Development of Genital organs and Gonads.pptx

Genital tract development

1. DEVELOPMENT OF GENITAL ORGANS AND GONADS PRESENTER-Sseremba Harold Edward SUPERVISOR-DR. Bwaga BMS 4.2-OBS&GYN

2. INTROUCTION The  reproductive system  is a collection of internal and external sex organs which work together for the purpose of sexual reproduction. For the first several weeks, all embryos are anatomically identical . Genetic and hormonal signals determine the direction of development (sex differentiation) . Key Bipotential Structures (Primordia) : Gonads: Uro g enital Ridges Internal Ducts: Mesonephric ( Wolffian ) Ducts Paramesonephric ( Müllerian ) Ducts External Genitalia (Developed in the cranial aspect of the ectodermal cloacal fossa): Genital Tubercle Urethral Folds Labioscrotal Swellings Urogenital sinus

3. EMBRYOLOGY

4. DEV’T OF GONADS XY → Medulla → SRY gene → TDF → Testes • Sertoli cells → MIF (AMF) → Regression of Müllerian ducts • Leydig cells → Testosterone → DHT (via 5α-reductase ) Male genitalia(Penis, Scrotum) → Wolffian ducts → Epididymis, Vas deferens, Seminal vesicle, Ejaculatory duct NB: Testes – Tubules ( Seminiferous tubules, Rete testis ) , Sertoli cells (MIF), Leydig (Testosterone), Sperm Gubernaculum – Guides descent of testes into scrotum XX → Cortex → No SRY → No TDF → Ovaries • Follicular cells → Estrogen → +Female genitalia • No Testes no Sertoli cells no MIF (+) Müllerian ducts → Fallopian tubes, Uterus, Upper 2/3 Vagina • No Leydig cells → No Testosterone → Wolffian ducts regress NB: Gubernaculum – Guides ovaries and ductal system into pelvis → Ovarian ligament & Round ligament

5. CONT’N

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7. Gonad Developmen t Testis Development (XY Embryos) Trigger: The SRY Gene on the Y chromosome produces Testis-Determining Factor (TDF) . Process: The medulla of the uro genital ridge develops into a testis. Timing: Differentiation begins around Week 7- 8 . Hormone Production: Fetal testes begin secreting Testosterone at about the 2nd to 4th month of fetal life, stimulated by human chorionic gonadotropins ( hCG ) from the placenta. Ovary Development (XX Embryos) Trigger: Absence of SRY gene (involves genes like WNT4, RSPO1). Process: The cortex of the uro genital ridge develops into an ovary. Timing: Begins around Weeks 8 –12 .   Key Event: Formation of primordial follicles (ova surrounded by granulosa cells).  The ovary contains about 6 million primordial follicles at the 7th or 8th month of intrauterine life, which decreases to about 1 million at birth.

8. Development of Internal Genital Organs Hormones secreted by the differentiated gonads drive the development of internal ducts . Specific Organ Development: The Fallopian Tube is developed from the cranial and horizontal part of the corresponding Müllerian duct at about 6–10th week. The Uterus and Upper 2/3 of vagina is developed from the caudal part of the two Müllerian ducts. Testicular Descent: Testosterone is also necessary for the descent of the testes from the abdominal cavity into the scrotum just before birth. Pathway Hormonal Action Resulting Structures Male Pathway Testosterone (from Leydig cells) stabilizes the Wolffian Ducts Epididymis, Vas Deferens, Seminal Vesicles Anti-Müllerian Hormone (AMH) (Müllerian Regression Factor, MRF) (from Sertoli cells) causes regression of the Müllerian Ducts Female Pathway (Default) In the absence of testosterone (and AMH), the Wolffian Ducts degenerate Müllerian Ducts develop into: Uterine ( Fallopian ) Tubes , Uterus , and Upper Vagina

9. Development of External Genitalia and Homology External genitalia develop from common primordia under hormonal influence. External genitalia develop around Weeks 8–12 postconception. • Male Pathway: Driven by Dihydrotestosterone (DHT) Testosterone is converted to DHT in the target cells. Genital Tubercle Penis Urethral Folds Penile Urethra Labioscrotal Swellings Scrotum Urogenital sinus prostate gland, prostatic urethra, membranous urethra, Cowper’s gland Female Pathway: The Default Pathway (Absence of Androgens) Genital Tubercle Clitoris, Vestibular bulbs Urethral Folds Labia Minora Labioscrotal Swellings Labia Majora  The Vestibule develops from the urogenital sinus Female Structure Homologous Male Structure Clitoris Penis Labia Majora Scrotum Labia Minora Penile Urethra and part of the skin of the penis Skene’s glands Prostate Vestibular Bulbs Bulb of the penis and corpus spongiosum

10. Summary of Differentiation and Key Roles Bipotential Primordium Male Development Female Development Genital Ridge Testis (via SRY/TDF) Ovary (no SRY) Wolffian Ducts Epididymis, Vas Deferens (via Testosterone) Degenerates Müllerian Ducts Degenerates (via AMH/MRF) Uterine Tubes, Uterus, Upper Vagina Genital Tubercle Penis (via DHT) Clitoris Labioscrotal Swellings Scrotum (via DHT) Labia Majora

11. Clinical Correlations: Disorders of Sexual Development (DSD) Androgen Insensitivity Syndrome (AIS) Cause: 46,XY karyotype, but a mutation in the androgen receptor prevents the body from responding to Testosterone or DHT . Presentation: External appearance is female. Internal structures include no uterus (because AMH is active and causes regression of Müllerian ducts) and undescended testes. 5-Alpha-Reductase Deficiency Cause: Deficiency in the enzyme needed to convert Testosterone to the potent androgen DHT . Effect: Results in undervirilized external genitalia at birth. Congenital Adrenal Hyperplasia (CAH) in Females Cause: 46,XX karyotype, where an enzyme defect leads to excess adrenal androgens. Effect: Ovaries and uterus are normal, but the external genitalia may be virilized (e.g., clitoromegaly). In some cases of genetic disorders, a female child may be born with external genitalia of male type ( pseudohermaphroditism ). Cryptorchidism Definition: Congenital disorder characterized by the failure of one or both testes to descend from the abdomen into the scrotum. Association: Males with untreated undescended testes (cryptorchidism) are prone to testicular cancer.

12. Other Clinical correlates Bicornuate Uterus Bicornate uterus is a relatively common structural defect. It occurs when there is  incomplete fusion  of the paramesonephric ducts.

13. CONT’N Hypospadias A condition in which there are one or more  abnormal openings  of the urethra along the  inferior  side of the penis. This is a result of incomplete closure of the urethral folds during development. Surgery is usually performed to correct the defect

14. REFERENCES Theakston, V. (2024, July 17). Development of the reproductive system . TeachMeAnatomy . https://teachmeanatomy.info/the-basics/embryology/reproductive-system Dutta, D. C. (2019). Textbook of DC Dutta’s obstetrics: Including perinatology and contraception (9th ed.). Jaypee Brothers Medical Publishers (P) Ltd. Sembulingam , K., & Sembulingam , P. (2012). Essentials of medical physiology (6th ed.). Jaypee Brothers Medical Publishers (P) Ltd. Ninja Nerd. (2025, January 1). Embryology | Development of reproductive system [Video]. YouTube. https://youtu.be/eKuO_526YCc