Reproductive System Development Flashcards
How long are gonads and genitalia morphologically indistinguishable
Up to week 7 of development
Urogenital ridges
. Paired columns of intermediate mesoderm running the length of the dorsal body wall
Gonadal ridge
. Med. portion
. Coelomic epithelium proliferates and gives rise to gonads
Nephrogenic ridge
. Lat. portion
. Gives rise to primitive kidney tubules and 2 sets of ducts that contribute to urinary and reproductive duct systems (mesonephric and paramesonepric. Mullarian ducts)
What occurs w/ gonad differentiation in weeks 4-6
. Primordial germ cells (future gametes) migrate from the yolk sac along dorsal mesentery and into gonadal ridge
What occurs in week 5 of gonad differentiation?
. Coelomic epithelium of gonadal ridge proliferates to form primary sex cords
. Testes or ovaries then develop based on presence of Y-chromosome in terms cells or not
SRY gene
. On Y-chromosome
. Encodes for production of protein testis-determining factor
Testis-determining factor
. If expressed, gonads develop into testes
. If not expressed, gonads develop into ovaries
Streak gonads
. Gonads that fail to develop into testes or ovaries
What occurs in weeks 6-7 of testis development?
. Primitive cords proliferate w/ TDF into testis (medullary) cords
. Testis cords from rete testis and seminiferous tubules
. Rete testis join efferent ductules from mesonephric tubules
. Spermatogonia take up residence in basal compartment of seminiferous tubules
. Somatic cells derived from mesoderm of gonadal ridge form Sertoli cells
Are testis primarily medulla or cortex?
. Medulla bc it contains seminiferous tubules and spermatogonia
. Cortex only contains tunica albuginea
What occurs in week 8 of testis develop?
Sertoli cells produce mullerian-inhibiting substance and testosterone
. suppresses development of paramesonephric ducts
. induces further development of non-ureter portions of mesonephric ducts and male external genitalia
.
Male Gubernaculum
. Mesenchymal condensation extends from caudal pole of each testis
. Distal end is anchored on body wall in inguinal region
. Elongation of torso causes testes to descend toward inguinal region
Where are testis located in week 28?
Descended retroperitoneal Lu from post. Abdominal wall to deep inguinal rings
.
Where is the testis location btw weeks 28 and 40?
. Descends through inguinal canals into scrotum
Cryptorchidism
. Testes fail to descend into scrota by 12th month postnatal
. Corrected surgically
. Failure to descend results in impairment of germ cell maturation
. Abdominal testes 40 times more likely to develop cancer than normal ones
Development of ovaries in weeks 4-7
. Primary sex cords initially proliferate and then degenerate w/o TDF
. Continued proliferation of gonadal ridge surface epithelium produces 2nd generation of cords (cortical cords) that are clustered in cortex fo ovary
. Oogonia invade cortical cords
. Cell of cortical cords give rise to follicular cells forming primordial follicles
Are ovaries cortex or medulla heavy?
. Cortex bc it contains majority of oogonia and ovarian follicles
. Medulla only has CT and blood vessels
Female gubernaculum
. Extends from caudal pole of each ovary
. Distal end is anchored to body wall in area of future labia majora
. Elongation of torso causes ovaries to descend toward inguinal region
. Ovaries descend on post. Abdominal wall but don’t pass through inguinal ring (rest inf. To rim of true pelvis)
Each ovary is attached to the body wall via _____
. Suspensory ligament of the ovary
. Anchored caudally by ovarian ligament and the round ligament of the uterus
Male reproductive duct systemdevelopment
. Mesonephric duct forms ductus epididymis, ductus deferens, seminal vesicle, and ejaculatory duct
. Mesonephric tubules (part of primitive mesonephric kidneys) for efferent ductules
. Paramesonephric duct is suppressed by MIS and degenerate
Paramesonephric duct development in female reproductive tract
. Develop into cranial parts of female reproductive tract
.Influenced by maternal and placental estrogens
. Non-ureteric portions of mesonephric ducts and tubules degenerate in absence of MIS and testosterone
T/F
Development of female reproductive ducts and external genitalia doe snot require presence of ovaries
Uterovaginal primordium
. Midline Y-shaped structure formed by fusion of caudal portions of paramesonephric ducts
. As paramesonephric ducts migrate med., they pull overlying peritoneum med.
. When ducts fuse, peritoneum creates broad ligament
. Forms uterus, cervical, and sup. 1/3 of vagina
. Surrounds splanchnic mesoderm forms myometrium and other smooth muscles
Uterine tube development
. From infused cranial portions of paramesonephric ducts
Abdominal Ostia of the uterine tubes
. Cranial ends of uterine tubes that are open to developing abdominal cavity
Sinovaginal bulbs
. Paired outgrowth from dorsal wall of UG sinus where uterovaginal primordium is in contact
. Bulbs fuse to form solid vaginal plate
. Plate elongates and canalizes by month 5 forming inf. 2/3 vagina
. Caudal end of plate adjacent to UG sinus doesn’t rupture but persists as thin membrane (hymen)
Imperforate hymen
. Obstructive congenital anomaly of female reproductive tract
. May require surgical intervention to allow for passage of menstrual fluid
Uterus didelphys
. Double or duplicated uterus resulting from non-fusion of caudal paramesonephric ducts
. Frequently assoc. w/ double vagina
Bicornuate uterus
. 2 uterine horns open into single vagina
Unicornurate uterus
Uterus w/ one horn
. Due to partial or complete atresia of paramesonephric duct on 1 side
Uterine agenesis
.absence of uterus
Vaginal atresia
. Absence of vagina due to lack of development of sinovaginal bulbs
. Boulder vagina results when sinovaginal bulbs fail to fuse
Week 4 development of external genitalia
. Mesoderm surrounding cloacal membrane forms swellings (cloacal folds)
. Cranial folds unite midline to form genital tubercle
. Caudal folds form urethral and anal folds
What occurs by end of week 6 in external genitalia?
. 2nd set of swelling
. Genital (labioscrotal) swellings appear lat. to urethral folds
. Urorectal septum divides cloaca into UG sinus and anorectal canal
Male external genitalia development?
. Develop under influence of testicular androgens
. Genital tubercle elongates to form phallus
. Elongation of genital tubercle pulls urethral folds ventrally resulting in formation of narrow urethral groove on ventral aspect of phallus
. Urethral groove closes in month 3 forming penile urethra
. Genital (labioscrotal) swellings migrate caudally and fuse to form the scrotum
Hypospadias
. Abnormal opening on ventral surface of penis from incomplete fusion of urethral folds
Epispadias
. Condition where urethra is open on dorsal surface of penis
. Due to caudal displacement of genital tubercle
. Frequently assoc. w/ exstrophy of bladder
Female external genitalia development
. Genital tubercle elongates slightly to form phallus (clit)
. Urethral folds remain unfused and persist as labia minora
. UG sinus gives rise to vestibule
. Genital (labioscrotal) swellings form labia majora
Klinefelter syndrome
. Occurs in genetic males w/ extra X chromosome
. Most common sex disorder
. Patients have dec. fertility, small testes dec. testosterone levels
. Gynecomastia present in 1/3 cases
Aneuploidogens
. Carcinogens (radiation, Tobacco smoke, pesticides)
Sperm cell aneuploidy is assoc w/ what??
Testicular cancer
Gonadal dysgenesis
. Turner’s syndrome
. Genetic females w/ XO genotype
. Streak gonads
. Female anatomy from circulating estrogens
. Short stature, webbed neck, broad chest
. Do not go through puberty w/o hormone treatments
Pure gonadal dysgenesis
. Occurs in genetic males or females, no chromosome abnormality
. Streak gonads from failed germ cell migration
. Develops female reproductive ducts and external genitalia
. Do not go through period w/o hormone treatments
. High risk of germ cell tumors assoc. w/ streak gonads
. Treatment: hormone replacement and excision of defective gonads
Androgen insensitivity syndrome (AIS)
. Genetic males
. Cells of body are unable to respond to androgens
. Develop female external anatomy, but MIS suppresses female duct development
. Normally not diagnosed until they mail to menstruate or have difficulties becoming pregnant
. Testes must be removed at puberty because they are susceptible to become cancerous
Congenital adrenal hyperplasia
. Affects production of cortisol by adrenal glands
. Results in excessive production of androgens
. In females have masculization of external genitalia
. In males they may start puberty early
