Male and female reproductive systems
Structure of the reproductive systems; microscopic anatomy of testis and ovary.
The essentials
The male reproductive system lies in the pelvis and includes a pair of testes, accessory ducts, glands and external genitalia. The testes sit in the scrotum, which keeps them about 2–2.5 °C below body temperature, necessary for spermatogenesis. Each testis has about 250 compartments called testicular lobules, each containing one to three highly coiled seminiferous tubules. These are lined by male germ cells (spermatogonia) and Sertoli cells, which nourish the germ cells. In the spaces between tubules are Leydig (interstitial) cells, which secrete androgens such as testosterone. Sperm pass through rete testis, vasa efferentia, epididymis, vas deferens, ejaculatory duct and urethra. Accessory glands are the paired seminal vesicles, a prostate and paired bulbourethral glands.
The female reproductive system includes a pair of ovaries, oviducts (fallopian tubes), uterus, cervix, vagina and external genitalia, along with mammary glands. Each ovary has a peripheral cortex and an inner medulla within the ovarian stroma. The fallopian tube has an infundibulum with fimbriae, a wider ampulla and a narrow isthmus. The uterus wall has three layers: outer perimetrium, middle thick muscular myometrium and inner glandular endometrium.
Key points
- Sertoli cells: nourish developing sperm; Leydig cells: secrete androgens.
- Seminal plasma comes from seminal vesicles, prostate and bulbourethral glands.
- Endometrium changes cyclically during the menstrual cycle; myometrium contracts strongly during childbirth.
- Mammary gland: alveoli → mammary tubules → mammary ducts → mammary ampulla → lactiferous duct.
Common mistakes
- The epididymis stores sperm; it is not where sperm are produced.
- The cervical canal together with the vagina forms the birth canal.