Reproductive System Development Flashcards by Emily Mosher

How long are gonads and genitalia morphologically indistinguishable

Up to week 7 of development

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Urogenital ridges

. Paired columns of intermediate mesoderm running the length of the dorsal body wall

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Gonadal ridge

. Med. portion

. Coelomic epithelium proliferates and gives rise to gonads

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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)

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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

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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

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SRY gene

. On Y-chromosome

. Encodes for production of protein testis-determining factor

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Testis-determining factor

. If expressed, gonads develop into testes

. If not expressed, gonads develop into ovaries

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Streak gonads

. Gonads that fail to develop into testes or ovaries

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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

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Are testis primarily medulla or cortex?

. Medulla bc it contains seminiferous tubules and spermatogonia
. Cortex only contains tunica albuginea

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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
.

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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

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Where are testis located in week 28?

Descended retroperitoneal Lu from post. Abdominal wall to deep inguinal rings
.

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Where is the testis location btw weeks 28 and 40?

. Descends through inguinal canals into scrotum

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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

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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

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Are ovaries cortex or medulla heavy?

. Cortex bc it contains majority of oogonia and ovarian follicles
. Medulla only has CT and blood vessels

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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