Reproductive Physiology – Prenatal Development, Endocrinology & Puberty

Vocabulary flashcards covering embryonic germ layers, pituitary development, sexual differentiation, hormone action mechanisms, major reproductive hormones, and factors governing puberty.

Endoderm

Embryonic germ layer that gives rise primarily to the endocrine system and internal organs.

Ectoderm

Embryonic germ layer that develops into the nervous system, skin and associated structures.

Mesoderm

Embryonic germ layer that forms the reproductive system, muscle, bone and blood.

Rathke’s pouch

Ectodermal pocket from the roof of the embryonic mouth that develops into the anterior pituitary.

Anterior pituitary origin

Derived from stomodeal ectoderm via Rathke’s pouch; secretes FSH, LH, etc.

Posterior pituitary origin

Develops from an outgrowth of the floor of the brain; stores and releases oxytocin.

SRY gene

Sex-determining region on the Y chromosome; its presence initiates male sexual differentiation.

SRY protein

Transcription factor produced from the SRY gene that promotes testis development and AMH production.

Mesonephric (Wolffian) duct

Embryonic duct system that becomes the epididymis and ductus deferens in males.

Paramesonephric (Müllerian) duct

Embryonic duct system that forms the oviducts, uterus, cervix and cranial vagina in females.

Alpha-fetoprotein

Fetal protein that binds estrogen, preventing it from entering the female brain and allowing surge center development.

Surge center (hypothalamus)

Region in the female hypothalamus that enables pre-ovulatory LH surges; absent in males.

Tonic center (hypothalamus)

Hypothalamic area that provides basal (pulsatile) GnRH secretion in both sexes.

Aromatization

Conversion of testosterone to estradiol in the male brain, leading to defeminization.

Peptide/Protein hormone mechanism

Hormone binds membrane GPCR → Gα activates adenylate cyclase → cAMP → protein kinase → new product synthesis.

Slow steroid mechanism

Steroid diffuses into cell, binds nuclear receptor, alters gene transcription and protein synthesis (hours).

Fast steroid mechanism

Steroid binds membrane receptor, triggers cAMP/protein kinase and Ca²⁺ changes (seconds-minutes).

Estrogen (ovary)

Steroid hormone regulating mating behavior and maintenance of the female duct system.

Testosterone (testis)

Steroid precursor of estrogen; drives male behavior, spermatogenesis and maintenance of male ducts.

Progesterone (corpus luteum)

Steroid that maintains pregnancy and inhibits uterine contractions.

Follicle-stimulating hormone (FSH)

Anterior pituitary glycoprotein that stimulates follicle growth, estrogen production and spermatogenesis.

Luteinizing hormone (LH)

Anterior pituitary glycoprotein stimulating ovulation, CL formation and Leydig cell testosterone synthesis.

Gonadotropin-releasing hormone (GnRH)

Hypothalamic peptide that triggers LH and FSH release from the anterior pituitary.

Oxytocin

Posterior pituitary peptide that stimulates myometrial and oviductal contractions for sperm transport.

Prostaglandin F₂α (PGF₂α)

Uterine lipid hormone that induces luteolysis and stimulates uterine contractions.

Female puberty – first estrus

Initial expression of standing heat indicating sexual receptivity; an external marker of puberty.

Metabolic threshold

Minimum body size and fat reserves required before a female can sustain pregnancy and reach puberty.

Male puberty criteria

Includes first mounting/erection, first ejaculation and attainment of a threshold sperm concentration.

GnRH pulse generator

Increase in frequency and amplitude of GnRH release that drives LH/FSH secretion at puberty.

Kisspeptin

Neuropeptide mediator of GnRH neuron activation; key genetic regulator of puberty onset.

Body size/fatness effect

Adequate growth and energy reserves accelerate puberty; poor nutrition delays it.

Seasonal breeder influence

Environmental photoperiod cues modulate timing of puberty in species breeding seasonally.

Social cue effect

Exposure to males or group housing of females can hasten puberty by altering pheromonal signals.