Anatomy & Physiology of the Female Reproductive System – Key Vocabulary

Learning Objectives

• Define key anatomical and physiological terms related to the female reproductive system.

• Identify and describe all external (vulvar) structures and their individual functions.

• Identify and describe all internal reproductive organs and their individual functions.

Terminology & Conceptual Grounding

• Vulva = collective term for all external female genitalia.

• Introitus = vaginal opening.

• Fourchette = posterior meeting point of the labia minora.

• Perineum = region between fourchette and anus; key for pelvic‐floor integrity.

• Gametes = sex cells (ovum & sperm).

• Capacitation = biochemical changes enabling sperm to fertilize an ovum.

• Zygote = fertilized egg; reaches the uterus in $4–7\ \text{days}$.

External Female Structures (Vulva)

• General Role

  • Provide protective barrier, sensory pleasure, entryway for sperm, and outlets for urine & menses.

Mons Pubis

• Rounded pad of subcutaneous fat covering the symphysis pubis.

• Cushion during coitus; develops pubic hair at puberty (secondary sexual trait).

Labia Majora

• Two large, fleshy folds extending from mons to perineum.

• Contain sebaceous/sweat glands & adipose; become pigmented post‐puberty.

• Protect labia minora, urethral meatus, and vaginal introitus.

Labia Minora

• Narrow folds located medial to labia majora; highly vascular, pink, moist mucosal surface.

• Meet anteriorly to form the prepuce over clitoris; posteriorly form fourchette.

• Rich blood supply supports sexual arousal & healing.

Clitoris

• Erectile organ homologous to male penis; Greek "klēitoris" = key.

• Rich vascular & nerve supply; sensitive to temperature, touch, pressure—primary organ of female sexual pleasure.

Vestibule

• Almond/oval‐shaped space bordered by labia minora, clitoris (anterior), and fourchette (posterior).

• Contains:

  • External urethral meatus (urinary opening).

  • Vaginal introitus (entrance).

  • Ducts of Bartholin’s glands (lubrication) & Skene’s glands (minor lubrication near urethra).

Bartholin’s (Greater Vestibular) Glands

• Two pea‐sized glands posterolateral to vaginal opening.

• Secrete alkaline mucus during arousal → ↓ friction & pain.

• Clinical note: can form cysts/abscesses requiring drainage.

Perineum

• Diamond‐shaped fibromuscular area between vulva & anus.

• Supports pelvic viscera, withstands intra‐abdominal pressure.

• Often incised (episiotomy) or torn in childbirth; integrity crucial for continence & sexual function.

Internal Female Structures

• Principal organs: Vagina, Uterus, Fallopian Tubes, Ovaries.

• Supported by ligaments (broad, round, ovarian, uterosacral, suspensory) & the bony pelvis.

Vagina

• Fibromuscular tube $8–10\ \text{cm}$ long; pH ≈ $4.5$ (acidic defense).

• Anterior to rectum, posterior to bladder/urethra.

• Layers: mucosal (rugae permit stretching), muscular, adventitia.

• Functions:

  • Exit for menstrual flow.

  • Organ of coitus.

  • Birth canal.

Uterus

• Hollow, thick‐walled, pear‐shaped; normal size ≈ $7.5 \times 5 \times 2.5\ \text{cm},\ 50–60\ \text{g}$.

• Positions: anteverted & anteflexed normally; can enlarge $\le 6\times$ in pregnancy.

• Parts:

  1. Body (Corpus)

  • Fundus = area superior to tubal entry.

  1. Isthmus

  • Narrow transition; becomes lower uterine segment late pregnancy.

  1. Cervix

  • "Neck" $2.5–3\ \text{cm}$; internal & external os; dilates to $\approx 10\ \text{cm}$ in labor.

• Layers:

  1. Perimetrium (serosa)—continuous laterally with broad ligaments.

  2. Myometrium—three smooth‐muscle layers:

  • Outer longitudinal (esp. fundus) → expulsive contractions.

  • Middle figure-8 (oblique) → hemostasis postpartum by vessel compression.

  • Inner circular → sphincter around tubes & internal os; prevents menses reflux & retains conceptus.

  1. Endometrium—vascular mucosa; cyclically thickens & sheds (menses/lochia).

  • Layers: Compact, Functional/Sponge (shed), Basal (regenerative).

• Functions: menstruation, implantation, fetal support, labor contractions.

Fallopian Tubes (Oviducts)

• Paired muscular tubes from uterine cornua to ovaries; reside in upper free edge of broad ligament.

• Length $8–14\ \text{cm}$ (avg $10\ \text{cm}$); four anatomical segments:

  1. Interstitial (Intramural) $1–2\ \text{cm}$—within myometrium.

  2. Isthmus $2–3\ \text{cm}$—straight, narrow.

  3. Ampulla $≈5\ \text{cm}$—widest; usual fertilization site.

  4. Infundibulum—funnel with fimbriae; one fimbria connects to ovary.

• Fimbriae create currents to capture ovum at ovulation (swell, become quasi‐erectile).

• Propulsion by cilia & peristalsis; provides nutritive fluid for early embryo.

• Functions: gamete transport, final oocyte maturation, sperm capacitation, site of fertilization, transport embryo/unfertilized ovum to uterus.

Ovaries

• Paired almond/oval organs: $1.5\ \text{cm}$ thick, $2.5\ \text{cm}$ wide, $3.5\ \text{cm}$ long; weight $4–8\ \text{g}$.

• Location: lateral pelvic wall, inferior‐posterior to tubes; attached via mesovarium & suspensory ligament.

• Regions:

  • Cortex—active outer zone producing oocytes & hormones (estrogen, progesterone).

  • Medulla—central connective tissue core with vessels/nerves.

  • Hilum—entry/exit for neurovascular bundle via mesovarium.

• Functions: oogenesis & steroidogenesis (estrogen = proliferative, progesterone = secretory & pregnancy maintenance).

Pelvic Support Structures

• Bony pelvis: ilium, ischium, pubis, sacrum, coccyx → cradle for organs.

• Ligaments: uterosacral, cardinal, pubocervical, round, broad, ovarian, suspensory.

• Muscles: levator ani group (pubococcygeus, iliococcygeus) & coccygeus form pelvic diaphragm resisting gravity & Valsalva forces.

• Clinical tie-in: pelvic floor dysfunction → prolapse, incontinence.

Physiological & Clinical Notes

• Vagina’s acidic milieu (pH $≈4.5$) derived from lactobacilli metabolism of glycogen → lactic acid; deters pathogens.

• Myometrial architecture ensures both effective labor (longitudinal) and postpartum hemostasis (figure-8).

• Tubal patency & ciliary function critical; scarring (PID) → ectopic pregnancy risk (commonly in ampulla).

• Cervical mucus cyclically changes (estrogen: thin, alkaline, "spinnbarkeit" for sperm entry; progesterone: thick plug guarding uterus in luteal phase/pregnancy).

• Endometrial receptivity ("window of implantation") aligns with progesterone surge.

Integrated Reproductive Function

1. Follicular phase (ovary) & proliferative phase (uterus) under estrogen ‑> endometrial thickening.

2. Ovulation triggered by LH surge; fimbriae capture oocyte; sperm undergo capacitation in tube.

3. Fertilization (ampulla) → zygote travels 4–7\ \text{days to uterus, assisted by cilia/peristalsis + tubal secretions.

4. Luteal phase: corpus luteum secretes progesterone → secretory endometrium; supports early embryo.

5. No fertilization → CL regression, progesterone drops → spiral artery spasm → menses (functional layer shed).

Ethical & Practical Implications / Real-World Relevance

• Understanding pelvic anatomy essential for safe obstetric interventions (e.g., episiotomy angles protect anal sphincter).

• Knowledge of cervical anatomy guides Pap smear collection & HPV vaccination impact.

• Tubal anatomy informs sterilization techniques (ligation at isthmus) and management of ectopic pregnancies.

• Hormonal functions underpin contraceptive design (combined vs. progestin-only) and HRT strategies.

• Pelvic floor education mitigates postpartum prolapse/incontinence.

Key Numerical / Dimensional References

• Fallopian tube length: $8–14\ \text{cm}$ (average $10\ \text{cm}$).

• Interstitial segment: $1–2\ \text{cm}$; Isthmus: $2–3\ \text{cm}$; Ampulla: $≈5\ \text{cm}$.

• Vagina length: $8–10\ \text{cm}$.

• Uterus mass: $50–60\ \text{g}$; pregnancy enlargement $\le 6\times$ size.

• Cervical dilation in labor: $\approx 10\ \text{cm}$.

• Ovarian size: $1.5\times 2.5\times 3.5\ \text{cm}$; weight $4–8\ \text{g}$.

• Vaginal pH: $4.5$.