The vas deferens (: vasa deferentia), ductus deferens (: ductūs deferentes), or sperm duct is part of the male

reproductive system The reproductive system of an organism, also known as the genital system, is the biological system made up of all the anatomical organs involved in sexual reproduction. Many non-living substances such as fluids, hormones, and pheromones are al ...

of many

vertebrates Vertebrates () are animals with a vertebral column (backbone or spine), and a cranium, or skull. The vertebral column surrounds and protects the spinal cord, while the cranium protects the brain. The vertebrates make up the subphylum Vertebra ...

. In mammals, spermatozoa are produced in the seminiferous tubules and flow into the epididymal duct. The end of the epididymis is connected to the vas deferens. The vas deferens ends with an opening into the ejaculatory duct at a point where the duct of the seminal vesicle also joins the ejaculatory duct. The vas deferens is a partially coiled tube which exits the abdominal cavity through the

inguinal canal The inguinal canal is a passage in the anterior abdominal wall on each side of the body (one on each side of the midline), which in males, convey the spermatic cords and in females, the round ligament of the uterus. The inguinal canals are lar ...

Etymology

''Vas deferens'' is

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

, meaning "carrying-away vessel" while ''ductus deferens'', also Latin, means "carrying-away duct".

Structure

The human vas deferens measures 30–35 cm in length, and 2–3 mm in diameter. It is continuous proximally with the tail of the epididymis, and exhibits a tortuous, convoluted initial/proximal section (which measures 2–3 cm in length). Distally, it forms a dilated and tortuous segment termed the ampulla of vas deferens before ending by uniting with a duct of the seminal vesicle to form the

ejaculatory duct The ejaculatory ducts (''ductus ejaculatorii'') are paired structures in the male reproductive system. Each ejaculatory duct is formed by the union of the vas deferens with the Excretory duct of seminal gland, duct of the seminal vesicle. They pa ...

. Together they form part of the

spermatic cord The spermatic cord is the cord-like structure in males formed by the vas deferens (''ductus deferens'') and surrounding tissue that runs from the deep inguinal ring down to each testicle. Its serosal covering, the tunica vaginalis, is an exten ...

Blood supply

The vasa deferentia are supplied with blood by accompanying arteries, the ( arteries of vas deferens). These arteries normally arises from the superior (sometimes inferior) vesical arteries, a branch of the

internal iliac arteries The internal iliac artery (formerly known as the hypogastric artery) is the main artery of the pelvis. Structure The internal iliac artery supplies the walls and viscera of the pelvis, the buttock, the reproductive organs, and the medial compart ...

Innervation

The vas deferens receives innervation from an autonomic plexus of post-ganglionic sympathetic fibres derived from the

inferior hypogastric plexus Inferior may refer to: * Inferiority complex * An anatomical term of location * Inferior angle of the scapula, in the human skeleton * ''Inferior'' (book), by Angela Saini * '' The Inferior'', a 2007 novel by Peadar Ó Guilín * Inferior good: ...

. It is innervated by a variety of nerve endings, although of the efferent nerves the sympathetic innveration dominates. Adrenergic junctions (those which release

noradrenaline Norepinephrine (NE), also called noradrenaline (NA) or noradrenalin, is an organic chemical in the catecholamine family that functions in the brain and body as a hormone, neurotransmitter and neuromodulator. The name "noradrenaline" (from ...

) are found in the

smooth muscle Smooth muscle is one of the three major types of vertebrate muscle tissue, the others being skeletal and cardiac muscle. It can also be found in invertebrates and is controlled by the autonomic nervous system. It is non- striated, so-called bec ...

layers. Cholinergic synapses and vasoactive intestinal peptide synapses are found in the

connective tissue Connective tissue is one of the four primary types of animal tissue, a group of cells that are similar in structure, along with epithelial tissue, muscle tissue, and nervous tissue. It develops mostly from the mesenchyme, derived from the mesod ...

of the

mucosa A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It ...

Anatomical relations

Within the spermatic cord, the vas deferens is situated posterior (and parallel to) the vessels of the spermatic cord. The vas deferens traverses the inguinal canal to reach the

pelvic cavity The pelvic cavity is a body cavity that is bounded by the bones of the pelvis. Its oblique roof is the pelvic inlet (the superior opening of the pelvis). Its lower boundary is the pelvic floor. The pelvic cavity primarily contains the reproduc ...

; it enters the pelvic cavity lateral to the inferior epigastric vessels. At the deep inguinal ring, the vas deferens diverges from the testicular vessels to pass medially to reach the base of the prostate posteriorly.

Histology

The vas deferens consists of an external adventitial sheath containing blood vessels and nerves, a muscular middle layer composed of three layers of smooth muscle (with a circular muscle layer interposed between two longitudinal muscle layers), and an internal mucosal lining consisting of pseudostratified columnar epithelium (which bears the non-motile stereocilia). The vas deferens has the greatest muscle-to-lumen ratio of any hollow organ.

Function

During

ejaculation Ejaculation is the discharge of semen (the ''ejaculate''; normally containing sperm) from the penis through the urethra. It is the final stage and natural objective of male sexual stimulation, and an essential component of natural conception. ...

, the smooth muscle in the walls of the vas deferens contracts reflexively, thus propelling the sperm forward. This is also known as

peristalsis Peristalsis ( , ) is a type of intestinal motility, characterized by symmetry in biology#Radial symmetry, radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an wikt:anterograde, anterograde dir ...

. The epithelial sodium channel ENaC is strongly expressed in smooth muscle cells of the vas deferens. It has been suggested that ENaC functions as a mechanosensor in vascular smooth muscle cells that initiate pressure‐induced constriction known as the "myogenic response". Ion channels ENaC and CFTR, aquaporin of type AQP9 are localized on the apical border of the epithelia. Thus, these channels are involved concurrently in the regulation of fluid and electrolyte balance in the lumen of the vas deferens. The sperm are transferred from each vas deferens into the urethra, partially mixing with secretions from the male accessory sex glands such as the seminal vesicles,

prostate gland The prostate is an male accessory gland, accessory gland of the male reproductive system and a muscle-driven mechanical switch between urination and ejaculation. It is found in all male mammals. It differs between species anatomically, chemica ...

and the bulbourethral glands, which form the bulk of

semen Semen, also known as seminal fluid, is a bodily fluid that contains spermatozoon, spermatozoa which is secreted by the male gonads (sexual glands) and other sexual organs of male or hermaphrodite, hermaphroditic animals. In humans and placen ...

Clinical significance

Damage to the vas deferens during inguinal hernia repair may cause infertility.

Contraception

vasectomy Vasectomy is an elective surgical procedure that results in male sterilization, often as a means of permanent contraception. During the procedure, the male vasa deferentia are cut and tied or sealed so as to prevent sperm from entering into ...

is a method of

contraception Birth control, also known as contraception, anticonception, and fertility control, is the use of methods or devices to prevent pregnancy. Birth control has been used since ancient times, but effective and safe methods of birth control only be ...

in which the vasa deferentia are permanently cut. In some cases, it can be reversed. A modern variation, vas-occlusive contraception, involves injecting an obstructive material into the ductus to block the flow of sperm.

Disease

The vas deferens may be obstructed, or it may be completely absent in a condition known as congenital absence of the vas deferens (CAVD, a potential feature of

cystic fibrosis Cystic fibrosis (CF) is a genetic disorder inherited in an autosomal recessive manner that impairs the normal clearance of Sputum, mucus from the lungs, which facilitates the colonization and infection of the lungs by bacteria, notably ''Staphy ...

), causing

male infertility Male infertility refers to a sexually mature male's inability to impregnate a fertile female. Male infertility can wholly or partially account for 40% of infertility among couples who are trying to have children. "A problem with the male is the s ...

. Acquired obstructions can occur due to infections. To treat these causes of male infertility, sperm can be harvested by testicular sperm extraction (TESE) or microsurgical epididymal sperm aspiration (MESA).

Uses in pharmacology and physiology

The vas deferens has a dense sympathetic innervation, making it a useful system for studying sympathetic nerve function and for studying drugs that modify neurotransmission. It has been used: * as a bioassay for the discovery of enkephalins, the endogenous opiates. * to demonstrate quantal transmission from sympathetic nerve terminals. * as the first direct measure of free Ca²⁺ concentration in a postganglionic nerve terminal. * to develop an optical method for monitoring packeted transmission (similar to quantal transmission).

Other animals

Most vertebrates have some form of duct to transfer the sperm from the

testes A testicle or testis ( testes) is the gonad in all male bilaterians, including humans, and is homologous to the ovary in females. Its primary functions are the production of sperm and the secretion of androgens, primarily testosterone. The ...

to the

urethra The urethra (: urethras or urethrae) is the tube that connects the urinary bladder to the urinary meatus, through which Placentalia, placental mammals Urination, urinate and Ejaculation, ejaculate. The external urethral sphincter is a striated ...

. In

cartilaginous fish Chondrichthyes (; ) is a class of jawed fish that contains the cartilaginous fish or chondrichthyans, which all have skeletons primarily composed of cartilage. They can be contrasted with the Osteichthyes or ''bony fish'', which have skeleto ...

and

amphibian Amphibians are ectothermic, anamniote, anamniotic, tetrapod, four-limbed vertebrate animals that constitute the class (biology), class Amphibia. In its broadest sense, it is a paraphyletic group encompassing all Tetrapod, tetrapods, but excl ...

s, sperm are carried through the archinephric duct, which also partially helps to transport urine from the kidneys. In

teleost Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...

s, there is a distinct sperm duct, separate from the

ureter The ureters are tubes composed of smooth muscle that transport urine from the kidneys to the urinary bladder. In an adult human, the ureters typically measure 20 to 30 centimeters in length and about 3 to 4 millimeters in diameter. They are lin ...

s, and often called the vas deferens, although probably not truly homologous with that in humans. The vas deferens loops over the ureter in placental mammals, but not in marsupial mammals. In cartilaginous fishes, the part of the archinephric duct closest to the testis is coiled up to form an

epididymis The epididymis (; : epididymides or ) is an elongated tubular genital organ attached to the posterior side of each one of the two male reproductive glands, the testicles. It is a single, narrow, tightly coiled tube in adult humans, in length; ...

. Below this are a number of small glands secreting components of the seminal fluid. The final portion of the duct also receives ducts from the kidneys in most species. In

amniote Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial animal, terrestrial and semiaquatic vertebrates. Amniotes evolution, evolved from amphibious Stem tet ...

s (

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

s, and

reptile Reptiles, as commonly defined, are a group of tetrapods with an ectothermic metabolism and Amniotic egg, amniotic development. Living traditional reptiles comprise four Order (biology), orders: Testudines, Crocodilia, Squamata, and Rhynchocepha ...

s), the archinephric duct has become a true vas deferens, and is used only for conducting sperm, never urine. As in cartilaginous fish, the upper part of the duct forms the epididymis. In many species, the vas deferens ends in a small sac for storing sperm. The only vertebrates to lack any structure resembling a vas deferens are the primitive

jawless fish Agnatha (; ) or jawless fish is a paraphyletic infraphylum of animals in the subphylum Vertebrata of the phylum Chordata, characterized by the lack of jaws. The group consists of both extant taxon, living (Cyclostomi, cyclostomes such as hagfish ...

es, which release sperm directly into the body cavity, and then into the surrounding water through a simple opening in the body wall.

Additional images

File:Illu repdt male.jpg, Male reproductive system. File:Gray402.png, Coronal section of pelvis, showing arrangement of fasciae. Viewed from behind. File:Gray547.png, The relations of the femoral and abdominal inguinal rings, seen from within the abdomen. Right side. File:Gray1146.png, The spermatic cord in the inguinal canal. File:Gray1152.png, Fundus of the bladder with the vesiculae seminales. File:Gray1156.png, Vertical section of bladder, penis, and urethra. File:Gray1160.png, Prostate with seminal vesicles and seminal ducts, viewed from in front and above. File:Illu quiz prostate01.jpg, Prostate File:Vas deferens.jpg, Microscopic cross section. File:Testis, spermatic vessels and vas deferens 2.jpg, Testis, spermatic vessels and vas deferens File:Slide2UMR.JPG, A deep dissection showing the vas deferens.

References

External links

* —"Inguinal Region, Scrotum and Testes: Layers of the Spermatic Cord" * —"The Male Pelvis: Distribution of the Peritoneum in the Male Pelvis" * * * () {{Authority control Human male reproductive system Mammal male reproductive system Scrotum Sex organs