Genital System Development

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Female uterus development

The male and female reproductive systems develop initially embryonically "indifferent", it is the product of the Y chromosome SRY gene that makes the "difference".

- Male     - Female

The paired mesonephric ducts (Wolffian ducts) and paramesonephric ducts (Müllerian ducts) contribute the majority of male and female internal genital tract respectively.

Development of this system commences in the embryo, continues through the fetal period then with key changes around birth, only completes functional development postnatally at puberty. The mesonephric/paramesonephric duct changes are one of the first male/female differences that occur in development, while external genitaila remain indeterminate in appearance for quite a while. The term "gonad" is used to refer to both the ovary and testis.

There are many different issues to consider in the development of the genital system. Importantly its sex chromosome dependence, late embryonic/fetal differential development, complex morphogenic changes, long time-course, hormonal sensitivity and hormonal influences make it a system prone to many different abnormalities.

This current page provides only a general introduction to the topic, use the links listed below to read about specific developmental topics.

Genital Links: genital | Lecture - Medicine | Lecture - Science | Lecture Movie | Medicine - Practical | primordial germ cell | meiosis | endocrine gonad‎ | Genital Movies | genital abnormalities | Assisted Reproductive Technology | puberty | Category:Genital
Female | X | X inactivation | ovary | corpus luteum | oocyte | uterus | vagina | reproductive cycles | menstrual cycle | Category:Female
Male | Y | SRY | testis | spermatozoa | ductus deferens | penis | prostate | Category:Male
Historic Embryology - Genital 
General: 1901 Urinogenital Tract | 1902 The Uro-Genital System | 1904 Ovary and Testis | 1912 Urinogenital Organ Development | 1914 External Genitalia | 1921 Urogenital Development | 1921 External Genital | 1942 Sex Cords | 1953 Germ Cells | Historic Embryology Papers | Historic Disclaimer
Female: 1904 Ovary and Testis | 1904 Hymen | 1912 Urinogenital Organ Development | 1914 External Genitalia | 1914 Female | 1921 External Genital | 1927 Female Foetus 15 cm | 1927 Vagina | 1932 Postnatal Ovary
Male: 1887-88 Testis | 1904 Ovary and Testis | 1904 Leydig Cells | 1906 Testis vascular | 1909 Prostate | 1912 Prostate | 1914 External Genitalia | 1915 Cowper’s and Bartholin’s Glands | 1920 Wolffian tubules | 1935 Prepuce | 1935 Wolffian Duct | 1942 Sex Cords | 1943 Testes Descent | Historic Embryology Papers | Historic Disclaimer

Some Recent Findings

Male urogenital development (stage 22)
  • Foxa1 and Foxa2 orchestrate development of the urethral tube and division of the embryonic cloaca through an autoregulatory loop with Shh[1] "Congenital anomalies of external genitalia affect approximately 1 in 125 live male births. Development of the genital tubercle, the precursor of the penis and clitoris, is regulated by the urethral plate epithelium, an endodermal signaling center. Signaling activity of the urethral plate is mediated by Sonic hedgehog (SHH), which coordinates outgrowth and patterning of the genital tubercle by controlling cell cycle kinetics and expression of downstream genes. The mechanisms that govern Shh transcription in urethral plate cells are largely unknown. Here we show that deletion of Foxa1 and Foxa2 results in persistent cloaca, an incomplete separation of urinary, genital, and anorectal tracts, and severe hypospadias, a failure of urethral tubulogenesis. Loss of Foxa2 and only one copy of Foxa1 results in urethral fistula, an additional opening of the penile urethra. Foxa1/a2 participate in an autoregulatory feedback loop with Shh, in which FOXA1 and FOXA2 positively regulate transcription of Shh in the urethra, and SHH feeds back to negatively regulate Foxa1 and Foxa2 expression. These findings reveal novel roles for Foxa genes in development of the urethral tube and in division of the embryonic cloaca."
  • Bmp4 is an essential growth factor for the initiation of genital tubercle (GT) outgrowth[2] "The external genitalia are appendage organs outgrowing from the posterior body trunk. Murine genital tubercle (GT), anlage of external genitalia, initiates its outgrowth from embryonic day (E) E10.5 as a bud structure. Several growth factors such as fibroblast growth factor (FGF), Wnt and Sonic hedgehog (Shh) are essential for the GT outgrowth. However, the mechanisms of initiation of GT outgrowth are poorly understood. We previously identified bone morphogenetic protein (Bmp) signaling as a negative regulator for GT outgrowth. We show here novel aspects of Bmp4 functions for GT outgrowth. We identified the Bmp4 was already expressed in cloaca region at E9.5, before GT outgrowth. To analyze the function of Bmp4 at early stage for the initiation of GT outgrowth, we utilized the Hoxa3-Cre driver and Bmp4 flox/flox mouse lines. Hoxa3 Cre/+ ; Bmp4 flox/flox mutant mice showed the hypoplasia of GT with reduced expression of outgrowth promoting genes such as Wnt5a, Hoxd13 and p63, whereas Shh expression was not affected. Formation of distal urethral epithelium (DUE) marked by the Fgf8 expression is essential for controlling mesenchymal genes expression in GT and subsequent its outgrowth. Furthermore, Fgf8 expression was dramatically reduced in such mutant mice indicating the defective DUE formation. Hence, current results indicate that Bmp4 is an essential growth factor for the initiation of GT outgrowth independent of Shh signaling. Thus, Bmp4 positively regulates for the formation of DUE. The current study provides new insights into the function of Bmp signaling at early stage for the initiation of GT outgrowth." BMP
  • Differences of sex development: the road to diagnosis[3] "The diagnosis and management of children born with ambiguous genitalia is challenging for clinicians. Such differences of sex development (DSDs) are congenital conditions in which chromosomal, gonadal, or anatomical sex is atypical. The aetiology of DSDs is very heterogenous and a precise diagnosis is essential for management of genetic, endocrine, surgical, reproductive, and psychosocial issues. In this Review, we outline a step-by-step approach, compiled in a diagnostic algorithm, for the clinical assessment and molecular diagnosis of a patient with ambiguity of the external genitalia on initial presentation. We appraise established and emerging technologies and their effect on diagnosis, and discuss current controversies."
More recent papers  
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Search term: Genital Embryology | Genital Development | Female Genital Development | Male Genital Development | Female Urogenital Development | Male Urogenital Development

Older papers  
These papers originally appeared in the Some Recent Findings table, but as that list grew in length have now been shuffled down to this collapsible table.

See also the Discussion Page for other references listed by year and References on this current page.

  • Immunohistochemical expression analysis of the human fetal lower urogenital tract[4] "We have studied the ontogeny of the developing human Male and Female urogenital tracts from 9 weeks (indifferent stage) to 16 weeks (advanced sex differentiation) of gestation by immunohistochemistry on mid-sagittal sections. Sixteen human fetal pelvises were serial sectioned in the sagittal plane and stained with antibodies to epithelial, muscle, nerve, proliferation and hormone receptor markers. Key findings are: (1) The corpus cavernosum in males and females extends into the glans penis and clitoris, respectively, during the ambisexual stage (9 weeks) and thus appears to be an androgen-independent event. (2) The entire human male (and female) urethra is endodermal in origin based on the presence of FOXA1, KRT 7, uroplakin, and the absence of KRT10 staining. The endoderm of the urethra interfaces with ectodermal epidermis at the site of the urethral meatus. (3) The surface epithelium of the verumontanum is endodermal in origin (FOXA1-positive) with a possible contribution of Pax2-positive epithelial cells implying additional input from the Wolffian duct epithelium. (4) Prostatic ducts arise from the endodermal (FOXA1-positive) urogenital sinus epithelium near the verumontanum. (5) Immunohistochemical staining of mid-sagittal and para-sagittal sections revealed the external anal sphincter, levator ani, bulbospongiosus muscle and the anatomic relationships between these developing skeletal muscles and organs of the Male and Female reproductive tracts."
  • Expression analysis identifies cascades of activation and repression and maps a putative regulator of mammalian sex determination[5] "In vertebrates, primary sex determination refers to the decision within a bipotential organ precursor to differentiate as a testis or ovary. Bifurcation of organ fate begins between embryonic day (E) 11.0-E12.0 in mice and likely involves a dynamic transcription network that is poorly understood. ...We provide strong evidence that Lmo4 (Lim-domain only 4) is a novel regulator of sex determination upstream of SF1 (Nr5a1), Sox9, Fgf9, and Col9a3. This approach can be readily applied to identify regulatory interactions in other systems."
  • Male reproductive tract abnormalities: More common after assisted reproduction?[6] "IVF and ICSI, by increasing the risks of prematurity, low birthweight, and multiple gestation, are indirect risk factors for developing male genital malformations. In infants with normal birhtweight or from singleton pregnancies, ICSI is a specific risk factor for hypospadias."
  • Temporal and spatial dissection of Shh signaling in genital tubercle development.[7] "Genital tubercle (GT) initiation and outgrowth involve coordinated morphogenesis of surface ectoderm, cloacal mesoderm and hindgut endoderm. GT development appears to mirror that of the limb. Although Shh is essential for the development of both appendages, its role in GT development is much less clear than in the limb. Here, by removing Shh at different stages during GT development in mice, we demonstrate a continuous requirement for Shh in GT initiation and subsequent androgen-independent GT growth."
  • Bmp7 expression and null phenotype in the urogenital system suggest a role in re-organization of the urethral epithelium.[8] "Signaling by Bone morphogenetic proteins (Bmps) has multiple and diverse roles in patterning and morphogenesis of the kidney, eye, limbs and the neural tube. ...Together, our analysis of Bmp7 expression and the null phenotype, indicates that Bmp7 may play an important role in re-organization of the epithelium during cloacal septation and morphogenesis of the genital tubercle."


  • Human Embryology (2nd ed.) Larson Chapter 10 p261-306
  • The Developing Human: Clinically Oriented Embryology (6th ed.) Moore and Persaud Chapter 13 p303-346
  • Before We Are Born (5th ed.) Moore and Persaud Chapter 14 p289-326
  • Essentials of Human Embryology, Larson Chapter 10 p173-205
  • Human Embryology, Fitzgerald and Fitzgerald Chapter 21-22 p134-152
  • Developmental Biology (6th ed.) Gilbert Chapter 14 Intermediate Mesoderm
UNSW Students
Mark Hill.jpg You have access the following online Embryology textbooks through the UNSW Library.
The Developing Human, 8th edn.jpg Moore, K.L. & Persuad, T.V.N. (2008). The Developing Human: clinically oriented embryology (8th ed.). Philadelphia: Saunders.
Larsen's human embryology 4th edn.jpg Schoenwolf, G.C., Bleyl, S.B., Brauer, P.R. and Francis-West, P.H. (2009). Larsen’s Human Embryology (4th ed.). New York; Edinburgh: Churchill Livingstone.

Historic-ovary.jpg Historic-testis.jpg


  • Understand the role of the Y chromosome in sex determination.
  • Understand the differences in male/female duct develpoment (mesonephric/paramesonephric).
  • Compare the development of the cloaca in the male and female.
  • Understand the developmental abnormalities in male and female development.


Genital Movies
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 ‎‎Renal Overview
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 ‎‎Female External‎‎
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 ‎‎Male External
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Uterus 001 icon.jpg
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Testis 001 icon.jpg
 ‎‎Testis Descent
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 ‎‎Gonad Vascular
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Mouse Primordial Germ Cell Migration
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 ‎‎Germ Cell E9.0
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 ‎‎Germ Cell E9.5
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 ‎‎Germ Cell E10.5
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Development Overview

Three main stages during development, mesonephric/paramesonephric duct changes are one of the first male/female differences that occur in development, while external genitaila remain indeterminate in appearance for quite a while.

  1. Differentiation of gonad (Sex determination)
  2. Differentiation of internal genital organs
  3. Differentiation of external genital organs

The 2nd and 3rd stages dependent on endocrine gonad. Reproductive development has a long maturation timecourse, begining in the embryo and finishing in puberty. (More? Puberty Development)

Gender by Ultrasound

A 2012 Czech ultrasound study[9] of 1222 singleton pregnancies has attempted to determine the earliest gestational age GA that fetal gender may reliably be determined. Their study concluded "when CRL ≥ 60 mm (gestational age ≥ 12+2). Male gender may already be reliably determined when CRL ≥ 55 mm (gestational age ≥ 12+0). If CRL < 50 mm (gestational age < 11+4) the gender cannot be reliably predicted."

Links: ultrasound

Sexual Development Genes

Table below modified from Table 1. Genes implicated in sexual development in mammals in a review article.[10]

Mammalian Sexual Development Genes
Gene (OMIM) Protein Function Gonad Phenotype of Null Mice Human Syndrome

Bipotential gonad
Wt1 Transcription factor Blockage in genital ridge development Denys-Drash, WAGR, Frasier syndrome
Sf1 Nuclear receptor Blockage in genital ridge development Embryonic testicular regression syndrome
Lhx9 Transcription factor Blockage in genital ridge development a
Emx2 Transcription factor Blockage in genital ridge development a
M33 Transcription factor Gonadal dysgenesis a
Testis-determining pathway
Gata4/Fog2 Transcription/cofactor Reduced Sry levels, XY sex reversal a
Sry Transcription factor XY sex reversal XY sex reversal (LOF); XX sex reversal (GOF)
Sox9 Transcription factor XY sex reversal Campomelic dysplasia, XX sex reversal (GOF)
Sox8 Transcription factor XY sex reversal in combination with partial loss of Sox9 function a
Fgf9 Signaling molecule XY sex reversal a
Dax1 Nuclear receptor Impaired testis cord formation and spermatogenesis Hypogonadism
Pod1 Transcription factor XY sex reversal a
Dhh Signaling molecule Impaired differentiation of Leydig and PM cells XY gonadal dysgenesis
Pgdra Receptor Reduction in mesonephric cell migration a
Pgds Enzyme No phenotype a
Arx Transcription factor Abnormal testicular differentiation X-linked lissencephaly with abnormal genitalia
Atrx Helicase ND ATRX syndrome
Insl3 Signaling factor Blockage of testicular descent Cryptorchidism
Lgr8 Receptor Blockage of testicular descent Cryptorchidism
Hoxa10 Transcription factor Blockage of testicular descent Cryptorchidism
Hoxa11 Transcription factor Blockage of testicular descent Cryptorchidism
Amh Hormone No Müllerian duct degeneration Persistent Müllerian duct syndrome
Misrl1 Receptor No Müllerian duct degeneration Persistent Müllerian duct syndrome
Pax2 Transcription factor Dysgenesis of mesonephric tubules a
Lim1 Transcription factor Agenesis of Wolffian and Müllerian ducts a
Dmrt1 Transcription factor Loss of Sertoli and germ cells XY femaleb
Ovary-determining pathway
Wnt4 Signaling molecule Müllerian duct agenesis, testosterone synthesis, and coelomic vessel formation XY female (GOF)
FoxL2 Transcription factor Premature ovarian failure BPES
Dax1 Nuclear receptor XY sex reversal (GOF) XY sex reversal (GOF)
RSPO1 Signaling molecule XX sex reversal (LOF) XX sex reversal (LOF)
Table Legend
  • BPES - blepharophimosis-ptosis-epicanthus inversus syndrome
  • GOF - gain-of-function mutation
  • LOF - loss-of-function mutation
  • ND - not determined
  • WAGR - Wilms' tumor-aniridia-genitourinary malformations-mental retardation
a No mutations in human sexual disorders identified to date.

b Candidate gene for 9p deletion, XY sex reversal.

Table data modified[10]

Orphan Nuclear Receptors

Orphan nuclear receptors are proteins with a nuclear receptor domain structure that lack identified signaling ligands.

Steroidogenic factor-1 (NR5A1, SF-1) and liver receptor homolog-1 (NR5A2, LRH-1) both bind to the same DNA sequences, with different and non-overlapping effects on targets (see review[11]).

  • SF-1 is expressed mainly in steroidogenic tissues - adrenal development, sexual differentiation, and Leydig cell function
  • LRH-1 in tissues of endodermal origin and gonads - development beyond gastrulation

Human Genital

Studies of human genital development are covered in several early historical studies[12][13][14][15][16][17] and a later 1980's review article based on the Carnegie Collection embryos.[18]

Human Embryonic Genital Development Studies
Structure Stage Range Carnegie Stages (Embryo No.) Study
Cloaca 11 - 19 11 (164), 13 (186}, 14 (80), 15 (2), 16 (221) 19 (43) Pohlman (1911)[12]
Rete 16 - 23 16 (1836), 17 (544), 18 (423; 511; 841), 19 (432), 20 (368; 460), 21 (22; 455; 2937), 23 (75; 782; 1945) Wilson {1926a}[15]
External genitalia 20, 23 20 (2393) 23 (950) Wilson (1926b)[16]
vagina 17 - 23 17 (353), 20 (966), 22 (584A; 4304; 4339; 4638), 23 (4205; 4289; 5725). Koff (1933)[17]
external genital embryonic to fetal 16 (792); 18 (492}; to fetal 100mm Spaulding (1921)[14]
pelvis 15 - 23 15, 16, 17, 18, 23 (no embryo numbers available) Pillet (1967-1971)[19][20][21][22]
Some data from[18] Links: genital | Carnegie Collection

Animal Models


Mouse gonad development timeline.jpg

Mouse E11.0 to E12.0 shows the critical transition in the gonad from a bipotential to sexually-differentiated state. Based upon transcriptome analysis.[5]


See also section Historic Embryology Images.

Johannes Müller (1801-1858)

Historic Images of Genital Changes

Urogenital Indifferent Urogenital Male Urogenital Female
Urogenital indifferent Urogenital male Urogenital female

Additional Images

Historic Embryology Images

Historic Disclaimer - information about historic embryology pages 
Mark Hill.jpg
Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)

Keith, A. (1902) Human Embryology and Morphology. London: Edward Arnold.

Chapter 9 - The Uro-genital System

The Uro-genital System: Fig. 79. Wolffian Body | Fig. 80. Wolffian and Genital Ridges | Fig. 81. Female Wolffian Body Remnants | Fig. 82. Male Wolffian Body Remnants |Fig. 83. Renal Bud | Fig. 84. Ureter in the Bladder | Fig. 85. Wolffian and Müllerian Ducts | Fig. 86. Genital Ducts 3rd month | Fig. 87. Müllerian Ducts 3rd month | Fig. 88. Uterus | Fig. 89. Uterus and Vagina | Fig. 90. Prostate remnants of Müllerian Ducts | Fig. 91. Prostate showing an unusual Uterus Masculinus | Fig. 92. Female Uro-genital Sinus | Fig. 93. Male Uro-genital Sinus | Fig. 94. Vagina and Uterus at 7th month | Fig. 95. Division of the Cloaca | Fig. 96. Imperforate Anus | Fig. 97. Cloacal Septum has failed to fuse with Perineal Septum | Fig. 98. The Uro-genital Cleft 2nd month | Fig. 99. Male bladder and urethra at birth | Fig. 100. Ectopia Vesicae | Fig. 101. Prostatic Tubules | Fig. 102. Testis in a foetus of 2£ months | Fig. 103. Testis at the 6th month | Fig. 104. Inguinal Canal and Coverings of the Testis | Fig. 105. Processus Vaginalis | Figures


  1. Gredler ML, Patterson SE, Seifert AW & Cohn MJ. (2020). Foxa1 and Foxa2 orchestrate development of the urethral tube and division of the embryonic cloaca through an autoregulatory loop with Shh. Dev. Biol. , 465, 23-30. PMID: 32645357 DOI.
  2. Kajioka D, Suzuki K, Nakada S, Matsushita S, Miyagawa S, Takeo T, Nakagata N & Yamada G. (2019). Bmp4 is an essential growth factor for the initiation of genital tubercle (GT) outgrowth. Congenit Anom (Kyoto) , , . PMID: 30714224 DOI.
  3. León NY, Reyes AP & Harley VR. (2019). Differences of sex development: the road to diagnosis. Lancet Diabetes Endocrinol , , . PMID: 30803928 DOI.
  4. Shen J, Isaacson D, Cao M, Sinclair A, Cunha GR & Baskin L. (2018). Immunohistochemical expression analysis of the human fetal lower urogenital tract. Differentiation , 103, 100-119. PMID: 30287094 DOI.
  5. 5.0 5.1 Munger SC, Natarajan A, Looger LL, Ohler U & Capel B. (2013). Fine time course expression analysis identifies cascades of activation and repression and maps a putative regulator of mammalian sex determination. PLoS Genet. , 9, e1003630. PMID: 23874228 DOI.
  6. Funke S, Flach E, Kiss I, Sándor J, Vida G, Bódis J & Ertl T. (2010). Male reproductive tract abnormalities: more common after assisted reproduction?. Early Hum. Dev. , 86, 547-50. PMID: 20674196 DOI.
  7. Lin C, Yin Y, Veith GM, Fisher AV, Long F & Ma L. (2009). Temporal and spatial dissection of Shh signaling in genital tubercle development. Development , 136, 3959-67. PMID: 19906863 DOI.
  8. Wu X, Ferrara C, Shapiro E & Grishina I. (2009). Bmp7 expression and null phenotype in the urogenital system suggest a role in re-organization of the urethral epithelium. Gene Expr. Patterns , 9, 224-30. PMID: 19159697 DOI.
  9. Lubusky M, Studnickova M, Skrivanek A, Vomackova K & Prochazka M. (2012). Ultrasound evaluation of fetal gender at 12-14 weeks. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub , 156, 324-9. PMID: 22660228 DOI.
  10. 10.0 10.1 Wilhelm D, Palmer S & Koopman P. (2007). Sex determination and gonadal development in mammals. Physiol. Rev. , 87, 1-28. PMID: 17237341 DOI.
  11. Meinsohn MC, Smith OE, Bertolin K & Murphy BD. (2019). The Orphan Nuclear Receptors Steroidogenic Factor-1 and Liver Receptor Homolog-1: Structure, Regulation, and Essential Roles in Mammalian Reproduction. Physiol. Rev. , 99, 1249-1279. PMID: 30810078 DOI.
  12. 12.0 12.1 Pohlman AG. The development of the cloaca in human embryos. (1911) Amer. J Anat. 12: 1-26.
  13. Wood-Jones F. The morphology of the external genitalia of the mammala. (1914) Lancet. 1017-1023.
  14. 14.0 14.1 Spaulding MH. The development of the external genitalia in the human embryo. (1921) Contrib. Embryol., Carnegie Inst. Wash. Publ. 81, 13: 69 – 88.
  15. 15.0 15.1 Wilson KM. Origin and development of the rete ovarii and the rete testis in the human embryo. (1926) Carnegie Instn. Wash. Publ. 362, Contrib. Embryol., Carnegie Inst. Wash., 17:69-88.
  16. 16.0 16.1 Wilson KM. Correlation of external genitalia and sex-glands in the human embryo. (1926) Carnegie Instn. Wash. Publ. 363, Contrib. Embryol., Carnegie Inst. Wash. 18: 23-30.
  17. 17.0 17.1 Koff A. Development of the vagina in the human fetus. (1933) Contrib. Embryol., Carnegie Inst. Wash. Publ. 443, 24: 59-60.
  18. 18.0 18.1 O'Rahilly R. (1983). The timing and sequence of events in the development of the human reproductive system during the embryonic period proper. Anat. Embryol. , 166, 247-61. PMID: 6846859
  19. Pillet J. Reconstruction des organes pelviens d’embryons humains de 12,5 et de 25 mm CR. (1967) Ass Anat 51: 819-827.
  20. Pillet J. Reconstruction du pelvis d’un embryon humain de 7.5 mm (Stade XVI de Streeter) CR. (1968) Ass Anat 52: 1013-1023.
  21. Pillet J (1969) Reconstruction des organes génito«-urinaires et des veines pelviennes d’un embryon de 12,5 mm (Stade XVII de Streeter) CR. Ass Anat 53 : 1817-1824.
  22. Pillet J. Reconstruction des organes pelviens d’un embryon de 5 mm (Stade XV de Streeter) CR. (1971) Ass Anat 54:705-715


Meinsohn MC, Smith OE, Bertolin K & Murphy BD. (2019). The Orphan Nuclear Receptors Steroidogenic Factor-1 and Liver Receptor Homolog-1: Structure, Regulation, and Essential Roles in Mammalian Reproduction. Physiol. Rev. , 99, 1249-1279. PMID: 30810078 DOI.

Bashamboo A, Eozenou C, Rojo S & McElreavey K. (2017). Anomalies in human sex determination provide unique insights into the complex genetic interactions of early gonad development. Clin. Genet. , 91, 143-156. PMID: 27893151 DOI.

Cohn MJ. (2011). Development of the external genitalia: conserved and divergent mechanisms of appendage patterning. Dev. Dyn. , 240, 1108-15. PMID: 21465625 DOI.

Nakhuda GS. (2008). The role of mullerian inhibiting substance in female reproduction. Curr. Opin. Obstet. Gynecol. , 20, 257-64. PMID: 18460940 DOI.


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Genital System Terms (expand to view) 
Note there are additional glossaries associated with spermatozoa, oocyte renal.
  • androgens - male sex hormones, such as testosterone, or the more potent dihydrotestosterone (DHT, 5α-dihydrotestosterone, androstanolone, 5α-androstan-17β-ol-3-one), formed by the enzyme 5α-reductase. Dihydrotestosterone).
  • androgen insensitivity syndrome - (AIS) Clinical term for a developmental abnormality affecting genital development, through a fetal tissue insensitivity to male hormones.
  • anogenital distance - (AGD) A clinical measure of a parameter sexually dimorphic for genital development. This distance, from the posterior aspect of the scrotum to the anal verge, has been used as a marker for endocrine disruption in animal studies and may be shorter in infant males with genital anomalies. Recently been shown that infertile men possessed significantly shorter mean AGD.
  • anorchia - (embryonic testicular regression, vanishing testis syndrome) Clinical term for the absence of testes in a 46,XY individual with a male phenotype. Rare abnormality with an incidence of about 1 in 20,000 male births, and occurs more frequently with cryptorchidism (1 in 177 cases).
  • Anti-Mullerian Hormone (AMH, Müllerian Inhibiting Substance, MIS, Müllerian Inhibiting Factor, MIF) A secreted glycoprotein factor (transforming growth factor-beta, TGF-beta superfamily) that regulates gonadal and genital tract development. In the male embryo, the Sertoli cell secrete AMH and inhibit paramesonephric (Mullerian) duct development. In postnatal males, AMH increases during the first month, reaching peak level at 6 months of age, and then slowly declines during childhood falling to low levels in puberty. In reproductive age women, AMH is produced in the ovary by the granulosa cells surrounding preantral and small antral follicles and serum levels may reflect the remaining follicle cohort and decrease with age. AMH | TGF-beta | OMIM - AMH
  • ascending testis — (Undescended testis, cryptorchidism) postnatal male genital abnormality where a previously descended testis no longer lies within the scrotum. Peak incidence occurs around 10 years of age (affects 1-2%) and may also occur as a complication of inguinal hernia surgery in children.
  • Bardet-Biedl syndrome - (BBS) is an abnormality with triallelic inheritance and is characterized by a rangne of multisystem abnormalities (cone-rod dystrophy, truncal obesity, postaxial polydactyly, cognitive impairment, neural development, male hypogonadotrophic hypogonadism, complex female genitourinary malformations, and renal dysfunction).
  • Bartholin gland - (greater vestibular gland) A pair of female external genital tract glands which secretes mucus to lubricate the vagina. The equivalent male gland is the Bulbourethral gland or Cowper's gland.
  • Template:Bicornuate uterus - ("heart-shaped" uterus) Female uterus (internal genital tract) abnormality, where the paramesonephric ducts (Müllerian ducts) fail to completely fuse forming two separate body parts that fuse close to the opening into the vagina.
  • broad ligament - Human female genital tract mesentery formed by a double fold of peritoneum that connects the uterus to the peritoneal floor and walls. Anatomically it has three parts: mesometrium (surrounding the uterus), mesosalpinx (surrounding the uterine tube) and mesovarium (surrounding the ovary).
  • bulbourethral gland - (Cowper's gland) A male genital tract gland which secretes a small amount of a thick clear mucous fluid prior to ejaculation, the alkaline content apparently buffers acidity of the urethra. The equivalent female genital tract gland is the greater vestibular gland or Bartholin gland.
  • chordee - abnormality of bending of the penis that may involve soft-tissue tethering. The second most common (8.6%) congenital penile anomaly and can be found associated with hypospadia.
  • cloaca - (cloacal cavity) The term describing the common cavity into which the intestinal, genital, and urinary tracts open in vertebrates. Located at the caudal end of the embryo it is located on the surface by the cloacal membrane. In many species this common cavity is later divided into a ventral urogenital region (urogenital sinus) and a dorsal gastrointestinal (rectal) region.
  • cloacal membrane - Forms the external lower membrane limit (caudal end) of the early gastrointestinal tract (GIT). This membrane is formed during gastrulation by ectoderm and endoderm without a middle (intervening) layer of mesoderm. The membrane breaks down to form the initial "anal opening" of the gastrointestinal tract. The upper end of the gastrointestinal tract has a similar embryonic membrane, the buccopharyngeal membrane.
  • clomiphene citrate - (CC) A fertility drug taken orally to promote the process of follicle/egg maturation in superovulation therapy. (CC) an anti-estrogen (MRL-41) therapy for WHO group II (eu-oestrogenic) infertility associated with polycystic ovary syndrome. Used for more than 40 years it is a simple, cheap treatment, with low side effects and yields a 25% live birth rate. Alternative therapeutics being considered are metformin, aromatase inhibitors and low-dose FSH.
  • congenital adrenal hyperplasia - (CAH, adrenal virilism) Abnormality of the fetal adrenal cortex, alters cortisol and androgens with different effects dependent upon sex: in females masculization of the external genitalia; in males, disorder often unnoticed until postnatally. In both sexes, accelerated skeletal growth and sexual maturation is seen in late childhood. Caused by a deficiency or absence of the enzyme 21-hydroxylase in the adrenal cortex. Grouped with the Disorders of Sex Development (DSD) and classified by Prader stages. (More? congenital adrenal hyperplasia | adrenal | genital abnormalities)
  • 'Cowper's gland - (bulbourethral gland) A male genital tract gland which secretes a small amount of a thick clear mucous fluid prior to ejaculation, the alkaline content apparently buffers acidity of the urethra. The equivalent female genital tract gland is the greater vestibular gland or Bartholin gland.
  • cryptorchid testes - (cryptorchidism) A male genital abnormality where the testes remain undescended in the abdominopelvic cavity or other non-scrotal locations. (More? cryptorchidism | Male)
  • DAX1 - (NR0B1) Original gene acronym for "D"osage sensitive sex reversal (DSS), "A"drenal hypoplasia congenita (AHC) critical region on the "X" chromosome, gene "1". Current gene name is Nuclear Receptor Subfamily 0, Group B, Member 1 (NR0B1), a nuclear hormone receptor involved in female ovary development. (More? HGNC | OMIM)
  • DAZL - Acronym for DAZ-like due to homology to DAZ (Deleted in AZoospermia), a gene on the long arm of the Y chromosome that is frequently deleted in infertile men with nonobstructive azoospermia. HGNC | OMIM)
  • delayed puberty - (Latin, pubertas = adulthood) An abnormal timing of puberty. Determined in boys by a lack of increase in testicular volume by the age of 14 years. In girls, no breast development by the age of 13.5 years and a lack of menstruation by the age of 16 years. There can also be a "pubertal arrest" where there is no progress in puberty over 2 year period.
  • DES - Acronym for Diethyl stilbestrol or diethylstilbetrol, a drug prescribed to women from 1938-1971 to prevent miscarriage in high-risk pregnancies. Acts as a potent estrogen (mimics natural hormone) and therefore a potential endocrine disruptor. Female fetus, increased risk abnormal reproductive tract and cancer. Male fetus, abnormal genitalia. Banned by USA FDA in 1979 as a teratogen, previously used as livestock growth promoter.
  • DHEA - (dehydroepiandrosterone, androstenolone) precursor of sex steroid hormones and is converted to testosterone and estradiol. Postnatally, an abundant circulating steroid produced in the adrenal gland. The fetal adrenal cortex produces dehydroepiandrosterone sulfate (DHEA-S) used by the placenta to produce estrogens. DHEA, androstenedione, and testosterone can be metabolized to epiandrosterone, and etiocholanolone. PMID 15635500
  • dihydrotestosterone - (DHT) The hormonally active form of testosterone (male sex hormone) produced by enzyme (5-alpha reductase) conversion. In the male embryo, this can occur in the genital skin which then supports external genital development. In the adult, this conversion occurs in a number of different tissues. A known treatment for prostate cancer include 5-alpha reductase inhibitors.
  • Disorder of Sex Development - (DSD) A new terminology to describe disorders of sex development. The previous human sex development terminology (intersex, true hermaphrodites, male pseudohermaphrodites and female pseudohermaphrodites) are considered outdated and stigmatising and have been replaced with this general term "Disorders of Sex Development" (DSD) established by the Consensus statement on management of intersex disorders. International Consensus Conference on Intersex. International Consensus Conference on Intersex organized by the Lawson Wilkins Pediatric Endocrine Society and the European Society for Paediatric Endocrinology. (More? PMID 16882788)
  • ductuli efferentes - In the testis (male gonad) series of tubular structures which arise from the rete testis and conduct spermatazoa into the ductus epididymidis. Their columnar epithelium lining consisting of both absorptive and ciliated cells (giving rise to "cogwheel appearance) which removes much of the fluid associated with the spermatazoa leaving the testes (also by the upper epididymis) thereby increasing the spermatazoa concentration. (More? testis)
  • ductus deferens - (vas deferens, Latin, deferens = carrying-away vessel) The excretory duct of the testis that is the continuation of the canal of the epididymis. Develops from the mesonephric duct. Anatomically beginning at the lower part of the tail of the epididymis it is at first very tortuous, but gradually becoming less twisted it ascends along the posterior border of the testis and medial side of the epididymis, and, as a constituent of the spermatic cord, traverses the inguinal canal to the abdominal inguinal ring. (More? ductus deferens | testis)
  • ductus epididymidis - (epididymidis) male testes tubular structure which arise from the ductuli efferentes and conduct spermatazoa into the ductus deferens (vas deferens). The long duct is lined by a tall pseudostratified columnar epithelium. (More? testis)
  • ectopic testis — (Undescended testis, cryptorchidism) male genital abnormality the testis is clinically palpated in a location outside the normal path of descent, such as the perineum or femoral area.
  • epispadias - Uncommon abnormality associated with the penis, 1 in 30,000 infant males, external urethral opening on the dorsal surface of penis.
  • epoophoron - (rete ovarii, broad ligament cyst) A group of epithelial tubules that can be located in the mesosalpinx possibly mesonephric duct in origin. Occurs when a segment of the mesonephric duct remains in the female, associated with either the ovary and broad ligament. This "male remnant" will appear as a cyst (broad ligament cyst, adnexal papillary cystadenoma of probable mesonephric origin, APMO) with an appearance that differs depending upon the state of differentiation when the original abnormality occurred.
  • estrogens - (oestrogens) Sex hormones found in both male and female. In the female, this hormone is produced by the ovaries and is responsible for development of secondary feminine sex characteristics. Together with progesterone these hormones also regulate changes that occur each menstrual cycle. In the male, Leydig cells produce estrogen into the rete testis fluid at variable levels in different species. During female development the fetal adrenal gland synthesises DHEA, an oestrogen precursor, converted by the placenta into estrogen (estradiol). During male embryonic development exposure to high levels of estrogen can lead to genital abnormalities.
  • follicle stimulating hormone - (FSH, gonadotropin) A glycoprotein hormone secreted by anterior pituitary (adenohypophysis gonadotrophs, a subgroup of basophilic cells) and acts on gametogenesis and other systems in both males and females. In females, FSH acts on the ovary to stimulate follicle development. Negative feedback by inhibin from the developing follicle decreases FSH secretion. In males, acts on the testis Sertoli cells to increase androgen-binding protein (ABP) that binds androgens and has a role in spermatogenesis.
  • Fraser syndrome - (cryptophthalmos-syndactyly syndrome) An autosomal recessive congenital malformation syndrome characterized by cryptophthalmos, syndactyly, and urogenital defects (bicornuate uterus, imperforate anus, anal stenosis or renal malformations).
  • Gartner's duct - A female developmental abnormality caused by the persistance of the mesonephric duct (normally lost in females) when the ureteric bud fails to separate from the mesonephric duct and can generate a broad ligament cyst or vaginal cyst. Named after Hermann Treschow Gartner (1785-1827) a Danish surgeon and anatomist.
  • genitalia - Latin, genitalis = “of or belonging to generation”)) The term used to describe either the external or internal male and female sexual and reproductive organs.
  • genital ridge - (gonadal ridge) The thickened epithelial/mesenchymal region adjacent and medial too the mesonephros. Primordial sex cells migrate into this region to form the indifferent gonad. These undifferentiated gonads have a cortex and a medulla. Female XX chromosome complex, cortex differentiates into an ovary, and medulla regresses. Male XY complex, medulla differentiates into a testis and cortex regresses.
  • genital tubercle - (GT) A prominence or rounded protuberance extending ventrally at the inferior end of the body of the embryo. It has initially a sexually indifferent external genitalia structure and contributes to either male (glans penis) and female (clitoris) external genitalia. The endodermally derived urethral epithelium lies within the genital tubercle and functions as an organizer by expression of sonic hedgehog (Shh). This signaling is required for initial genital tubercle formation and for ectoderm induction for urethral tube closure.
  • germ cell - (primordial germ cell, gonocyte) Term used to describe the embryonic population of cells that will form either the spermatozoa (sperm) progenitor in the embryonic testes or oocyte (egg) progenitor present in the primordial follicle ovary from birth, located in the stroma of the ovary cortex beneath the tunica albuginea. In humans, these cells initially migrate during week 5-6 into the genital ridge which will later form the gonad.
  • gonadotropin - (Greek, gonos = seed; gonadotrophin, Gn) Three separate endocrine factors form the gonadotropins. Two from the anterior pituitary, luteinizing hormone (LH) and follicle stimulating hormone (FSH). The third produced by the implanting conceptus trophoblast cells and the corpus leutum in primates chorionic gonadotropin (CG), the human form is human chorionic gonadotropin (hCG). Both luteinizing hormone and follicle stimulating hormone are stimulated for release by the hypothalamus gonadotropin releasing hormone.
  • greater vestibular gland (Bartholin gland) A pair of female external genital tract glands which secretes mucus to lubricate the vagina. The equivalent male gland is the Bulbourethral Gland or Cowper's Gland.
  • gubernaculum - A mesenchymal structure occurring associated with gonad development and involved in testes descent. Two factors, insulin-like peptide hormone 3 (INSL3) and androgen, have been shown to be involved with gubernaculum development. Insulin-like peptide 3 (INSL3) hormone receptor is RXFP20.
  • Mayer-Rokitansky syndrome - (MRK anomaly, Rokitansky-Küster-Hauser syndrome, RKH syndrome, RKH) congenital absence of the vagina, dyspareunia, vaginal agenesis.
  • Müllerian inhibiting substance - (MIS, anti-Müllerian hormone, AMH) A secreted glycoprotein factor (transforming growth factor-beta, TGF-beta superfamily) that regulates gonadal and genital tract development. In the male embryo, the Sertoli cell secrete AMH and inhibit paramesonephric (Müllerian) duct development. In postnatal males, AMH increases during the first month, reaching peak level at 6 months of age, and then slowly declines during childhood falling to low levels in puberty. In reproductive age women, AMH is produced in the ovary by the granulosa cells surrounding preantral and small antral follicles and serum levels may reflect the remaining follicle cohort and decrease with age.
  • Ohno's law - A genetic evolutionary theory that suggests that the mammalian X chromosomes are conserved among species. Named after Susumu Ohno 大野 乾 (1928 – 2000) a Japanese-American geneticist and evolutionary biologist.
  • perineal body - (central tendon of perineum) anatomical connection between muscles of the pelvic floor. In males, it is found between the bulb of penis and the anus. In females, provides support of the lower part of the vagina and the function of the anal canal.
  • Prader stages - (Prader scale) Clinical term used to describe the congenital adrenal hyperplasia (CAH) virilization of female genitalia. Two normal (Stage 0 – Normal female genitalia; Stage 6 – Normal male genitalia) and five distinct abnormal stages (1 to 5 increasing virilisation).
  • prepuce - external genital term describing in the male the penis foreskin, in the female the fold of skin surrounding the clitoris.
  • primordial germ cell - (germ cell, gonocyte) Term used to describe the embryonic population of cells that will form either the spermatozoa (sperm) progenitor in the embryonic testes or oocyte (egg) progenitor present in the primordial follicle ovary from birth, located in the stroma of the ovary cortex beneath the tunica albuginea. In humans, these cells initially migrate during week 5-6 into the genital ridge which will later form the gonad.
  • hermaphrodite - (Disorder of Sex Development, DSD) This historic terminology is no longer applied to abnormal sexual development and has been replaced with the term (Disorder of Sex Development (DSD). Humans having both male and female reproductive organs, occurs in both male and female forms and mixed ovotesticular DSD.
  • hydrocele - (Greek, hydro = water, coele/koilia = cavity) a fluid-filled cavity of either testis or spermatic cord, where peritoneal fluid passes into a patent processus vaginalis.
  • hydrocolpos - Clinical condition caused by accumulation of fluid in the vagina due to developmental obstruction by either an imperforate hymen or a transverse vaginal septum. Associated complications include: multiple urinary tract infections, hydrocolpos infection, sepsis, failure to thrive, ruptured hydrocolpos, and development of hydronephrosis in previously normal kidneys.
  • hydrosalpinx - (Greek, hydro = water + salpinx = trumpet) Accumulation of interstitial fluid (edematous) in either one or both blocked uterine tubes or fallopian tubes due to a previous tubal infection. (Salpinx refers to the trumpet shape of the uterine tube. This blockage can impact upon maternal fertility and may require in vitro fertilization (IVF) techniques for reproduction.
  • hypospadias - A male external genital abnormality resulting from a failure of male urogenital folds to fuse in various regions and are therefore classified by the location of the opening meatus). This is the most common penis abnormality (1 in 300) and one of the highest in the list of frequently reported birth defects. (More? hypospadias)
  • infundibulum - The uterus funnel-shaped initial segment of uterine tube (oviduct or Fallopian tube) opening into peritoneal cavity and connected to the ampulla. The peritoneal opening sitting over the ovary.
  • inguinal canal - The anatomical pathway for male testes descent from the abdominal cavity (fetal) into the scrotum.
  • interstitial cell - (Leydig cell) Male gonad (testis) cell that secrete the androgen testosterone, beginning in the fetus. Required for internal and external male genital development.
  • Leydig cell - (interstitial cell) Male gonad (testis) cell that secrete the androgen testosterone, beginning in the fetus. These cells are named after Franz von Leydig (1821 - 1908) a German scientist who histologically described these cells.
  • ligamentum teres - (ligamentum teres uteri, Hunter's ligament) The round ligament of uterus which maintains the ventral uterine position.
  • luteinizing hormone - (LH, gonadotropin, lutropin, Interstitial Cell Stimulating Hormone, ICSH) Glycoprotein hormone releasd from anterior pituitary hormone that acts on the gonad and has a role in male and female reproduction. In female, increase in concentration during the menstrual cycle triggers ovulation (release of the oocyte). In male, stimulates testis interstital cell (Leydig cell) production of testosterone. Gonadotrophins have been used clinically in humans for the treatment of female infertility.
  • Mayer-Rokitansky-Kuster-Hauser syndrome - (MRKH) Abnormality of development of the female genital tract: partial or complete absence (agenesis) of the uterus; absent or hypoplastic vagina; normal fallopian tubes, ovaries, normal external genitalia and normal female chromosome pattern (46, XX). Has an incidence of approximately 1 in 4500 newborn girls and has been associated with a microdeletion at 17q12.
  • mediastinum testis - (Latin, medialis = middle) A single conical mass of connective tissue within the testis (male gonad) which extends from the tunica albuginea (cortical thick capsule surrounding the testis) into the seminiferous tubule region (medullary). Embedded within this connective tissue are the rete testis component of the duct conduction system for spermatozoa.
  • mesonephric duct - (Wollfian duct) An early developing urogenital paired duct system that initially runs the length of the embryo, that will differentiate and form the male reproductive duct system (ductus deferens). In females, this duct degenerates occasionally some remnants may remain associated in broad ligament.
  • mesorchium - A peritoneal fold attaching the testes to the mesonephros during development.
  • mesovarium - The mesentry of the ovary formed from a fold of the broad ligament that attaches the ovary through this structure pass the vessels and nerves to the ovary, entering at the hilus of the ovary.
  • Müllerian duct - (paramesonephric duct) An embryonic paired duct system that will form the epithelial lining of female reproductive organs: utererine tube, uterus, upper vaginal canal. This duct system degenerate in male gonadal development. Named after Johannes Peter Müller (1801-1858) a German scientist.
  • orchidometer - (orchiometer) A clinical instrument used to measure postnatal testis volume using 12 beads ranging from 1 to 25 millilitres.
  • ovarian reserve - (ovarian reserve markers) Clinical term describing the ability for follicular development in ovaries in response to gonadotropins. This reserve value is relevant for fertility and in vitro fertilization treatments and a number of different ovarian reserve serum and ovarian markers have been identified: baseline follicle stimulating hormone (FSH) levels, baseline anti-Müllerian hormone (AMH) levels, and antral follicle count (AFC). In addition, with reproductive aging there is seen both a quantitative and a qualitative reduction of the primordial follicle pool available.
  • ovary - The two female gonads where female germ cells (oocytes, eggs) are generated and also the source of estrogen and progesterone the female hormones regulating secondary sex characteristics and menstrual cycle uterine changes. The ovary is embryonically formed from primordial germ cells entering region of the paired mesonephric ducts (Wolffian ducts) which are lost in females.
  • oviduct - (uterine horn, fallopian tube, oviduct, salpinx) see uterine tube. A pair of tubular structures designed to transport the oocyte (egg) from the ovary to the uterus body.
  • paramesonephric duct - (Müllerian duct) (Greek, para = "beside") The paired ducts that lie beside the mesonephric ducts, that will differentiate in the female embryo to form the female internal genital tract (uterine tubes, uterus, upper vaginal canal). Paramesonephric duct differentiation in females requires Wnt (WNT7a, WNT5a) signaling through the intracellular β-catenin pathway.
  • para-urethral gland - (Skene gland, Skene's gland, lesser vestibular glands, female prostate gland) Female genital glands on the anterior wall of the vagina and around the lower end of the urethra. Named in 1880 after Alexander Johnston Chalmers Skene (1838-1900) an American gynaecologist.
  • raphe - Anatomical line of fusion of the urogenital folds lying along the urethra and scrotum in male external genitalia.
  • rectouterine pouch - (Pouch of Douglas or rectovaginal) Anatomical description of the female peritoneal cavity lying between the back wall of the uterus and rectum.
  • rete testis - (Latin, rete = "net", refers to a network) The duct (epithelial tubules) conduction system for spermatazoa embedded within the mediastinum (connective tissue) located in the center of the testis (male gonad) derived from the mesonephric duct, and allow spermatazoa to travel from the seminiferous tubules to the vasa efferentia.
  • scrotoplasty - (oscheoplasty) Clinical surgical term for the repair or plastic surgery of the scrotum. This procedure is often associated with the repair of hypospadia.
  • seminiferous tubule - (spermatogenic epithelium) Male genital testis structure where spermatozoa develop within the wall. Consists of outer smooth muscle layer, spermatogonia, sertoli cells and maturing spermatozoa.
  • sertoli cell - The supporting cells in the testes (male gonad) that induce primordial germ cells to commit to sperm development. Support is nutritional and mechanical, as well as forming a blood-testis barrier. In development, these cells secrete anti-Mullerian hormone (AMH), which causes the Mullerian duct (paramesonephric duct) to regress, and help to induce other somatic cells to differentiate into Leydig cells.
  • sex chromosome - Term used to describe both the male Y chromosome and the female X chromosome. All other chromosomes that are not the sex chromosomes in the genome are described as autosomes. These terms are also used in describing the location or inheritance of genes and/or genetic disorders.
  • sinovaginal bulbs - The caudal ends of the paired mesonephric ducts (Wolffian ducts) thought to be involved in vaginal development, they are under negative control by androgens.
  • spermatogenesis - (Greek, genesis = origin, creation, generation) The term used to describe the process of diploid spermatagonia division and differentiation to form haploid spermatozoa within the testis (male gonad). The process includes the following cellular changes: meiosis, reoorganization of DNA, reduction in DNA content, reorganization of cellular organelles, morphological changes (cell shape). The process following meiosis is the change in cell shape and organization, called spermiogenesis.
  • spermatogenic epithelium - Term used to describe the wall of the seminiferous tubule consisting of spermatogonia, developing spermatozoa stages and sertoli cells.
  • spermatogonia - (spermatogonial stem cell) These cells form in the embryo from the primordial germ cell and are located in the seminiferous tubule adjacent to the basal membrane. The cells can either divide and separate to renew the stem cell population, or they divide and stay together as a pair (Apr spermatogonia) connected by an intercellular cytoplasmic bridge to begin to differentiate and eventually form spermatozoa.
  • spermatozoa - (spermatozoon, singular term) The male haploid gamete cell produced by meiosis in the testis (male gonad) seminiferous tubule. In humans, produced from puberty onwards and develop from the diploid stem cell the spermatogonia. The developmental meiosis is called spermatogenesis and the final morphologiccal (shape) change is called spermeiogenesis. The mature human spermatozoon formed from the spermatid has a head, neck and tail and is about 60 µm long. At ejaculation these cells undergo capacitation (activation) and become motile.
  • testis - (Latin testis = "witness", plural testes) Anatomically the male gonad where male germ cells (spermatozoa) are generated and also the source of testosterone (male hormone). Embryonically formed from primordial germ cells entering region of the paired mesonephric ducts (Wolffian ducts) which are preserved in male gonad development and lost in females.
  • testis cord - (sex cord) The embryonic precursor of the seminiferous tubule. These form embryonically initially as a complex series of parallel transverse loops separated by interstitial cells. During fetal development these cords elongate and expand leading to the convoluted structure of the seminiferous epithelium.
  • testis-determining factor - (TDF, Sry, Testis-Determining Factor on Y, TDY ) Protein name for the protein transcription factor product of the Sry gene on the Y chromosome responsible for maleness. This protein is a member of the high mobility group (HMG)-box family of DNA binding proteins. See also the transcription factor SRY-related protein, SOX9 (SRY-related high-mobility group (HMG) box 9)
  • testosterone - A steroidal hormone secreted by the gonad (testis and ovary) and in males is the androgen which regulates genital (gonadal and tract), secondary sex characteristics and neural development. The steroid is converted to the active metabolite dihydrotestosterone (DHT) by the enzyme 5-alpha reductase for the genital effects and estradiol by the enzyme aromatase for the neural effects.
  • true undescended testis — (Undescended testis, cryptorchidism) male genital abnormality the testis lies along the expected path of descent but has never been present in the scrotum.
  • tubal factor - A structural or functional damage of one or both fallopian tubes that reduces fertility, described as tubal factor infertility (TFI).
  • tunica albuginea - A dense mesenchymal connective tissue layer lying between germinal epithelium and cortical region of female ovary, or the equivilaent capsule of the male testis forming a thick fibrous capsule. Male forms the testicular septations and the mediastinal testis. Female lies under the surface epithelium of the ovary.
  • tunica vaginalis - The serous membrane pouch covering the testis formed from the saccus vaginalis of the peritoneum.
  • unicornuate uterus - An abnormality of uterine development where the paramesonephric ducts (Mullerian ducts) fail to fuse. A single paramesonephric duct can fuse with the vaginal plate and will opens into the vagina, while the other duct forms a diverticulum. There are a range of additional uterine abnormalities based upon the degree of initial duct fusion and regression. Uterus didelphys (double uterus) is a rare condition where the entire tract is separated.
  • urogenital fold - (urogenital ridges, urethral folds) The ventral portion of the original cloacal folds, which contribute to the formation of the urethral groove on the ventral aspect of the genital tubercle. In females, these folds remain separate. In males, these folds will later fuse, failure of complete fusion leads to the male genital abnormality hypospadia.
  • uteric bud - Renal (kidney) development term for paired lateral diverticulum epithelial tubes arising from each mesonephric duct near its cloacal connection. This branch from the mesonephric duct extends into the intermediate mesoderm (metanephric mesenchyme) inducing the surrounding this mesoderm (metanephric blastema) to differentiate. The uteric bud gives rise to the renal collecting ducts, calyces, pelvis and developing ureters.
  • uterine body - Anatomical term describing the region of the uterus above the uterine isthmus and below the opening of the uterine tubes.
  • uterine duplication - (uterus didelphys, double uterus, uterus didelphis, bicorporeal uterus) Rare uterine developmental abnormality where the paramesonephric ducts (Mullerian ducts) completely fail to fuse generating two separate uterus parts each connected to the cervix and having an ovary each. Failure of fusion of lower paramesonephric ducts, with either double or single vagina. ESHRE/ESGE classification of uterine anomalies - U3.
  • uterine isthmus - Anatomical term describing the region between the uterine body (corpus) and the cervix.
  • uterine gland - (endometrial gland) The simple tubular glands formed by invagination of the uterine endometrium (a columnar epithelium of ciliated cells and secretory cells). The glands extend into the underlying thick vascular stromal layer. The glands line the uterus body and change in appearance and secretion during the menstrual cycle. The glands secretions function to provide the initial nutritional support of the conceptus and may have a role in maintaining adhesion.
  • uterine tube - (uterine horn, oviduct, fallopian tube, salpinx) A pair of tubular structures that transport the oocyte (egg) from the ovary to the uterus body. They are located laterally on the upper uterus and consist medial to lateral of three main parts: isthmus (medial constricted third), ampulla (intermediate dilated portion) and infundibulum (containing the abdominal opening/ostium, surrounded by finger-like fimbriae). The tube has structurally several layers: a lining mucosa (mix of ciliated and secretory epithelium), a middle muscularis layer (inner circular muscle layer and an outer longitudinal layer) and outer serous layer (peritoneal).
  • uterus - The female internal genital (reproductive) tract forming a hollow muscular walled organ, embryonically derived from the paramesonephric ducts. The human uterus has two uterine tubes (fallopian tubes, oviducts) where the first week of development occurs and a single hollow body where implantation of the blastocyst normally occurs. Following puberty, the non-pregnant uterus (epithelium and underlying stroma) undergoes cyclic changes under the influence of hormones, the menstrual cycle. This cycle of uterine changes ceases during pregnancy. In pregnancy, the uterus contributes the maternal component of the placenta.
  • vagina - Part of female genitalia formed from the paramesonephric duct develops as a muscular tube between the uterus and vestibule.
  • vulva - (Latin, volva or vulva = "female genitals"; vulvar vestibule) Term used to describe the external genital organs (genitalia) of the female.
  • Wolffian duct - (mesonephric duct, preferred terminology), A developmental duct that runs from the mesonephros to cloaca. The duct in male differentiates to form the ductus deferens and in female the same structure regresses. Historically named after Caspar Friedrich Wolff (1733-1794), a German scientist and early embryology researcher and is said to have established the doctrine of germ layers.
  • X chromosome - The female sex chromosome, which following sexual reproduction is inherited from each parent in females, and inherited from the mother in males. This inheritence pattern impacts upon the pattern of genetic disease. In females, a single X chromosome is inactivated in each cell. X chromosome
  • X Inactivation - Process that occurs in all cells within females, each cell has 2 copies of the X chromosome (one from father and one from mother) one of copy of which is randomly inactivated throughout the entire body in order to maintain gene dosage. Recent studies have shown that this process starts in female human preimplantation-stage embryos, by accumulation of Xist RNA on one of the two X chromosomes starting around the 8-cell stage. X Inactivation
  • Y chromosome - The male sex chromosome which contains the sry gene producing Testis-Determining Factor required for male phenotype and can only be inherited from father. In humans the chromosome contains 200+ genes and consists of 50 million base pairs. Testis-Determining Factor (TDF; Testis-Determining Factor on Y, TDY ) is a protein transcription factor and a member of the high mobility group (HMG)-box family of DNA binding proteins. See also the transcription factor SRY-related protein, SOX9 (SRY-related high-mobility group (HMG) box 9). Y Chromosome
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