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Sexual characteristics are physical traits of an organism (typically of a sexually dimorphic organism) which are indicative of or resultant from biological sexual factors. These include both primary sex characteristics, such as gonads, and secondary sex characteristics.
In humans, sex organs or primary sexual characteristics, which are those a person is born with, can be distinguished from secondary sex characteristics, which develop later in life, usually during puberty. The development of both is controlled by sex hormones produced by the body after the initial fetal stage where the presence or absence of the Y-chromosome and/or the SRY gene determine development.
Male primary sex characteristics are the penis, the scrotum and the ability to ejaculate when matured. Female primary sex characteristics are the vulva, vagina, uterus, fallopian tubes, cervix, and the ability to give birth and menstruate when matured. [1]
Hormones that express sexual differentiation in humans include:
The following table lists the typical sexual characteristics in humans (even though some of these can also appear in other animals as well):
| Level of definition | Female | Male |
|---|---|---|
| Biological levels (Sex) | ||
| Sex chromosomes | XX in humans | XY in humans |
| Primary sexual characteristics | ||
| Gonads | ovaries | testicles |
| Levels of sex hormones | high estrogen and gestagens (including progesterone); low androgens (including testosterone) | high androgens (including testosterone) |
| Anatomy of internal genitalia | clitoral crura, vagina, uterus, fallopian tubes | corpora cavernosa, prostate, vas deferens, seminal vesicles |
| Anatomy of external genitalia | vulva, which includes the glans clitoridis, labia, clitoral hood and vaginal opening | scrotum, penis, foreskin, fused perineum |
| Secondary sexual characteristics | ||
| Larger breasts, wider hips, shorter height, more body fat, less muscle mass, less facial hair, less body hair, higher vocal pitch frequency, less lung capacity, [2] smaller heart [3] | more facial hair, more body hair, smaller breasts, lower drop in vocal pitch frequency, development of "triangular" body form, taller height, less body fat, more muscle mass, narrower hips, more lung capacity, [4] larger heart [3] | |
| Both sexes | Pubic hair, underarm hair | |
In invertebrates and plants, hermaphrodites (which have both male and female reproductive organs either at the same time or during their life cycle) are common, and in many cases, the norm.
In other varieties of multicellular life (e.g. the fungi division, Basidiomycota), sexual characteristics can be much more complex, and may involve many more than two sexes. For details on the sexual characteristics of fungi, see: Hypha and Plasmogamy.
Secondary sex characteristics in non-human animals include manes of male lions, long tail feathers of male peafowl, the tusks of male narwhals, enlarged proboscises in male elephant seals and proboscis monkeys, the bright facial and rump coloration of male mandrills, and horns in many goats and antelopes. [5]
A secondary sex characteristic is a physical characteristic of an organism that is related to or derived from its sex, but not directly part of its reproductive system. In humans, these characteristics typically start to appear during puberty. In animals, they can start to appear at sexual maturity. In humans, secondary sex characteristics include enlarged breasts and widened hips of females, facial hair and Adam's apples on males, and pubic hair on both. In non-human animals, secondary sex characteristics include, for example, the manes of male lions, the bright facial and rump coloration of male mandrills, and horns in many goats and antelopes.
A sex organ, also known as a reproductive organ, is a part of an organism that is involved in sexual reproduction. Sex organs constitute the primary sex characteristics of an organism. Sex organs are responsible for producing and transporting gametes, as well as facilitating fertilization and supporting the development and birth of offspring. Sex organs are found in many species of animals and plants, with their features varying depending on the species.
An androgen is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This includes the embryological development of the primary male sex organs, and the development of male secondary sex characteristics at puberty. Androgens are synthesized in the testes, the ovaries, and the adrenal glands.
Gametogenesis is a biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes. Depending on the biological life cycle of the organism, gametogenesis occurs by meiotic division of diploid gametocytes into various gametes, or by mitosis. For example, plants produce gametes through mitosis in gametophytes. The gametophytes grow from haploid spores after sporic meiosis. The existence of a multicellular, haploid phase in the life cycle between meiosis and gametogenesis is also referred to as alternation of generations.
In biology, mating is the pairing of either opposite-sex or hermaphroditic organisms for the purposes of sexual reproduction. Fertilization is the fusion of two gametes. Copulation is the union of the sex organs of two sexually reproducing animals for insemination and subsequent internal fertilization. Mating may also lead to external fertilization, as seen in amphibians, fishes and plants. For most species, mating is between two individuals of opposite sexes. However, for some hermaphroditic species, copulation is not required because the parent organism is capable of self-fertilization (autogamy); for example, banana slugs.
Sexual maturity is the capability of an organism to reproduce. In humans, it is related to both puberty and adulthood. However, puberty is the process of biological sexual maturation, while the concept of adulthood is generally based on broader cultural definitions.
Sexual differentiation is the process of development of the sex differences between males and females from an undifferentiated zygote. Sex determination is often distinct from sex differentiation; sex determination is the designation for the development stage towards either male or female, while sex differentiation is the pathway towards the development of the phenotype.
Aspergillus is a genus consisting of several hundred mold species found in various climates worldwide.
Lymphangioleiomyomatosis (LAM) is a rare, progressive and systemic disease that typically results in cystic lung destruction. It predominantly affects women, especially during childbearing years. The term sporadic LAM is used for patients with LAM not associated with tuberous sclerosis complex (TSC), while TSC-LAM refers to LAM that is associated with TSC.
Reproductive biology includes both sexual and asexual reproduction.
Male is the sex of an organism that produces the gamete known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilisation. A male organism cannot reproduce sexually without access to at least one ovum from a female, but some organisms can reproduce both sexually and asexually. Most male mammals, including male humans, have a Y chromosome, which codes for the production of larger amounts of testosterone to develop male reproductive organs.
The human reproductive system includes the male reproductive system which functions to produce and deposit sperm; and the female reproductive system which functions to produce egg cells, and to protect and nourish the fetus until birth. Humans have a high level of sexual differentiation. In addition to differences in nearly every reproductive organ, there are numerous differences in typical secondary sex characteristics.
Löfgren syndrome is a type of acute sarcoidosis, an inflammatory disorder characterized by swollen lymph nodes in the chest, tender red nodules on the shins, fever and arthritis. It is more common in women than men, and is more frequent in those of Scandinavian, Irish, African and Puerto Rican heritage. It was described in 1953 by Sven Halvar Löfgren, a Swedish clinician. Some have considered the condition to be imprecisely defined.
In law, sex characteristic refers to an attribute defined for the purposes of protecting individuals from discrimination due to their sexual features. The attribute of sex characteristics was first defined in national law in Malta in 2015. The legal term has since been adopted by United Nations, European, and Asia-Pacific institutions, and in a 2017 update to the Yogyakarta Principles on the application of international human rights law in relation to sexual orientation, gender identity, gender expression and sex characteristics.
Group IID secretory phospholipase A2 is an enzyme that in humans is encoded by the PLA2G2D gene.
Dynein axonemal heavy chain 5 is a protein that in humans is encoded by the DNAH5 gene.
Ventilator-associated lung injury (VALI) is an acute lung injury that develops during mechanical ventilation and is termed ventilator-induced lung injury (VILI) if it can be proven that the mechanical ventilation caused the acute lung injury. In contrast, ventilator-associated lung injury (VALI) exists if the cause cannot be proven. VALI is the appropriate term in most situations because it is virtually impossible to prove what actually caused the lung injury in the hospital.
The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are also important accessories to the reproductive system. Unlike most organ systems, the sexes of differentiated species often have significant differences. These differences allow for a combination of genetic material between two individuals, which allows for the possibility of greater genetic fitness of the offspring.
This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms. It is intended as introductory material for novices; for more specific and technical definitions from sub-disciplines and related fields, see Glossary of cell biology, Glossary of genetics, Glossary of evolutionary biology, Glossary of ecology, Glossary of environmental science and Glossary of scientific naming, or any of the organism-specific glossaries in Category:Glossaries of biology.
William N. Rom is the Sol and Judith Bergstein Professor of Medicine and Environmental Medicine, Emeritus at New York University School of Medicine and former Director of the Division of Pulmonary, Critical Care and Sleep Medicine at New York University and Chief of the Chest Service at Bellevue Hospital Center, 1989–2014. He is Research Scientist at the School of Global Public Health at New York University and Adjunct Professor at the NYU Robert F. Wagner Graduate School of Public Service. He teaches Climate Change and Global Public Health and Environmental Health in a Global World.
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