Lecture 03: Female Reproductive System

HoyaDocs — Repro Block | USMLE Step 1 Preparation

Lecture 03 — Overview

Female Reproductive System · HoyaDocs Repro Block

Page Summaries

🥚 Ovarian Follicles
Ovary zones · Primordial → Primary → Secondary → Graafian · Two-cell theory · Ovulation · Corpus luteum → Corpus albicans
Practice Qs: 1–3
🎺 Oviduct
Four regions (infundibulum · ampulla · isthmus · interstitial) · Mucosa/muscularis/serosa · Ciliated & peg cells · Ectopic pregnancy
Practice Qs: 4–6
🩸 Uterus & Menstrual Cycle
Endo/myo/perimetrium · Functionalis vs. basalis · HPO axis · Menses · Proliferative · Secretory · Luteal-placental shift
Practice Qs: 7–10
🌸 Cervix, Vagina & Breast
Ecto/endocervix + transformation zone · Vaginal pH · External genitalia · Bartholin & Skene glands · Mammary TDLU · Prolactin/oxytocin
Practice Qs: 11–14

Official Learning Objectives Map

1 Know the structure and function of the different follicles in the ovary Follicles ▼
2 Know the different components of the oviduct Oviduct ▼
3 Know the structure of the uterus and understand the integration of pituitary hormones and follicular development as they pertain to the menstrual cycle Uterus & Cycle ▼
4 Know the structure and function of the vagina, vestibular glands, external genitalia and mammary glands Vulva & Breast ▼

LO 1 — Ovarian Follicles

Folliculogenesis · Two-Cell Theory · Corpus Luteum · HoyaDocs Repro Block

Learning Objectives Covered
  • LO 1: Know the structure and function of the different follicles in the ovary
On This Page
  1. Gross Organization of the Ovary
  2. Primordial Follicle (Dormant Pool)
  3. Unilaminar & Multilaminar Primary Follicles
  4. Secondary (Antral) Follicle
  5.   ↳ Two-Cell / Two-Gonadotropin Theory
  6. Graafian (Mature/Tertiary) Follicle
  7. Ovulation & Meiotic Arrest Release
  8. Corpus Luteum & Corpus Albicans
  9. Summary Table — All Follicle Stages

🧠 Testing Your Understanding!

Testing Your Understanding — LO 1, Question 1

A 29-year-old woman undergoing workup for infertility is found to have a homozygous loss-of-function mutation in the aromatase gene (CYP19A1). Predict the hormonal, follicular, and clinical consequences of this defect, and explain why both the patient AND her mother experienced virilization during the patient's prenatal life.

Consider: two-cell theory, theca-to-granulosa relay, placental aromatase, maternal-fetal hormone crosstalk

✓ Answer: Aromatase deficiency blocks conversion of androgens to estrogens in granulosa cells — and in the placenta during pregnancy.

In the ovary, granulosa cells cannot convert theca-derived androstenedione to estradiol → low estradiol, elevated androgens in the follicle. Consequences: (1) failure of follicular maturation because estrogen is required for granulosa-cell proliferation and LH receptor upregulation → anovulation and infertility; (2) no positive estradiol feedback → no LH surge; (3) high FSH (no negative feedback); (4) ovarian cysts from chronic stimulation. During fetal life, placental aromatase normally converts fetal adrenal androgens (DHEA-S → T) to estrogens; without it, androgens cross back to the mother → maternal virilization during pregnancy that resolves post-partum, and 46,XX virilization of the fetus. At puberty: delayed secondary sex characteristics, tall stature (estrogen closes growth plates), and osteoporosis risk. Consider: why would treatment include low-dose estrogen replacement? (To close growth plates, develop secondary sex characteristics, and prevent osteoporosis.)

Testing Your Understanding — LO 1, Question 2

A pathologist reviews an ovarian biopsy from a postmenopausal woman with new-onset vaginal bleeding. Microscopy shows solid and tubular arrangements of neoplastic cells with scattered Call–Exner bodies (small rosettes of cells around eosinophilic fluid). Identify the tumor, explain the hormone it most likely secretes, and predict the endometrial finding.

Consider: granulosa-cell embryology, Call–Exner bodies, estrogen-driven endometrial pathology

✓ Answer: Adult granulosa-cell tumor (sex-cord stromal tumor) secreting estrogen → endometrial hyperplasia → bleeding.

Granulosa cells are the FSH-responsive / aromatase-containing cells of the follicle; tumors retain their estrogen-producing capacity. Call–Exner bodies — small follicle-like rosettes of granulosa cells around eosinophilic, Call-Exner fluid — are pathognomonic on histology. Postmenopausally, estrogen secretion causes endometrial hyperplasia and, with time, ↑ risk of endometrial adenocarcinoma; bleeding is the presenting sign. In children, granulosa-cell tumors cause precocious puberty. Treatment: surgical resection; long-term surveillance for late recurrence. Consider: how would a theca-cell (thecoma) or Sertoli-Leydig tumor differ? (Thecoma also makes estrogen but without Call-Exner bodies; Sertoli-Leydig tumors typically cause virilization via androgens.)

LO 2 — Oviduct (Fallopian Tube)

Four Regions · Mucosa/Muscularis/Serosa · Ectopic Pregnancy · HoyaDocs Repro Block

Learning Objectives Covered
  • LO 2: Know the different components of the oviduct
On This Page
  1. Overview & Four Regions
  2. Histologic Layers (Mucosa · Muscularis · Serosa)
  3.   ↳ Ciliated vs. Peg (Secretory) Cells
  4. Function — Gamete & Embryo Transport
  5. Clinical Correlates — Ectopic Pregnancy, PID, Salpingitis

🧠 Testing Your Understanding!

Testing Your Understanding — LO 2, Question 1

A 24-year-old woman with a history of two prior episodes of gonococcal cervicitis presents to the ED with acute unilateral pelvic pain and a positive urine β-hCG. Transvaginal ultrasound shows an empty uterus and a 2-cm adnexal mass with surrounding free fluid. Trace the pathophysiology from the original infection to the current presentation, and name the most likely tubal sub-site of the abnormal implantation.

Consider: PID → tubal scarring → impaired ciliary function; segments of the oviduct and their roles in transport; common ectopic sites

✓ Answer: Ampullary ectopic pregnancy from chronic salpingitis → impaired embryo transport.

Prior gonococcal/chlamydial cervicitis ascends to cause salpingitis → PID. Inflammation damages the ciliated epithelium and causes intraluminal scarring / adhesions, which impairs peristaltic and ciliary transport. A fertilized embryo moving from the ovary through the tube becomes "stuck" in the convoluted ampulla (the widest segment with the most mucosal folds — and by far the most common ectopic site, 70–80%). The embryo implants into thin tubal wall; β-hCG rises but abnormally; the mass grows until it either regresses, is surgically/medically treated, or ruptures with life-threatening hemorrhage. Management here (stable, β-hCG presumably low, early): methotrexate. Unstable or rupturing: salpingectomy. Consider: why would interstitial (pars interstitialis) ectopics be more catastrophic? (Thick myometrium disguises the growth; rupture causes massive hemorrhage from uterine vessels.)

Testing Your Understanding — LO 2, Question 2

A researcher is studying the epithelial cells of the fallopian tube. Using fluorescent microscopy, she labels one cell type that shows dense apical cilia. She then observes the cell's response to estrogen and progesterone. Predict the morphologic and functional changes that occur across the menstrual cycle.

Consider: estrogen-dependent ciliation, peg-cell secretion, luteal-phase changes

✓ Answer: Estrogen drives ciliation and secretory activity (peak at ovulation); progesterone suppresses them in the luteal phase.

The tubal epithelium alternates between a follicular (estrogenic) phenotype and a luteal (progestational) phenotype. During the follicular phase, rising estradiol induces cilia growth, increases ciliary beat frequency, and stimulates peg-cell secretory activity — peaking around ovulation to facilitate oocyte pickup and early embryo transport. In the luteal phase, progesterone from the corpus luteum down-regulates estrogen receptors, causing deciliation and decreased secretion (prepares the uterus, not the tube, for implantation). These changes parallel the functional shift from "transport" to "pregnancy maintenance." Consider: if a patient has anovulation and chronic unopposed estrogen, how would the tubal epithelium appear? (Persistently "ovulation-like" — hyperciliated and hypersecretory.)

LO 3 — Uterus & Menstrual Cycle

Uterine Histology · HPO Axis · Follicular / Luteal Phases · HoyaDocs Repro Block

Learning Objectives Covered
  • LO 3: Know the structure of the uterus and understand the integration of pituitary hormones and follicular development as they pertain to the menstrual cycle
On This Page
  1. Uterine Wall — Endometrium, Myometrium, Perimetrium
  2. Endometrium — Functionalis & Basalis
  3. Hypothalamic-Pituitary-Ovarian Axis
  4. Menstrual Cycle — Three Phases
  5.   ↳ Menses (Days 0–5)
  6.   ↳ Proliferative / Follicular (Days 6–14)
  7.   ↳ Secretory / Luteal (Days 15–28)
  8. If Fertilization Occurs — hCG Rescue
  9. Integrated Cycle Table

🧠 Testing Your Understanding!

Testing Your Understanding — LO 3, Question 1

A 27-year-old patient undergoing IVF is given a GnRH agonist daily for 2 weeks prior to her egg-retrieval cycle to prevent a premature LH surge. Explain — at the receptor and cellular level — how a GnRH agonist paradoxically suppresses LH/FSH when endogenous GnRH stimulates it.

Consider: GnRH pulsatility, receptor desensitization, initial flare effect

✓ Answer: Continuous (non-pulsatile) GnRH receptor stimulation downregulates pituitary gonadotrophs → LH and FSH suppression.

Physiologic GnRH is pulsatile (~every 90 minutes); the gonadotroph's GnRH receptor cycles through binding, signaling, internalization, and resensitization. When a long-acting GnRH agonist (leuprolide, goserelin) provides constant receptor occupation, there is an initial flare (24–72 h of ↑ LH/FSH), followed by receptor down-regulation, internalization, and uncoupling from signaling pathways. After 1–2 weeks, LH and FSH fall to nearly undetectable levels, producing a "medical castration" state. In IVF, this prevents the endogenous LH surge from triggering ovulation prematurely during controlled ovarian stimulation. Clinical uses include: prostate cancer (androgen suppression), endometriosis, uterine fibroids, precocious puberty, and transgender care. Consider: how does a GnRH antagonist (e.g., ganirelix, degarelix) differ? (Immediate competitive blockade — no flare — also used in IVF.)

Testing Your Understanding — LO 3, Question 2

A 22-year-old woman presents with 6 months of amenorrhea following a dilatation and curettage for retained products of conception. She has normal FSH, LH, estradiol, and progesterone on blood work, and a progesterone challenge test fails to induce withdrawal bleeding. Name the diagnosis, explain the pathology, and describe the histologic reason for the amenorrhea.

Consider: functionalis vs. basalis, basal arteries, endometrial regeneration

✓ Answer: Asherman syndrome — intrauterine adhesions from damage to the basalis.

Overly aggressive curettage can strip or scar the basalis — the non-shedding deep layer supplied by straight arteries and responsible for regenerating the functionalis each cycle. Without an intact basalis, the functionalis cannot be rebuilt, so estrogen and progesterone can't create a new shedding layer — leading to secondary amenorrhea despite a normal hormonal axis. Diagnostic: a progesterone withdrawal test fails (no layer to shed); hysterosalpingography or hysteroscopy shows intrauterine synechiae. Treatment: hysteroscopic lysis of adhesions + estrogen therapy to promote regrowth; some clinicians place an IUD or balloon stent to prevent re-adhesion. Fertility can often be restored. Consider: why is progesterone alone insufficient to induce bleeding here? (No endometrial substrate — the basalis is scarred, so there are no spiral arteries or functionalis to respond.)

LO 4 — Cervix, Vagina, External Genitalia & Mammary Glands

Transformation Zone · Vestibular Glands · Breast Histology · HoyaDocs Repro Block

Learning Objectives Covered
  • LO 4: Know the structure and function of the vagina, vestibular glands, external genitalia, and mammary glands
On This Page
  1. Cervix & Transformation Zone
  2. Vagina — Three Layers + Epithelium
  3. External Genitalia (Clitoris, Labia, Vestibule)
  4. Vestibular Glands — Bartholin & Skene
  5. Mammary Glands — Structure & Clinical
  6. Male/Female Analogous Structures Summary

🧠 Testing Your Understanding!

Testing Your Understanding — LO 4, Question 1

A 54-year-old postmenopausal patient presents with recurrent vaginal itching, burning, and dyspareunia. On exam, the vaginal epithelium is thin, pale, and friable with petechiae. Vaginal pH is 6.5. Explain the underlying histologic and microbiologic changes, and propose a physiologically-based treatment.

Consider: estrogen's role in vaginal epithelium, glycogen, lactobacilli, and pH

✓ Answer: Atrophic vaginitis from estrogen deficiency → treat with topical (vaginal) estrogen.

In reproductive years, estrogen drives glycogen accumulation in superficial squamous cells of the vagina. When these cells desquamate, lactobacilli ferment the glycogen into lactic acid, maintaining a protective vaginal pH of 3.8–4.5. After menopause, estrogen withdrawal → thin, atrophic epithelium with minimal glycogen → loss of lactobacilli dominance → pH rises (often > 5) → increased susceptibility to bacterial vaginosis, candidiasis, UTI, and mechanical trauma during intercourse (friable mucosa). Treatment: topical vaginal estrogen (cream, tablet, or ring) restores glycogen, re-establishes lactobacilli, lowers pH, and thickens the epithelium. Topical delivery minimizes systemic absorption, which is preferred over oral estrogen for localized symptoms. Consider: why might this patient also have stress urinary incontinence? (Estrogen supports urethral and bladder-neck tissue; its withdrawal weakens these structures.)

Testing Your Understanding — LO 4, Question 2

A new mother is breastfeeding and experiences painful engorgement. When her infant begins to suckle, she feels a rush of warmth and her milk begins to flow. Name the two pituitary hormones involved, describe their specific actions on breast tissue, and explain the physiology of the let-down reflex.

Consider: anterior vs. posterior pituitary, alveolar secretion, myoepithelial contraction, neuroendocrine reflex

✓ Answer: Prolactin (anterior pituitary) drives milk synthesis; oxytocin (posterior pituitary) drives ejection via myoepithelial contraction.

Milk production requires two distinct pituitary hormones acting on different targets in the mammary gland: (1) Prolactin from the anterior pituitary acts on luminal secretory epithelium of the alveoli to synthesize milk proteins, lipids, and lactose. Dopamine tonically inhibits prolactin; suckling suppresses dopamine → prolactin rises. (2) Oxytocin from the posterior pituitary acts on myoepithelial cells wrapped around alveoli and ducts → contraction → milk ejection ("let-down"). The let-down reflex is a neuroendocrine arc: infant suckling → afferent signal via nerves → paraventricular & supraoptic nuclei → posterior pituitary → oxytocin release into blood. Oxytocin also causes postpartum uterine contractions (involution of the uterus and reduced bleeding). Consider: why might a patient with a prolactin-secreting pituitary adenoma experience galactorrhea AND amenorrhea? (Prolactin suppresses GnRH → hypogonadotropic hypogonadism → anovulation.)

Practice Questions

Lecture 03 — Female Reproductive System · HoyaDocs Repro Block

LO 1 — Ovarian Follicles (Q1–Q3)

Question 1

A 28-year-old woman is evaluated for infertility and oligomenorrhea. Labs show LH 22 mIU/mL, FSH 6 mIU/mL (LH:FSH ratio > 3), elevated testosterone, and mildly elevated free androgens. Pelvic ultrasound shows bilateral enlarged ovaries with multiple small antral follicles arranged peripherally. Which of the following best explains the hormonal and follicular findings?

A. Primary ovarian insufficiency with elevated FSH

B. Hyperprolactinemia suppressing GnRH

C. Elevated LH:FSH ratio driving theca androgen production with insufficient granulosa aromatization

D. Congenital adrenal hyperplasia (21-hydroxylase deficiency)

E. Granulosa-cell tumor secreting estrogen

✓ Correct: C — Polycystic ovary syndrome (PCOS).

PCOS features a distortion of the two-cell theory. Elevated LH overstimulates theca cells to produce excess androstenedione/testosterone, but relatively low FSH means granulosa cells have inadequate aromatase activity → androgens are not converted to estradiol effectively. Result: hyperandrogenism (hirsutism, acne), anovulation, and multiple arrested antral follicles (the "string of pearls" US appearance). A (POI) would show ↑↑ FSH. B (prolactinoma) would suppress LH. D (CAH) would show ↑ 17-OH progesterone. E (granulosa tumor) would show elevated estradiol and a unilateral mass.

Question 2

A researcher observes developing ovarian follicles under a light microscope. In one follicle, the primary oocyte is surrounded by a clear glycoprotein layer, several layers of granulosa cells, and outer stromal cells that have begun to organize into a distinct inner secretory layer. No fluid-filled cavity is yet visible. Which follicular stage is depicted?

A. Primordial follicle

B. Unilaminar primary follicle

C. Multilaminar primary follicle

D. Secondary (antral) follicle

E. Graafian follicle

✓ Correct: C — Multilaminar primary follicle.

Three key features confirm the stage: (1) a zona pellucida has formed (the clear glycoprotein layer) — this first appears at the multilaminar primary stage; (2) multiple layers of granulosa cells (vs. single layer in unilaminar primary); (3) theca interna differentiation has begun (stromal cells forming a secretory layer). Critically, no antrum is visible yet — that defines the next stage (secondary/antral follicle). A (primordial) has single squamous follicular cells and no zona pellucida. B (unilaminar primary) has only one layer of granulosa and developing zona pellucida. D (antral) requires a fluid cavity. E (Graafian) has an eccentric oocyte, cumulus oophorus, and a very large antrum.

Question 3

A woman with amenorrhea of 10 weeks is confirmed pregnant with β-hCG of 45,000 mIU/mL. She undergoes bilateral oophorectomy during the 10th week for a non-pregnancy-related emergency. Which of the following best describes why her pregnancy continues normally?

A. The placenta has already taken over progesterone production (luteal-placental shift)

B. hCG directly maintains the endometrium independent of the ovaries

C. The corpus luteum produces most of the estrogen

D. FSH maintains endometrial thickness

E. The fetal adrenal produces progesterone in sufficient amounts

✓ Correct: A — Luteal-placental shift occurs around weeks 8–10, with the placenta assuming progesterone production.

In the first ~8 weeks of pregnancy, the corpus luteum is the main source of progesterone, maintained by β-hCG (which mimics LH). Between weeks 8 and 10, the placenta takes over progesterone production — this is the luteal-placental shift. After this point, the corpus luteum (and thus the ovaries) becomes dispensable for pregnancy maintenance. In this case, at 10 weeks, oophorectomy is well-tolerated because the placenta is already the dominant source. B is incorrect — hCG acts on the ovary, not directly on the endometrium. C is wrong in the mature placental period. D — FSH has no role here; it's suppressed. E — fetal adrenal produces steroid precursors, not substantive progesterone at this stage.

LO 2 — Oviduct / Fallopian Tube (Q4–Q6)

Question 4

A 22-year-old woman presents to the ED with 6 hours of severe left lower quadrant pain, one episode of vomiting, and vaginal spotting. Urine β-hCG is positive at 3,200 mIU/mL. Transvaginal ultrasound shows no intrauterine gestation and a 2.5-cm complex mass in the left adnexa with surrounding free pelvic fluid. Which section of the oviduct is the most likely site of implantation?

A. Fimbriae

B. Infundibulum

C. Ampulla

D. Isthmus

E. Pars interstitialis

✓ Correct: C — Ampulla, the most common site of ectopic pregnancy (~70–80%).

The ampulla is the longest, widest section of the fallopian tube with highly folded mucosa — both the normal site of fertilization and by far the most common location for ectopic implantation. Scarring from prior PID, endometriosis, or tubal surgery impairs the ciliary and peristaltic transport → embryo gets stuck in the convoluted mucosa and implants. B (infundibulum) and A (fimbriae) are much less common. D (isthmus) is second-most common. E (pars interstitialis) is rare but the most dangerous due to catastrophic hemorrhage when it ruptures.

Question 5

A gynecologist performs a tubal ligation for permanent contraception by applying clips to the narrowest, most muscular segment of the fallopian tube just before it enters the uterus. Which segment is clipped?

A. Infundibulum

B. Ampulla

C. Isthmus

D. Pars interstitialis

E. Fimbriae

✓ Correct: C — Isthmus, the preferred site of tubal ligation.

The isthmus is the shortest and narrowest segment of the fallopian tube (just before it enters the uterus) with the thickest muscular wall. These features make it the ideal site for clips or rings in tubal ligation — occlusion is reliable, and the sturdy wall holds the ligation well. Ampullary occlusion is avoided because of its wider lumen and mucosal folds. Fimbrial surgery (salpingectomy of fimbriae) is another contraceptive option, especially given recent evidence that high-grade serous ovarian cancers often arise there.

Question 6

An investigator labels the two epithelial cell types of the fallopian tube. Estrogen administration causes cell type A to grow more apical cilia and cell type B to increase secretion of tubal fluid. Progesterone dampens both. Which statements about cell types A and B are correct?

A. Cell A is a ciliated cell; cell B is a peg (non-ciliated secretory) cell — both are estrogen-dependent

A. Cell A is a goblet cell; cell B is a ciliated cell — both are progesterone-dependent

C. Cell A is a ciliated cell; cell B is a paneth cell — both are independent of steroid hormones

D. Cell A is a neuroendocrine cell; cell B is a mucus cell — both are androgen-dependent

E. Cell A is a Sertoli cell; cell B is a Leydig cell

✓ Correct: A — Ciliated cells and peg (non-ciliated secretory) cells are the two epithelial cell types of the oviduct, both estrogen-dependent.

The simple columnar epithelium of the fallopian tube has exactly two cell types: (1) ciliated cells with apical cilia that beat toward the uterus to propel the oocyte/embryo; (2) peg cells (non-ciliated secretory) that secrete tubal fluid rich in glycoproteins and nutrients for the oocyte, sperm capacitation, and early embryo. Both are estrogen-responsive — cilia and secretion peak at ovulation. Progesterone (luteal phase) causes deciliation and reduced secretion. B (goblet) is intestinal/respiratory. C (paneth) is intestinal. D (neuroendocrine) is incorrect. E (Sertoli/Leydig) are testicular.

LO 3 — Uterus & Menstrual Cycle (Q7–Q10)

Question 7

A 25-year-old woman tracks her menstrual cycle and consistently has a 35-day cycle. She wants to know when she ovulates. Based on the physiology of the luteal phase, on approximately which day of her cycle does ovulation most likely occur?

A. Day 14

B. Day 17

C. Day 21

D. Day 28

E. Day 35

✓ Correct: C — Day 21 (35-day cycle minus 14-day luteal phase).

The luteal phase is essentially fixed at ~14 days — the corpus luteum's lifespan is programmed unless rescued by hCG. Cycle-length variation comes from the follicular phase. Therefore, ovulation = (cycle length) − 14. For a 35-day cycle: 35 − 14 = day 21. Day 14 (A) applies only to the canonical 28-day cycle. This rule is critical for fertility counseling and natural family planning — a common patient question.

Question 8

A 34-year-old woman undergoes an endometrial biopsy on cycle day 24. Histology shows elongated, tortuous glands with a "saw-toothed" appearance, coiled spiral arteries, and prominent stromal edema. Which of the following ovarian and hormonal states is consistent with these histologic findings?

A. Dominant follicle actively producing estradiol; progesterone low

B. Corpus luteum producing progesterone (and some estradiol)

C. Primordial follicle pool with low hormone production

D. Corpus albicans scar with no hormonal output

E. Atretic follicles with anovulation and absent hormone production

✓ Correct: B — Active corpus luteum secreting progesterone (secretory/luteal phase endometrium).

The histologic features described — coiled "saw-tooth" glands, spiral arteries, and stromal edema/decidualization — are pathognomonic of the secretory (luteal) phase, driven by progesterone from the corpus luteum. Day 24 is firmly in the luteal phase of a 28-day cycle. A (proliferative) would show straight tubular glands and mitotically active stroma. C, D, and E all describe low-hormone states that do not produce the secretory transformation.

Question 9

A 45-year-old woman with uterine fibroids is started on monthly leuprolide injections to shrink the fibroids before surgery. Three days after her first dose, she reports worsening pelvic pain and heavy bleeding. By week 2, her bleeding has stopped. Which mechanism explains the transient worsening followed by suppression?

A. Initial GnRH-receptor flare followed by receptor downregulation and gonadotropin suppression

B. Direct toxicity of leuprolide on uterine smooth muscle

C. Competitive antagonism of the androgen receptor

D. Inhibition of aromatase leading to estrogen depletion

E. Blockade of LH receptors on the corpus luteum

✓ Correct: A — Leuprolide is a GnRH agonist: initial "flare" (↑ LH/FSH) followed by receptor desensitization and gonadotropin suppression.

Physiologic GnRH is pulsatile; constant receptor stimulation causes internalization and uncoupling of gonadotroph GnRH receptors. For the first 1–2 weeks of leuprolide therapy, there is a paradoxical flare (↑ LH/FSH, ↑ estradiol) before receptor desensitization suppresses gonadotropin release and creates a hypoestrogenic state. The hypoestrogenic environment shrinks estrogen-dependent fibroids. Clinical pearl: to prevent the flare in prostate cancer treatment, patients are co-treated with an androgen-receptor antagonist (flutamide, bicalutamide) for the first month.

Question 10

A 30-year-old woman has had amenorrhea for 6 months following a D&C for retained products of conception 1 year ago. Her serum FSH, LH, and estradiol are normal. After a progestin challenge (oral medroxyprogesterone acetate), she does not have withdrawal bleeding. Hysterosalpingography shows filling defects consistent with intrauterine adhesions. Which endometrial layer is most directly affected?

A. Myometrium

B. Perimetrium

C. Functionalis of the endometrium

D. Basalis of the endometrium

E. Cervical transformation zone

✓ Correct: D — Damage to the basalis (Asherman syndrome).

The basalis is the deep, non-shedding endometrial layer supplied by straight arteries. It regenerates the functionalis after every menses. Aggressive instrumentation (D&C, especially postpartum for retained POC) or severe endometritis can strip or scar the basalis → intrauterine adhesions (Asherman syndrome). Without a functional basalis, no new functionalis is formed — so progestin withdrawal cannot induce bleeding despite normal hormones. Treatment: hysteroscopic lysis of adhesions + estrogen therapy to promote basalis regrowth.

LO 4 — Cervix, Vagina, External Genitalia & Breast (Q11–Q14)

Question 11

A 38-year-old woman has an abnormal Pap smear showing high-grade squamous intraepithelial lesion (HSIL). Colposcopy with biopsy of the transformation zone confirms CIN III with extensive koilocytic change. PCR identifies HPV type 16. Which viral proteins drive the malignant transformation, and what cellular pathways do they disable?

A. E1 and E2 — inactivate telomerase

B. E6 and E7 — E6 degrades p53 and E7 inactivates Rb

C. L1 and L2 — capsid proteins that drive replication

D. Tax protein — activates NF-κB

E. HBx — disrupts cell cycle via p21

✓ Correct: B — HPV E6 degrades p53; E7 inactivates Rb → loss of cell-cycle checkpoints.

High-risk HPV types (16, 18, 31, 33, 45, etc.) produce two oncoproteins that disable core tumor-suppressor pathways: E6 promotes ubiquitin-mediated degradation of p53 (the G1/S DNA-damage checkpoint) and E7 binds and inactivates Rb (releasing E2F → unopposed cell-cycle progression). Together they produce uncontrolled proliferation in the transformation zone where immature squamous metaplastic cells are most susceptible. This drives dysplasia → CIN → invasive cervical cancer. L1/L2 are capsid proteins (basis for Gardasil vaccine). Tax is from HTLV-1 (ATLL). HBx is from HBV (hepatocellular carcinoma).

Question 12

An 18-year-old woman presents with a painful, tender swelling at the 4 o'clock position posterolateral to the vaginal introitus. There is overlying erythema and induration. Gram stain of expressed fluid grows gram-negative diplococci. The abscess is located in a gland that is the female homologue of which male structure?

A. Prostate

B. Bulbourethral (Cowper's) gland

C. Seminal vesicle

D. Epididymis

E. Glans penis

✓ Correct: B — Bartholin's gland abscess; Bartholin's is the homologue of the male bulbourethral (Cowper's) gland.

Bartholin's glands sit at the 4 and 8 o'clock positions posterolateral to the vaginal introitus and drain via a duct into the vestibule. An abscess typically presents as a painful, tender, fluctuant mass with erythema. Causative organisms include Neisseria gonorrhoeae, Chlamydia trachomatis, and mixed aerobic/anaerobic flora. Treatment is incision and drainage (often with Word catheter) plus antibiotics. Male homologue: bulbourethral (Cowper's) gland — both arise from the urogenital sinus and produce lubricating mucus during arousal. Prostate (A) is the male homologue of Skene's glands, NOT Bartholin's.

Question 13

A 25-year-old woman in her third day postpartum begins breastfeeding her newborn. When her infant latches and begins suckling, she experiences uterine cramping and a rush of milk from both breasts. Which hormone is primarily responsible for the milk ejection and uterine cramping, and where is it released?

A. Prolactin — anterior pituitary

B. Oxytocin — posterior pituitary

C. FSH — anterior pituitary

D. Estradiol — ovaries

E. Dopamine — hypothalamus

✓ Correct: B — Oxytocin from the posterior pituitary.

Suckling triggers the let-down reflex: sensory afferents from the nipple → hypothalamic paraventricular (PVN) and supraoptic (SON) nuclei → oxytocin release from the posterior pituitary. Oxytocin acts on myoepithelial cells around breast alveoli → milk ejection, and on uterine smooth muscle → contraction (involution of the uterus post-partum, decreased bleeding, and the characteristic breastfeeding cramps). Prolactin (A) — made in response to the same suckling cue, but its role is milk synthesis, not ejection. Dopamine (E) inhibits prolactin release; FSH (C) and estradiol (D) are not involved in lactation mechanics.

Question 14

A pathologist examines a needle biopsy from a suspicious breast mass. Low-power microscopy shows malignant epithelial cells confined within a duct-like space; surrounding the cells are spindle-shaped cells that stain positive for p63 and smooth muscle actin. High-power views show no evidence of basement membrane invasion. Which best classifies this lesion?

A. Invasive ductal carcinoma

B. Ductal carcinoma in situ (DCIS)

C. Lobular carcinoma in situ (LCIS)

D. Fibroadenoma

E. Paget disease of the breast

✓ Correct: B — Ductal carcinoma in situ (DCIS): malignant cells within the duct, intact myoepithelial layer, no invasion through basement membrane.

The key histologic feature distinguishing in-situ from invasive carcinoma is the preserved myoepithelial layer (positive for p63, SMA, calponin) surrounding the neoplastic duct. DCIS is confined to the ducts and has not breached the basement membrane — it is a non-obligate precursor to invasive ductal carcinoma. A would lack the myoepithelial layer. C (LCIS) would show loss of E-cadherin and non-cohesive cells in lobules. D (fibroadenoma) is a benign biphasic tumor with stromal proliferation. E (Paget disease) shows intraepithelial malignant cells in the nipple skin, often with underlying DCIS or invasive cancer. Management of DCIS: wide local excision ± radiation; some estrogen-receptor-positive cases also get endocrine therapy.