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.
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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.
Arterial supply
Each testis is supplied by the ipsilateral testicular artery which arises from the aorta, just below the origin of renal arteries. The artery descends into the scrotum within the spermatic cord via the inguinal canal.
Venous drainage
The testis is drained by the pampiniform plexus in the scrotum, which ascends as the testicular veins through the inguinal canal. 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 aorticorenal ganglia.
Development
See: testicular development and descent
Variant anatomy
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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
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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 visualized 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.
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
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gamuts
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neoplastic
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traumatic
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infections
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granulomatous disease
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vascular
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others
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