CORONA RADIATA — the innermost granulosa layer is released WITH the oocyte at ovulation (along with the zona pellucida)
Ovulation & meiotic arrests (LO1)
Prophase I (diplotene) — arrested since fetal life; can last 40+ years until LH surge
Meiosis I completes → secondary oocyte + first polar body (~hours before ovulation)
Metaphase II — at the moment of ovulation
FERTILIZATION (sperm entry) → meiosis II completes → second polar body extruded
Mittelschmerz — unilateral lower abdominal pain at mid-cycle from peritoneal irritation by follicular fluid/blood at ovulation
Progesterone has a thermogenic effect → basal body temp rises ~0.5°F post-ovulation (used in BBT charting for fertility tracking)
Corpus luteum lifecycle (LO1)
PROGESTERONE (+ some estradiol)
LH maintains CL in early luteal phase; progesterone negative feedback drops LH → CL regresses by days 24–28 → corpus albicans
Syncytiotrophoblast secretes β-hCG starting ~day 21–22 → hCG MIMICS LH → rescues CL → continued progesterone output until weeks 8–10
Weeks 8–10 of gestation — placenta takes over progesterone production; CL regresses to corpus albicans by ~week 12
Theca-lutein cysts — bilateral cystic enlargement from very high hCG; seen in complete hydatidiform mole, choriocarcinoma, and multiple gestations; regresses as hCG normalizes
Ovarian tumor clinical correlates (LO1)
Granulosa-cell tumor: secretes ESTROGEN → postmenopausal bleeding + endometrial hyperplasia; in children = precocious puberty; pathognomonic histology = CALL–EXNER BODIES
PCOS: ↑ LH:FSH ratio → excess theca androgens with insufficient aromatization → hyperandrogenism + anovulation
Epithelial ovarian cancer arising from the surface (germinal) epithelium — serous carcinoma most common subtype
LO 2
ON EXAM — 4 segments lateral→medial (I-A-I-I), ampulla = fertilization + ~70–80% of ectopics, isthmus = tubal ligation, ciliated + peg cells both ESTROGEN-dependent, PID (GC/Chlamydia) → scarred cilia → ectopic/infertility/hydrosalpinx, Fitz-Hugh-Curtis = violin-string perihepatic adhesions, methotrexate for stable early ectopic
Four oviduct segments — lateral to medial (LO2)
Segment
Shape / feature
Clinical / HY point
Infundibulum
Trumpet-shaped opening into peritoneum, fringed by FIMBRIAE
Fimbriae sweep the ovulated oocyte into the tube via ciliary currents
Ampulla
Longest, most dilated segment; complex labyrinthine mucosal folds
SITE OF FERTILIZATION (~99%); MOST COMMON site of ectopic pregnancy (70–80%)
Isthmus
Shortest, narrowest segment just before entering the uterus
Thick muscular wall; preferred site of TUBAL LIGATION (sterilization)
Pars interstitialis (intramural)
Segment that traverses the uterine wall (myometrium)
Interstitial ectopic is rare but CATASTROPHIC — high hemorrhage risk from uterine vessels
Histologic layers (LO2)
Simple columnar; mucosal folds (plicae) MOST prominent in the AMPULLA (labyrinthine appearance)
Inner circular + outer longitudinal smooth muscle; THICKEST in the ISTHMUS → site of tubal ligation
Continuous with the BROAD LIGAMENT (mesosalpinx); oviducts are intraperitoneal
FALSE — tubal epithelial cells never make oocytes; high-grade serous carcinoma often originates in the FIMBRIAL epithelium → BRCA carriers need risk-reducing salpingo-oophorectomy (RRSO), not just oophorectomy
Two tubal epithelial cell types (LO2)
Cell type
Function
Hormonal regulation
Ciliated cells
Beat cilia TOWARD THE UTERUS → move oocyte / early embryo medially; create fimbriae currents that draw in the oocyte
ESTROGEN-dependent — cilia density and beat frequency PEAK at ovulation
Peg (secretory) cells
Secrete tubal fluid (glycoproteins, nutrients) that nourishes oocyte / embryo and supports sperm capacitation
ESTROGEN-dependent — secretory activity peaks mid-cycle
Luteal-phase progesterone DECREASES ciliary activity + estrogen-receptor expression → deciliation; shifts epithelium from transport mode to pregnancy-maintenance mode
Timeline from ovulation → implantation (LO2)
Fimbriae sweep over the ovarian surface; cilia draw the oocyte + corona radiata into the infundibulum
Proliferates under estrogen; secretes under progesterone
Preserved regardless of hormones — regenerates the functionalis each cycle
Fate in the cycle
SHEDS at menstruation
NEVER sheds — regenerates the functionalis
Asherman syndrome — damage to the BASALIS from overly aggressive D&C or endometritis → fibrous intrauterine adhesions (synechiae) → no functionalis can regenerate → secondary amenorrhea + infertility. Tx: hysteroscopic lysis of adhesions + estrogen to stimulate regrowth
Progesterone withdrawal FAILS to produce bleeding — no functionalis substrate to shed, despite a normal hormonal axis
Continuous (non-pulsatile) GnRH DESENSITIZES the pituitary → shuts down LH + FSH. This is the mechanism of GnRH AGONISTS (leuprolide, goserelin) used long-term
(1) Prostate cancer (androgen suppression); (2) Endometriosis; (3) Central precocious puberty; (4) Uterine fibroids (shrinkage before surgery); (5) IVF (prevent premature LH surge)
GnRH ANTAGONISTS (ganirelix, degarelix) provide IMMEDIATE competitive receptor blockade → NO initial flare; also used in IVF and prostate cancer
Reproductive-age women have more columnar epithelium exposed on the ectocervix (ectropion) → larger TZ area → more opportunity for HPV-driven dysplasia → heightened screening in this age group
In-utero DIETHYLSTILBESTROL (DES) exposure — mothers given DES for threatened miscarriage (1940s–70s) → daughters have clear-cell vaginal adenocarcinoma risk
Suckling → afferent nerves → PARAVENTRICULAR + SUPRAOPTIC nuclei of hypothalamus → posterior pituitary → oxytocin released into blood → myoepithelial contraction → milk ejection
Placental estrogen + progesterone INHIBIT prolactin action on the breast during pregnancy (so no lactogenesis in utero). After delivery, placental hormones drop → prolactin is unopposed → lactogenesis begins
Prolactin SUPPRESSES GnRH pulse generator → hypogonadotropic hypogonadism → anovulation → amenorrhea. Treat with dopamine agonist (cabergoline, bromocriptine) to restore normal prolactin
BRCA1 / BRCA2 mutations → markedly elevated breast + ovarian cancer risk. Management: enhanced surveillance, or risk-reducing bilateral mastectomy and/or salpingo-oophorectomy (RRSO)
Male/female homologues — master review (LO4)
Female
Male
Common origin
Ovary
Testis
Gonadal ridge (indifferent gonad)
Clitoris
Glans + shaft of penis
Genital tubercle
Labia minora
Ventral penile shaft
Urogenital folds (unfused)
Labia majora
Scrotum
Labioscrotal swellings (unfused)
Bartholin's gland
Bulbourethral (Cowper's) gland
Urogenital sinus
Skene's gland
Prostate gland
Urogenital sinus
Round ligament of uterus
Gubernaculum testis
Gubernaculum
LO 1–4 · USMLE Step 1 Style
8 questions — cover all 4 LOs. Use these after finishing all tabs.
Q1. A 29-year-old woman undergoing infertility workup is found to have homozygous loss-of-function mutations in CYP19A1 (aromatase). Which set of findings is MOST expected?
A. Low androgens, low estradiol, low FSH, normal ovulation
B. High androgens, low estradiol, high FSH, anovulation
C. High estradiol, low androgens, low FSH, menorrhagia
D. Normal estradiol, low LH, normal follicular development
E. High estradiol, high progesterone, regular cycles
B — High androgens, low estradiol, high FSH, anovulation. Without aromatase, granulosa cells cannot convert theca-derived androstenedione → estradiol. Theca continues to make androgens under LH, so androgens accumulate, estradiol is low, positive feedback never occurs (no LH surge), and FSH rises from loss of estradiol negative feedback. The patient has anovulatory infertility. In fetal life, the absence of placental aromatase causes maternal AND fetal virilization during pregnancy.
Q2. A pathologist examines an ovarian biopsy from a postmenopausal woman with new-onset vaginal bleeding and endometrial hyperplasia on biopsy. Microscopy of the ovarian mass shows solid and tubular arrangements of cells with scattered Call–Exner bodies. Which hormone is this tumor MOST likely secreting, and from which cell of origin?
A. Progesterone — corpus luteum cell tumor
B. Testosterone — Leydig cell tumor
C. Estrogen — granulosa cell tumor
D. hCG — choriocarcinoma
E. Inhibin B — Sertoli cell tumor
C — Estrogen secreted by an adult granulosa-cell tumor. Granulosa cells are the FSH-responsive, aromatase-containing cells of the follicle. Tumors retain estrogen production; the pathognomonic finding is Call–Exner bodies (small follicle-like rosettes around eosinophilic fluid). Postmenopausal estrogen drives endometrial hyperplasia and bleeding; in children the same tumor causes precocious puberty.
Q3. A 24-year-old woman with two prior episodes of gonococcal cervicitis presents with unilateral pelvic pain and a positive β-hCG. Transvaginal ultrasound shows an empty uterus and a 2-cm right adnexal mass. Which segment of the fallopian tube is the MOST likely site of implantation?
A. Fimbriae of the infundibulum
B. Ampulla
C. Isthmus
D. Pars interstitialis (intramural segment)
E. Ovarian surface
B — Ampulla. The ampulla is the longest, widest, most convoluted segment and the normal site of fertilization — so an embryo with impaired tubal transport (from PID-scarred cilia) implants here in ~70–80% of ectopic pregnancies. The pars interstitialis is a much rarer site but far more dangerous due to hemorrhage risk from uterine vessels when it ruptures.
Q4. A 22-year-old woman presents with 6 months of secondary amenorrhea after a D&C for retained products of conception. FSH, LH, estradiol, and progesterone are all normal for cycle phase. A progesterone withdrawal challenge fails to produce bleeding. What is the MOST likely cause?
A. Premature ovarian insufficiency
B. Sheehan syndrome (postpartum pituitary necrosis)
C. Asherman syndrome — damage to the endometrial basalis
D. Prolactinoma
E. Polycystic ovary syndrome
C — Asherman syndrome. The endometrial basalis is normally retained and regenerates the functionalis each cycle. Aggressive curettage or endometritis can scar the basalis with intrauterine adhesions; without it, no functionalis can be built to shed — so progesterone withdrawal can't cause bleeding (no substrate). The hormonal axis is intact, which rules out POI, Sheehan, prolactinoma, and PCOS. Tx: hysteroscopic adhesiolysis + estrogen to stimulate regrowth.
Q5. A 27-year-old patient undergoing IVF is given daily leuprolide for 2 weeks prior to egg retrieval to prevent a premature LH surge. What BEST explains how a GnRH agonist ends up SUPPRESSING LH/FSH when endogenous GnRH normally stimulates them?
A. Competitive antagonism at pituitary GnRH receptors
B. Direct suppression of hypothalamic GnRH neurons
C. Continuous (non-pulsatile) GnRH receptor occupation → receptor down-regulation + desensitization
D. Negative feedback from increased testosterone
E. Inhibition of aromatase in granulosa cells
C — Continuous receptor occupation desensitizes pituitary gonadotrophs. Physiologic GnRH is pulsatile. Constant GnRH-agonist exposure causes an initial 24–72 h flare (↑ LH/FSH), followed by receptor internalization, downregulation, and signaling uncoupling → near-complete suppression after 1–2 weeks ("medical castration"). Uses: IVF (prevent premature LH surge), prostate cancer, endometriosis, fibroids, precocious puberty. GnRH antagonists (ganirelix, degarelix) block receptors immediately with no flare.
Q6. A 34-year-old G3P0 with two prior complete hydatidiform moles presents with bilaterally enlarged cystic ovaries on ultrasound. β-hCG is markedly elevated. Which structure accounts for the ovarian finding?
A. Endometrioma
B. Granulosa-cell tumor
C. Theca-lutein cysts
D. Corpus luteum cyst
E. Mature cystic teratoma
C — Bilateral theca-lutein cysts. Very high β-hCG (as in complete mole, choriocarcinoma, multiple gestations) chronically stimulates theca cells → bilaterally enlarged cystic ovaries. The cysts regress as hCG normalizes after mole evacuation. Key stem: "bilateral cystic ovaries + massively elevated β-hCG."
Q7. A 54-year-old postmenopausal woman presents with vaginal itching, burning, and dyspareunia. On exam, the vaginal epithelium is thin, pale, and friable; vaginal pH is 6.5. Which single physiologic change MOST directly explains the pH shift?
A. Increased Candida colonization
B. Estrogen withdrawal → ↓ glycogen in superficial squamous cells → ↓ Lactobacillus fermentation
C. Progesterone excess thickening cervical mucus
D. Increased prolactin suppressing vaginal secretions
E. Androgen excess altering vaginal flora
B — Estrogen withdrawal → ↓ glycogen → ↓ lactobacilli → pH rises. In reproductive years, estrogen drives glycogen accumulation in superficial squamous cells. When these cells desquamate, lactobacilli ferment glycogen into lactic acid → pH 3.8–4.5. Post-menopause, estrogen withdrawal thins the epithelium, minimizes glycogen, and allows non-lactobacillus flora to dominate → pH rises >5 → atrophic vaginitis + susceptibility to BV/candida. Treatment: topical vaginal estrogen.
Q8. A new mother experiences a warm rush and milk flow when her infant latches. Which pair of hormones and actions BEST explains the "let-down reflex" and milk production?
A. Prolactin drives ejection; oxytocin drives synthesis
B. Prolactin drives synthesis in alveolar luminal cells; oxytocin drives ejection via myoepithelial contraction
C. Estrogen drives both synthesis and ejection
D. Dopamine drives synthesis; prolactin drives ejection
E. hPL drives synthesis; hCG drives ejection
B — Prolactin (anterior pituitary) synthesis; Oxytocin (posterior pituitary) ejection. Prolactin acts on the luminal secretory epithelium of the alveoli to synthesize milk components; dopamine tonically inhibits prolactin, so suckling (which suppresses dopamine) raises prolactin. Oxytocin acts on the myoepithelial cells surrounding alveoli and ducts to contract them and eject milk. The let-down reflex: suckling → afferent nerves → PVN/SON in hypothalamus → posterior pituitary → oxytocin release.