أسئلة الرابعة والخامسة أناتومي Repro

Sex Differentiation

• Sex is genetically determined at fertilization
• Gonads morphologically differentiate around the 7th week
• External genitalia phonetically differentiate between the 3rd and 5th months
• SRY genes encode for testis-determining factors in males, which induces;
  • Leydig cells to secrete testosterone which differentiates mesonephric ducts and male external genitalia
  • Sertoli cells secrete MIS, which causes degeneration of paramesonephric ducts
• Females without the SRY gene exhibit;
  • No leydig cells resulting in no testosterone, causing failure of the differentiation of mesonephric ducts and associated external genitalia
  • No sertoli cells results in no MIS, so maternal estrogens stimulate the differentiation of paramesonephric ducts and female genitalia

Gonadal Development

• Coelomic epithelium is the surface of the lateral plate mesoderm:
• The genital ridge develops from intermediate mesoderm
• Primordial germ cells originate from the endoderm of the GIT

Anomalies of the Gonads

• Gonadal dysgenesis results from improper gonads formation due to the failed migration of primordial germ cells
  • Maternal estrogens may cause external genitalia to appear female

Hermaphrodites Intersex

• True hermaphrodites have a mix of ovi-testis tissue, with predominantly female external genitalia
• Pseudo-hermaphrodites:
  • Male pseudo-hermaphrodites are XY males with testes, but external genitalia resembling that of females
  • This is caused by a lack of testicular testosterone or tissue insensitivity, known as Androgen Insensitivity Syndrome
  • Female pseudo-hermaphrodites are XX females with ovaries, but external genitalia resembling that of males
  • This results from an increase in ACTH and androgen release from the adrenal cortex, leading to congenital adrenal hyperplasia causing masculinization of female genitalia

Stages of Gonadal Development

• The indifferent stage involves:
  • Primordial germ cells that appear in the yolk sac during the 4th week
  • Migration of primordial germ cells through the dorsal mesentery during the 5th week
  • Primordial germ cells reach the genital ridge around the 6th week
  • Coelomic epithelial cells proliferate, forming primary sex cords

Testis Development

• During the 7th week, which is the different stage;
  • Primary sex cords penetrate the medulla and proliferate, creating testis cords
  • The testis gets separated from surface epithelium by the tunica albuginea
  • Leydig cells, originating from the genital ridge, starts secreting testosterone in the 8th week
  • By the 4th month, testis cords transform into horseshoe-shaped seminiferous tubules

Ovary Development

• During ovary development:
  • Primary sex cords disappear, and secondary sex cords are formed from the surface epithelium
  • Primitive germ cells are incorporated into secondary sex cords
  • Follicles are formed by the 4th month, consisting of oogonium surrounded by follicular cells
  • The surface epithelium gets separated from the follicles by a thin fibrous tunica albuginea
  • Active mitosis of oogonia occurs during fetal life

Testicular Descent

• Definition: Testicular descent is the migration of the testis from lumbar region to the scrotum

Factors Helping Testicular Descent

• The gubernaculum ligament connects the testis to the scrotum
• Testosterone hormone allows the gubernaculum to contract
• The processus vaginalis dilates the passage of the gubernaculum
• Intra-abdominal pressure increases due to liver size
• Degeneration of the mesonephric kidney

Stages of Testicular Descent

• Internal Descent:
  • Testis begins to descend at 8 weeks
  • Testis reaches the iliac fossa by 10 weeks
  • Testis reaches the deep inguinal ring by 12 weeks
• External Descent:
  • Testis is found in the inguinal canal at 7 months
  • Testis is found in the superficial inguinal ring at 8 months
  • Testis is found in the scrotum at 9 months

Results of Testicular Descent

• Testis drags with its blood supply and nerves
• Formation of the inguinal canal
• The testis has multiple coverings consisting of;
  • External spermatic fascia from the external oblique
  • Cremastric muscle and fascia from the internal oblique
  • Internal spermatic fascia from the fascia transversalis

Fate of Gubernaculum

• The gubernaculum forms a vestige at the bottom of the scrotum

Fate of Processus Vaginalis

• Fate of the Processus Vaginalis: The proximal part forms a vestige of the processus vaginalis while the distal part forms tunica vaginalis

Anomalies of Testicular Descent

• Undescended Testis Cryptorchidism:
  • Testis remains in the abdomen, iliac fossa, or inguinal canal, caused by Defective development of gubernaculum and low testosterone secretion
• Ectopic Testis:
  • It is due to abnormal lower attachment of gubernaculum
  • Potential ectopic sites include the root of penis, perineum, and front of thigh
• Persistent Processus Vaginalis:
  • Failure of obliteration of the processus vaginalis results in:
  • Congenital inguinal hernia, where an intestinal loop descends into the scrotum
  • Congenital hydrocele, where tunica vaginalis is filled with peritoneal fluid

Ovarian Descent

• Ovarian descent is the migration of the ovary from the lumbar region to the pelvic region
• Factors helping ovarian descent include:
  • The gubernaculum ligament, which connects the ovary to the labia majora
  • The increase in intra-abdominal pressure due to liver size
  • The degeneration of the mesonephric kidney
• Stages: Internal descent from lumbar to pelvic region. Migration of ovary from lumbar to pelvic region drags it’s blood supply
• The gubernaculum divides into ovarian and round ligaments
• The processus vaginalis obliterates except to form canal of nuck.

Duct System Development

• Indifferent stage: There are two duct systems:
  • Mesonephric Wolffian duct
  • Para-mesonephric Mullarian duct
• Male duct system

Different Stage

• The mesonephric tubules give rise to:

  • Vasa efferentia
  • Paradidymus

• The mesonephric Wolffian duct gives rise to:

  • Appendix of epididymis
  • Epididymis
  • Vas deferens
  • Seminal vesicle
  • Ejaculatory duct
  • Ureteric bud that forms:
    • Ureter and collecting units of the kidney
    • Trigone of the urinary bladder

• The paramesonephric Mullarian duct degenerates except for the Appendix of the testis and Prostatic utricle

• Prostate develops as an endodermal mass projection from the prostatic urethra

• Bulbourethral develops as an endodermal mass projecting from the penile urethra

• Female duct system

Different stage

• The mesonephric tubules degenerate except for the epoophron and paroophron
• The mesonephric Wolffian duct degenerates except for:
  • Gartner's duct
  • Ureteric bud forms the Ureter and collecting units of the kidney, and Trigone of urinary bladder
• The paramesonephric Mullarian duct gives rise to:
  • The cranial vertical part: forming the uterine tube
  • The middle horizontal part: forming the fundus and body of the uterus
  • The caudal vertical part: forming the cervix and upper 1/3 of the vagina
• Anomalies of uterus:
  • Uterus didelphys: Double uterus, double cervix, and double vagina from complete failure of fusion
  • Uterus bicornis bicollis: Double uterus and double cervix but single vagina from partial failure of fusion
  • Uterus bicornis unicollis: Double uterus, single cervix, and single vagina from partial failure of fusion
  • Bipartite uterus: A small septum remains in the upper part of the uterine cavity
  • Arcuate uterus (depressed fundus): Minor degree of imperfect fusion
  • Unicornuate uterus: Uterus with a rudimentary horn due to retarded growth of one paramesonephric duct

Development of Vagina

• The upper 1/3 originates from the mesoderm, where the utero vaginal canal projects at the back of the urogenital sinus, known as the Mullarian tubercle
• The lower 2/3 originates from the endoderm, where two masses from the urogenital sinus fuse over the Mullarian tubercle to form the vaginal plate, growing cranially
• Vaginal atrasia: The vaginal plate does not canalize
• Lumen: the vaginal plate canalize except for the thin fibrous junction between vagina and urogenital sinus

Anomalies of Vagina

• Vaginal atresia: the vaginal plate is not canalized
• Imperforate hymen: failure of perinatal orifice formation in hymen causing delayed menstruation at puberty

External Genitalia

Indifferent Stage

• Genital tubercle: Mesodermal elevation in front of the urogenital membrane
• Urogenital folds: Ectoderm, located on each side of the vestibule
• Genital swellings: Mesoderm, located on either side of the urogenital fold

Different Stage