Testis Development

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Historic testis drawing

The male gonad is the testis (pl, testes).

The initial difference in male and female gonad development are dependent on testis-determining factor (TDF) the protein product of the Y chromosome SRY gene. Recent studies have indicated that additional factors may also be required for full differentiation. The seminiferous tubules are considered the parenchyma of the testis. Within the developing testis the three main differentiating cell types are: gamete forming cells (spermatogonia), support cells (Sertoli cells) and hormone secreting cells (Leydig or interstitial cells).

Postnatally in humans, at 2 months of age, primordial germ cells (gonocytes) are replaced by adult dark (Ad) and pale (Ap) spermatogonia that make up the spermatogonial stem cell (SSC) population that at puberty will commence differentiation into spermatozoa.

Testis - Seminiferous Tubule
Testis histology 006.jpg Testis histology 011.jpg
pre-puberty post-puberty
Genital Links: Introduction | Lecture - Medicine | Lecture - Science | Medicine - Practical | Primordial Germ Cell | Meiosis | Female | Ovary | Oocyte | Uterus | Vagina | Reproductive Cycles | Menstrual Cycle | Male | Testis | Spermatozoa | Penis | Prostate | Genital Movies | Abnormalities | Assisted Reproductive Technology | Puberty | Category:Genital
Historic Embryology - Genital 
1902 The Uro-Genital System | 1912 Urinogenital Organ Development | 1915 Cowper’s and Bartholin’s Glands | 1921 Urogenital Development | 1921 External Genital Development | 1927 Female Foetus 15 cm | 1932| Postnatal Ovary | 1935 Prepuce | 1935 Wolffian Duct | 1942 Sex Cords | 1943 Testes Descent | Historic Disclaimer

Some Recent Findings

Gadd45g and Sex Determination Model[1]
  • Sertoli Cell Wt1 Regulates Peritubular Myoid Cell and Fetal Leydig Cell Differentiation during Fetal Testis Development[2] "Sertoli cells play a significant role in regulating fetal testis compartmentalization to generate testis cords and interstitium during development. The Sertoli cell Wilms' tumor 1 (Wt1) gene, which encodes ~24 zinc finger-containing transcription factors, is known to play a crucial role in fetal testis cord assembly and maintenance. ... In summary, Wt1 regulates the development of FLC and interstitial progenitor cell lineages through Notch signaling, and it also plays a role in PMC development. Collectively, these effects confer fetal testis compartmentalization. See also - Sertoli cells control peritubular myoid cell fate and support adult Leydig cell development in the prepubertal testis PMID 24803659
  • R-spondin 1/dickkopf-1/beta-catenin machinery is involved in testicular embryonic angiogenesis[3] "Testicular vasculogenesis is one of the key processes regulating male gonad morphogenesis. The knowledge of the molecular cues underlining this phenomenon is one of today's most challenging issues and could represent a major contribution toward a better understanding of the onset of testicular morphogenetic disorders. R-spondin 1 has been clearly established as a candidate for mammalian ovary determination. Conversely, very little information is available on the expression and role of R-spondin 1 during testicular morphogenesis. This study aims to clarify the distribution pattern of R-spondin 1 and other partners of its machinery during the entire period of testicular morphogenesis and to indicate the role of this system in testicular development. Our whole mount immunofluorescence results clearly demonstrate that R-spondin 1 is always detectable in the testicular coelomic partition, where testicular vasculature is organized, while Dickkopf-1 is never detectable in this area. Moreover, organ culture experiments of embryonic male UGRs demonstrated that Dickkopf-1 acted as an inhibitor of testis vasculature formation. Consistent with this observation, real-time PCR analyses demonstrated that DKK1 is able to slightly but significantly decrease the expression level of the endothelial marker Pecam1."
  • Gadd45g is essential for primary sex determination, male fertility and testis development[1] "In humans and most mammals, differentiation of the embryonic gonad into ovaries or testes is controlled by the Y-linked gene SRY. Here we show a role for the Gadd45g protein in this primary sex differentiation. ...The molecular cause of the sex reversal was the failure of Gadd45g(-/-) XY gonads to achieve the SRY expression threshold necessary for testes differentiation, resulting in ovary and Müllerian duct development. These results identify Gadd45g as a candidate gene for male infertility and 46,XY sex reversal in humans."
  • Prenatal testosterone and dihydrotestosterone exposure disrupts ovine testes development [4] "Androgens play important roles during the first trimester of intrauterine life, coinciding with genital tract differentiation, during virilization and maintenance of secondary male characteristics and during initiation of spermatogenesis. ... Findings from this study demonstrate that exposure to excess testosterone/5α-dihydrotestosterone (DHT) during male fetal sexual differentiation have differential effects on post-pubertal testicular size, seminiferous tubule size and function, sperm motility, and testosterone concentrations." Sheep Development
  • Oestrogen blocks the nuclear entry of SOX9 in the developing gonad of a marsupial mammal.[5] "We have uncovered a mechanism by which oestrogen can regulate gonadal development through the nucleocytoplasmic shuttling of SOX9. This may represent an underlying ancestral mechanism by which oestrogen promotes ovarian development in the gonads of nonmammalian vertebrates. Furthermore, oestrogen may retain this function in adult female mammals to maintain granulosa cell fate in the differentiated ovary by suppressing nuclear translocation of the SOX9 protein."
  • The evolutionary history of testicular externalization and the origin of the scrotum[6] "We mapped four character states reflecting the position of testes and presence of scrotum onto recent mammalian phylogeny. Our results are interpreted as follows: as to the presence of testicondy in Monotremata and most of Atlantogenata, which represent the basal group of all eutherians, we argue that primary testicondy represents a plesiomorphic condition for Eutheria as well as for all mammals. This is in opposition to the previous hypothesis of Werdelin and Nilsonne that the scrotum may have evolved before the origin of mammals and then repeatedly disappeared in many groups including monotremes. We suggest that the scrotum evolved at least twice during the evolutionary history of mammals, within Marsupialia and Boreoeutheria, and has subsequently been lost by many groups; this trend is especially strong in Laurasiatheria. We suggest that the recent diversity in testicular position within mammals is the result of multiple selection pressures stemming from the need to provide conditions suitable for sperm development and storage, or to protect the male gonads from excessive physical and physiological disturbance."
  • FGF signaling directs a center-to-pole expansion of tubulogenesis in mouse testis differentiation.[7] "These observations imply that center-to-pole FGF9 diffusion directs a poleward expansion of testiculogenic programs along the anteroposterior axis of developing XY gonads."
More recent papers  
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This table shows an automated computer PubMed search using the listed sub-heading term.

  • Therefore the list of references do not reflect any editorial selection of material based on content or relevance.
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Search term: Testis Embryology

Bora Altinkilic, Adrian Pilatz, Thorsten Diemer, Julia Wolf, Martin Bergmann, Sarah Schönbrunn, Uwe Ligges, Hans-Christian Schuppe, Wolfgang Weidner Prospective evaluation of scrotal ultrasound and intratesticular perfusion by color-coded duplex sonography (CCDS) in TESE patients with azoospermia. World J Urol: 2017; PubMed 28429094

Tengfei Liu, Lingling Wang, Hong Chen, Yufei Huang, Ping Yang, Nisar Ahmed, Taozhi Wang, Yi Liu, Qiusheng Chen Molecular and Cellular Mechanisms of Apoptosis during Dissociated Spermatogenesis. Front Physiol: 2017, 8;188 PubMed 28424629

Jose Bouzada, Teresa Vázquez, Manuel Duran, Vincent Delmas, Theresa Larkin, Miguel A Cuesta, Jose SañUDO New insights into the morphogenesis of the gubernaculum testis and the inguinal canal. Clin Anat: 2017; PubMed 28422355

Badreldin H Ali, Khalid A Al Balushi, Mohammed Ashique, Asem Shalaby, Mohammed A Al Kindi, Sirin A Adham, Turan Karaca, Sumaya Beegam, Priya Yuvaraju, Abderrahim Nemmar Chronic Water-Pipe Smoke Exposure Induces Injurious Effects to Reproductive System in Male Mice. Front Physiol: 2017, 8;158 PubMed 28420996

Li Ge, Li-Hua Wei, Chang-Qing Du, Guo-Hua Song, Ya-Zhuo Xue, Hao-Shen Shi, Ming Yang, Xin-Xin Yin, Run-Ting Li, Xue-Er Wang, Zhen Wang, Wen-Gang Song Hydrogen-rich saline attenuates spinal cord hemisection-induced testicular injury in rats. Oncotarget: 2017; PubMed 28404953


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 ‎‎Male External
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 ‎‎Testis Descent
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 ‎‎Gonad Vascular
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Links: Movies

Development Overview

Male urogenital development (stage 22)
Fetal gonad retinoid receptor expression[8]

Sex Determination

  • Humans (week 5-6)
  • Germ cells migrate into gonadal ridge
  • Gonads (male/female) identical at this stage, Indifferent

Gonad Development

  • dependent on sex chromosome
  • Y testes
  • No Y ovary


SRY protein (Testes determining factor, TDF) binds DNA Transcription factor, Bends DNA 70-80 degrees

Internal Genital Organs

  • All embryos form paired
  • Mesonephric duct, see kidney development
  • Paramesonephric duct, Humans 7th week Invagination of coelomic epithelium Cord grows and terminates on urogenital sinus
  • Male Gonad (testes) secretes Mullerian duct inhibitory factor (MDIF) which causes regression of paramesonephric duct
  • Male Gonad (testes) secretes Testosterone which retains mesonephric duct

External Genital Organs

  • All embryos initially same (indifferent)
  • Testosterone differentiates male

Week 8

Carnegie stage 22

Stage 22 image 302.jpg Stage 22 image 301.jpg

Developing testis is shown to the centre right. These images show the position, size and histological development of the testis in week 8 of human development (Carnegie stage 22, last embryonic week).

Human Stage 22: Testis - labeled overview | Testis - unlabeled overview | Testis - unlabeled detail | Testis - labeled detail | Testis Development | Carnegie stage 22 | Movie - Urogenital stage 22

Sertoli Cells

Adult Seminiferous tubule showing spermatozoa developmental stages
Adult Seminiferous tubule showing spermatozoa developmental stages
Gonadal supporting cell development
Gonadal supporting cell development

These cells provide support for spermatozoa development within the seminiferous tubule. In the mouse, these cells are derived from the coelomic epithelium along with other testis somatic cells.[9] Their differentiation is regulated by the presence of a Y chromosome and in turn regulates Leydig cell differentiation. Sertoli cells direct testis morphogenesis, organizing testis cord formation, establishing testis vasculature and inducing differentiation of peritubular myoid cells and fetal Leydig cells. At puberty the immature Sertoli cells cease to proliferate and differentiate.

Sertoli cell functions include:

  • regulation of spermatogenesis through endocrine FSH and testosterone
  • regulation of the intratubular and intercellular environment adluminal to the tight junctional complexes
    • meiotic and post-meiotic germ cells are sequestered by Sertoli-Sertoli junctional complexes
  • generate adluminal compartment isolated from both serum and lymph
  • attachment of germ cells through unique intermediate filament (desmosome-like junctions) and microfilament (actin- ectoplasmic specializations, ESs) junctions[10]
    • to prevent premature sloughing of immature germ cells from the seminiferous epithelium
    • desmosome-like junctions are initially present (up to step 8 spermatids)
    • ectoplasmic specializations then replace this junction (in step 8 spermatids)

(see also review[11])

Ultrastructural description of human Sertoli cells[12]

  • 7 weeks - first morphologically recognised in testicular cords, organised as primordial germ cells surrounded by pre-Sertoli cells.
  • 7 to 8 weeks - basal lamina of the cords becomes distinguishable, pre-Sertoli cells the rough endoplasmic reticulum develops.
  • 14 to 20 weeks - pre-Sertoli cells maintain their general morphology whereas the most significant change is the maximum development of Leydig cells.

Molecular factors:

  • Follicle Stimulating Hormone (FSH) -> Krüppel-like factor 4 (KLF4)
  • Krüppel-like factor 4 (KLF4) - zinc finger transcription factor, terminal differentiation of epithelial cells.
  • Epidermal Growth Factor (EGF)
  • Transforming Growth Factor-beta (TGFbeta)

Leydig Cells

Seminiferous tubule cross-section and supporting cells

Interstitial or Leydig cells, named after german zoologist Franz von Leydig (1821 - 1908) who first histologically described them in 1850.[13] Their initial development appears to be influenced by Sertoli cell differentiation.

These cells produce the male testicular androgens and have a role during life prenatally (fetal) and postnatally during puberty onward.

A recent study[14] has looked at the postnatal development of Lydia cells from stem cells:

  • early postnatal testis - interstitial compartment undifferentiated mesenchymal-like stem cells
  • adult testis - peritubular and perivascular locations quiescent stem cells (nestin, PDGFRα, COUP-TFII, CD51 and CD90)

Factors regulating division

  • proliferation - DHH (Desert hedgehog), FGF2, PDGFBB, activin and PDGFAA
  • suppression of proliferation - TGFβ, androgen and PKA signaling.

Fetal Leydig Cells

Have a hormonal role in male genitalia differentiation and are lost postnatally. These cells arise approximately at 6 weeks (human) and 12.5 dpc (mouse) and there appears to be differences in hormonal sensitivity between the species. Their initial differentiation requires both luteinizing hormone (LH) and adrenocorticotrophic hormone (ACTH) and therefore normal pituitary development.

Activin A - acts upon Sertoli cells to promote their embryonic proliferation[15]

(More? Endocrine - Pituitary Development)

Adult Leydig Cells

Have a hormonal role in puberty, secondary sex characteristics and sexual maturation. Their initial differentiation from peritubular mesenchymal cells does not require gonadotropin, but development and function are dependent upon luteinizing hormone (LH).

The cells differentiate with three discrete stages (newly formed, immature, mature) leading to a decrease in proliferation and increasing testosterone biosynthetic capacity. Insulin-like growth factor I (IGF-I) stimulates proliferation of immature cells and promotes their maturation. Testosterone and estrogen inhibit the process of precursor cell differentiation and may be responsible for the cessation of proliferation in the adult Leydig cells.

Leydig Cell Electron Micrographs
Leydig cell PMID13693345 EM02.jpg Leydig cell PMID13693345 EM03.jpg
Low power EM High power EM

EM images above from historic study of the opossum testis.[16]

Peritubular Myoid Cells

These cells surround the seminiferous tubules and express androgen receptors from fetal life through to adulthood.


Adult Epididymis Histology
Mouse postnatal epididymis development[17]

Both the ductus epididymis and ductus deferens differentiate from the mesonephric duct (Wollfian duct) elongation (cell proliferation). In the case of the epididymis, elongation also is associated with extensive coiling, the adult human epididymis about 6 metres in length (mouse 1m, rat 3m). Embryonic growth is regulated by androgens, members of the PCP pathway, and inhibin beta A. While postnatally androgens and other growth factors may have roles in final maturation. (see review[18]) The ductus epididymis is lined by a very tall pseudostratified columnar epithelium, consisting of principal cells with long stereo cilia.

Following puberty, the epididymis is involved in maturation of the spermatozoa released from the seminiferous tubules and their storage.

  • middle segment - site of final functional maturation of the spermatozoa.
  • terminal segment - site of storage of the mature spermatozoa.

Anatomically the adult epididymis consists of 3 regions:

  • body or central portion.
  • head (globus major) upper enlarged extremity.
  • tail (globus minor) lower pointed extremity, continuous with the ductus deferens (vas deferens).

The head is intimately connected with the upper end of the testis by means of the efferent ductules of the gland; the tail is connected with the lower end by cellular tissue, and a reflection of the tunica vaginalis (tunica vaginalis propria testis) the serous covering of the testis.

The lateral surface, head and tail of the epididymis are free and covered by the serous membrane; the body is also completely invested by it, excepting along its posterior border; while between the body and the testis is a pouch, named the sinus of the epididymis (digital fossa). The epididymis is connected to the back of the testis by a fold of the serous membrane.

Testis Descent

Testis descent is thought to have 2 phases:

  1. transabdominal descent - dependent on insulin-like hormone 3 (INSL3).
  2. inguinoscrotal descent - dependent on androgens.

The regulation of testis descent is still being investigated and several different factors have been identified that may have roles in descent. The first stage of testicular descent occurs 10–15 weeks of gestation with the testes moving to the inguinal region.

The gubernaculum (gubernaculum Hunteri) is the caudal inguinoscrotal ligament that connects the testis to the lower abdomen. The cranial suspensory ligament (mesonephric ligament) is the cranial ligament that connects the tesitis to the posterior abdominal wall.

  • Insulin-like factor 3 (INSL3, relaxin-like factor) from fetal leydig cells acting through its receptor (Rxfp2) and BMP and WNT signaling pathways to promote testis descent.
  • Calcitonin gene-related peptide (CGRP) from genitofemoral nerve suggested to mediate the inguinoscrotal testicular descent.
  • Epidermal growth factor (EGF) may promote by activating the androgen responsive systems.

Testis-descent start.jpg Testis-descent end.jpg
Testis 001 icon.jpg
 ‎‎Testis Descent
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Before Descent End of Descent Testis Descent Movie

Links: OMIM - INSL3


Newborn - cryptorchidism normal birthweight[19]

The external location of the testes in the scrotum acts as a local thermo-regulator and provides a temperature environment below that of the general body temperature.[20] This thermal function is essential for normal spermatogenesis and cryptorchidism therefore affects fertility.

  • abnormality of either unilateral or bilateral testicular descent, occurring in up to 30% premature and 3-4% term males.
  • Descent may complete postnatally in the first year, failure to descend can result in sterility.

Testis descent is thought to have 2 phases:

  1. transabdominal descent - dependent on insulin-like hormone 3 (INSL3).
  2. inguinoscrotal descent - dependent on androgens.

Management of cryptorchidism in children: guidelines.[21] "Cryptorchidism is best diagnosed clinically, and treated by surgical orchiopexy at age 6-12 months, without a routine biopsy. If no testis is palpable, or if other signs of hypovirilisation such as hypospadias are present, the chromosomal sex and hormonal status must be assessed. Laparoscopy is the best way of diagnosing and managing intra-abdominal testes."


Clinical term for (embryonic testicular regression, vanishing testis syndrome) 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).

A recent study has identified undetectable plasma concentrations of anti-Müllerian hormone (AMH) and inhibin B and an elevated plasma FSH, together with 46,XY complement are sufficient for diagnosis of anorchia. Genetic analysis showed that NR5A1 and other genes (INSL3, SRY, LGR8 , MAMLD1) implicated in gonadal development and testicle descent were also not mutated.[22]


Male testosterone and AMH level graph.jpg

Human Male Testosterone and Anti-Müllerian Hormone (AMH) relative levels[23]

  • AMH production by Sertoli cells .
  • Testosterone production by Leydig cells.

In humans at puberty, hormonal and morphological changes occur within the gonad and other systems (secondary sex characteristics). Within the testis the immature Sertoli cells cease to proliferate and differentiate. Spermatogonium proliferate and spermatogenesis begins, and it takes about 70 days for cells to mature from the diploid spermatogonium to a primary spermatocyte. This maturation occurs in waves along the seminiferous tubules.

Links: Puberty Development

Blood-Testis Barrier

Within the testis seminiferous tubules the Sertoli cells located near the basement membrane act as an initial cellular barrier with many functions, but often described as forming a "blood-testis barrier". (see review[24]


  • prevent substances reaching the developing spermatozoa (through drug transporters)
  • establish a basal and adluminal (apical) compartment (specialized microenvironment)
  • provide an immunological privilege status of the testis (anti-sperm antibodies are not developed)


Testis Histology Links: Testis Development | Spermatozoa Development | Histology

Human (young): overview labeled | overview unlabeled | convoluted seminiferous tubules x10 | x40 | x40 | tunica albuginea x20
Human (adult): overview x2 | convoluted seminiferous tubules labeled | x10 | x20 | x40 | x40 | epididymis ductulus efferens | ductus epididymidis | epithelium | overview x4 | x10 | x20 | x40 | ductus deferens labeled overview | epithelium | overview x2 | x10 | x40
Human spermatozoa: x20 | x40 | x100
Human Stage 22: Testis - labeled overview | Testis - unlabeled overview | Testis - unlabeled detail | Testis - labeled detail | Testis Development | Carnegie stage 22 | Movie - Urogenital stage 22
Rabbit: convoluted seminiferous tubules x20 | x100
Mouse: postnatal epididymis | 14 days postnatal | 33 days postnatal | 45 days postnatal | 2 months postnatal
Spermatozoa Development (expand to see terms)  

Spermatozoa Development

  • acrosome - Cap-shaped cellular structure formed from the golgi apparatus and contains enzymes to dissolve the oocyte (egg) zona pellucida for fertilisation.
  • acrosome compaction - Acrosome reshaping process in final stages of spermatogenesis (spermatid to spermatozoa).
  • acrosome reaction - Chemical change within the spermatozoa following binding to the zona pellucida, only acrosome reacted spermatozoa have an ability to fuse with oocytes.
  • annulus - Cytoskeletal (septin) structure located between the midpiece and principal piece regions of the tail, thought to form a diffusion barrier between these two domains. PMID 20042538
  • asthenozoospermia - (asthenospermia) Term for reduced sperm motility and can be the cause of male infertility.
  • axoneme - (axonema) The basic structure in cilia and eukaryotic flagella and in the spermatozoa tail, consisting of parallel microtubules in a characteristic "9 + 2" pattern. This pattern describes 9 outer microtubule doublets (pairs) surrounding 2 central singlet microtubules, in humans 50 μm long. The motor protein dynenin move the outer microtubules with respect to the central pair, bending the cilia and generating motility. Note that prokaryotic bacteria have a similar process (flagellum) that uses an entirely different mechanism for motility.
  • blood-testis barrier - (BTB) Formed by tight junctions, basal ectoplasmic specializations, desmosome-like junctions and gap junctions between adjacent Sertoli cells near the basement membrane of the seminiferous epithelium.
  • capacitation - term describing the process by which spermaozoa become capable of fertilizing an oocyte, requires membrane changes, removal of surface glycoproteins and increased motility.
  • CatSper - cationic (Ca2+) channel of spermatozoa, progesterone activated involved in hyperactivation, acrosome reaction, and possibly chemotaxis.
  • centriole - a microtubule organising centre. First required for axoneme formation (distal centriole) that is lost and a second for pronuclei formation (proximal) following fertilisation. Rodents loose both and only have maternal centrioles.
  • connecting piece - linkage between the spermatozoa head and the midpiece of the tail. PMID 22767409
  • cytoplasmic bridges - Transient cytoplasm connections between spermatids arising from one spermatogonium due to incomplete cytokinesis.
  • diploid - (Greek, di = double + ploion = vessel) Having two sets of chromosomes, the normal state for all cells other than the gametes.
  • end piece - Last portion of the spermatozoa tail region.
  • fibrous sheath - cytoskeletal structure surrounding the axoneme and outer dense fibers, defining the extent of the principal piece region.
  • haploid - (Greek, haploos = single) Having a single set of chromosomes as in mature germ/sex cells (oocyte, spermatozoa) following reductive cell division by meiosis. Normally cells are diploid, containing 2 sets of chromosomes.
  • Leydig cell - (interstitial cell) Male gonad (testis) cell which 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.
  • meiosis - The cell division that occurs only in production of germ cells where there is a reduction in the number of chromosomes (diploid to haploid) which is the basis of sexual reproduction. All other non-germ cells in the body divide by mitosis.
  • midpiece - (middle piece) spermatozoa tail initial segment of axoneme surrounded outer dense fibres then by mitochondria. Next in the tail is the principal piece then finally the end piece.
  • mitosis - The normal division of all cells, except germ cells, where chromosome number is maintained (diploid). In germ cell division (oocyte, spermatozoa) meiosis is a modified form of this division resulting in reduction in genetic content (haploid). Mitosis, division of the nucleus, is followed by cytokinesis the division of the cell cytoplasm and the cytoplasmic contents. cytokinesis overlaps with telophase.
  • outer dense fibres - (ODF, outer dense fibers) cytoskeletal structures that surround the axoneme in the middle piece and principal piece of the spermatozoa tail.
  • primary spermatocyte - arranged in the seminiferous tubule wall deep (luminal) to the spermatogonia. These large cells enter the prophase of the first meiotic division. (More? Meiosis)
  • principal piece - Spermatozoa tail segment containing the plasma membrane calcium channels (CatSper1 and CatSper2) required for hyperactivation of motility. Region is partially separated from the midpiece by a barrier called the annulus.
  • Sertoli cells - (sustentacular cell) These cells are the spermatozoa supporting cells, nutritional and mechanical, as well as forming a blood-testis barrier. The cell cytoplasm spans all layers of the seminiferous tubule. The cells are named after Enrico Sertoli (1842 - 1910), and italian physiologist and histologist.
  • sperm annulus - (Jensen's ring; Latin, annulus = ring) A region of the mammalian sperm flagellum connecting the midpiece and the principal piece. The annulus is a septin-based structure formed from SEPT1, 4, 6, 7 and 12. Septins are polymerizing GTPases that can act as a scaffold forming hetero-oligomeric filaments required for cytokinesis and other cell cycle roles.
  • spermatogenesis - (Greek, genesis = origin, creation, generation) The term used to describe the process of diploid spermatagonia division and differentiation to form haploid spermatazoa 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 final process of change in cell shape is also called spermiogenesis.
  • spermatogenesis - (Greek, genesis = origin, creation, generation) The maturation process of the already haploid spermatazoa into the mature sperm shape and organization. This process involves reorganization of cellular organelles (endoplasmic reticulum, golgi apparatus, mitochondria), cytoskeletal changes (microtubule organization) and morphological changes (cell shape, acrosome and tail formation).
  • spermatogonia - The cells located in the seminiferous tubule adjacent to the basal membrane that 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 differentiate and eventually form spermatazoa.
  • spermatozoa head - Following spermiogenesis, the first region of the spermatozoa containing the haploid nucleus and acrosome. In humans, it is a flattened structure (5 µm long by 3 µm wide) with the posterior part of nuclear membrane forming the basal plate region. The human spermatozoa is about 60 µm long, actively motile and divided into 3 main regions (head, neck and spermatozoa tail).
  • spermatozoa neck - Following spermiogenesis, the second region of the spermatozoa attached to basal plate, transverse oriented centriole, contains nine segmented columns of fibrous material, continue as outer dense fibres in tail. In humans, it forms a short structure (1 µm). The human spermatozoa is about 60 µm long, actively motile and divided into 3 main regions (head, neck and tail).
  • spermatozoa tail - Following spermiogenesis, the third region of the spermatozoa that has a head, neck and tail). The tail is also divided into 3 structural regions a middle piece, a principal piece and an end piece. In humans: the middle piece (5 µm long) is formed by axonema and dense fibres surrounded by mitochondria; the principal piece (45 µm long) fibrous sheath interconnected by regularly spaced circumferential hoops; the final end piece (5 µm long) has an axonema surrounded by small amount of cytoplasm and plasma membrane.
  • spermatogonial stem cells - (SSCs) The spermatagonia cells located beside the seminiferous tubule basal membrane that 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 differentiate and eventually form spermatazoa.
  • spermatozoon - singular form of of spermatozoa.
  • sperm protein 56 - A component of the spermatozoa acrosomal matrix released to the sperm surface during capacitation.
Other Terms Lists  
Terms Lists: ART | Birth | Bone | Cardiovascular | Cell Division | Gastrointestinal | Genetic | Hearing | Heart | Immune | Integumentary | Neural | Oocyte | Palate | Placenta | Renal | Spermatozoa | Ultrasound | Vision | Historic | Glossary
Links: Spermatozoa Histology | Histology Stain H&E | Histology Stains



  • Y chromosome gene for a transcription factor
  • member of the high mobility group (HMG)-box family of DNA binding proteins
  • human - 204 amino acid protein [25]
Links: OMIM - Sry


  • autosomal transcription factor
  • Development of XY females - presence of only a single functional copy of the transcription factor encoding genes SOX9, SF1, or WT1 (Note- not all XY humans are sex-reversed if only a single copy of a normal SF1 or WT1 allele is present)
  • A nuclear export signal within the high mobility group domain regulates the nucleocytoplasmic translocation of SOX9 during sexual determination[26]

Other roles

  • Cartilage - essential for chondrocyte differentiation
  • Hearing - otic placode formation, maintenance of progenitors in the otic epithelium

Links: Sox9 | Cartilage Development | Inner Ear Development


  • transcription factor, named Friend of Gata2
  • human - (8q23) 1,151 amino acid nuclear protein that contains 8 zinc finger motifs[27]
  • dosage critical for fetal testis development in mice[28]
Links: OMIM - Fog2


Gadd45g and Sex Determination Model[1]

Growth Arrest- And Dna Damage-Inducible Gene (GADD45, GAMMA; GADD45G)

A Recent mouse study[1] has shown that Gadd45g protein has a role in primary sex differentiation. Knockout mice (Gadd45g(-/-) XY gonads) resulted in a a sex reversal.

Links: OMIM - Gadd45g


  • transcription factor
  • dosage critical for fetal testis development in mice[28]



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Lacy J Barton, Michelle G LeBlanc, Ruth Lehmann Finding their way: themes in germ cell migration. Curr. Opin. Cell Biol.: 2016, 42;128-137 PubMed 27484857

Massimo De Felici The Formation and Migration of Primordial Germ Cells in Mouse and Man. Results Probl Cell Differ: 2016, 58;23-46 PubMed 27300174

Terje Svingen, Peter Koopman Building the mammalian testis: origins, differentiation, and assembly of the component cell populations. Genes Dev.: 2013, 27(22);2409-26 PubMed 24240231

Barry T Hinton, Maureen M Galdamez, Ann Sutherland, Daniela Bomgardner, Bingfang Xu, Rana Abdel-Fattah, Ling Yang How do you get six meters of epididymis inside a human scrotum? J. Androl.: 2011, 32(6);558-64 PubMed 21441421

| J. Androl.


Elena M Kaftanovskaya, Shu Feng, Zaohua Huang, Yingchun Tan, Agustin M Barbara, Sukhjinder Kaur, Anne Truong, Ivan P Gorlov, Alexander I Agoulnik Suppression of insulin-like3 receptor reveals the role of β-catenin and Notch signaling in gubernaculum development. Mol. Endocrinol.: 2011, 25(1);170-83 PubMed 21147849

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C F Heyns The gubernaculum during testicular descent in the human fetus. J. Anat.: 1987, 153;93-112 PubMed 2892824

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