Anatomy of the Male Pelvis

Question 1

What is the normal ultrasound appearance of the testis?

Answer 1

• Normal size: 2-3cm in width, 3-5cm in length
• Size decreases with age
• Atrophic testis demonstrates lobular structure of the testis radiating to the periphery from the mediastinum
• Mediastinum is a hyperechoic area
  Useful landmark to assess true longitudinal and transverse projections of the testis

Question 2

describe the anatomy of the epididymis

Answer 2

• Convoluted tube 6-7cm in length
• Consists of head, body and tail and runs posterolateral to the testis
• Usually mildly heterogeneous, iso/hyperechoic compared to testes
• The head is the largest, 5-12mm in length
• Low grade flow should be seen
• Post-vasectomy, epididymal body may demonstrate dilated ducts

Question 3

Describe the embryological development of the male reproductive system

Answer 3

• Male/female morphological characteristics begin to develop at 7 weeks
  
  • Both male and female embryos have two pairs of genital ducts
  • Mesonephric (Wolffian) ducts = important in the development of the male reproductive system
  • Paramesonephric (Mullerian) ducts = important in the development of the female reproductive system
  • Male phenotype requires the Y-chromosome
    ○ Gene for testis determining factor (TDF)
    ○ Absence of TDF results in the formation of an ovary
  • Testes produce testosterone and antimullerian hormone (AMH)
  • AMH suppresses development of paramesonephric ducts
  • Testosterone induces masculine differentiation of the mesonephric duct
  • Proximal mesonephric duct becomes highly convoluted to form the epididymis
  • Remainder of the mesonephric duct forms the ductus deferens and the ejaculatory duct
  • Lateral outgrowth from the caudal end of each mesonephric duct gives rise to the seminal vesicle
    ○ Gland that produces a secretion that nourishes sperm
  • Other glands that are important in the male genital system are derived from the urethra
  • Prostate arises from the prostatic part of the urethra
  • Bulbouretheral glands develop from paired outgrowths from the spongey part of the urethra
    ○ Secretions contribute to semen
    Testosterone induces masculinisation of the external genitalia with the formation of the penis and scrotum

Question 4

Describe the development of the inguinal canal?

Answer 4

• Inguinal canals provide pathways for the testes to descend from the intra-abdominal position through the anterior abdominal wall into the scrotum
  
  • Inguinal canal is a 4cm long oblique canal that extends from the deep to superficial inguinal ring
  • Deep inguinal ring is situated in the transversalis fascia
  • Superficial ring is a hiatus in the aponeurosis of the oliquus externus
  • The two rings do not coincide
  • In the male, the inguinal canal contains:
    ○ Ilioinguinal nerve
    ○ Spermatic cord

Question 5

Describe the anatomy of the male reproductive system

Answer 5

• Organs of the male reproductive system produce, sustain and transport sperm, and produce hormones:
  ○ Testes
  ○ Duct system
  ○ Accessory glands
  ○ Penis
  
  • Testes are located in the scrotum and the function is to produce sperm and secrete testosterone
  • Sperm cells pass through a series of ducts to reach the outside of the body
    ○ After leaving the testis, the sperm cells travel through the epididymis, ductus deferens, ejaculatory duct and the urethra
  • Accessory glands are the seminal vesicles, prostate gland and bulbourethral glands
    ○ Secrete fluid that enters the urethra
    Penis consists of three columns of erectile tissue wrapped in connective tissue and covered with skin