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Human Body Study

Vasculature and Nerves

The blood, lymph, and nerve supply of the testis — small in volume but unusually organised, because the testis is held outside the body cavity and needs an active temperature-control system to keep its blood supply a few degrees below body core.

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.

Arterial supply

Section titled “Arterial supply”
  • Testicular artery — a long, slim branch that comes straight off the abdominal aorta just below the renal arteries. It travels down through the abdomen, into the inguinal canal, and along the spermatic cord to enter the testis at the mediastinum. The unusual aortic origin is a developmental footprint — the testis began life in the abdomen and dragged its blood supply with it during descent.
  • Anastomoses — small branches from the cremasteric artery (a branch of the inferior epigastric) and the artery of the vas deferens contribute, but the testicular artery is the dominant supply and there is little collateral cover — twist the cord (testicular torsion) and the testis becomes ischaemic within hours.

Venous drainage — the pampiniform plexus

Section titled “Venous drainage — the pampiniform plexus”

Veins leaving the testis fuse into a plexus — a network of 10–12 small veins that wraps around the testicular artery like a basket as it ascends in the spermatic cord. This is the pampiniform plexus (“tendril-like”). Two consequences:

  • Countercurrent heat exchange — cool venous blood returning from the scrotum surrounds the warm arterial blood descending from the abdomen. Heat is exchanged across the vessel walls, so the arterial blood arrives at the testis 2–4 °C cooler than core temperature — which is the temperature spermatogenesis needs.
  • Pulse damping — the basket also softens the arterial pulse, lowering the pulsatile pressure load on the small intratesticular vessels.

The plexus eventually condenses into a single testicular vein on each side. The left drains into the left renal vein at a right angle (a setup prone to back-pressure); the right drains directly into the inferior vena cava. This asymmetry is why varicoceles are far more common on the left.

Lymphatic drainage

Section titled “Lymphatic drainage”

Lymph from the testis follows the testicular artery upward all the way to the para-aortic (lumbar) lymph nodes at the level of the renal vessels — not to the inguinal nodes (which drain the scrotal skin instead). The split matters clinically: testicular cancer spreads to the para-aortic nodes, scrotal-skin disease to the inguinals.

Nerves

Section titled “Nerves”
  • Sympathetic fibres from the renal and aortic plexuses run with the testicular artery. They control vascular tone and a little contractile activity in the peritubular myoid layer.
  • Visceral afferents travel back along the same path. Testicular pain refers to the lower abdomen and flank along T10–T11 dermatomes — which is why testicular torsion and orchitis often present with abdominal pain.

What it does

Section titled “What it does”
  • Delivers oxygen and substrate to the seminiferous tubules and Leydig cells.
  • Cools the arterial blood through countercurrent exchange in the pampiniform plexus — a structural part of the testis’s temperature-control system.
  • Drains sperm-free interstitial fluid and a fraction of the testosterone output through lymphatics; carries the bulk of testosterone away in venous blood.
  • Refers pain — the autonomic supply means testicular pain is felt centrally in the abdomen, not in the scrotum.

Key idea

Section titled “Key idea”

The testis is unusual in living outside the body but being plumbed from deep inside it. The testicular vessels run the full length of the abdomen, and the pampiniform plexus exists specifically to bring the arterial temperature down before it reaches the seminiferous tubules. Lose that cooling — or twist the cord and lose flow entirely — and spermatogenesis fails fast.