Week 6 Scrotum and Testes Part 1

Learning Objectives

• Identify and describe anatomical structures of the scrotum and testes, including the spermatic cord.

• Describe the normal sonographic appearance of the scrotum, testes, and spermatic cord.

Anatomy Overview

• Structures Involved:

• 

Scrotum

• Description:

  • Dual chambered protrusion of skin and muscle containing the testes, epididymis, and spermatic cord.

  • Located between the penis and anus, extending from the perineum.

• Wall Structure:

  • Composed of several layers (2-8 mm thick):

  • Superficial to deep:

  • Pigmented skin with rugal folds

  • Superficial fascia and dartos muscle

  • External spermatic fascia

  • Cremasteric fascia

  • Internal spermatic fascia

  • Tunica vaginalis

  • Tunica albuginea (visceral layer covers testes)

  • 

• Scrotal Contents:

  • Testes

  • Epididymis

  • Testicular and epididymal appendages

  • Distal part of spermatic cord

• Arterial Supply:

  • Posterior scrotal branches of the perineal artery

  • Anterior scrotal branches of the deep external pudendal artery

  • Cremasteric artery

• Venous Drainage:

  • Accompanied by scrotal veins

• 

Testes

• Function: Production of sperm and testosterone.

• Anatomical Details:

• 

  • Paired ovoid shape measuring approximately:

  • Length: $3-5 ext{ cm}$

  • Anteroposterior (AP): $3 ext{ cm}$

  • Transverse (TR): $2-4 ext{ cm}$

  • Volume: $12-19 ext{ cc}$

  • Size decreases with age.

  • Spermatozoa produced by seminiferous tubules, transported to rete testes in mediastinum.

  • Efferent tubules convey sperm to epididymis for storage.

  • Appendix testis represents developmental remnants of the mullerian duct.

• Layers Covering Testes:

• 

  • Tunica Vaginalis:

  • Covers anterior surface and sides, derived from peritoneum with lubricating fluid.

  • Tunica Albuginea:

  • The fibrous capsule that protects the testes.

• Arterial Supply:

  • Supplied through testicular arteries and branches of the cremasteric artery.

• Venous Drainage:

  • Via pampiniform plexus; left testicular vein drains into left renal vein, while right drains directly to inferior vena cava (IVC)

• 

Embryology

• Development:

  • Testes arise from the gonadal ridge near mesonephric ridge of intermediate cell mass.

  • Week 8: Testis attaches to lower abdominal wall; descent starts with the processus vaginalis forming.

  • Fetal Development Stages:

  • 4th month: Testes near deep inguinal ring.

  • 7th month: Testes within the deep inguinal ring.

  • Following weeks: Descent into scrotum.

Ultrasound Appearance

• Testes:

  • Medium homogeneous appearance.

  • Tunica albuginea visible as a thin echogenic line surroudning the testes

  • Tunica invaginates to form a linear ehcogenic mediastinum testis

  • Rete testis may appear as a hypoechoic region near mediastinum and easily visible if dilated

  • Appnedix testis can be seen if combined with a hydrocele

  • 

  • 

  • 

• Epididymis:

  • Size: 6-7 cm, structure divided into head, body, and tail.

  • Begins superiorly and runs posterolateral to the testes

  • Head: superior to upper of testes, contains 10 - 15 efferent ductucles from the rete testis which forms a single duct in body and tail. This duct becomes the vas deferens and moves into the spermatic cord

  • Body: smaller than the head and follows the posterorlateral aspect of the testes from upper to lower pole

  • Tail: slightly larger than the body and sits posterior to the lower portion of testes

  • Appendix of the epididymis: small protuberance from the head

  • Ultrasound appearance: similiar or hypoechoic to testes; coarse echotexture

  • 

• Spermatic Cord:

  • Contains various structures:

  • Ductus deferens, testicular artery, pampiniform plexus, lymphatics, nerves.

  • Appears echogenic on ultrasound; color Doppler shows testicular artery and plexus.

  •