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Male Reproductive System — Adult Health Nursing (BSc Nursing 2nd Year)

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1. Overview

1. Testes (gonads) — produce spermatozoa and testosterone
2. Genital ducts — transport spermatozoa (epididymis, vas deferens, ejaculatory ducts)
3. Accessory glands — seminal vesicles, prostate, bulbourethral glands
4. Penis — copulatory and excretory organ

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2. Testes

Structure

• Each testis is enclosed in a dense connective tissue capsule called the tunica albuginea, which thickens posteriorly to form the mediastinum testis
• Septa from the mediastinum divide each testis into ~250 pyramidal lobules, each containing 1–4 seminiferous tubules
• The testes descend into the scrotum during fetal life, bringing a peritoneal sac (the tunica vaginalis)

Temperature Regulation

• Sweat evaporation from scrotal skin
• Pampiniform plexus — a venous network surrounding the testicular artery in the spermatic cord; acts as a countercurrent heat exchanger
• Dartos muscle (scrotum) and cremaster muscle (spermatic cord) — contract or relax to move testes closer to or away from the body

Leydig Cells (Interstitial Cells)

• Located between seminiferous tubules
• Large polygonal cells with abundant smooth endoplasmic reticulum (SER) and mitochondria
• Produce testosterone under stimulation by LH (ICSH — Interstitial Cell Stimulating Hormone) from the anterior pituitary

Clinical Conditions

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3. Spermatogenesis

Stages

Sertoli Cells

• Columnar "nurse cells" lining the seminiferous tubule
• Form the blood-testis barrier (tight junctions between adjacent Sertoli cells), protecting developing sperm from immune attack
• Secrete androgen-binding protein (ABP) to concentrate testosterone near developing sperm
• Produce inhibin B — a feedback inhibitor of FSH from the pituitary
• Phagocytose excess cytoplasm shed during spermiogenesis

Spermiogenesis (key steps)

1. Golgi phase — acrosomal vesicles form; flagellum begins to develop
2. Cap phase — acrosomal cap covers ~half the nucleus; nucleus condenses
3. Acrosome phase — nucleus elongates; mitochondria aggregate around midpiece (ATP for flagellar motion)
4. Maturation phase — excess cytoplasm shed; mature spermatozoon released into lumen

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4. Hypothalamic-Pituitary-Gonadal (HPG) Axis

Hypothalamus
    ↓ GnRH (pulsatile)
Anterior Pituitary
    ↓ LH          ↓ FSH
Leydig cells    Sertoli cells
(Testosterone)  (Spermatogenesis + Inhibin B)
    ↓ Negative feedback
Hypothalamus & Pituitary

• GnRH (decapeptide) — secreted in pulses from arcuate nucleus; stimulates pituitary gonadotrophs
• LH → stimulates Leydig cells → testosterone production
• FSH → stimulates Sertoli cells → supports spermatogenesis
• Testosterone → negative feedback on hypothalamus and pituitary
• Inhibin B → specifically inhibits FSH secretion

Actions of Testosterone

• Development of male secondary sexual characteristics (body hair, voice deepening, muscle mass)
• Activation and maintenance of spermatogenesis
• Development and maintenance of male sex accessory organs
• Anabolic effects (bone, muscle)
• Libido and behavior

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5. Genital Ducts

Epididymis

• A single, tightly coiled duct (~6 m long) on the posterior surface of each testis
• Divided into head (caput), body (corpus), tail (cauda)
• Function: sperm maturation and storage (~12–20 days transit time)
• Sperm acquire motility and fertilizing capacity during epididymal transit
• Pseudostratified columnar epithelium with stereocilia (microvilli) that absorb fluid and resorb excess cytoplasm

Vas Deferens (Ductus Deferens)

• A thick-walled muscular tube that ascends in the spermatic cord
• Expands into an ampulla near the bladder before joining the seminal vesicle duct
• At ejaculation: strong peristaltic contractions propel spermatozoa toward the urethra
• Vasectomy (surgical contraception) — vas deferens is cut or ligated

Ejaculatory Ducts

• Formed by the union of the ampulla of the vas deferens and the duct of the seminal vesicle
• Pass through the prostate gland and open into the prostatic urethra

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6. Accessory Glands

Seminal Vesicles

• Two highly tortuous tubes (~15 cm each), posterior to the bladder
• Produce ~70% of ejaculate volume (2–5 mL total)
• Secretion contains:
  • Fructose — main energy source for sperm
  • Prostaglandins — stimulate female reproductive tract contractions
  • Fibrinogen — causes semen to coagulate after ejaculation
  • Citrate, inositol, ascorbic acid

Prostate Gland

• Weight ~20 g in adult; surrounds the urethra just below the bladder
• Contains 30–50 tubuloacinar glands embedded in fibromuscular stroma
• Secretion (~25% of ejaculate) contains:
  • Prostate-Specific Antigen (PSA) — serine protease that liquefies semen
  • Zinc, citric acid, acid phosphatase
  • Antibacterial properties
• Prostate is divided into peripheral zone (most common site of carcinoma), transitional zone (site of BPH), and central zone
• Contains corpora amylacea (calcified concretions) — increases with age

Bulbourethral Glands (Cowper's Glands)

• Paired, pea-sized mucous glands at the base of the penis
• Secrete a clear, alkaline, mucoid fluid before ejaculation
• Lubricates the urethra and neutralizes residual urinary acidity

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7. Semen Composition

• Volume ≥ 1.4 mL
• Sperm concentration ≥ 16 million/mL
• Total motility ≥ 42%
• Normal morphology ≥ 4%

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8. Penis

• Contains two corpora cavernosa (erectile tissue) and one corpus spongiosum (surrounds the urethra)
• Glans penis — distal expansion of corpus spongiosum; covered by prepuce (foreskin) if not circumcised
• Erection: parasympathetic stimulation → NO (nitric oxide) release → smooth muscle relaxation → vasodilation → engorgement of erectile tissue
• Ejaculation: sympathetic stimulation → peristalsis of vas deferens and accessory glands; somatic nerves → rhythmic contractions of bulbospongiosus muscle

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9. Common Disorders — Nursing Relevance

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10. Nursing Assessment of Male Reproductive Health

1. History: urinary symptoms (frequency, hesitancy, weak stream), sexual function, STI history, fertility concerns, pain
2. Physical examination: inspection and palpation of scrotum, testes (note size, symmetry, tenderness), inguinal nodes
3. Investigations:
   • PSA (prostate-specific antigen)
   • Semen analysis
   • Scrotal ultrasound — testicular masses, varicocele
   • Urinalysis / urine culture
   • Testosterone levels
4. Health education:
   • Testicular self-examination monthly
   • Safe sexual practices
   • Scrotal hygiene
   • Prompt reporting of scrotal pain, swelling, or urinary changes

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• Medical Physiology (Boron & Boulpaep), pp. 1593–1595
• Junqueira's Basic Histology: Text and Atlas, 17e, pp. 1055–1090