Male Anatomy

• Internal structures produce sperm, semen, and sex hormones

  • testes, prostate, seminal vesicles, bulbourethral glands, and spermatic duct

• external structures support internal structures and facilitate micturition and sperm transfer

  • scrotum and penis

Testes

• oval and slightyly flattened (~4cm X 2.5cm)

• surrounded by tunica albugineea

  • fibrous connective tissue that protects the seminiferous tubules and extends internally to form the mediastinum testis

• enclosed by the tunica vaginalis

  • serous membrane sac derived from abdominal peritoneum

  • visceral layer covers the testis

  • parietal layer lines the inner scrotum

  • cavity of the tunica vaginalis (cavum vaginale) with small amount of fluid

• sperm produced in the seminiferous tubules

  • germ cells → become sperm

    • nurse (sertoli) cells → support and nourish

• seminiferous tubules coiled into lobules

  • ~300 lobules

  • 1-3 seminiferous tubules per lobule

  • clusters of interstitial endocrine cells

    • secrete testosterone

• tailless sperm move out of lobule into the rete testis (housed within the mediastinum testis)

  • sperm to efferent ductules → epididymis

• sperm mature (gain tail) in the epididymis

  • features a head, body, and tail

    • sperm stored in the tail until ejaculation

Out of the Testes

• sperm mature (gain tail) in the epididymis

  • fertile 40-60 days

  • reabsorbed if not ejaculated

• sperm exits epididymis via spermatic duct

  • a.k.a “ductus deferens” or “vas deferens”

  • unites with seminal vesicle duct to form ejaculatory ducts (passes through prostate)

  • part of the spermatic cord

    • also includes blood/lymph vessels and nerves

    • enclosed by the tunica vaginalis

Blood Supply

• testes supplied by the testicular arteries

  • arise from the abdominal aorta

    • just below the renal arteries

• vas deferens supplied by the deferential a.

  • branch of the inferior vesical a.

  • gives off vasal branches

• pampiniform plexus drains

  • right testiculaar v. to IVC

  • left testicular v. to the left renal v. → IVC

Scrotum

• pouch of skin, muscle, and connective tissue containing testes, spermatic cord, and associated structures

  • left testis often descends lower than right

  • divided into left/right compartments by internal median septum

• features the cremaster muscle

  • muscle derived from the internal oblique

  • has both skeletal and smooth muscle fibers

    • supplied by the genitofemoral nerve

  • cremasteric a. from inferior epigastric a.

• feature the dartos muscle

  • smooth muscle with connective tissue

  • wrinkles the scrotal skin for thermoregulation

Penis

• 3 major parts:

  • root - not externally visible

    • contains 3 erectile tissues and two muscles

      • 2 crura + bulb of the penis

      • ischiocavernosus m. and bulbospongiosus m.

  • body (shaft) - 3 erectile tissue cylinders

    • 2 corpora cavernosa + 1 coprus spongiosum

  • glans (head) - formed by the distal exapnsion of the corpus spongiosum

    • feature the external urethral orifice

• also has prepuce or “foreskin” that is retractable and attached by a frenulum

Prepuce

• similar to clitoral hood in females

  • densley innervated and highly sensitive

• inner surface and facing surface covered with thin mucous membrane

  • membranes fused in infancy/childhood

    • gradually separate later

    • anchored only by a frenulum in adulthod

      • frenulum cut or removed in circumcision

Erectile Tissues

• corpus spongiosum (1 on the ventral side)

  • encloses spongy (penile) urethra

    • prevents closure of urethra dring erection

  • distal ends enlarged to form glans penis

  • proximal end dilated and ensheathed by bulbospongiosus muscle

• corpus canvernosum (2 on dorsal side)

  • diverge from pubic arch as 2 crura

  • covered by the ischiocavernosus muscle

  • each features a deep artery for blood flow

Major Muscles

• bulbospongiosus m.

  • contracts to empty urethra

  • helps to sustain erection

• ischiocavernosus m.

  • contracts to force blood into corpora cavernosa for sustaining an erection

  • can be repeatedly contracted/relaxed

    • “kegels” → can help reduce premature ejaculation and increase intensity of erection

      • only effective if preformed for several minutes, multiple times a day for 1-3 months

Blood Supply

• main blood supply via branches of the internal pudendal artery

  • becomes the commin penile artery

    • 3 branches: dorsal, bulbourethral, and cavernous aa.

      • dorsal a. → blood to the glans while engorged

      • bulbourethral a. → blood to corpus spongiosum and penile bulb

      • cavernous a. (a.k.a “deep a.”) → blood to the corpora cavernosa and branches into helicine aa. throughout penile body

        • helicine aa. supplies erectile tissues

          • curvy and constricted while flaccid

          • straight and dilated while erect

Venous Drainage

• blood from the corpora cavernosa drains via the trabecular network

  • into the subtunical venous plexus

    • then into the emissary veins

      • emissary vv. drain either into the internal pudendal vv. or into the deep dorsal v.

        • deep dorsal v. drains via the periprostatic plexus

• emissary vv. compressed during erection to prevent drainage of blood

  • tunica albuginea surrounds penis and resricts venous outflow to help sustain erection

Accessory Glands

• seminal vesicles (paired)

  • fluid contains nutrients for sperm (60% of semen)

  • empties fluid into ejaculatory duct

• prostate (surrounds urethra and ejaculatory duct

  • comprised of 30-50 tubuloacinar glands

  • fluid nourishes/protects sperm (30% of semen)

  • empties fluid directly into the urethra

• bulbourethral glands (near bulb of penis)

  • primary producers of pre-ejaculate, a clear lubricant that prepares for intercourse

  • protect sperm by neutralizing urine in the urethra

  • empties fluid directly into the urethra