The scrotum or scrotal sac is an

anatomical Anatomy () is the branch of biology concerned with the study of the structure of organisms and their parts. Anatomy is a branch of natural science that deals with the structural organization of living things. It is an old science, having it ...

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 do n ...

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

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur or ...

s. 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 referr ...

testes A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testoster ...

epididymis The epididymis (; plural: epididymides or ) is a tube that connects a testicle to a vas deferens in the male reproductive system. It is a single, narrow, tightly-coiled tube in adult humans, in length. It serves as an interconnection between the ...

, 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 pampiniform plexus (from Latin ''pampinus'', a tendril, + ''forma'', form) is a venous plexus – a network of many small veins found in the human male spermatic cord, and the suspensory ligament of the testicle, suspensory ligament of the ov ...

. 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, ...

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 Pubic hair is terminal body hair that is found in the genital area of adolescent and adult humans. The hair is located on and around the sex organs and sometimes at the top of the inside of the thighs. In the pubic region around the pubis bon ...

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 boy. ...

. 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 Homology may refer to: Sciences Biology *Homology (biology), any characteristic of biological organisms that is derived from a common ancestor *Sequence homology, biological homology between DNA, RNA, or protein sequences * Homologous chrom ...

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 majo ...

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

fusiform Fusiform means having a spindle-like shape that is wide in the middle and tapers at both ends. It is similar to the lemon-shape, but often implies a focal broadening of a structure that continues from one or both ends, such as an aneurysm on a b ...

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 reli ...

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

bat Bats are mammals of the order Chiroptera.''cheir'', "hand" and πτερόν''pteron'', "wing". With their forelimbs adapted as wings, they are the only mammals capable of true and sustained flight. Bats are more agile in flight than most bi ...

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...

s, and

insectivore A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant that eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores wer ...

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 The appendix of the epididymis (or pedunculated hydatid) is a small stalked appendage (sometimes duplicated) on the head of the epididymis. It is usually regarded as a detached efferent duct. This structure is derived from the Wolffian duct (Mes ...

Cavity of tunical albuginea Cavity may refer to: Biology and healthcare *Body cavity, a fluid-filled space in many animals where organs typically develop **Gastrovascular cavity, the primary organ of digestion and circulation in cnidarians and flatworms *Dental cavity or too ...

* 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 The efferent ducts (or efferent ductules or ductuli efferentes or ductus efferentes or vasa efferentia) connect the rete testis with the initial section of the epididymis.Hess 2018 There are two basic designs for efferent ductule structure: * ...

Epididymis The epididymis (; plural: epididymides or ) is a tube that connects a testicle to a vas deferens in the male reproductive system. It is a single, narrow, tightly-coiled tube in adult humans, in length. It serves as an interconnection between the ...

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 polyhedral ...

Lobule of testes In anatomy, a lobe is a clear anatomical division or extension of an organ (as seen for example in the brain, lung, liver, or kidney) that can be determined without the use of a microscope at the gross anatomy level. This is in contrast to the muc ...

Paradidymis The term paradidymis (organ of Giraldés) is applied to a small collection of convoluted tubules, situated in front of the lower part of the spermatic cord, above the head of the epididymis. These tubes are lined with columnar ciliated epitheliu ...

* 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 A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testoster ...

* Tunica albuginea of testis * Tunica vaginalis parietal layer * Tunica vaginalis visceral layer *

Tunica vasculosa testis The tunica vasculosa is the vascular layer of the testis, consisting of a plexus In neuroanatomy, a plexus (from the Latin term for "braid") is a branching network of vessels or nerves. The vessels may be blood vessels (veins, capillaries) or ly ...

* 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, a ...

. 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 cel ...

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 Spermatogenesis is the process by which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testis. This process starts with the mitotic division of the stem cells located close to the basement membrane of the tubule ...

. Temperature control is accomplished by the

smooth muscle Smooth muscle is an involuntary non-striated muscle, so-called because it has no sarcomeres and therefore no striations (''bands'' or ''stripes''). It is divided into two subgroups, single-unit and multiunit smooth muscle. Within single-unit mus ...

s 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 Elephantidae an ...

whale Whales are a widely distributed and diverse group of fully aquatic placental marine mammals. As an informal and colloquial grouping, they correspond to large members of the infraorder Cetacea, i.e. all cetaceans apart from dolphins and ...

s, and

marsupial mole Marsupial moles, the Notoryctidae , are highly specialized marsupial mammals, known from two species found at the Australian interior. * ''Notoryctes typhlops'' (southern marsupial mole, known as the ''itjaritjari'' by the Pitjantjatjara and Yan ...

s – have internal testes and no scrotum. Unlike placental mammals, some male

marsupials Marsupials are any members of the mammalian infraclass Marsupialia. All extant marsupials are endemic to Australasia, Wallacea and the Americas. A distinctive characteristic common to most of these species is that the young are carried in a po ...

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 kera ...

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

hydrocele A hydrocele is an accumulation of serous fluid in a body cavity. A hydrocele testis, the most common form of hydrocele, is the accumulation of fluids around a testicle. It is often caused by fluid collecting within a layer wrapped around the testi ...

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

varicocele varicocele is an abnormal enlargement of the pampiniform venous plexus in the scrotum. This plexus of veins drains blood from the testicles back to the heart. The vessels originate in the abdomen and course down through the inguinal canal as part ...

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 third ...

epididymo-orchitis Epididymitis is a medical condition characterized by inflammation of the epididymis, a curved structure at the back of the testicle. Onset of pain is typically over a day or two. The pain may improve with raising the testicle. Other symptoms may ...

* 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 an u ...

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 can v ...

undescended testes Cryptorchidism, also known as undescended testis, is the failure of one or both testes to descend into the scrotum. The word is from Greek language, Greek () 'hidden' and () 'testicle'. It is the most common birth defect of the male genital tra ...

* Chyloderma *

mumps MUMPS ("Massachusetts General Hospital Utility Multi-Programming System"), or M, is an imperative, high-level programming language with an integrated transaction processing key–value database. It was originally developed at Massachusetts Gener ...

scabies Scabies (; also sometimes known as the seven-year itch) is a contagious skin infestation by the mite ''Sarcoptes scabiei''. The most common symptoms are severe itchiness and a pimple-like rash. Occasionally, tiny burrows may appear on the skin ...

* 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, armp ...

Chancroid Chancroid ( ) is a bacterial sexually transmitted infection characterized by painful sores on the genitalia. Chancroid is known to spread from one individual to another solely through sexual contact. However, there have been reports of accidenta ...

('' Haemophilus ducreyi'') * Chlamydia ('' Chlamydia trachomatis'') * Gonorrhea (''

Neisseria gonorrhoeae ''Neisseria gonorrhoeae'', also known as ''gonococcus'' (singular), or ''gonococci'' (plural), is a species of Gram-negative diplococci bacteria isolated by Albert Ludwig Sigesmund Neisser, Albert Neisser in 1879. It causes the sexually transmit ...

'') *

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 donovano ...

or (''

Klebsiella granulomatis ''Klebsiella granulomatis'' is Gram-negative, rod-shaped bacterium of the genus ''Klebsiella'' known to cause the sexually transmitted disease granuloma inguinale (or donovanosis). It was formerly called ''Calymmatobacterium granulomatis''. It ...

'') *

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, an ...

(''

Treponema pallidum ''Treponema pallidum'', formerly known as ''Spirochaeta pallida'', is a spirochaete bacterium with various subspecies that cause the diseases syphilis, bejel (also known as endemic syphilis), and yaws. It is transmitted only among humans. It is ...

'') * 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