Scrotal sac
Function
Scrotum regulates the temperature of the testes and maintains it at 35 degrees Celsius (95 degrees Fahrenheit), two degrees below the optimal body temperature of 37 degrees Celsius (98.6 degrees Fahrenheit). Higher temperatures affect spermatogenesis.
Thermoregulation is achieved through movement of the smooth muscles of the scrotum - testicles are moved either closer to or further away from the abdomen depending on the ambient temperature. This is accomplished by the cremaster muscle in the abdomen and the dartos fascia (muscular tissue under the skin) (Pic.1).
Having scrotum and testicles situated outside the abdominal cavity provides additional features. The external scrotum is not affected by abdominal pressure. This may prevent the emptying of the testes before the sperm are matured sufficiently for fertilization. Another advantage is it protects the testes from jolts and compressions associated with an active lifestyle.
Development
Male sex hormones are secreted by the testes later in embryonic life to cause the development of secondary sex organs. The scrotum is developmentally homologous to the labia minora and labia majora. The raphe does not exist in females.
Reproductive organs and tissues develop in females and males begin during the fifth week after fertilization. The gonadal ridge grows behind the peritoneal membrane. By the sixth week, string-like tissues called primary sex cords form within the enlarging gonadal ridge. Externally, a swelling called the genital tubercule appears over the cloacal membrane.
Up until the eighth week after fertilization, the reproductive organs do not appear to be different between the male and female and are called in-differentiated. Testosterone secretion starts during week eight, reaches peak levels during week 13 and eventually decreses to very low levels by the end of the second trimester. In boys, testicles start to descend during 3rd month after fertilization. A state at which only one of the testicles descends is called unilateral cryptorchidism or even monorchismus. Bilateral cryptorchidism leads to sterility. Testosterone causes masculinization of labioscrotal folds into scrotum. The scrotal raphe is formed when the embryonic urethral groove closes by week 12 (Pic. 2).
Anatomical structure
The testes are located in a skin-covered highly pigmented muscular sack called scrotum that extends from the body behind the penis (Pic.3). One testis is typically lower than the other, which can prevent testis from being evenly compressed (and possibly damaged) in case of an impact to the testicular area.
Perineal raphe is a small, vertical, slightly raised ridge of scrotal skin under which scrotal septum is located. It appears as a thin longitudinal line that runs front to back over the entire scrotum.
Scrotum becomes covered with pubic hair during puberty. The left testis is typically lower in right-handed men, and vice versa in left-handed men.
Internal structure
Additional tissues and organs reside inside the scrotum (Pic. 4):
An accumulation of clear fluid in the tunica vaginalis, the most internal of membranes containing a testicle.
Absence of sperm in the ejaculate despite normal spermatogenesis, caused by an obstruction of the genital tract.
A physical syndrome described by pain or burning sensation of the urethra or perineum during or following ejaculation.
The inability of the testicles to produce sperm or testosterone.
In the case of cryptorchidism one or both testes are absent from the scrotum. It is is the most common etiologic factor of azoospermy in the adult.
Male gonads which produce both sperm and androgens, such as testosterone, and are active throughout the reproductive lifespan of the male.
A medical condition whose main symptom is low sexual desire.
The failure to achieve a clinical pregnancy after 12 months or more of regular unprotected sexual intercourse.
A frustration caused by a discrepancy between a person's desired and achieved sexual activity.
Diagnostic symptom of varicocele after palpation of the scrotum.
