Biology Today — January 2018

Ureter

Symphysis pubis

Prostatic urethra

Corpus spongiosum

Testicular artery and vein

Bulbospongiosus muscle

Epididymis

Corpus cavernosum

Scrotum

Testis Cross section

Rectum

Bladder

Seminal vesicle

Common ejaculation duct

Deep dorsal veins of penis

Urogenital diaphragm

Bulbourethral glands

Scrotal skin

Dartos muscle

Cremasteric muscle

Internal spermatic fascia

Tunica vaginalis

Anus

Prepuce

Glans penis

Penile urethra

Vas deferens

Prostate gland

Fig.: Lateral view of male reproductive system

SCROTUM

• The scrotum is a dual-chambered sack of skin and muscles suspended from groin which contains the testes and some of
  the male sex accessory ducts. It is homologous to the labia majora of females. It is an extension of the perineum and is
  located between the penis and anus. Underneath the skin of the scrotum is a layer of involuntary smooth muscle, the tunica
  dartos. Just under it another layer of muscle is present the cremaster which is a voluntary striated muscle. Scrotum remains
  connected with the abdomen or pelvic cavity by inguinal canals. Spermatic cord passes into the testis through inguinal canal.

Function

• The main purpose of scrotum is to
  provide appropriate temperature for
  optimal sperm production. The scrotum
  maintains the testes at around 34°C,
  i.e., a temperature slightly lower than
  the core body temperature (37°C)
  as high temperature hampers the
  development of sperms. Temperature
  receptors are located in the scrotum.
  The temperature is controlled by
  scrotal movement of the testes away
  or towards the body depending on the
  environmental temperatures. Moving the testes away from the abdomen and increasing the exposed surface area allow a
  faster dispersion of excess heat. This is done by means of contraction and relaxation of the cremaster muscle and the dartos
  muscle in the scrotum. In case the temperature drops, the movement of scrotum towards the pelvic cavity allows the testes
  to absorb heat from the rest of body so that they do not get chilled.

In humans, temperature regulation is not the only function of scrotum. It also prevents the testes from being subjected to various

abdominal pressures that may be exerted by the abdominal muscles (if testes were present in abdominal cavity) and thereby

prevents rapid emptying of both testes and epididymes before maturation of sperms.

However, some mammals like elephants and marine mammals retain testes in abdomen but they have special mechanisms to

prevent inadvertent emptying.

Inguinal ligament

Inguinal canal

Superficial inguinal ring

Cremaster muscle

Scrotum containing the

dartos muscle Raphe

Scrotal cavity

Scrotal septum

Ductus deferens

Venous plexus

Artery

Nerve

Spermatic

cords

Formed from

spermatic artery,

vein and nerve

bound together

with connective

tissue.

Fig.: Scrotum with a portion of covering removed to display testis and related structures