Microscopic Anatomy of Reproductive System

Introduction to Reproductive Histology - Tiny Tubes & Tissues

• Focuses on microscopic organization: tubules, follicles, specialized cells.
• Germ Cells are fundamental:
  • Spermatogonia (♂): Line seminiferous tubules, become sperm.
  • Oogonia (♀): In ovarian follicles, become oocytes.
• Essential Supporting Cells:
  • Sertoli cells (testis): Nourish sperm, form blood-testis barrier.
  • Granulosa cells (ovary): Support oocyte, produce estrogen.

⭐ Sertoli cells secrete Anti-Müllerian Hormone (AMH), vital for male sexual differentiation.

Male: Testis & Spermatogenesis - Sperm Factory Secrets

• Testis Microanatomy:
  • Seminiferous Tubules: Coiled; site of sperm production. Lined by spermatogenic epithelium (Sertoli & germ cells).
  • Sertoli Cells: Columnar; form blood-testis barrier; nourish germ cells; secrete ABP, inhibin. 📌 Sertoli Supports Spermatogenesis.
  • Leydig Cells: Interstitial; produce testosterone (LH-stimulated). Eosinophilic; may contain Reinke crystals.
• Spermatogenesis: Spermatogonia to spermatozoa; ~74 days.

*   Spermiogenesis: Metamorphosis of spermatids (no division). Acrosome formation, nuclear condensation, flagellum development.

⭐ The blood-testis barrier, by Sertoli cell tight junctions, protects developing sperm (antigenically foreign) from autoimmune attack.

Male: Ducts & Glands - The Delivery Network

• Epididymis: Pseudostratified columnar epithelium with stereocilia (non-motile microvilli); sperm maturation & storage.
• Vas Deferens: Pseudostratified columnar epithelium; thick 3-layered muscularis (L-C-L) for peristalsis.
• Seminal Vesicles: Pseudostratified columnar; secrete alkaline, viscous fluid (~70% semen volume) rich in fructose.
• Prostate Gland: Tubuloalveolar glands; secretes milky, acidic fluid with PSA, acid phosphatase. Corpora amylacea common.
• Bulbourethral Glands: Mucous secretion (pre-ejaculate) for lubrication.

⭐ Corpora amylacea are characteristic calcified glycoproteins found in the prostate gland, increasing with age.

Female: Ovary & Oogenesis - Eggcellent Adventures

• Ovary: Cortex (follicles, germinal epithelium, tunica albuginea), Medulla (vasculature).
• Oogenesis: Oogonia ($2n$) → Primary Oocyte ($2n$, Prophase I arrest) → Secondary Oocyte ($n$, Metaphase II arrest post-Meiosis I) → Ovum ($n$, post-Meiosis II if fertilized).
• Folliculogenesis & Corpus Luteum:

![Ovary histology: follicles, corpus luteum](https://ylbwdadhbcjolwylidja.supabase.co/storage/v1/object/public/notes/L1/Anatomy_Microscopic_Anatomy_Microscopic_Anatomy_of_Reproductive_System/5fcd435f-443e-4602-8ff5-07b30fa07b85.gif)

⭐ Primary oocytes arrest in Diplotene (Prophase I) until puberty; Secondary oocytes arrest in Metaphase II until fertilization.

Female: Uterus, Tubes & Vagina - Womb With A View

• Fallopian Tubes (Salpinx): Mucosa: ciliated columnar (transport), peg cells (secretory). Ampulla: fertilization site.
• Uterus:
  • Endometrium: Simple columnar. Stratum functionalis (spiral arteries, sheds), Stratum basalis (regenerates).

-   Myometrium: Thick smooth muscle; hypertrophy in pregnancy.
-   Perimetrium: Outer serosa.

• Cervix: Endocervix (columnar, mucus), Ectocervix (strat. squamous NK). Transformation Zone (SCJ): dysplasia risk.
• Vagina: Strat. squamous NK epithelium, glycogen-rich (acidic pH via lactobacilli). No glands.

⭐ Arias-Stella reaction: nuclear atypia & cytoplasmic clearing in endometrial glands; benign, seen in pregnancy or with progestins.

High‑Yield Points - ⚡ Biggest Takeaways

• Sertoli cells: form blood-testis barrier, secrete ABP (Androgen Binding Protein), inhibin, and MIF (Müllerian Inhibiting Factor).
• Leydig cells: located in testicular interstitium, produce testosterone in response to LH (Luteinizing Hormone).
• Ovarian follicles: progress from primordial → primary → secondary → Graafian follicle (mature, pre-ovulatory).
• Corpus luteum: formed post-ovulation, secretes progesterone and estrogen, vital for early pregnancy.
• Endometrium: stratum functionalis (sheds during menstruation) and stratum basalis (regenerative layer).
• Cervix: transformation zone (squamocolumnar junction) is a key site for HPV infection and dysplasia.
• Placenta: Syncytiotrophoblast produces hCG & hPL; cytotrophoblast is the proliferative stem cell layer of villi.