Sexual differentiation and female reproductive system

What does “bipotential gonad” mean?

A fetal gonad that can become either testes or ovaries.

Until what week are fetal gonads bipotential?

Until about 8 weeks.

When can anatomical sex differences be detected?

Around 16 weeks.

Where do bipotential gonads form?

Next to the developing kidneys.

What is the mesonephros?

An early kidney structure that contributes to reproductive ducts.

What does the Wolffian duct become?

Epididymis and vas deferens (male internal structures).

What does the Müllerian duct become?

Uterine tubes, uterus, cervix, and upper vagina.

What hormone destroys the Müllerian duct?

Anti-Müllerian hormone (AMH).

Where is AMH produced?

Nurse (Sertoli) cells of seminiferous tubules.

What hormone promotes Wolffian duct development?

Testosterone.

Where is testosterone produced?

Interstitial (Leydig) cells of the testes.

What hormone promotes Müllerian duct development?

Estrogen.

Where is estrogen produced?

Granulosa cells of ovarian follicles.

What male structures are remnants of Müllerian ducts?

prostatic utricle and appendix of testis.

What female structure is a remnant of Wolffian ducts?

Epoophoron.

What causes an arcuate uterus?

Incomplete fusion of Müllerian ducts.

What causes a double uterus and double vagina?

No fusion of Müllerian ducts.

Where do testes originally form?

Inside the body cavity.

What structure guides testes descent?

Gubernaculum testis.

When does final testes descent occur?

At birth.

What is cryptorchidism?

Failure of testes to descend.

How common is cryptorchidism?

Second most common male genital defect.

What is an inguinal hernia?

Intestines push into the scrotum through a weak inguinal canal.

At 7 weeks, what do all embryos look like externally?

The same.

What hormone determines external genital development?

Dihydrotestosterone (DHT).

Genital tubercle becomes what?

Glans penis or clitoris.

Urogenital folds become what?

Urethra or labia minora.

Labioscrotal folds become what?

Scrotum or labia majora.

What is hypospadias?

Misplaced urethral opening on the ventral penis.

Most common male genital defect?

Hypospadias.

What causes penile agenesis?

No genital tubercle.

What causes a double (bifid) penis?

Two genital tubercles.

What causes micropenis?

Pituitary hormone deficiency.

Is female development the “default”?

No — it requires active signaling.

What gene on the Y chromosome triggers male development?

SRY.

What happens if SRY is present?

Embryo develops male.

What happens if SRY is absent?

Female external characteristics, but no ovaries.

SRY works with what gene?

SOX9

What genes are required for female development?

FoxL2 and Wnt4

What regulates female pathway upstream?

R-spondin (Rspo1)

How do SRY and Rspo1 interact?

They oppose each other to determine sex

What is an XX male?

An individual with XX chromosomes but male characteristics due to SRY crossover.

What is true hermaphroditism?

Presence of both ovarian and testicular tissue (ovotestis).

What is a gynandromorph

One ovary and one testis

What is pseudohermaphroditism?

Chromosomal and gonadal sex match, external genitalia do not.

Chromosomal sex in Androgen Insensitivity Syndrome (AIS)?

XY

Testosterone levels in AIS?

Normal

Why does AIS cause female external appearance

No androgen receptors.

What happens to Müllerian ducts in AIS?

They regress.

Testes location in AIS?

Undescended.

Chromosomal sex in CAH?

XX

What hormone is deficient in CAH?

Cortisol

What hormone is overproduced?

Androgens

External genital appearance in CAH?

Masculinized

Internal reproductive organs in CAH?

Uterus and ovaries present.

What causes guevedoces?

5-alpha-reductase deficiency.

Why do guevedoces appear female at birth?

Cannot convert testosterone to DHT.

What happens at puberty in guevedoces?

Penis develops, testes descend, sperm production begins.

Why is fertility still impossible? (guevedoces)

External anatomy prevents intromission.

What are the primary functions of the ovaries?

Produce female gametes (ova) and secrete estrogen and progesterone.

What shape are the ovaries?

Lumpy, almond-shaped organs.

What hormones do ovaries produce?

Estrogens and progesterone.

What are the two main internal regions of the ovary?

Cortex and medulla.

What occurs in the ovarian cortex?

Oogenesis (egg production).

What is the function of the ovarian medulla?

Contains blood vessels and connective tissue.

What is an ovarian follicle?

A “little bag” that contains and supports an oocyte.

What two cell types make up a follicle?

Granulosa cells and theca cells.

How often does follicle maturation result in ovulation?

About one mature egg per month.

What are the four stages of follicular growth?

Primordial → Primary → Secondary → Tertiary (Graafian).

How long does follicular growth take?

Several months.

What is ovulation?

Release of an oocyte from the ovary.

How many follicles are ovulated per month?

One

What is the stigma?

A weak spot in the ovarian wall where ovulation occurs.

What stage of meiosis is the ovulated egg arrested in?

Second meiotic division - metaphase II

What structure forms after ovulation?

Corpus luteum.

How many follicles are present at birth (per ovary)?

About 2 million.

How many follicles remain at puberty?

About 200,000.

How many follicles are ovulated in a lifetime?

About 400–500.

What happens to the rest of the follicles?

Atresia (apoptotic cell death).

How many follicles reach tertiary stage each month?

About 40, but only one ovulates.

What is the corpus luteum?

The remnant of the follicle after ovulation.

What cells make up the corpus luteum?

Luteinized granulosa cells.

What is the function of the corpus luteum?

Secretes hormones to support pregnancy.

What does the corpus luteum become if pregnancy does not occur?

Corpus albicans.

What is PCOS?

A disorder where cysts form from unovulated follicles.

How common is PCOS?

Affects 5–10% of women.

How does PCOS affect fertility?

Disrupts ovulation.

Common symptoms of PCOS?

Hirsutism (excessive growth of coarse, dark hair), obesity, diabetes risk.

How is PCOS commonly treated?

Hormonal birth control.

Most common type of ovarian cancer?

Epithelial cancer.

Why is the ovarian epithelium vulnerable to cancer?

It must repair after every ovulation.

What reduces ovarian cancer risk?

Fewer ovulations (pregnancy, nursing, oral contraceptives).

Why is ovarian cancer dangerous?

grows quickly and can progress from early stages to advanced within a year

No effective screening; poor prognosis.

Function of uterine tubes?

Transport oocyte and site of fertilization.

What is the infundibulum?

Funnel-shaped end with fimbriae that receive the egg.

What is the ampulla?

Site of fertilization.

What is the isthmus?

Narrow portion leading to uterus.

How do uterine tubes move the oocyte?

Cilia movement and smooth muscle contractions.

What is an ectopic pregnancy?

Implantation outside the uterus.

Most common site of ectopic pregnancy?

Uterine tubes.