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Anatomy & Physiology: The Male Reproductive System

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  • What are the four main tasks of the reproductive system?

    1. Form specialized gametes (sperm and ova)
    2. Bring male and female gametes together via sexual intercourse
    3. Combine genetic information through fertilization to form a zygote
    4. Support fetus development (gestation) and birth (parturition)

  • What are the primary sex organs (gonads) and their two essential products?

    Gonads are testes in males and ovaries in females. They produce gametes (sperm and ova) via meiosis and sex hormones (testosterone in males; estrogens and progesterone in females).

  • What is the Hypothalamic-pituitary-gonadal (HPG) axis?

    A hormonal system involving the hypothalamus, anterior pituitary, and gonads that regulates gamete and hormone production through GnRH, FSH, LH, sex hormones, and inhibin feedback.

  • How does puberty activate the HPG axis?

    Hypothalamus becomes less sensitive to sex hormone inhibition, releasing GnRH in pulses, stimulating anterior pituitary to release FSH and LH, which then stimulate gonads to produce more sex hormones until adult hormone patterns are established.

  • List the main ducts sperm travel through from testes to outside the body.

    Epididymis → Ductus deferens → Ejaculatory duct → Urethra

  • What are the three male accessory glands and their contributions to semen?

    Seminal glands (~70% semen volume, fructose-rich alkaline fluid), prostate (~30% semen volume, milky acidic fluid with enzymes), bulbo-urethral glands (mucus for lubrication and neutralizing urine acidity).

  • Where does spermatogenesis occur and when does it begin?

    Occurs in the seminiferous tubules of the testes and usually begins at puberty (~14 years of age).

  • Name the four important cell types in the seminiferous tubules.

    Sustentocytes (nurse cells), spermatogenic cells, myoid cells (smooth muscle-like), and interstitial endocrine (Leydig) cells.

  • What are the three major phases of spermatogenesis?

    1. Mitosis of spermatogonia
    2. Meiosis of spermatocytes
    3. Spermiogenesis (transformation of spermatids into sperm)

  • Describe the mitosis phase of spermatogenesis.

    Spermatogonia divide by mitosis; type A cells maintain stem cell pool, type B cells become primary spermatocytes.

  • What happens during meiosis in spermatogenesis?

    Primary spermatocytes undergo meiosis I to form two secondary spermatocytes, which undergo meiosis II to form four spermatids.

  • What is spermiogenesis?

    Process where spermatids elongate, lose excess cytoplasm, and develop a tail to become mature sperm.

  • What are the three major regions of a sperm cell?

    Head (genetic material and acrosome), midpiece (mitochondria for ATP), and tail (flagellum for movement).

  • What is the role of sustentocytes in spermatogenesis?

    Support developing sperm, form blood-testis barrier via tight junctions, and protect haploid cells from immune attack.

  • How is male reproductive function hormonally regulated?

    GnRH from hypothalamus stimulates FSH and LH release from anterior pituitary; LH stimulates testosterone from Leydig cells; FSH stimulates sustentocytes to release androgen-binding protein; testosterone and inhibin provide negative feedback.

  • What is the function of androgen-binding protein (ABP)?

    ABP binds testosterone in seminiferous tubules to maintain high local testosterone levels, promoting spermatogenesis.

  • Describe the negative feedback effects of testosterone and inhibin.

    Testosterone inhibits GnRH, FSH, and LH release; inhibin selectively inhibits FSH release from the anterior pituitary.

  • What are the effects of testosterone during puberty?

    Stimulates spermatogenesis, growth and maturation of sex organs, development of secondary sex characteristics, and libido.

  • List some male secondary sex characteristics induced by testosterone.

    Pubic, axillary, facial hair growth; deepening voice; increased bone and muscle mass; thicker, oilier skin; increased basal metabolic rate.

  • How long does spermatogenesis take from primary spermatocyte to mature sperm?

    Approximately 64–72 days.

  • What happens to immature sperm after spermatogenesis in the testes?

    They are pushed by testicular fluid into the epididymis, where they gain motility and fertilizing ability.