Testes

The testes (singular: testis) are paired male gonads responsible for the production of spermatozoa and the secretion of androgens, primarily testosterone. Enclosed in a fibrous capsule and suspended in the scrotum by the spermatic cords, the testes are vital for male fertility and secondary sexual characteristics. They develop intra-abdominally and descend into the scrotum during fetal life. Each testis is surrounded by multiple layers derived from the anterior abdominal wall, and its internal structure consists of tightly coiled seminiferous tubules, interstitial tissue, and an intricate duct system for sperm transport.

Structure

Each testis is ovoid in shape and flattened from side to side. It is enclosed in a dense fibrous capsule called the tunica albuginea, which sends septa into the testis, dividing it into lobules. Within each lobule lie seminiferous tubules, where spermatogenesis occurs.

• Shape: Ovoid
• Size: Approximately 4–5 cm long, 2.5 cm wide, 3 cm anteroposterior
• Weight: ~10–15 grams each in adults

Coverings of the Testis

From superficial to deep:

1. Skin (scrotum)
2. Dartos fascia and muscle
3. External spermatic fascia (from external oblique aponeurosis)
4. Cremasteric muscle and fascia (from internal oblique)
5. Internal spermatic fascia (from transversalis fascia)
6. Tunica vaginalis: Serous membrane with parietal and visceral layers (remnant of processus vaginalis)
7. Tunica albuginea: Thick fibrous capsule enclosing testicular parenchyma

Internal Structure

• Lobules: About 250 in each testis, separated by fibrous septa
• Seminiferous tubules: 1–4 highly coiled tubules per lobule where spermatogenesis occurs
• Straight tubules: Connect seminiferous tubules to rete testis
• Rete testis: A network of channels in the mediastinum testis
• Efferent ductules: Connect rete testis to the epididymis

Location

The testes are located in the scrotum, which hangs below and posterior to the base of the penis. The scrotum provides an external environment that is cooler than the body core, essential for optimal spermatogenesis. Each testis is suspended by a spermatic cord within its own hemiscrotum.

Relation	Structure
Anterior and lateral	Visceral layer of tunica vaginalis
Posterior	Epididymis
Superior	Testicular artery, pampiniform plexus (within spermatic cord)

Function

• Spermatogenesis: Production of sperm in seminiferous tubules under the influence of FSH and testosterone
• Hormone Secretion: Leydig cells in the interstitial tissue secrete testosterone, essential for development of male reproductive structures and secondary sexual traits

Blood Supply

• Arterial: Testicular artery (branch of abdominal aorta at L2)
• Venous drainage: Pampiniform plexus → Testicular vein
  • Right testicular vein → inferior vena cava
  • Left testicular vein → left renal vein

Lymphatic Drainage

• Pre-aortic and para-aortic lymph nodes at L1–L2 level

Innervation

• Sympathetic: Testicular plexus from T10–T11 spinal levels
• Afferent: Follows sympathetic pathways — testicular pain refers to periumbilical region

Histology

Seminiferous Tubules

• Lined by germinal epithelium (spermatogonia, spermatocytes, spermatids, spermatozoa)
• Sertoli cells: Support and nourish developing sperm; form blood-testis barrier

Interstitial Tissue

• Leydig cells: Found between tubules; secrete testosterone under LH stimulation

Embryological Development

• Derived from intermediate mesoderm in the genital ridge (5th–6th week)
• Germ cells migrate from yolk sac
• Descend from posterior abdominal wall → inguinal canal → scrotum (completed by ~9th month)
• Accompanied by processus vaginalis (forms tunica vaginalis)

Clinical Significance

• Cryptorchidism: Failure of one or both testes to descend into scrotum; associated with infertility and malignancy risk
• Hydrocele: Accumulation of serous fluid in tunica vaginalis
• Varicocele: Dilated pampiniform plexus, more common on the left; may affect spermatogenesis
• Testicular torsion: Twisting of the spermatic cord causing ischemia; surgical emergency
• Orchitis: Inflammation of the testis, often viral (e.g., mumps)
• Testicular cancer: Usually germ cell tumors; spread via para-aortic lymphatics