with adjacent bone. Between the epiphysis and diaphysis (the long midsection of the long bone) lies the metaphysis, including the epiphyseal plate (growth plate). At the joint, the epiphysis is covered with articular cartilage; below that covering is a zone similar to the epiphyseal maturation and closure.^[8] Estradiol levels rise earlier and reach higher levels in women than in men.

Puberty onset

The onset of puberty is associated with high GnRH Gonadotropin-releasing hormone , also known as Luteinizing-hormone releasing hormone (LHRH) and luliberin, is a tropic peptide hormone responsible for the release of FSH and LH from the anterior pituitary. GnRH is synthesized and released from neurons within the hypothalamus pulsing, which precedes the rise in sex hormones, LH Luteinizing hormone is a hormone produced by the anterior pituitary gland and FSH Follicle-stimulating hormone is a hormone found in humans and other animals. It is synthesized and secreted by gonadotropes of the anterior pituitary gland. FSH regulates the development, growth, pubertal maturation, and reproductive processes of the body. FSH and Luteinizing hormone (LH) act synergistically in reproduction.^[9] Exogenous GnRH pulses cause the onset of puberty.^[10] Brain tumors which increase GnRH output may also lead to premature puberty^[11]

The cause of the GnRH rise is unknown. Leptin Leptin is a 16 kDa protein hormone that plays a key role in regulating energy intake and energy expenditure, including appetite and metabolism. It is one of the most important adipose derived hormones. The Ob(Lep) gene (Ob for obese, Lep for leptin) is located on chromosome 7 in humans might be the cause of the GnRH rise. Leptin has receptors in the hypothalamus which synthesizes GnRH.^[12] Individuals who are deficient in leptin fail to initiate puberty.^[13] The levels of leptin increase with the onset of puberty, and then decline to adult levels when puberty is completed. The rise in GnRH might also be caused by genetics. A study^[14] discovered that a mutation in genes encoding both Neurokinin B It is found in higher concentration in pregnant women suffering pre-eclampsia and can bind the immune-cloaking molecule phosphocholine as well as the Neurokinin B receptor can alter the timing of puberty. The researchers hypothesized that Neurokinin B might play a role in regulating the secretion of Kisspeptin Kisspeptin , the product of the gene Kiss1 is a G-protein coupled receptor ligand for GPR54. Kiss1 was originally identified as a human metastasis suppressor gene that has the ability to suppress melanoma and breast cancer metastasis. It is recently become clear that kisspeptin-GPR54 signaling has an important role in initiating GnRH secretion at, a compound responsible for triggering direct release of GnRH Gonadotropin-releasing hormone , also known as Luteinizing-hormone releasing hormone (LHRH) and luliberin, is a tropic peptide hormone responsible for the release of FSH and LH from the anterior pituitary. GnRH is synthesized and released from neurons within the hypothalamus as well as indirect release of LH Luteinizing hormone is a hormone produced by the anterior pituitary gland and FSH Follicle-stimulating hormone is a hormone found in humans and other animals. It is synthesized and secreted by gonadotropes of the anterior pituitary gland. FSH regulates the development, growth, pubertal maturation, and reproductive processes of the body. FSH and Luteinizing hormone (LH) act synergistically in reproduction.

Physical changes in boys

Testicular size, function, and fertility

In boys, testicular enlargement is the first physical manifestation of puberty (and is termed gonadarche Gonadarche refers to the earliest gonadal changes of puberty. In response to pituitary gonadotropins, the ovaries in girls and the testes in boys begin to grow and increase the production of the sex steroids, especially estradiol and testosterone).^[15] Testes in prepubertal boys change little in size from about 1 year of age to the onset of puberty, averaging about 2–3 cm in length and about 1.5–2 cm in width. Testicular size continues to increase throughout puberty, reaching maximal adult size about 6 years after the onset of puberty. After the boy's testicles have enlarged and developed for about one year, the length and then the breadth of the shaft of the penis will increase and the glans penis and corpora cavernosa will also start to enlarge to adult proportions.^[16] While 18–20 cc is an average adult size, there is wide variation in testicular size in the normal population.^[17]

The testes have two primary functions: to produce hormones A hormone is a chemical released by a cell in one part of the body, that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. It is essentially a chemical messenger that transports a signal from one cell to another. All multicellular organisms produce hormones; and to produce sperm. The Leydig cells Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the testicle. They produce testosterone in the presence of luteinizing hormone . Leydig cells are polyhedral in shape, display a large prominent nucleus, an eosinophilic cytoplasm and numerous lipid-filled vesicles produce testosterone Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands. It is the principal male sex hormone and an anabolic steroid, which in turn produces most of the male pubertal changes. Most of the increasing bulk of testicular tissue is spermatogenic tissue (primarily Sertoli A Sertoli cell is a 'nurse' cell of the testes that is part of a seminiferous tubule and Leydig cells Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the testicle. They produce testosterone in the presence of luteinizing hormone . Leydig cells are polyhedral in shape, display a large prominent nucleus, an eosinophilic cytoplasm and numerous lipid-filled vesicles). Sperm can be detected in the morning urine of most boys after the first year of pubertal changes, and occasionally earlier^{[citation needed]}. On average, potential fertility in boys is reached at 13 years old, but full fertility will not be gained until 14–16 years of age^{[citation needed]}.

During puberty, a male's scrotum will become larger and begin to dangle or hang below the body as opposed to being up tight, to accommodate the production of sperm whereby the testicles need a certain temperature to be fertile.

Pubic hair

Pubic hair often appears on a boy shortly after the genitalia begin to grow. The pubic hairs are usually first visible at the dorsal (abdominal) base of the penis. The first few hairs are described as stage 2. Stage 3 is usually reached within another 6–12 months, when the hairs are too many to count. By stage 4, the pubic hairs densely fill the "pubic triangle." Stage 5 refers to the spread of pubic hair to the thighs In humans the thigh is the area between the pelvis and the knee. Anatomically, it is part of the lower limb and upward towards the navel The navel is a scar on the abdomen, caused when the umbilical cord is removed from a newborn baby. All placental mammals have a navel. It is fairly conspicuous in humans as part of the developing abdominal hair The term abdominal hair refers to the hair that grows on the abdomen of humans and non-human mammals, in the region between the pubic area and the thorax . The growth of abdominal hair follows the same pattern on nearly all mammals, vertically from the pubic area upwards and from the thorax downwards to the umbilicus (navel). The abdominal hair of.

Body and facial hair

In the months and years following the appearance of pubic hair, other areas of skin that respond to androgens may develop androgenic hair Androgenic hair, colloquially body hair, is the terminal hair on the human body developed during and after puberty. It is differentiated from the head hair and less visible vellus hair. Androgenic denotes its growth is related to the level of androgens in the individual. Due to a normally higher level of androgens, men tend to have more androgenic. The usual sequence is: underarm The axilla is the area on the human body directly under the joint where the arm connects to the shoulder (axillary) hair, perianal hair Androgenic hair, colloquially body hair, is the terminal hair that develops on the human body during and after puberty. It is differentiated from the head hair and less visible vellus hair. The growth of androgenic hair is related to the level of androgens in the individual. Due to a normally higher level of androgen, men tend to have more, upper lip hair A moustache is facial hair grown on the upper lip. It may or may not be accompanied by a beard, hair around the entire face, sideburn Sideburns or sideboards are patches of facial hair grown on the sides of the face, extending from the hairline to below the ears and worn with an unbearded chin. The term "sideburns" is a 19th century corruption of the original burnsides, named after American Civil War general Ambrose Burnside, a man known for his unusual facial (preauricular) hair, periareolar hair, and the beard A beard is the collection of hair that grows on the chin, cheeks and neck, but not the upper lip, typically of men. Usually, only males going through puberty or post-pubescent males are able to grow beards. However, women with hirsutism may develop a beard. When differentiating between upper and lower facial hair, a beard specifically refers to area.^[2] As with most human biological processes, this specific order may vary among some individuals. Arm, leg, chest The term chest hair is generally used to describe hair that grows on the chest of human males, in the region between the neck and the abdomen. Chest hair, which is a secondary sex characteristic, develops during and after puberty. It is therefore part of the androgenic hair, abdominal, and back hair become heavier more gradually. There is a large range in amount of body hair among adult men, and significant differences in timing and quantity of hair growth among different racial groups.^[1] Facial hair is often present in late adolescence, but may not appear until significantly later.^[18][19] Facial hair will continue to get coarser, darker and thicker for another 2–4 years after puberty.^[18] Some men do not develop full facial hair for up to 10 years after the completion of puberty.^[18] Chest hair may appear during puberty or years after.^[1] Not all men have chest hair.

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