Male Reproductive System Study Guide for the Reproductive System

Major Organs and Sperm Pathway

  • Major Components: Includes the testes, duct system (epididymis, vas deferens, ejaculatory duct, urethra), accessory glands, and the penis.

  • Sperm Pathway: Seminiferous tubules $\rightarrow$ Rete testis $\rightarrow$ Epididymis (12–16 days12\text{--}16\,\text{days} maturation) $\rightarrow$ Vas deferens $\rightarrow$ Ejaculatory duct $\rightarrow$ Urethra.

Testicular Anatomy and Physiology

  • Structure: Located in the scrotum for lower temperature maintenance.

  • Cellular Functions:

    • Seminiferous tubules: Site of spermatogenesis (sperm production).

    • Leydig cells: Secrete testosterone.

    • Sertoli cells: Nourish sperm and produce inhibin.

  • General Functions: Regulation of secondary sexual characteristics, maintenance of muscle mass, and bone density.

Duct System and Accessory Glands

  • Epididymis: Responsible for sperm maturation (motility acquisition), storage, and fluid absorption.

  • Vas Deferens: Propels sperm via peristalsis and forms part of the spermatic cord.

  • Seminal Vesicles (60%60\% of semen): Secrete fructose for energy, prostaglandins for sperm movement, and fibrinogen for temporary clotting.

  • Prostate Gland (30%30\% of semen):

    • Secretes alkaline fluid to neutralize vaginal acidity.

    • Contains clotting factors and fibrinolysin (liquefaction).

    • Converts testosterone to DHT (dihydrotestosterone) via 5-alpha reductase5\text{-alpha reductase}.

    • Primary site for BPH and prostate cancer.

  • Bulbourethral (Cowper) Glands: Produce mucus for lubrication and neutralize acidic urine residue.

Penis Structure and Function

  • Anatomy: Composed of two corpora cavernosa and one corpus spongiosum.

  • Functions: Serves as the copulatory organ for sperm delivery, facilitates urinary excretion, and enables erection through vascular engorgement.

Spermatogenesis and Hormonal Regulation

  • Spermatogenesis Sequence: Spermatogonia (mitosis) $\rightarrow$ Primary spermatocyte (Meiosis I) $\rightarrow$ Secondary spermatocyte (Meiosis II) $\rightarrow$ Spermatid $\rightarrow$ Spermiogenesis $\rightarrow$ Sperm.

  • HPG Axis:

    • GnRH stimulates LH (acts on Leydig cells for Testosterone) and FSH (acts on Sertoli cells for Spermatogenesis).

    • Negative Feedback: Regulated by Testosterone and Inhibin.

  • Testosterone Effects: Increases muscle mass, bone growth, RBC production, and deepens the voice.

Clinical Pathophysiology

  • Hypogonadism:

    • Primary (Testicular failure): ↑LH/FSH\uparrow \text{LH/FSH} and ↓Testosterone\downarrow \text{Testosterone} (e.g., Klinefelter syndrome XXY).

    • Secondary (Pituitary/Hypothalamic): ↓LH/FSH\downarrow \text{LH/FSH} and ↓Testosterone\downarrow \text{Testosterone} (e.g., Pituitary adenoma).

  • Male Infertility:

    • Oligospermia: < 15\,\text{million/mL}.

    • Causes: Varicocele (increased temperature), endocrine issues (low FSH), or obstructive blockages in the vas deferens.