Scrotal anatomy and physiology

Testicle is surrounded by a dense fibrous capsule called:

Tunica albuginea

Septula arise from the tunica albuginea to form…

Mediastinum testis

Mediastinum testis

Creases an incomplete septum and provides support for testicular vessels

Each testicle contains approximately ______ seminiferous tubules that converge to form 20-30 larger ___________

840; Efferent ducts

The efferent ducts form channels called the RETE TESTIS that …

Carry the seminal fluid from the testicle to the epididymis

Average testical size

Length: 3-5cm

Width: 2-4cm

AP: 3cm

In pediatric pts, testicular volumes can be calculated using

Lambert formula = length x width x height x 0.71

Ellipsoid formula = length x width x height x 0.52

Tunica vaginalis

Extension of the peritoneum into the scrotal sac

Normally there is a small amount of fluid between layers

• Visceral layer: Inner later covering the testes, epi and lower part of spermatic cord

• Parietal layer: lines the walls of the scrotal pouch

Tunica albuginea

Thin layer of tissue that is in direct contact with the testicular tissue

Folds of this layer form sections within the testicles called the mediastinum testis

The rete testis is a series of channels within mediastinum

Blood vessels and ductules enter/exit the testicle at the mediastinum

The visceral layer of the tunica vaginalis covers the

Tunica albuginea

Epididymis

Curved lying posterior lateral to the testicle

Usually 6-7cm in length

Head (globus major) - formed by tubules from rete testis, 10-12cm width

Tubules converge into ductus epididymis which forms the body and tail (globus minor), 1-2mm width

Appendix testis

Remnant of Mullerian duct

Small ovoid structure usually located between the superior pole and epididymal head

Spermatic cord

Holds the vas deferens, cremasteric, deferential and testicular arteries, pampiniform plexus of veins, lymph vessels, nerves

Scrotal wall

Skin - outermost layer

Dartos - muscle layer that forms scrotal raphe and separates the two testicles

Tunica vaginalis - Inner layer

Right and left gonadal arteries (testicular arteries)

Originate from anterior aorta to supply blood to the testicles

Normally low resistance, RI 0.5-0.75

Capsular artery courses along testicle periphery and produces branches called Centripetal arteries

Centripetal arteries

Course through the parenchyma to deliver O2 blood to tissues

These arteries are sampled with Doppler to assess testicular perfusion

Normally demonstrate low resistance, high flow volume

Deferential artery

Originates from the internal iliac artery

Feeds epi and vas deferens

High resistance, RI >0.75

Cremasteric artery

Originates from external iliac artery

Feeds peri-testicular tissues

High resistance, RI >0.75

Venous drainage

Pampiniform plexus is the network of small veins that merge to form the testicular vein

Right testicular vein drains directly into IVC

Left testicular vein drains into left renal vein

Testicles function

Exocrine = sperm production

Endocrine = Testosterone production

Epididymis function

Sperm maturation

Ejaculatory duct function

Sperm and seminal vesicle fluid

Urethra

Drainage channel for semen, sperM and urine

Seminal vesicle

Secretes alkaline component of semen and nutrients for sperM

Prostate gland

Secretes alkaline fluid into semen

Cowper gland

Secretes mucous for lubrication

Exam indications for testicular

Palpable mass (#1), pain, swelling, hydrocele, trauma, torsion, neoplasm

Use ____ for comparison views for echotexture and vascularity → keep setting same through exam for color

Dual screen

USA testicle

Homogenous, uniform, medium level echoes

Mediastinum testis seen as a linear echogenic band within testicle

Tunica albuginea not normally visualized

Doppler waveforms demonstrate antegrade, monophasic flow

Testicles normally have low vascular resistance and moderate antegrade diastolic flow

Epididymis USA

Normally isoechoic or mildly hyperechoic to testicle

Head is best evaluated in the long plane as a triangular or crescent shaped structure superior to the upper pole of the teste

Body and tail are usually located posterior and inferior to the head

Normal variants

Epididymal cysts (<4mm), epididymal calcs, minimal hydrocele, testicular cyst (2-3mm), testicular band, bilobed testicle, polyorchidism

What is the dense fibrous layer that is in direct contact with the testicle?

Tunica albuginea

What layer is an extension of the peritoneum

Tunica vaginalis

The mediastinum testes is formed by folds of the …

Tunica albuginea

Which of the following lies posterior lateral to the testicle?

Rete testis

Epididymis

Medial raphe

Dartos muscle

Epididymis

The ________ arteries encircle the testicle and the ____________ arteries penetrate the testicular parenchyma

Capsular; centripetal

The centripetal arteries normally demonstrate __________flow while the deferential arteries normally demonstrate _________

Low resistance; High resistance

The left testicular artery originated from the ____________ and the left testicular vein empties into __________

Aorta; Left renal vein

When evaluating a patient with testicular pain:

The US system settings should be established while scanning the UNAFFECTED side and remain unchanged when scanning the affected side