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Human Body Study

Scrotum and Spermatic Cord

The supporting apparatus that holds the testes outside the body and connects them to the abdomen. The scrotum is the skin sac that houses them; the spermatic cord is the suspension that carries everything — vessels, nerves, and the vas deferens — between the testis and the abdominal cavity.

Schematic of the testis A labelled diagram of the testis. The left figure is a cut-away sagittal view showing the fibrous capsule (tunica albuginea), the septa dividing the testis into lobules, the coiled seminiferous tubules within each lobule, the mediastinum testis with its rete testis, the efferent ductules leaving the testis, the epididymis draped along its posterior border (head, body, tail), the vas deferens, and the spermatic cord with its testicular artery and pampiniform venous plexus. The centre figure is a magnified cross-section of a single seminiferous tubule with adjacent interstitium, showing tall Sertoli cells spanning the tubule wall, the spermatogenic lineage maturing from basement membrane to lumen, peritubular myoid cells, and Leydig cells in the interstitial space. The testis — cut-away and tubule cross-section scrotum mediastinum head body tail testicular artery pampiniform plexus vas deferens seminiferous tubule (cross-section) lumen capillary Scrotum & spermatic cord the skin sac that holds both testes outside the body,and the cord that suspends each testis carrying itsvessels, nerves, and vas deferens. Vasculature & nerves the testicular artery and the pampiniform venousplexus that cools it; lymphatics; autonomic nerves. Tunics & lobules the tough fibrous capsule (tunica albuginea), theserous outer tunica vaginalis, and the septa carvingthe testis into ~250 wedge-shaped lobules. Seminiferous tubules the tightly coiled tubes within each lobule wheresperm are made — about 250 m of tubule per testis. Intratesticular ducts straight tubules feed the rete testis (a networkin the mediastinum), which drains via efferentductules to the head of the epididymis. Sertoli cells tall nurse cells spanning the tubule wall;their tight junctions form the blood-testis barrier. Spermatogenic cells the germ-cell lineage, base to lumen — spermatogonia→ spermatocytes → spermatids → spermatozoa. Leydig cells endocrine cells between the tubules — thesource of testosterone, driven by LH. Interstitial tissue the loose stroma between tubules — capillaries,lymphatics, macrophages, and connective tissue. Left: sagittal cut-away of one testis with its epididymis and spermatic cord. Centre: magnified seminiferous tubule and adjacent interstitium. Not to scale.

Scrotum — layers (outside in)

Section titled “Scrotum — layers (outside in)”
  • Skin — thin, pigmented, often rugose, with sweat glands and sparse hair. A midline raphe marks the embryonic fusion line of the two halves.
  • Dartos muscle and fascia — a thin sheet of smooth muscle embedded in superficial fascia, just under the skin. It is involuntary and tonically active.
  • External spermatic fascia — a continuation of the external oblique aponeurosis from the abdominal wall.
  • Cremaster muscle and fascia — a thin layer of striated skeletal muscle in fascial slips, derived from the internal oblique.
  • Internal spermatic fascia — derived from the transversalis fascia.
  • Tunica vaginalis — the serous sac (see tunics and lobules) wrapping each testis individually inside the scrotum.

The two testes sit in separate compartments divided by a septum — so an injury or infection can stay confined to one side.

Thermoregulation by the scrotum

Section titled “Thermoregulation by the scrotum”

Two muscles do the work:

  • Dartos (smooth, autonomic) — slow, tonic. Wrinkles the scrotal skin in the cold to shrink the sac and bring the testes close to the warm body wall; relaxes in heat to flatten the skin and increase its surface area for radiative cooling.
  • Cremaster (skeletal, somatic via the genitofemoral nerve) — fast, reflexive. Elevates the testis closer to the body in the cold, in fear, or during the cremasteric reflex (stroke the medial thigh and the testis lifts); relaxes to let it hang lower in the heat.

Together with the pampiniform plexus’s countercurrent cooling (see vasculature and nerves), they hold the testis ~2–4 °C below core temperature — the working range for spermatogenesis.

Spermatic cord — contents

Section titled “Spermatic cord — contents”

The cord is everything bundled together between the deep inguinal ring and the testis. Surgically, it has three vessels, three nerves, three “other structures”:

  • Three arteries
    • Testicular artery — the main supply (from the abdominal aorta).
    • Cremasteric artery — from the inferior epigastric, supplies the cremaster and fascia.
    • Artery of the vas deferens — from a branch of the internal iliac, runs with the vas.
  • Three nerves
    • Genital branch of the genitofemoral nerve — motor to the cremaster, sensory to the scrotal skin.
    • Sympathetic fibres — to the testicular vessels and the smooth muscle of the vas.
    • Ilioinguinal nerve — strictly speaking lies on rather than in the cord, but is conventionally counted: sensory to the upper scrotum.
  • Three “other structures”
    • Vas deferens — carries sperm out.
    • Pampiniform plexus — the venous basket that cools the artery.
    • Lymphatics — draining to the para-aortic nodes.
  • Plus the processus vaginalis remnant — the (usually obliterated) embryonic peritoneal tube that the testis came down inside. If it stays open, it becomes the route for an indirect inguinal hernia or a communicating hydrocele.

What it does

Section titled “What it does”
  • Houses the testes in a temperature-controlled compartment outside the body.
  • Adjusts testicular temperature through the dartos and cremaster, the macroscopic half of the cooling system (the pampiniform plexus is the microscopic half).
  • Suspends and connects each testis to the abdomen through the spermatic cord, carrying everything in and out.
  • Reflexively protects the testes — the cremasteric reflex pulls them upward in moments of threat.

Key idea

Section titled “Key idea”

The scrotum is not merely a container — it is part of the testis’s physiology. Spermatogenesis happens at 33–35 °C, not 37 °C, and the dartos, cremaster, and pampiniform plexus together hold that temperature. Cryptorchidism (an undescended testis sitting in the abdomen) impairs spermatogenesis and substantially raises cancer risk for exactly this reason: it is the wrong temperature.