3. Medulla — loose CT with blood vessels, nerves, lymphatics.
Clinical: Most ovarian cancers arise from the germinal epithelium.
Primordial Follicle
What cells surround the oocyte in a primordial follicle, and at what stage of meiosis is the oocyte arrested?
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Answer
Primordial follicle: oocyte surrounded by a single layer of squamous follicular cells (+ stromal cells outside).
All follicles exist in this stage at birth, arrested in prophase I of meiosis.
Do NOT respond to FSH until puberty. Each cycle, ~20 are recruited and upgrade their follicular cells to columnar/granular (granulosa cells).
Primary Follicles
Differentiate unilaminar vs. multilaminar primary follicles. When does the zona pellucida form?
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Answer
Unilaminar primary follicle: oocyte surrounded by a single layer of granulosa cells (cuboidal/columnar) + basal lamina. Zona pellucida begins forming.
Multilaminar primary follicle: hyperplasia → multiple layers of granulosa cells. Now the zona pellucida is fully visible (proteoglycan-rich ECM between oocyte & granulosa — synthesized by BOTH). Stromal cells begin differentiating into theca interna.
Secondary (Antral) Follicle
What defines the secondary follicle? What is OMI, and what does the theca interna do that the theca externa doesn't?
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Answer
Defined by the antrum — a fluid-filled space containing hyaluronic acid-rich liquor folliculi with OMI (Oocyte Meiosis Inhibitor), which arrests the oocyte in prophase II.
Theca interna: steroidogenic cells → produce androstenedione → aromatized by granulosa cells into estrogen (2-cell hypothesis).
What are the corona radiata and cumulus oophorus, and where is the oocyte located in a Graafian follicle?
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Answer
Graafian follicle = dominant follicle. Oocyte is eccentrically located, surrounded by granulosa cells connected to the mature follicle by a granulosa pedicle.
Corona radiata:innermost single layer of granulosa cells directly hugging the oocyte (travels WITH the oocyte at ovulation).
Cumulus oophorus: accumulations of granulosa cells continuous with the pedicle — attaches the oocyte complex to the follicle wall.
Ovulation — LH Surge
What triggers the LH surge, and what happens to meiosis at ovulation?
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Answer
Rising estrogen (from the dominant Graafian follicle) → LH surge.
What is the basic structural unit of the mammary gland? What changes in active (lactating) vs. inactive glands?
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Answer
Compound tubuloalveolar glands grouped into lobes separated by dense CT (and fat). Milk drains through branching ducts → lactiferous ducts → lactiferous sinuses → nipple.
Inactive gland: predominantly ducts + adipose/CT, few secretory units. Active (lactating) gland: extensive tubuloalveolar secretory units with lumens full of milk; reduced stromal fat.
The three basic regions of an adult ovary are: the outer ___________ epithelium (simple cuboidal), the ___________ (contains follicles), and the innermost ___________ (loose CT with vessels).
Hint: Most ovarian cancers arise from the outermost layer.
FIB 02 — Meiotic Arrest
All primordial follicles at birth are arrested in ___________ I of meiosis. The antral follicle's OMI (Oocyte Meiosis Inhibitor) keeps them arrested in ___________ II. After the LH surge at ovulation, meiosis resumes but arrests again in ___________ II, where it stays until fertilization.
Hint: Prophase I → Prophase II → Metaphase II.
FIB 03 — Two-Cell Model
In the two-cell hypothesis, ___________ interna cells produce androstenedione (in response to LH), which is then aromatized into estrogen by the ___________ cells (in response to FSH).
Hint: "LH likes the theca; FSH feeds the granulosa."
FIB 04 — Corpus Luteum
After ovulation, granulosa cells become granulosa lutein cells and now produce ___________, while theca interna cells become theca lutein cells and now produce ___________. If pregnancy doesn't occur, the CL regresses into a white scar called the corpus ___________.
FIB 05 — Oviduct Parts
The 4 parts of the fallopian tube from ovary to uterus are: ___________ (with fimbriae), ___________ (site of fertilization), ___________ (shortest), and intramural portion.
FIB 06 — Endometrium Layers
The endometrium has two sublayers: the superficial ___________ is shed during menstruation, and the deep ___________ regenerates the lining. The functionalis is supplied by ___________ (coiled) arteries.
Hint: Spiral arteries are hormonally responsive; straight arteries supply the deep layer.
FIB 07 — Menstrual Cycle Phases
Days 0–5 = ___________ phase. Days 6–14 = ___________ (or follicular) phase, driven by estrogen. Days 15–28 = ___________ (or luteal) phase, driven by progesterone.
FIB 08 — LH Surge & Ovulation
Rising ___________ (hormone) from the dominant Graafian follicle triggers the ___________ surge, which overrides OMI and causes the follicle to rupture at ovulation (~day ___________ of a 28-day cycle).
Hint: Estrogen switches from negative to positive feedback when it reaches a threshold.
FIB 09 — Cervix Epithelium
The ectocervix is lined by stratified squamous ___________-keratinized epithelium; the endocervix is lined by simple ___________ epithelium. The junction between the two (the ___________ zone) is where cervical cancer most frequently arises.
Hint: HPV 16/18 cause most cervical cancers here — Pap smears sample this zone.
FIB 10 — Vestibular Gland Homologues
Bartholin's (greater vestibular) glands secrete mucus for lubrication and are homologous to the male ___________ glands. Skene (paraurethral) glands secrete lubricating fluid and are homologous to the male ___________.
Hint: "Big Bar = Bulbourethral; Skene = Prostate."
Instructions: Drag and drop the items into the correct order, then click "Check Order." Use "Show Answer" if you get stuck.
Drill 1 — Follicular Stages: Primordial → Corpus Albicans
Arrange these 7 stages of follicle maturation from earliest (at birth) to final degeneration.
Test Trap Mode: Each statement is either TRUE or FALSE as written. Many are designed to catch common exam errors. Click T or F — then read the explanation carefully.
Trap 01 — Oocyte Arrest
"At birth, all primordial follicles contain oocytes arrested in metaphase II of meiosis."
FALSE. Primordial follicles are arrested in prophase I at birth — where they stay until puberty. After the LH surge at ovulation, meiosis resumes and re-arrests in metaphase II. Metaphase II arrest only occurs AFTER ovulation and is only broken by fertilization. Classic order: prophase I → prophase II (in antral follicles, via OMI) → metaphase II.
Trap 02 — 2-Cell Hypothesis
"Granulosa cells produce androgens, which theca interna cells then convert into estrogen."
FALSE. Completely reversed. The theca interna cells (LH-stimulated) produce androstenedione, which the granulosa cells (FSH-stimulated, expressing aromatase) convert into estrogen. Mnemonic: "LH likes L-theca; FSH feeds F-granulosa." This is the classic 2-cell 2-gonadotropin model.
Trap 03 — Corpus Luteum
"In the corpus luteum, granulosa lutein cells still produce estrogen while theca lutein cells now produce progesterone."
FALSE. Also reversed. In the CL, granulosa lutein cells NOW make progesterone (their main CL product) — a switch from the estrogen they made before ovulation. Theca lutein cells now make estrogen — also a switch from androstenedione. This hormone "swap" is why the corpus luteum secretes both progesterone (dominant) + estrogen in the secretory phase.
Trap 04 — Endometrial Regeneration
"After menstruation, the functionalis regenerates the basalis."
FALSE. Backwards. The basalis (deep layer) is preserved during menses and regenerates the functionalis (superficial layer) in the proliferative phase. The functionalis is what sheds. Basalis is supplied by straight arteries (not hormonally sensitive), while functionalis is supplied by spiral/coiled arteries (estrogen/progesterone-responsive; constrict during ischemic phase).
Trap 05 — Ectocervix Epithelium
"The ectocervix is lined by stratified squamous KERATINIZED epithelium, like the skin."
FALSE. The ectocervix (and vagina) are lined by stratified squamous NON-keratinized epithelium — because they are moist internal surfaces. Keratinization is reserved for dry external surfaces (skin, labia minora/majora surface). The non-keratinized ectocervix meets the simple columnar endocervix at the transformation zone, the primary site of HPV-driven cervical cancer.
Trap 06 — Fertilization Site
"Fertilization most commonly occurs in the isthmus of the fallopian tube because it is the shortest segment."
FALSE. Fertilization occurs in the ampulla, not the isthmus. The ampulla is the longest and most dilated segment with complex mucosal folds that create a favorable environment (transudative fluid accumulation). Sperm travel uterus → isthmus → ampulla, where they encounter the ovum. The isthmus is the shortest segment closer to the uterus. Ectopic pregnancy most commonly occurs in the ampulla for the same reason.
Trap 07 — Menstrual Cycle Timing
"The luteal (secretory) phase varies considerably in length, while the follicular (proliferative) phase is fixed at ~14 days."
FALSE. Reversed. The luteal phase is FIXED at ~14 days (determined by corpus luteum lifespan — CL degenerates after ~14 days if no hCG). The follicular phase is VARIABLE — this is why cycle length differs between women. Clinical pearl: ovulation is ~14 days BEFORE the next menstrual period (not 14 days after the current one).
Trap 08 — Corpus Luteum-Placental Shift
"If pregnancy occurs, the corpus luteum must produce progesterone for the entire 9-month gestation."
FALSE. The corpus luteum-placental shift: hCG from the implanting blastocyst maintains the CL through the first trimester. Around weeks 8–10, the placenta takes over production of progesterone and estrogen — and the CL gradually regresses. Clinical relevance: removing the CL (e.g., oophorectomy) before week 10 risks miscarriage; after that, the placenta alone sustains pregnancy.
Follicular Stages — Full Reference
Stage
Granulosa Layer
Oocyte Stage
Defining Features
Primordial
Single squamous layer
Prophase I (arrested)
Present at birth; does not respond to FSH until puberty
Unilaminar primary
Single cuboidal/columnar layer
Prophase I
Zona pellucida begins forming; basal lamina present
Multilaminar primary
Multiple granulosa layers
Prophase I
Zona pellucida fully developed; theca interna starts
Secondary (Antral)
Multilayered + antrum
Prophase II (OMI-arrested)
Antrum with liquor folliculi + OMI; theca interna → androstenedione
Graafian (Tertiary)
Corona radiata + cumulus oophorus
Prophase II
Dominant follicle; eccentric oocyte attached by pedicle