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Gonads
A gonad, sex gland, or reproductive gland is a mixed gland and sex organ that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sperm in the form of Spermatozoon, spermatozoa. The female gonad, the ovary, produces egg cells. Both of these gametes are haploid cells. Some hermaphroditic animals (and some humanssee Ovotesticular syndrome) have a type of gonad called an ovotestis. Evolution It is hard to find a common origin for gonads, but gonads most likely evolved independently several times. Regulation The gonads are controlled by luteinizing hormone (LH) and follicle-stimulating hormone (FSH), produced and secreted by gonadotropic cell, gonadotropes or gonadotrophins in the anterior pituitary gland. This secretion is regulated by gonadotropin-releasing hormone (GnRH) produced in the hypothalamus. Development The gonads develop from three sources ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Testis Determining Factor
Sex-determining region Y protein (SRY), or testis-determining factor (TDF), is a DNA-binding protein (also known as gene-regulatory protein/transcription factor) encoded by the ''SRY'' gene that is responsible for the initiation of male sex determination in therian mammals ( placentals and marsupials). ''SRY'' is an intronless sex-determining gene on the Y chromosome. Mutations in this gene lead to a range of disorders of sex development with varying effects on an individual's phenotype and genotype. SRY is a member of the SOX (SRY-like box) gene family of DNA-binding proteins. When complexed with the steroidogenic factor 1 (SF-1) protein, SRY acts as a transcription factor that causes upregulation of other transcription factors, most importantly SOX9. Its expression causes the development of primary sex cords, which later develop into seminiferous tubules. These cords form in the central part of the yet-undifferentiated gonad, turning it into a testis. The now-induc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Testicle
A testicle or testis ( testes) is the gonad in all male bilaterians, including humans, and is Homology (biology), homologous to the ovary in females. Its primary functions are the production of sperm and the secretion of Androgen, androgens, primarily testosterone. The release of testosterone is regulated by luteinizing hormone (LH) from the anterior pituitary gland. Sperm production is controlled by follicle-stimulating hormone (FSH) from the anterior pituitary gland and by testosterone produced within the gonads. Structure Appearance Males have two testicles of similar size contained within the scrotum, which is an extension of the abdominal wall. Scrotal asymmetry, in which one testicle extends farther down into the scrotum than the other, is common. This is because of the differences in the vasculature's anatomy. For 85% of men, the right testis hangs lower than the left one. Measurement and volume The volume of the testicle can be estimated by palpating it and compari ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sex Organ
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. Sex organs are typically differentiated into male and female types. In animals (including humans), the male sex organs include the testicles, epididymis, epididymides, and penis; the female sex organs include the clitoris, Ovary, ovaries, oviducts, and vagina. The testicle in the male and the ovary in the female are called the ''primary sex organs''. All other sex-related organs are known as ''secondary sex organs''. The outer parts are known as the genitals or external genitalia, visible at birth in both sexes, while the in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genital Ridge
In embryology, the genital ridge (genital fold or gonadal ridge) is the developmental precursor to the gonads. The genital ridge initially consists mainly of mesenchyme and cells of underlying mesonephric origin. Once oogonia enter this area they attempt to associate with these somatic cells. Development proceeds and the oogonia become fully surrounded by a layer of cells (pre- granulosa cells). The genital ridge appears at approximately five weeks, and gives rise to the sex cords. Associated genes Genes associated with the developing gonad can be categorized into those that form the sexually indifferent gonad, those that determine whether the indifferent gonad will differentiate as male or female, and those that promote differentiation into male or female parts. Genes that form the sexually indifferent gonad are '' SF1'' and ''WT1''. Genes that determine sex are '' SRY'', ''SOX9'', and '' DAX1''. Genes driving the differentiation into male or female structures are ''SF1'' ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypogonadism
Hypogonadism means diminished functional activity of the human gonad, gonads—the testicles or the ovary, ovaries—that may result in diminished biosynthesis, production of sex hormones. Low androgen (e.g., testosterone) levels are referred to as hypoandrogenism and low estrogen (e.g., estradiol) as hypoestrogenism. These are responsible for the observed signs and symptoms in both males and females. Hypogonadism, commonly referred to by the symptom "low testosterone" or "low T", can also decrease other hormones secreted by the gonads including progesterone, dehydroepiandrosterone, DHEA, anti-Müllerian hormone, activin, and inhibin. Spermatogenesis, Sperm development (spermatogenesis) and ovulation, release of the egg from the ovaries (ovulation) may be impaired by hypogonadism, which, depending on the degree of severity, may result in partial or complete infertility. In January 2020, the American College of Physicians issued clinical guidelines for testosterone (medication), ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Development Of The Gonads
The development of the gonads is part of the prenatal development of the reproductive system and ultimately forms the testicles in males and the ovaries in females. The immature ova originate from cells from the dorsal endoderm of the yolk sac. Once they have reached the gonadal ridge they are called oogonia. Development proceeds and the oogonia become fully surrounded by a layer of connective tissue cells (pre-granulosa cells). In this way, the rudiments of the ovarian follicles are formed. In the testicle, a network of tubules fuse to create the seminiferous tubules. Via the rete testis, the seminiferous tubules become connected with outgrowths from the mesonephros, which form the efferent ducts of the testicle. The descent of the testicles consists of the opening of a connection from the testis to its final location at the anterior abdominal wall, followed by the development of the gubernaculum, which subsequently pulls and translocates the testicle down into the developi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Y Chromosome
The Y chromosome is one of two sex chromosomes in therian mammals and other organisms. Along with the X chromosome, it is part of the XY sex-determination system, in which the Y is the sex-determining chromosome because the presence of the Y chromosome causes offspring produced in sexual reproduction to be of male sex. In mammals, the Y chromosome contains the SRY gene, which triggers development of male gonads. The Y chromosome is passed only from male parents to male offspring. Overview Discovery The Y chromosome was identified as a sex-determining chromosome by Nettie Stevens at Bryn Mawr College in 1905 during a study of the mealworm ''Tenebrio molitor''. Edmund Beecher Wilson independently discovered the same mechanisms the same year, working with Hemiptera. Stevens proposed that chromosomes always existed in pairs and that the smaller chromosome (now labelled "Y") was the pair of the X chromosome discovered in 1890 by Hermann Henking. She realized that th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Heterocrine Gland
Heterocrine glands (or composite glands) are the glands which function as both exocrine gland and endocrine gland. These glands exhibit a unique and diverse secretory function encompassing the release of proteins and non-proteinaceous compounds, endocrine and exocrine secretions into both the bloodstream and ducts respectively. This duality allows them to serve crucial roles in regulating various physiological processes and maintaining homeostasis. These include the gonads (testicles and ovaries), pancreas and salivary glands. Pancreas releases digestive enzymes into the small intestine via ducts (exocrine) and secretes insulin and glucagon into the bloodstream (endocrine) to regulate blood sugar level. Testes produce sperm, which is released through ducts (exocrine), and they also secrete androgens into the bloodstream (endocrine). Similarly, ovaries release ova through ducts (exocrine) and produce estrogen and progesterone (endocrine). Salivary glands secrete saliva through du ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anterior Pituitary Gland
The anterior pituitary (also called the adenohypophysis or pars anterior) is a major organ of the endocrine system. The anterior pituitary is the glandular, anterior lobe that together with the posterior pituitary (or neurohypophysis) makes up the pituitary gland (hypophysis) which, in humans, is located at the base of the brain, protruding off the bottom of the hypothalamus. The anterior pituitary regulates several physiological processes, including stress, growth, reproduction, and lactation. Proper functioning of the anterior pituitary and of the organs it regulates can often be ascertained via blood tests that measure hormone levels. Structure The pituitary gland sits in a protective bony enclosure called the sella turcica (''Turkish chair/saddle''). It is composed of three lobes: the anterior, intermediate, and posterior lobes. In many animals, these lobes are distinct. However, in humans, the intermediate lobe is but a few cell layers thick and indistinct; as a resul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hermaphroditic
A hermaphrodite () is a sexually reproducing organism that produces both male and female gametes. Animal species in which individuals are either male or female are gonochoric, which is the opposite of hermaphroditic. The individuals of many taxonomic groups of animals, primarily invertebrates, are hermaphrodites, capable of producing viable gametes of both sexes. In the great majority of tunicates, mollusks, and earthworms, hermaphroditism is a normal condition, enabling a form of sexual reproduction in which either partner can act as the female or male. Hermaphroditism is also found in some fish species, but is rare in other vertebrate groups. Most hermaphroditic species exhibit some degree of self-fertilization. The distribution of self-fertilization rates among animals is similar to that of plants, suggesting that similar pressures are operating to direct the evolution of selfing in animals and plants. A rough estimate of the number of hermaphroditic animal species is 6 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gonadotropin-releasing Hormone
Gonadotropin-releasing hormone (GnRH) is a releasing hormone responsible for the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) from the anterior pituitary. GnRH is a tropic peptide hormone synthesized and released from GnRH neurons within the hypothalamus. GnRH is inhibited by testosterone. The peptide belongs to gonadotropin-releasing hormone family. It constitutes the initial step in the hypothalamic–pituitary–gonadal axis. Structure The identity of GnRH was clarified by the 1977 Nobel Laureates Roger Guillemin and Andrew V. Schally: pyroGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2 As is standard for peptide representation, the sequence is given from amino terminus to carboxyl terminus; also standard is omission of the designation of chirality, with assumption that all amino acids are in their L- form. The abbreviations are the standard abbreviations for the corresponding proteinogenic amino acids, except for ''pyroGlu'', whic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ovotestis
An ovotestis is a gonad with both Testicle, testicular and Ovary, ovarian aspects. In humans, ovotestes are an infrequent anatomical variation associated with gonadal dysgenesis. The only mammals where ovotestes are not characteristic of an infrequent variation are mole (animal), moles, wherein females possess ovotestes along with a masculinized clitoris. These ovotestes in nonpregnant female moles secrete eight times as much testosterone as the ovotestes of pregnant moles. In invertebrates that are normally hermaphroditic, such as most gastropods (snails and slugs) in the clade Eupulmonata, an ovotestis is a common feature of the reproductive anatomy. In mice, ovotestes are structured such that the central region is testicular tissue while the poles both contain ovarian tissue. Experiments involving the SOX9 gene, which is initiated by the Testis-determining factor, SRY region of the Y chromosome, have shown the gene's requirement for testicular differentiation from the presence of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
