Scrotum
Encyclopedia
In some male
mammal
s the scrotum is a dual-chambered protuberance of skin
and muscle
containing the testicle
s and divided by a septum
. It is an extension of the perineum
, and is located between the penis
and anus
. In humans and some other mammals, the base of the scrotum becomes covered with curly pubic hair
s at puberty
. The scrotum is homologous
to the labia majora
in females.
in the abdomen and the dartos
fascia (muscular tissue under the skin) in the scrotum
However, this may not be the main function of the scrotum. The volume of sperm produced by the testes is small (0.1-0.2 ml). It has been suggested that if testes were situated within the abdominal cavity that they would be subjected to the regular changes in abdominal pressure that is exerted by the abdominal muscles. This squeezing and relaxing would result in the more rapid emptying of the testes and epididymis of sperm before the spermatozoa
were matured sufficiently for fertilization. Some mammals—elephants and marine mammals, for example—do keep their testes within the abdomen and there may be mechanisms to prevent this inadvertent emptying.
Contraction of the abdominal muscles, and changes in intra-abdominal pressure, often can lift and lower the testicles within the scrotum. Contraction of the muscle fibers of the dartos
tunic (or fascia) is completely involuntary and results in the appearance of increased wrinkling and thickening of the scrotal skin. The testicles are not directly attached to the skin of the scrotum, so this dartos
contraction results in their sliding toward the abdomen. They also, in some men, can be lifted the same way by tightening the anus and pelvic muscles, doing Kegel exercise
s.
Although the ideal temperature for sperm growth varies between species, it usually appears, in warm-blooded species, to be a bit cooler than internal body temperature, necessitating the scrotum. Since this leaves the testicles vulnerable in many species, there is some debate on the evolutionary advantage of such a system. One theory is that the impregnation of females who are ill is less likely when sperm is highly sensitive to elevated body temperatures. An alternative explanation is to protect the testes from jolts and compressions associated with an active lifestyle. Animals that have stately movements—such as elephants, whales, and marsupial moles—have internal testes and no scrotum.
A common problem of the scrotum is the development of masses. Common scrotal masses include
Other conditions include:
Male
Male refers to the biological sex of an organism, or part of an organism, which produces small mobile gametes, called spermatozoa. Each spermatozoon can fuse with a larger female gamete or ovum, in the process of fertilization...
mammal
Mammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s the scrotum is a dual-chambered protuberance of skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
and muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
containing the testicle
Testicle
The testicle is the male gonad in animals. Like the ovaries to which they are homologous, testes are components of both the reproductive system and the endocrine system...
s and divided by a septum
Septum
In anatomy, a septum is a wall, dividing a cavity or structure into smaller ones.-In human anatomy:...
. It is an extension of the perineum
Perineum
In human anatomy, the perineum is a region of the body including the perineal body and surrounding structures...
, and is located between the penis
Penis
The penis is a biological feature of male animals including both vertebrates and invertebrates...
and anus
Anus
The anus is an opening at the opposite end of an animal's digestive tract from the mouth. Its function is to control the expulsion of feces, unwanted semi-solid matter produced during digestion, which, depending on the type of animal, may be one or more of: matter which the animal cannot digest,...
. In humans and some other mammals, the base of the scrotum becomes covered with curly pubic hair
Pubic hair
Pubic hair is hair in the frontal genital area, the crotch, and sometimes at the top of the inside of the legs; these areas form the pubic region....
s at puberty
Puberty
Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...
. The scrotum is homologous
Homology (biology)
Homology forms the basis of organization for comparative biology. In 1843, Richard Owen defined homology as "the same organ in different animals under every variety of form and function". Organs as different as a bat's wing, a seal's flipper, a cat's paw and a human hand have a common underlying...
to the labia majora
Labia majora
The labia majora are two prominent longitudinal cutaneous folds that extend downward and backward from the mons pubis to the perineum and form the lateral boundaries of the pudendal cleft, which contains the labia minora, interlabial sulci, clitoral hood, clitoral glans, frenulum clitoridis, the...
in females.
Function
The function of the scrotum appears to be to keep the temperature of the testes slightly lower than that of the rest of the body. For human beings, the temperature should be one or two degrees Celsius below body temperature (around 37 degrees Celsius or 99 degrees Fahrenheit); higher temperatures may be damaging to sperm count. The temperature is controlled by the scrotum moving the testicles closer to the abdomen when the ambient temperature is cold, and further away when it is hot. 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 muscleCremaster muscle
-Contraction:Its function is to raise and lower the testes in order to regulate the temperature of the testes and promote spermatogenesis. Contraction may also occur during arousal which can prevent injury to the testicles during sex....
in the abdomen and the dartos
Dartos
The dartos fascia is a fat-free layer of smooth muscular fiber outside the external spermatic fascia but below the skin. It is a continuation of Scarpa's fascia, which is a membranous layer of the subcutaneous tissue in the abdominal wall...
fascia (muscular tissue under the skin) in the scrotum
However, this may not be the main function of the scrotum. The volume of sperm produced by the testes is small (0.1-0.2 ml). It has been suggested that if testes were situated within the abdominal cavity that they would be subjected to the regular changes in abdominal pressure that is exerted by the abdominal muscles. This squeezing and relaxing would result in the more rapid emptying of the testes and epididymis of sperm before the spermatozoa
Spermatozoon
A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...
were matured sufficiently for fertilization. Some mammals—elephants and marine mammals, for example—do keep their testes within the abdomen and there may be mechanisms to prevent this inadvertent emptying.
Contraction of the abdominal muscles, and changes in intra-abdominal pressure, often can lift and lower the testicles within the scrotum. Contraction of the muscle fibers of the dartos
Dartos
The dartos fascia is a fat-free layer of smooth muscular fiber outside the external spermatic fascia but below the skin. It is a continuation of Scarpa's fascia, which is a membranous layer of the subcutaneous tissue in the abdominal wall...
tunic (or fascia) is completely involuntary and results in the appearance of increased wrinkling and thickening of the scrotal skin. The testicles are not directly attached to the skin of the scrotum, so this dartos
Dartos
The dartos fascia is a fat-free layer of smooth muscular fiber outside the external spermatic fascia but below the skin. It is a continuation of Scarpa's fascia, which is a membranous layer of the subcutaneous tissue in the abdominal wall...
contraction results in their sliding toward the abdomen. They also, in some men, can be lifted the same way by tightening the anus and pelvic muscles, doing Kegel exercise
Kegel exercise
A pelvic floor exercise, more commonly called a Kegel exercise , consists of contracting and relaxing the muscles that form part of the pelvic floor, which are now sometimes colloquially referred to as the "Kegel muscles". Several tools exist to help with these exercises, though many are ineffective...
s.
Innervation
| Nerve | Surface |
|---|---|
| genital branch of genitofemoral nerve Genital branch of genitofemoral nerve The genital branch of the genitofemoral nerve arises from the ventral primary divisions of L1 and L2 spinal nerve roots, passes outward on the Psoas major, and pierces the fascia transversalis, or passes through the deep inguinal ring; it then descends behind the spermatic cord to the scrotum,... |
anterolateral |
| Anterior scrotal nerves Anterior scrotal nerves The anterior scrotal nerves are branches of the ilioinguinal nerve. The equivalent nerves in the female are the anterior labial nerves.... (from ilioinguinal nerve Ilioinguinal nerve The ilioinguinal nerve is a branch of the first lumbar nerve . It separates from the first lumbar nerve along with the larger iliohypogastric nerve.... ) |
anterior |
| Posterior scrotal nerves Posterior scrotal nerves The posterior scrotal branches or ""posterior labial branches"" are two in number, medial and lateral. They are branches of the perineal nerve, which is itself is a branch of the pudendal nerve... (from perineal nerve Perineal nerve The perineal nerve is a nerve arising from the pudendal nerve that supplies the perineum.-Structure:The perineal nerve is the inferior and larger of the two terminal branches of the pudendal nerve, is situated below the internal pudendal artery.... ) |
posterior |
| perineal branches of posterior femoral cutaneous nerve Perineal branches of posterior femoral cutaneous nerve The perineal branches of the posterior femoral cutaneous nerve are distributed to the skin at the upper and medial side of the thigh.One long perineal branch, inferior pudendal , curves forward below and in front of the ischial tuberosity, pierces the fascia lata, and runs forward beneath the... |
inferior |
Health issues
A study has indicated that use of a laptop computer positioned on the lap can affect sperm production negatively.A common problem of the scrotum is the development of masses. Common scrotal masses include
- Sebaceous cystSebaceous cystA sebaceous cyst is a term that loosely refers to either epidermoid cysts or pilar cysts . Because an epidermoid cyst originates in the epidermis and a pilar cyst originates from hair follicles, by definition, neither type of cyst is strictly a sebaceous cyst...
, also called an epidermal cyst - hydroceleHydroceleA hydrocoele denotes a pathological accumulation of serous fluid in a body cavity. It can also be noted as a minor malformation of newborns due to high levels of lead in the mother's blood during pregnancy....
- hematoceleHematoceleA hematocele is a collection of blood in a body cavity. The term is generally used to refer to the collection of blood in the tunica vaginalis around the testicle. Hematoceles are often more painful than a hydrocele....
- spermatoceleSpermatoceleSpermatocele is a retention cyst of a tubule of the rete testis or the head of the epididymis distended with barely watery fluid that contains spermatozoa. Spermatoceles are the most common cystic condition encountered within the scrotum. They vary in size from several millimeters to many...
- varicoceleVaricoceleVaricocele , also known as varicoscele or varicose seal, is an abnormal enlargement of the vein that is in the scrotum draining the testicles. The testicular blood vessels originate in the abdomen and course down through the inguinal canal as part of the spermatic cord on their way to the testis...
Other conditions include:
- Blisters: Caused by chafing or scratching of the scrotum while the scrotum is damp. Often seen in males undergoing pubertyPubertyPuberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...
, as emerging pubic hairs cause the urge to itch. Powdering the scrotum to absorb moisture can help to prevent this issue. - contact dermatitisContact dermatitisContact dermatitis is a term for a skin reaction resulting from exposure to allergens or irritants . Phototoxic dermatitis occurs when the allergen or irritant is activated by sunlight....
: may cause redness, burning, swelling, and itching of the entire scrotum. Can result from soaps, solvents, detergents, and natural irritants such as poison ivy. - inguinal herniaInguinal herniaAn inguinal hernia is a protrusion of abdominal-cavity contents through the inguinal canal. They are very common , and their repair is one of the most frequently performed surgical operations....
- yeast infection
- swelling resulting from conditions external to the scrotum, including:
- heart failure
- kidney or liver disease
- Cherry angiomaCherry angiomaCherry angiomas, also known as Campbell De Morgan spots or Senile angiomas, are cherry red papules on the skin containing an abnormal proliferation of blood vessels. They are the most common kind of angioma...
- testicular torsionTesticular torsionTesticular torsion is when the spermatic cord to a testicle twists, cutting off the blood supply. The most common symptom is acute testicular pain and the most common underlying cause is a congenital malformation known as a "bell-clapper deformity". The diagnosis is often made clinically but if it...
- cello scrotumCello scrotumCello scrotum is a hoax medical condition originally published as a brief case report in the British Medical Journal in 1974. As its name suggests, it was purportedly an affliction of the scrotum affecting male players of the cello.-History:...
, which was revealed in 2009 to be a hoax