Introduction
Week 9, the indifferent stage of external genitalia.
The external male genitalia consists of the penis and scrotum containing the testis.
Mesonephric duct = Wolffian duct.
Some Recent Findings
- Immunohistochemical expression analysis of the human fetal lower urogenital tract[1] "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."
- Development of the human penis and clitoris[2] "The human penis and clitoris develop from the ambisexual genital tubercle. To compare and contrast the development of human penis and clitoris, we used macroscopic photography, optical projection tomography, light sheet microscopy, scanning electron microscopy, histology and immunohistochemistry. The human genital tubercle differentiates into a penis under the influence of androgens forming a tubular urethra that develops by canalization of the urethral plate to form a wide diamond-shaped urethral groove (opening zipper) whose edges (urethral folds) fuse in the midline (closing zipper). In contrast, in females, without the influence of androgens, the vestibular plate (homologue of the urethral plate) undergoes canalization to form a wide vestibular groove whose edges (vestibular folds) remain unfused, ultimately forming the labia minora defining the vaginal vestibule. The neurovascular anatomy is similar in both the developing human penis and clitoris and is the key to successful surgical reconstructions."
- Contrasting mechanisms of penile urethral formation in mouse and human[3] "This paper addresses the developmental mechanisms of formation of the mouse and human penile urethra and the possibility that two disparate mechanisms are at play. It has been suggested that the entire penile urethra of the mouse forms via direct canalization of the endodermal urethral plate. While this mechanism surely accounts for development of the proximal portion of the mouse penile urethra, we suggest that the distal portion of the mouse penile urethra forms via a series of epithelial fusion events. Through review of the recent literature in combination with new data, it is unlikely that the entire mouse urethra is formed from the endodermal urethral plate due in part to the fact that from E14 onward the urethral plate is not present in the distal aspect of the genital tubercle. Formation of the distal portion of the mouse urethra receives substantial contribution from the preputial swellings that form the preputial-urethral groove and subsequently the preputial-urethral canal, the later of which is subdivided by a fusion event to form the distal portion of the mouse penile urethra. Examination of human penile development also reveals comparable dual morphogenetic mechanisms. However, in the case of human, direct canalization of the urethral plate occurs in the glans, while fusion events are involved in formation of the urethra within the penile shaft, a pattern exactly opposite to that of the mouse. The highest incidence of hypospadias in humans occurs at the junction of these two different developmental mechanisms. The relevance of the mouse as a model of human hypospadias is discussed."
- Complex epithelial remodeling underlie the fusion event in early fetal development of the human penile urethra[4] "The opening zipper progresses from proximal to distal along the shaft of the penis and clitoris into the glans in identical fashion in both sexes. The closing zipper mechanism is active only in males and is not a single process but rather a series of layered fusion events, uniquely different from the simple fusion of two epithelial surfaces as occurs in formation of the palate and neural tube."
- Modifications of erectile tissue components in the penis during the fetal period[5] "The penile erectile tissue has a complex microscopic anatomy with important functions in the mechanism of penile erection. The knowledge of such structures is necessary for understanding the normal physiology of the adult penis. Therefore, it is important to know the changes of these penile structures during fetal development. This study aims to analyze the development of the main components of the erectile tissue, such as collagen, smooth muscle fibers and elastic system fibers, in human fetuses. We found strong correlation between the elements analyzed with fetal age, both in corpus cavernosum and corpus spongiosum. The growth rate of these elements was more intense during the second trimester (13 to 24 WPC) of gestation, both in corpus cavernosum and in corpus spongiosum. There is greater proportional amount of collagen in the corpus spongiosum than in corpus cavernosum during all fetal period. In the corpus spongiosum, there is about four times more collagen than smooth muscle fibers and elastic system fibers, during all fetal period studied. "
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Search term: Penis Embryology | Penis Development
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Movies
Mesonephic Duct Development
The paired mesonephic ducts (Wolffian ducts) go through a series of developmental changes to form the male internal genital tract.
Initiation
Invagination
Elongation
- Links:
Foreskin Development
Foreskin development occurs during the second trimester.[6]
- GA week 12 (Week 10) - ectoderm circular invagination at the glandular periphery now grows ventrally.
- GA week 13 (Week 12) - glans partially covered by the foreskin.
- GA week 16-17 (Week 14-15) - glans almost completely covered by the foreskin.
- GA week 18-19 (Week 16-17) - complete foreskin was formed.
- GA week 20 (Week 18) - entirely involves the glans.
Postnatal Development
Abnormalities
Hypospadia
External urethral opening on the ventral surface of penis, can extend back into scrotum. Abnormality due to failure of genital fold fusion during fetal development of the male external genitalia.
| Hypospadia Classification
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Meatus Opening
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| Anterior
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on inferior surface of glans penis
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| Coronal
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in balanopenile furrow
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| Distal
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on distal third of shaft
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| Penoscrotal
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at base of shaft in front of scrotum
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| Scrotal
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on scrotum or between the genital swellings
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| Perineal
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behind scrotum or genital swellings
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| Links: Genital Abnormalities | Penis Development
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Epispadias
Uncommon abnormality associated with the penis, 1 in 30,000 infant males, external urethral opening on the dorsal surface of penis.
Endocrine Disruptors
Endocrine disruptors in female reproductive tract development and carcinogenesis.[7]
Additional Images
Historic
References
- ↑ 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.
- ↑ Baskin L, Shen J, Sinclair A, Cao M, Liu X, Liu G, Isaacson D, Overland M, Li Y & Cunha GR. (2018). Development of the human penis and clitoris. Differentiation , 103, 74-85. PMID: 30249413 DOI.
- ↑ Liu G, Liu X, Shen J, Sinclair A, Baskin L & Cunha GR. (2018). Contrasting mechanisms of penile urethral formation in mouse and human. Differentiation , 101, 46-64. PMID: 29859371 DOI.
- ↑ Shen J, Overland M, Sinclair A, Cao M, Yue X, Cunha G & Baskin L. (2016). Complex epithelial remodeling underlie the fusion event in early fetal development of the human penile urethra. Differentiation , 92, 169-182. PMID: 27397682 DOI.
- ↑ Gallo CB, Costa WS, Furriel A, Bastos AL & Sampaio FJ. (2014). Modifications of erectile tissue components in the penis during the fetal period. PLoS ONE , 9, e106409. PMID: 25170760 DOI.
- ↑ Favorito LA, Balassiano CM, Costa WS & Sampaio FJ. (2012). Development of the human foreskin during the fetal period. Histol. Histopathol. , 27, 1041-5. PMID: 22763876 DOI.
- ↑ <pubmed>19709900</pubmed>
Reviews
Cunha GR & Baskin L. (2018). Development of human male and female urogenital tracts. Differentiation , 103, 1-4. PMID: 30262219 DOI.
Articles
Liu X, Liu G, Shen J, Yue A, Isaacson D, Sinclair A, Cao M, Liaw A, Cunha GR & Baskin L. (2018). Human glans and preputial development. Differentiation , 103, 86-99. PMID: 30245194 DOI.
Isaacson D, Shen J, Overland M, Li Y, Sinclair A, Cao M, McCreedy D, Calvert M, McDevitt T, Cunha GR & Baskin L. (2018). Three-dimensional imaging of the developing human fetal urogenital-genital tract: Indifferent stage to male and female differentiation. Differentiation , 103, 14-23. PMID: 30262218 DOI.
Liu G, Liu X, Shen J, Sinclair A, Baskin L & Cunha GR. (2018). Contrasting mechanisms of penile urethral formation in mouse and human. Differentiation , 101, 46-64. PMID: 29859371 DOI.
Wisniewski H & Terry RD. (1968). Further studies on experimental neurofibrillary tangles. J. Neuropathol. Exp. Neurol. , 27, 149-50. PMID: 5690451
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Cite this page: Hill, M.A. (2024, May 29) Embryology Penis Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Penis_Development
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- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
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