Lecture 21: Embryology of the Femal Reproductive System

7 weeks

in the first ________________, the embryo is sexually indifferent

Week 5

When:

-genital ridge differentiates and begins to form indifferent gonad

-paramesonephric ducts form

-primordial germ cells are incorporated into the indifferent gonad

Week 6

When:

-primordial germ cells are incorporated into the indifferent gonad

Week 7

When:

-Urorectal septum fuses with and divides the cloacal membrane

-Medula and gonadal cords of the indifferent gonad regress

-Cortex and cortical cords of the indifferent gonad develop

Week 8

When:

-Urogenital membrane partially disintegrates

-Distal paramesonephric ducts fuse

4th - 5th Month

When:

Meiosis begins in primary oocytes

5th - 6th Month

When:

Vaginal plate opens

Early Week 4

When:

-Lateral folding translocates Intermediate mesoderm to the dorsal body wall

-Nephrogenic cord differentiates; Pronephros and pronephric duct forms

Mid Week 4

When:

Folding of the caudal embryo creates the cloaca; Genital tubercle forms

Late Wek 4

When:

Mesonephros forms; Pronephric duct becomes the mesonephric duct

Intermediate Mesoderm

the urogenital system develops from the ________________________ of the posterior abdominal wall

Urogenital Ridge

the urogenital system forms a longitudinal elevation along the dorsal body wall called the _____________________

Week 4

When:

gonads are part of the urogenital ridge

Week 5

When:

• Epithelium of the ridge proliferates

• Forms gonadal ridge

Primordial Germ Cells

• Originate in the epiblast and migrate through the primitive streak to reside among endoderm cells in the wall of the yolk sac

• Recognizable 24 days after fertilization

Gonadal Ridges

During folding, the umbilical vesicle is incorporated into the embryo which moves the germ cells along the dorsal mesentery to the __________________________

Week 6

When:

• Primordial germ cells invade gonadal ridge

• Form gonadal cords (or sex cords)

• Indifferent gonad

The gonads do not develop

What happens if the primordial germ cells do NOT reach the gonadal ridges?

SRY gene

-sex-determining region on the Y chromosome

• Produces a protein [testes determining factor (TDF)] that determines testicular differentiation

TDF

protein that determines testicular differentiation

Genital Ridge

What is the indifferent structure:

Male derivative: Testes

Female derivative: ovary

Primordial Germ Cells

What is the indifferent structure:

Male derivative: Spermatozoa

Female derivative: Ova

Sex Cords

What is the indifferent structure:

Male derivative: Seminiferous tubules

Female derivative: Follicular cells

Mesonephric Tubules

What is the indifferent structure:

Male derivative: Efferent ductules and paradidymis

Female derivative: Oophoron and Paroophoron

Mesonephric Ducts

What is the indifferent structure:

Male derivative: appendix of epididymis, epididymal duct, ductus deferens, ejaculatory duct, seminal vesicles

Female derivative: appendix of ovary, gartner's duct

Mesonephric Ligaments

What is the indifferent structure:

Male derivative: gubernaculum testis

Female derivative: round ligaments

Paranmesonephric Ducts

What is the indifferent structure:

Male derivative: appendix of testis, prostate utricle

Female derivative: uterine tubes, uterus, upper vagina

Definitive Urogenital Sinus

What is the indifferent structure:

Male derivative: penile urethra, bulbourethral glands

Female derivative: lower vagina, vaginal vestibule

Early Urogenital Sinus

What is the indifferent structure:

Male derivative: urinary bladder, prostatic urethra, prostate gland

Female derivative: urinary bladder, urethra, glands of skene

Genital Tubercle

What is the indifferent structure:

Male derivative: penis

Female derivative: clitoris

Genital Folds

What is the indifferent structure:

Male derivative: floor of penile urethra

Female derivative: labira minora

Genital Swellings

What is the indifferent structure:

Male derivative: scrotum

Female derivative: labia majora

TDF

In the absence of ________________ the primitive gonadal cords disassociate into irregularly organized cell clusters

Week 7

When do gonads begin to develop?

Oogonia

femal germ cell

1. Gonadal cords form and degenerate

2. Secondary (cortical) cords develop

3. Secondary cords scatter into isolated cell clusters which will form primordial follicles

three steps of ovary development

Primary oocytes

the the 4th month, oogonias turn into ________________________

5th month

when does production of oocytes stop?

Lower segment of the Gubernaculum

embryologic origin of the round ligament of the uterus

Upper segment of the Gubernaculum

embryologic origin of the Ovarian Ligament

Gubernaculum

• Fibrous structure

• Attaches indifferent gonad to internal surface of labioscrotal swellings

-relatively inelastic

Week 6

when do both genital ducts present?

Urinary Tract

the mesonephric duct becomes the __________________

Reproductive tract

the paramesonephric duct becomes the ______________________

Cranial Region of Paramesonephric Ducts

embryologic origin of fallopian tubes

Uterovaginal Primodium

embryologic origin of:

• Uterus and cervix

• Superior 1/3 of vagina

Uterovaginal Primordium

the caudal region of the paramesonephric ducts becomes the __________________

Paramesonephric Ducts

ducts that project into the dorsal wall of the cloaca

Mesonephric Ducts

• Regresses in females but remnants persist that may be clinically significant after puberty

Epoophoron

-homolog to epididymis in males

-lateral part of mesosalpinx and mesovarium

Gartner's Ducts

-The remnants of the mesonephric ducts that can be found in the vagina as blind cysts or ducts

-typically no clinical significance

Broad Ligament of the Uterus

the urogenital ridges moves MEDIAL to form the ________________________

Uterus and Cervic

the Paramesonephric ducts fuse to form the _____________ and ________________

Week 8

When:

• Fusion of mesonephric ducts

• Regression of mesonephric ducts (absence of testosterone)

• Regression of uterine septum at midline to form uterine cavity

• Caudal mesonephric ducts joins to uterovaginal plate

Testosterone

there is regression of mesonephric ducts in the absence of _____________________

Urogenital Sinus

embryologic origin of the lower vagina

Hymen

separates lumen of vagina from the urogenital sinus

3rd Month

When:

-Urogenital sinus form sinovaginal bulbs and vaginal plate.

• Canalization of vaginal

plate

Cloacal Folds

Mesenchyme from primitive streak migrate to form _________________________

Clitoris

Cranially, the folds unite to form genital tubercle and later will form the _______________________

Labia Minora

the urethral folds anteriorly become the _______________________

Labia Majora

On either side of the urethral folds are the genital swellings that will form ________________

Hypoplasia/agenesis/atresia

no development of the uterus

Unicornuate

only one uterine horn

Didelphys

two separate uterine bodies

Bicornuate

small common body, two uterine horns

Septate

one body but internal septum

Imperforate Hymen

• Persistent membrane at vaginal opening

• Remnant of urogentital sinus formation

• Presentation- primary amenorrhea, cyclic pain without bleeding, tender mass, dyspareunia