The scrotum or scrotal sac is an anatomical

male Male (symbol: ♂) is the sex of an organism that produces the gamete (sex cell) known as sperm, which fuses with the larger female gamete, or ovum, in the process of fertilization. A male organism cannot reproduce sexually without access to ...

reproductive structure located at the base of the

penis A penis (plural ''penises'' or ''penes'' () is the primary sexual organ that male animals use to inseminate females (or hermaphrodites) during copulation. Such organs occur in many animals, both vertebrate and invertebrate, but males d ...

that consists of a suspended dual-chambered sac of skin and smooth muscle. It is present in most terrestrial male mammals. The scrotum contains the

external spermatic fascia The external spermatic fascia (intercrural or intercolumnar fascia) is a thin membrane, prolonged downward around the surface of the spermatic cord and testis. It is separated from the dartos tunic by loose areolar tissue. It is occasionally refe ...

, testes, epididymis, and

ductus deferens The vas deferens or ductus deferens is part of the male reproductive system of many vertebrates. The ducts transport sperm from the epididymis to the ejaculatory ducts in anticipation of ejaculation. The vas deferens is a partially coiled tube w ...

. It is a distention of the perineum and carries some abdominal tissues into its cavity including the testicular artery, testicular vein, and pampiniform plexus. The

perineal raphe The perineal raphe is a visible line or ridge of tissue on the body that extends from the anus through the perineum to scrotum (male) or labia majora (female). It is found in both males and females, arises from the fusion of the urogenital folds, a ...

is a small, vertical, slightly raised ridge of scrotal skin under which is found the

scrotal septum The septum of the scrotum is a vertical layer of fibrous tissue that divides the two compartments of the scrotum. It consists of flexible connective tissue. Its structure extends to the skin surface of the scrotum as the scrotal raphe. It is an ...

. It appears as a thin longitudinal line that runs front to back over the entire scrotum. In humans and some other mammals the scrotum becomes covered with pubic hair at

puberty Puberty is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction. It is initiated by hormonal signals from the brain to the gonads: the ovaries in a girl, the testes in a ...

. The scrotum will usually tighten during penile erection and when exposed to cold temperatures. One testis is typically lower than the other to avoid compression in the event of an impact. The scrotum is biologically homologous to the

labia majora The labia majora (singular: ''labium majus'') are two prominent longitudinal cutaneous folds that extend downward and backward from the mons pubis to the perineum. Together with the labia minora they form the labia of the vulva. The labia maj ...

in females. Although present in most boreoeutherian mammals, the external scrotum is absent in fusiform

marine mammal Marine mammals are aquatic mammals that rely on the ocean and other marine ecosystems for their existence. They include animals such as seals, whales, manatees, sea otters and polar bears. They are an informal group, unified only by their ...

s, such as whales and seals, as well as in some lineages of land mammals, such as the afrotherians, xenarthrans, and numerous families of bats, rodents, and insectivores.

Structure

Nerve supply

Blood supply

Skin and glands

The skin on the scrotum is more highly pigmented compared to the rest of the body. The septum is a connective tissue membrane dividing the scrotum into two cavities.

Lymphatic system

The scrotum lymph drains initially into the superficial inguinal lymph nodes, this then drains into the deep inguinal lymph nodes. The deep inguinal lymph nodes drain into the common iliac which ultimately releases lymph into the cisterna chyli.

Asymmetry

One testis is typically lower than the other, which is believed to function to avoid compression in the event of impact; in humans, the left testis is typically lower than the right. An alternative view is that testis descent asymmetry evolved to enable more effective cooling of the testicles.

Internal structure

Additional tissues and organs reside inside the scrotum and are described in more detail in the following articles: * Appendix of epididymidis * Cavity of tunical albuginea * Cremaster muscle * Dartos *

Ductus Deferens The vas deferens or ductus deferens is part of the male reproductive system of many vertebrates. The ducts transport sperm from the epididymis to the ejaculatory ducts in anticipation of ejaculation. The vas deferens is a partially coiled tube w ...

* Efferent ductules * Epididymis *

Leydig cell Leydig cells, also known as interstitial cells of the testes and interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the testicle and produce testosterone in the presence of luteinizing hormone (LH). They are polyhedra ...

* Lobule of testes * Paradidymis * Rete testes *

Scrotal septum The septum of the scrotum is a vertical layer of fibrous tissue that divides the two compartments of the scrotum. It consists of flexible connective tissue. Its structure extends to the skin surface of the scrotum as the scrotal raphe. It is an ...

* Seminiferous tubule * Sertoli cell * Spermatic cord * Testes * Tunica albuginea of testis * Tunica vaginalis parietal layer * Tunica vaginalis visceral layer * Tunica vasculosa testis * Vas deferens

Development

Genital homology between sexes

Male sex hormones are secreted by the testes later in embryonic life to cause the development of secondary

sex organs A sex organ (or reproductive organ) is any part of an animal or plant that is involved in sexual reproduction. The reproductive organs together constitute the reproductive system. In animals, the testis in the male, and the ovary in the female, ...

. The scrotum is developmentally homologous to the

. The raphe does not exist in females. Reproductive organs and tissues develop in females and males begin during the fifth week after fertilization. The

genital ridge The genital ridge (or gonadal ridge) is the precursor to the gonads. The genital ridge initially consists mainly of mesenchyme and cells of underlying mesonephric origin. Once oogonia enter this area they attempt to associate with these somatic ce ...

grows behind the peritoneal membrane. By the sixth week, string-like tissues called primary sex cords form within the enlarging genital 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 declines to very low levels by the end of the second trimester. The testosterone causes the masculinization of the labioscrotal folds into the scrotum. The scrotal raphe is formed when the embryonic, urethral groove closes by week 12.

Scrotal growth and puberty

Though the testes and scrotum form early in embryonic life, sexual maturation begins upon entering

. The increased secretion of testosterone causes the darkening of the skin and development of pubic hair on the scrotum.

Function

The scrotum regulates the temperature of the testes and maintains it at , i.e. two or three degrees below the body temperature of . Higher temperatures affect spermatogenesis. Temperature control is accomplished by the smooth muscles of the scrotum moving the testicles either closer to or further away from the abdomen dependent upon the ambient temperature. This is accomplished by the cremaster muscle in the abdomen and the dartos fascia (muscular tissue under the skin). Having the scrotum and testicles situated outside the abdominal cavity may provide additional advantages. The external scrotum is not affected by abdominal pressure. This may prevent the emptying of the testes before the sperm were matured sufficiently for fertilization. Another advantage is it protects the testes from jolts and compressions associated with an active lifestyle. Animals that move at a steady pace – such as

elephant Elephants are the largest existing land animals. Three living species are currently recognised: the African bush elephant, the African forest elephant, and the Asian elephant. They are the only surviving members of the family Elephantida ...

s, whales, and marsupial moles – have internal testes and no scrotum. Unlike placental mammals, some male marsupials have a scrotum that is anterior to the penis, which is not homologous to the scrotum of placental mammals, although there are several marsupial species without an external scrotum. In humans, the scrotum may provide some friction during intercourse, helping to enhance the activity.

Clinical significance

A study has indicated that use of a laptop computer positioned on the lap can negatively affect sperm production.

Diseases and conditions

The scrotum and its contents can develop diseases or incur injuries. These include: * Candidiasis (yeast infection) *

sebaceous cyst A sebaceous cyst is a term commonly used to refer to either: * Epidermoid cysts (also termed epidermal cysts, infundibular cyst) * Pilar cysts (also termed trichelemmal cysts, isthmus-catagen cysts) Both of the above types of cysts contain ker ...

epidermal cyst The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the ...

* hydrocele * hematocele * Molluscum contagiosum * spermatocele *Paget's disease of the scrotum * varicocele *

inguinal hernia An inguinal hernia is a hernia (protrusion) of abdominal-cavity contents through the inguinal canal. Symptoms, which may include pain or discomfort especially with or following coughing, exercise, or bowel movements, are absent in about a thir ...

* epididymo-orchitis * testicular torsion * genital warts *

testicular cancer Testicular cancer is cancer that develops in the testicles, a part of the male reproductive system. Symptoms may include a lump in the testicle, or swelling or pain in the scrotum. Treatment may result in infertility. Risk factors include a ...

dermatitis Dermatitis is inflammation of the skin, typically characterized by itchiness, redness and a rash. In cases of short duration, there may be small blisters, while in long-term cases the skin may become thickened. The area of skin involved c ...

* undescended testes * Chyloderma * mumps * scabies * herpes *

pubic lice Pediculosis pubis (also known as "crabs" and "pubic lice") is an infestation by the pubic louse, ''Pthirus pubis'', a wingless insect which feeds on blood and lays its eggs (nits) on mainly pubic hair. Less commonly, hair near the anus, armpi ...

* Chancroid ('' Haemophilus ducreyi'') * Chlamydia ('' Chlamydia trachomatis'') * Gonorrhea ('' Neisseria gonorrhoeae'') *

Granuloma inguinale Granuloma inguinale is a bacterial disease caused by ''Klebsiella granulomatis'' (formerly known as ''Calymmatobacterium granulomatis'') characterized by genital ulcers. It is endemic in many less-developed regions. It is also known as donov ...

or ('' Klebsiella granulomatis'') *

Syphilis Syphilis () is a sexually transmitted infection caused by the bacterium '' Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, a ...

('' Treponema pallidum'') * scrotum eczema * scrotal psoriasis disease * Riboflavin deficiency * Chimney sweeps' carcinoma

Bibliography

; Books * * * * *

References

{{Authority control Mammal male reproductive system Integumentary system Human male reproductive system Sex organs Testicle