What are the three components of the Jost paradigm?

Genetic sex, gonadal sex, phenotypic (genital) sex

What determines genetic sex?

Type of sex chromosomes at fertilization

What determines gonadal sex?

Chromosomal sex

What determines phenotypic sex?

Hormones produced by gonads

What gene determines testis development?

SRY gene on Y chromosome

What happens if SRY is present?

Bipotential gonads → testes

What happens in absence of Y chromosome?

Ovaries develop by default

What syndrome is XXY?

Klinefelter syndrome

Key features of Klinefelter syndrome?

Tall, gynecomastia, small testes, infertility

What syndrome is XO?

Turner syndrome

Key features of Turner syndrome?

Short stature, streak ovaries, no menstruation

What hormone do Sertoli cells produce?

Müllerian inhibiting hormone (MIH)

What does MIH do?

Regression of Müllerian ducts

What do Leydig cells produce?

Testosterone

What does testosterone do?

Develops male internal genitalia

What hormone forms male external genitalia?

DHT

What happens in females due to absence of MIH?

Müllerian ducts develop into female structures

What happens in absence of testosterone?

Wolffian ducts regress

What are Müllerian duct derivatives?

Uterus, fallopian tubes, inner vagina

What are Wolffian duct derivatives?

Epididymis, vas deferens, seminal vesicles

What is congenital adrenal hyperplasia?

XX with excess androgens → masculinization

What causes it?

↓ cortisol → ↑ ACTH → ↑ androgens

What is androgen insensitivity syndrome?

XY but body insensitive to androgens → female phenotype

What triggers puberty?

↑ GnRH → ↑ LH & FSH → ↑ sex steroids

What regulates GnRH secretion?

Genetics + environmental factors

What hormone is linked to energy status and puberty?

Leptin

What happens in menopause?

Follicle depletion → ↓ estrogen, progesterone, inhibin

What happens to FSH in menopause?

Increases (loss of negative feedback)

What are functions of placenta?

Endocrine, exchange, immune protection

What hormone maintains corpus luteum early?

hCG

What does hPL do?

GH-like, anti-insulin → ↑ glucose for fetus

What does progesterone do in pregnancy?

↓ uterine contractions, maintain pregnancy

What does estrogen do in pregnancy?

↑ uterine growth, ↑ breast ducts

What initiates labor?

Oxytocin + prostaglandins + stretch

What hormone inhibits contractions?

Progesterone

What hormone causes milk synthesis?

Prolactin

What hormone causes milk ejection?

Oxytocin

What is galactopoiesis?

Maintenance of lactation

What are phases of uterine cycle?

Menstrual, proliferative, secretory

What triggers menstrual phase?

↓ estrogen and progesterone

What hormone dominates proliferative phase?

Estrogen

What hormone dominates secretory phase?

Progesterone

What happens during proliferative phase?

Endometrial growth

What happens during secretory phase?

Gland secretion, implantation prep

Where does fertilization occur?

Ampulla of uterine tube

How long are sperm viable?

~5 days

How long is oocyte viable?

12–24 hours

What is capacitation?

Sperm maturation in female tract enabling fertilization

What prevents polyspermy?

Cortical reaction + zona pellucida hardening

What happens after fertilization?

Zygote forms → mitosis → morula

What is morula?

Solid ball of cells (3–4 days)

What is blastocyst?

Inner cell mass + trophoblast + cavity

What becomes placenta?

Trophoblast

What becomes embryo?

Inner cell mass

When does implantation occur?

~6–7 days after fertilization

What is syncytiotrophoblast?

Fused trophoblast invading endometrium

What is oogenesis?

Oogonia → oocyte → ovum

When does meiosis I begin?

Fetal life

When is meiosis II completed?

After fertilization

What is the end result of oogenesis?

1 ovum + polar bodies

What is the ovarian cycle divided into?

Follicular phase and luteal phase

What triggers ovulation?

LH surge

What causes LH surge?

High estrogen (positive feedback)

What do granulosa cells do?

Produce estrogen, support oocyte

What do theca cells do?

Produce androgens (→ converted to estrogen)

What is inhibin?

Hormone that inhibits FSH

What happens in early follicular phase?

Low estrogen → negative feedback

What happens in late follicular phase?

High estrogen → positive feedback → LH surge