Male and Female Reproductive Systems Explained
Male Reproductive System
The male reproductive tract follows this path: Seminiferous Tubules, Epididymis, Vas Deferens, Ejaculatory Duct, Urethra, and Penis.
Testes and Scrotum
The testes are paired gonads suspended in the tunica vaginalis. The scrotum consists of skin, dartos muscle, superficial scrotal fascia, cremaster muscle, and tunica vaginalis. The dartos and cremaster muscles regulate testicular temperature (~35°C) for spermatogenesis. The testes are perfused by the testicular artery and drained by the pampiniform plexus.
Seminiferous Tubules and Spermatogenesis
These convoluted tubules contain spermatogenic cells and Sertoli cells. Sertoli cells form the blood-testis barrier and produce androgen-binding protein (ABP), antimullerian hormone (AMH), and inhibin B. Spermatogenesis follows this sequence: Spermatogonium (diploid) → Primary spermatocyte → Secondary spermatocytes (haploid) → Spermatids → Spermatozoa.
Ducts and Accessory Glands
- Intratesticular: Tubuli recti and rete testis transport sperm; efferent ducts concentrate sperm.
- Extratesticular: The epididymis facilitates motility; the vas deferens propels sperm.
- Seminal Vesicles: Provide 70% of semen volume (fructose and semenogelins).
- Prostate Gland: Provides 30% of volume (Zn2+, HCO3-, and PSA for liquefaction).
- Bulbourethral Glands: Secrete lubricating, neutralizing fluid.
Penile Function
Erection is mediated by parasympathetic (PNS) activity and nitric oxide, causing arterial dilation. Emission moves semen into the urethra, while expulsion involves rhythmic contractions of the bulbospongiosus and pelvic muscles.
Male Puberty and Hormones
GnRH stimulates FSH (Sertoli cells/sperm) and LH (Leydig cells/testosterone). Testosterone is converted to DHT (via 5α-reductase) for prostate development and estradiol (via aromatase) in Sertoli cells.
Female Reproductive System
The ovaries contain the cortex (oogenic cells) and medulla. Oogonia undergo mitosis, and by birth, primary oocytes are arrested in prophase of meiosis I.
Follicular Development
- Primordial: Arrested in meiosis I.
- Primary: Cuboidal granulosa cells; theca interna produces androstenedione.
- Secondary: FSH-dependent; secretes liquor folliculi.
- Tertiary/Graafian: Mature follicles ready for ovulation.
Ovulation and Cycle
The LH surge triggers the completion of meiosis I, follicular rupture, and ovulation. The remaining follicle becomes the corpus luteum, which secretes progesterone and estrogen. If fertilization does not occur, the corpus luteum regresses into the corpus albicans, leading to menses.
Fertilization and Implantation
Fertilization typically occurs in the ampulla of the fallopian tubes. The zygote travels to the uterus for implantation within 5–7 days.
Clinical Conditions
- Endometriosis: Endometrial tissue grows outside the uterus.
- PCOS: Characterized by >20 antral follicles, impacting fertility.
- Turner Syndrome: Underdeveloped ovaries.
- Congenital Adrenal Hyperplasia: Can cause ambiguous external genitalia in XX individuals.