Testes

The testes (singular: testis), also known as the testicles, are the male gonads and are contained within the scrotum. The testes are responsible for the production of sperm and testosterone.

Terminology

The term testis (plural testes) is preferred by the Terminologia Anatomica, over testicle. The adjectival form remains testicular ⁶.

Gross anatomy

At birth, testes measure approximately 1.5 cm (length) x 1 cm (width), reaching ~4 mL volume at puberty ¹.

Normal adult testes are ovoid and measure approximately 3 cm (AP) x 2-4 cm (TR) x 3-5 cm (length), with a volume of 12.5-19 mL ². However, the size of the testes decreases with age.

From the mediastinum testis, several radiating septa extend into the testis forming 250-400 lobules. Each of these lobules contains 2-3 seminiferous tubules. Seminiferous tubules carry the sperm via tubuli recti into a dilated space within the mediastinum testis which is known as the rete testis, which drains into the epididymis through 10-15 efferent ductules ¹. Efferent ducts in the head of the epididymis (globus major) unite to form a single duct (globus minor) in the body and tail region, which continues as the ductus deferens (vas deferens). 

Arterial supply

The testes are supplied by testicular arteries, arising from the aorta, just below the origin of renal arteries.

Venous drainage

The testes are drained by a plexus of veins (pampiniform plexus), which continue as the testicular veins. The right testicular vein directly drains into the inferior vena cava (IVC), while the left testicular vein drains into the left renal vein.

Lymphatic drainage

Lymphatic drainage of the testes is through lymphatics running with the testicular arteries, draining into para-aortic lymph nodes.

Innervation

Testes receive autonomic (sympathetic) innervation from the spermatic plexus, originating from the para-aortic ganglia.

Variant anatomy

• polyorchidism (very rare)
  • bilobed testes: thought to be a variant of polyorchidism
• testicular appendages: may arise from the testes and have a variable incidence
• arrest of testicular descent
• both testes in one scrotal sac
• bell clapper deformity ⁵
  • abnormally high attachment of the tunica vaginalis on the spermatic cord which predisposes the testes to torsion
  • seen in 5-16% of males, most of which are bilateral

Radiographic appearance

Ultrasound

See also: Testicular and scrotal ultrasound

The normal testes have a homogeneous, moderately echogenic pattern. A testis is surrounded by a thin echogenic fibrous band, which represents the visceral component of the tunica vaginalis and the tunica albuginea. In the absence of intrascrotal fluid, the tunica is usually visualizedvisualised only at its hilum as an echogenic structure, where it invaginates into the testis, to form the mediastinum testis.

Doppler

Intratesticular arteries are low resistance vessels with a mean resistive index (RI) of 0.62 (0.48-0.75) ¹.

MRI

• T1: testes and epididymides have homogenously intermediate signal
• T2: testes have hyperintense signal, with slightly lower signal in the epididymides

Tunica albuginea has hypointense signal on both T1 and T2 weighted images.

Development

See: testicular descent

History and etymology

"Testicle" is thought to arise from the Latin word "testis" (witness, one who "testifies"). The connection between a witness and the term for a male sex organ is thought to be that the testes are a sign of virility and under Roman law, no person was allowed to be a witness unless his testes were present (i.e. neither eunuchs nor women were felt to be reliable witnesses!) ⁴.

Related pathology

• gamuts
  • unilateral testicular lesions
  • bilateral testicular lesions
  • paratesticular lesions
• neoplastic
  • testicular cancer
• traumatic
  • testicular fracture
  • testicular dislocation
  • intratesticular haematoma
• infections
  • orchitis
• granulomatous disease
  • testicular sarcoidosis
  • testicular tuberculosis
• vascular
  • segmental testicular infarction
  • testicular vasculitis
• others
  • torsion testes
  • splenogonadal fusion
  • testicular microlithiasis