BGDB Sexual Differentiation - Late Embryo: Difference between revisions
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==Week 8== | ==Week 8== | ||
{| | |||
| width=500px|<html5media height="520" width="505">File:Stage22_URG3d.mp4</html5media> | |||
This page shows | [[Media:Stage22_URG3d.mp4|'''Click Here''' to play on mobile device]] | ||
| valign="top" | '''Begin by observing the internal structure of the embryo at the end of week 8.''' | |||
'''Colour code:''' | |||
* <font color=chocolate>'''Adrenal Glands'''</font> (brown - fetal adrenal cortex and neural crest medulla) | |||
* <font color=coral>'''Kidneys'''</font> (orange - metanephros) | |||
* <font color=limegreen>'''Gonads'''</font> (green - developing testes) | |||
* <font color=red>'''Urinary Bladder'''</font> (red - urogenital sinus) | |||
* <font color=gold>'''Urethra'''</font> (yellow - urethra) | |||
* This page shows selected excerpts from whole cross-sections of the human embryo (week 8, stage 22) late embryonic period. | |||
* Read the description with the serial section excerpt and then use the link below each image (click section number) to see the full cross-section image. | |||
* They are organised in sequence as if you were travelling downward through the embryo (that is why the kidney comes first). | |||
Week 8, Carnegie stage 22, male. [[Urogenital_System_3D_stage_22_Movie|Page]] | |||
|} | |||
At this stage in male and female development, both the mesonephric (Wolffian) and paramesonephric (Mullerian) ducts are still present in both sexes. | |||
{| | |||
|+ '''Human Embryo''' (week 8, stage 22) pelvic level cross-section. | |||
| [[File:Stage 22 image 196.jpg|400px]] | |||
| [[File:Stage_22_image_214.jpg|400px]] | |||
|- | |||
| [[:File:Stage 22 image 196.jpg|G5 urogenital]] | |||
| [[:File:Stage_22_image_214.jpg|urogenital]] | |||
|} | |||
===Embryo (week 8, Stage 22) Renal=== | |||
{| class="prettytable" | |||
|[[File:Stage_22 image 083.jpg|160px]] | |||
E6: R,L adrenal glands under diaphragm. | |||
[[File:Stage_22 image 084.jpg|160px]] | |||
E7: Large adrenal glands. Inferior vena cava. Thoracic aorta. | |||
| [[File:Stage_22 image 085.jpg|160px]] | |||
| [[File:Stage_22 image 086.jpg|160px]] | |||
| [[File:Stage_22 image 087.jpg|160px]] | |||
|- | |||
| | |||
| F1: Adrenal glands. R. Kidney. Autonomic ganglia (partly the adrenal medulla precursors). | |||
| F2: Kidneys (note retroperitoneal location). Cortex. Medulla. L. Adrenal gland. Superior mesenteric artery. Inferior vena cava. | |||
| F3: R testis (note its location relative to the R adrenal). L adrenal. R renal hilus. large channels are branches of ureteric tree. | |||
|- | |||
| [[File:Stage_22 image 088.jpg|160px]] | |||
| [[File:Stage_22 image 089.jpg|160px]] | |||
| [[File:Stage_22 image 090.jpg|160px]] | |||
| [[File:Stage_22 image 091.jpg|160px]] | |||
|- | |||
| F4: R kidney and R ureter. Inferior vena cava. L. kidney, L renal hilus and L ureter. R testis with R mesonephric duct (precursor of vas deferens). L testis. Umbilical arteries passing into umbilical cord allantois between them. | |||
| F5: Kidneys. Ureters. Note umbilical arteries and allantois. Also note how R testis and mesonephric structures are attached to parietal peritoneum by a mesogonad. | |||
| F6: Kidneys. Ureters. Note umbilical arteries and allantois. Also note how R testis and mesonephric structures are attached to parietal peritoneum by a mesogonad. | |||
| F7: In F7, (dorsal to R testis and liver) note with the distinct lumen of the mesonephric duct, almost solid column of paramesonephric cells and remnants of mesonephric tubules. "mesogonad". Ureters. Bladder with submucosa and detrusor muscle. Umbilical arteries. Division of aorta. | |||
|- | |||
| [[File:Stage_22 image 092.jpg|160px]] | |||
| [[File:Stage_22 image 093.jpg|160px]] | |||
| [[File:Stage_22 image 094.jpg|160px]] | |||
| [[File:Stage_22 image 095.jpg|160px]] | |||
|- | |||
| G1: Ureters, Bladder. Umbilical arteries. Testis with remains of mesonephros (dorsal), mesonephric duct and paramesonephric cells. Sigmoid colon and mesocolon. | |||
| G2: Ureters being displaced ventrally, crossing common iliac arteries. Sigmoid colon. Bladder. Mesonephric ducts (lateral) and paramesonephric ducts (smaller, medial) located dorsal to bladder. | |||
| G3: Ureters (cut twice): descending dorsal to bladder and ascending ventrally to enter the bladder at trigone, through the submucosa). Fusion of paramesonephric ducts. Paired mesonephric ducts. Umbilical arteries looping off common iliac arteries. Pubic symphysis. Colon. | |||
| G4: Most caudal part of loop of ureters. Urethra emerging from bladder. Mesonephric ducts. Rectocolic junction. | |||
|- | |||
| [[File:Stage_22 image 096.jpg|160px]] | |||
| [[File:Stage_22 image 097.jpg|160px]] | |||
| [[File:Stage_22 image 098.jpg|160px]] | |||
| | |||
|- | |||
| G5: Urethra (in region of future prostate gland - note crescentic shape). Rectum. Rectovesical pouch. Between G4 and G5, each mesonephric duct (vas deferens) has joined the prostatic urethra (caudal to the ureters), thereby increasing the caliber of the latter. | |||
| G6: Penile urethra, emerging inferiorly to the glans penis. Scrotal swellings (appear before testis descends). | |||
| G7: Penile urethra, emerging inferiorly to the glans penis. Scrotal swellings (appear before testis descends). | |||
| '''Note F7 MS term:''' ''"inebriated Puffin" ''(dorsal to R testis and liver) lumen of the mesonephric duct (eye), almost solid column of paramesonephric cells (beak) and remnants of mesonephric tubules (body). | |||
|} | |||
==Urinary System Development== | ==Urinary System Development== | ||
===Development of the Urinary Bladder=== | |||
{| | |||
| width=380px|<html5media height="500" width="360">File:Urogenital_sinus_001.mp4</html5media> | |||
| width=440px|<html5media height="415" width="420">File:Urogenital_septum_001.mp4</html5media> | |||
| '''Division of the Cloaca''' | |||
* weeks 4 to 6 - the cloaca is separated into: | |||
** anteriorly - '''urogenital sinus''' | |||
** posteriorly - '''rectum''' | |||
* Separation is achieved by downward growth of the '''urorectal septum''' | |||
** a portion of hundgut endoderm and mesoderm | |||
* urogenital sinus enlargement forms the '''primitive bladder''' | |||
* surrounding mesoderm will contribute the '''detrusor muscle''' | |||
** this is superiorly continuous with the '''allantois''' | |||
* week 8 (Stage 21) - the cloacal membrane perforates. | |||
[[Urogenital Sinus Movie]] [[Urogenital Septum Movie]] | |||
|} | |||
<gallery> | |||
File:Gray0991.jpg | |||
File:Gray0992.jpg | |||
</gallery> | |||
===Development of the Urethra=== | |||
Further development of the urinary system outflow tract, the urethra, varies depending on the sex of the embryo. | |||
* '''Males''' - the pelvic urethra forms the membranous urethra, the prostatic urethra and penile urethra. (The sex of the above animation and sections is male) | |||
* '''Females''' - the pelvic urethra forms the membranous urethra and the vestibule of the vagina. | |||
===Early Development of the Kidney=== | |||
{| | |||
| width=420px|<html5media height="280" width="400">File:Nephron_development.mp4</html5media> | |||
| | |||
* Adult kidneys (the metanephroi) form from day 35, from a portion of the intermediate mesoderm called the metanephric blastema (or metanephric mesenchyme). | |||
* Ureteric buds, outgrowths from the end of the mesonephric ducts, induce the metanephric blastema. | |||
* Upon contact, they begin to lengthen and bifurcate rapidly in the metanephric blastema – these branches differentiate into the collecting ducts. | |||
* Both the ureteric buds and the metanephric blastema begin to differentiate; interestingly each induces differentiation in the other structure. | |||
** The ureteric bud is induced by the metanephric blastema to form the collecting tubules, renal pelvis and ureters. | |||
** The metanephric blastema is induced to form the nephrons. | |||
'''Note''' - Nephrogenesis is the formation of the nephron (shown in the second part of this animation) occurs in the [[BGDB_Sexual_Differentiation_-_Fetal#Fetal_Kidney|fetal period]] with all of the nephrons formed prenatally by 30 to 34 weeks ({{GA}} 32 to 36 weeks). | |||
|} | |||
{| | |||
| width=320px|<html5media height="280" width="400">File:Renal blood 01.mp4</html5media> | |||
| | |||
* starts in week 5 and is completed by week 15. | |||
* week 6 - the kidneys begin to change their relative position, described as "ascent of the kidneys", to their correct anatomical position. | |||
* week 9 - the rising movement is completed. | |||
* During the ascent, the kidneys also become vascularised via the dorsal aorta. | |||
* As this ascent occurs, the mesonephric ducts and the ureters enter the wall of the developing bladder. | |||
|} | |||
==Genital System Development== | ==Genital System Development== | ||
{| | |||
| [[File:Stage22 mesonephros.jpg]] | |||
'''Male Human Embryo''' (week 8, stage 22) | |||
Detail from cross-section showing mesonephros, mesonephric duct, paramesonephric duct and developing testis. | |||
| Until the end of the 6th week the male and female genital systems are indistinguishable. Sex differentiation is based upon the presence of the specific sex chromosomes. | |||
* '''week 5''' - the primordial germ cells migrate to the region of the future gonads. Cells from the coelomic epithelium and the mesonephros proliferate, forming genital ridges medial to the mesonephros. | |||
* '''week 6''' - these cells surround the germ cells, together forming the primitive sex cords. They contain distinct cortical and medullary regions. | |||
** Also in the 6th week, the paramesonephric or Müllerian ducts form, lateral to the mesonephric ducts. | |||
|} | |||
===Male=== | |||
{| | |||
| [[File:Stage_22_image_302.jpg|200px]] | |||
| [[File:Stage_22_image_301.jpg|200px]] | |||
| [[File:Stage 22 image 194.jpg|200px]] | |||
|- | |||
| [[:File:Stage_22_image_302.jpg|peritoneal cavity]] | |||
| [[:File:Stage_22_image_301.jpg|rete tesits]] | |||
| [[:File:Stage 22 image 194.jpg|G3 testis]] | |||
|} | |||
* '''week 8''' - males Sertoli cells secrete anti müllerian hormone (AMH), which causes regression of the paramesonephric ducts between the 8th and 10th weeks. | |||
* '''week 9 to 10''' - gonadal cells begin to produce testosterone, which maintains the mesonephric ducts. | |||
Mesonephric (Wolffian) ducts go on to form the internal genital tract: | |||
* rete testis | |||
* efferent ductules (ductuli efferentes) | |||
* ductus deferens (vas deferens) | |||
[[File:Male_testosterone_and_AMH_level_graph.jpg|400px]] | |||
Male hormone levels | |||
===Female=== | |||
[[File:Urogenital female.jpg|thumb|Female]] | |||
* during the same time course as above, the opposite occurs. | |||
* The sex cords degenerate and the genital ridge forms secondary cortical sex cords. | |||
* These induce the primordial germ cells to form the ovarian follicles. | |||
* Due to the lack of AMH and testosterone, the mesonephric ducts degenerate | |||
'''Paramesonephric (Müllerian) ducts''' form the internal female genital tract | |||
* {{uterus}} - uterine (fallopian) tubes, uterus body | |||
* {{vagina}} | |||
In both sexes, the external genitalia appear similar until week 12 ({{GA}} week 14). | |||
==Trigone== | ==Trigone== | ||
{| | |||
| width=460px|<html5media height="380" width="450">File:Trigone_001.mp4</html5media> | |||
The mesonephric duct (purple) has lateral branches forming the uteric bud (kidney) both these fuse into the wall of the bladder (yellow). The mesonephric duct then moves inferiorly to the level of the pelvic urethra. | [[Media:Trigone_001.mp4|'''Click Here''' to play on mobile device]] | ||
| This animation shows the historic interpretation of trigone development between Week 4 and 6. (See [[BGDB_Sexual_Differentiation_-_Late_Embryo#Trigone_2|current research on trigone development). | |||
* The mesonephric duct (purple) has lateral branches forming the uteric bud (kidney) | |||
* both these fuse into the wall of the bladder (yellow). | |||
* The mesonephric duct then moves inferiorly to the level of the pelvic urethra. | |||
{{Trigone movie links}} | |||
|} | |||
<br> | |||
{{BGDB_Sexual_Differentiation - Late Embryo Interactive}} | |||
<br> | |||
{{BGDB SexDiffn}} | |||
==Additional Information== | |||
{{Med Prac additional Information}} | |||
{{Genital Links}} | |||
===Trigone=== | |||
[[File:Gray1140.jpg|thumb|150px|adult bladder trigone]] | |||
The dorsal bladder region bounded by the 2 ureters and the urethra form the region known as the trigone. The classical embryology description of the origin of this region was from the mesonephric duct (Wolffian duct), as shown in this animation. | |||
More recent mouse studies suggest that this bladder region is endodermal and not mesodermal in origin.{{#pmid:19914648|PMID19914648}} Using a similar mouse model, this trigone embryonic region appears to contain most of the bladder progenitor cells.{{#pmid:24992712|PMID24992712}} Any mesonephric duct (Wolffian duct) located in the mouse trigone region appears to be developmentally lost by apoptosis.{{#pmid:19568352|PMID19568352}} | |||
In contrast, the prostatic central zone, seminal vesicle, and ejaculatory ducts all originate from the mesonephric duct (Wolffian duct).{{#pmid:20413145|PMID20413145}} | |||
===Seminal Vesicle=== | |||
The prostatic central zone, seminal vesicle, and ejaculatory ducts all originate from the mesonephric duct (Wolffian duct).{{#pmid:20413145|PMID20413145}} | |||
{{Seminal vesicle}} | |||
==References== | |||
<references/> | |||
{{Genital terms}} | |||
{{ | {{BGDBFooter}} |
Latest revision as of 21:33, 2 June 2019
Practical 12: Sex Determination | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities | 2011 Audio |
Week 8
<html5media height="520" width="505">File:Stage22_URG3d.mp4</html5media> | Begin by observing the internal structure of the embryo at the end of week 8.
Week 8, Carnegie stage 22, male. Page |
At this stage in male and female development, both the mesonephric (Wolffian) and paramesonephric (Mullerian) ducts are still present in both sexes.
G5 urogenital | urogenital |
Embryo (week 8, Stage 22) Renal
Urinary System Development
Development of the Urinary Bladder
<html5media height="500" width="360">File:Urogenital_sinus_001.mp4</html5media> | <html5media height="415" width="420">File:Urogenital_septum_001.mp4</html5media> | Division of the Cloaca
|
Development of the Urethra
Further development of the urinary system outflow tract, the urethra, varies depending on the sex of the embryo.
- Males - the pelvic urethra forms the membranous urethra, the prostatic urethra and penile urethra. (The sex of the above animation and sections is male)
- Females - the pelvic urethra forms the membranous urethra and the vestibule of the vagina.
Early Development of the Kidney
<html5media height="280" width="400">File:Nephron_development.mp4</html5media> |
Note - Nephrogenesis is the formation of the nephron (shown in the second part of this animation) occurs in the fetal period with all of the nephrons formed prenatally by 30 to 34 weeks (GA 32 to 36 weeks). |
<html5media height="280" width="400">File:Renal blood 01.mp4</html5media> |
|
Genital System Development
Male
peritoneal cavity | rete tesits | G3 testis |
- week 8 - males Sertoli cells secrete anti müllerian hormone (AMH), which causes regression of the paramesonephric ducts between the 8th and 10th weeks.
- week 9 to 10 - gonadal cells begin to produce testosterone, which maintains the mesonephric ducts.
Mesonephric (Wolffian) ducts go on to form the internal genital tract:
- rete testis
- efferent ductules (ductuli efferentes)
- ductus deferens (vas deferens)
Male hormone levels
Female
- during the same time course as above, the opposite occurs.
- The sex cords degenerate and the genital ridge forms secondary cortical sex cords.
- These induce the primordial germ cells to form the ovarian follicles.
- Due to the lack of AMH and testosterone, the mesonephric ducts degenerate
Paramesonephric (Müllerian) ducts form the internal female genital tract
In both sexes, the external genitalia appear similar until week 12 (GA week 14).
Trigone
<html5media height="380" width="450">File:Trigone_001.mp4</html5media> | This animation shows the historic interpretation of trigone development between Week 4 and 6. (See [[BGDB_Sexual_Differentiation_-_Late_Embryo#Trigone_2|current research on trigone development).
|
Late Embryo Interactive Component
Attempt the Quiz - Late Embryo | ||
---|---|---|
Here are a few simple Quiz questions that relate to Late Embryo from the lecture and practical.
|
Practical 12: Sex Determination | Early Embryo | Late Embryo | Fetal | Postnatal | Abnormalities | 2011 Audio |
Additional Information
Additional Information - Content shown under this heading is not part of the material covered in this class. It is provided for those students who would like to know about some concepts or current research in topics related to the current class page. |
Trigone
The dorsal bladder region bounded by the 2 ureters and the urethra form the region known as the trigone. The classical embryology description of the origin of this region was from the mesonephric duct (Wolffian duct), as shown in this animation.
More recent mouse studies suggest that this bladder region is endodermal and not mesodermal in origin.[1] Using a similar mouse model, this trigone embryonic region appears to contain most of the bladder progenitor cells.[2] Any mesonephric duct (Wolffian duct) located in the mouse trigone region appears to be developmentally lost by apoptosis.[3]
In contrast, the prostatic central zone, seminal vesicle, and ejaculatory ducts all originate from the mesonephric duct (Wolffian duct).[4]
Seminal Vesicle
The prostatic central zone, seminal vesicle, and ejaculatory ducts all originate from the mesonephric duct (Wolffian duct).[4]
References
- ↑ Tanaka ST, Ishii K, Demarco RT, Pope JC, Brock JW & Hayward SW. (2010). Endodermal origin of bladder trigone inferred from mesenchymal-epithelial interaction. J. Urol. , 183, 386-91. PMID: 19914648 DOI.
- ↑ Sun W, Wilhelmina Aalders T & Oosterwijk E. (2014). Identification of potential bladder progenitor cells in the trigone. Dev. Biol. , 393, 84-92. PMID: 24992712 DOI.
- ↑ Mendelsohn C. (2009). Using mouse models to understand normal and abnormal urogenital tract development. Organogenesis , 5, 306-14. PMID: 19568352
- ↑ 4.0 4.1 Quick CM, Gokden N, Sangoi AR, Brooks JD & McKenney JK. (2010). The distribution of PAX-2 immunoreactivity in the prostate gland, seminal vesicle, and ejaculatory duct: comparison with prostatic adenocarcinoma and discussion of prostatic zonal embryogenesis. Hum. Pathol. , 41, 1145-9. PMID: 20413145 DOI.
Genital System Terms (expand to view) |
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Note there are additional glossaries associated with spermatozoa, oocyte renal.
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Cite this page: Hill, M.A. (2024, April 27) Embryology BGDB Sexual Differentiation - Late Embryo. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/BGDB_Sexual_Differentiation_-_Late_Embryo
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G