The vas deferens or ductus deferens is part of the

male reproductive system The male reproductive system consists of a number of sex organs that play a role in the process of human reproduction. These organs are located on the outside of the body and within the pelvis. The main male sex organs are the penis and the t ...

of many

vertebrates Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, wi ...

. The ducts transport sperm from the

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 t ...

to the

ejaculatory duct The ejaculatory ducts (''ductus ejaculatorii'') are paired structures in male anatomy. Each ejaculatory duct is formed by the union of the vas deferens with the duct of the seminal vesicle. They pass through the prostate, and open into the ureth ...

s in anticipation of

ejaculation Ejaculation is the discharge of semen (the ''ejaculate''; normally containing sperm) from the male reproductory tract as a result of an orgasm. It is the final stage and natural objective of male sexual stimulation, and an essential compone ...

. The vas deferens is a partially coiled tube which exits the abdominal cavity through the inguinal canal.

Etymology

''Vas deferens'' is

Latin Latin (, or , ) is a classical language belonging to the Italic branch of the Indo-European languages. Latin was originally a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through the power ...

, meaning "carrying-away vessel"; the plural version is ''vasa deferentia''. ''Ductus deferens'' is also Latin, meaning "carrying-away duct"; the plural version is ''ducti deferentes''.

Structure

There are two vasa deferentia, connecting the left and right

with the

seminal vesicle The seminal vesicles (also called vesicular glands, or seminal glands) are a pair of two convoluted tubular glands that lie behind the urinary bladder of some male mammals. They secrete fluid that partly composes the semen. The vesicles are 5� ...

s to form the

in order to move sperm. The (human) vas deferens measures 30–35 cm in length, and 2–3 mm in diameter. The vas deferens is continuous proximally with the tail of the epididymis. The vas deferens 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

. The vas deferens forms part of the spermatic cord.

Blood supply

The vas deferens is supplied by an accompanying artery ( artery of vas deferens). This artery normally arises from the

superior Superior may refer to: *Superior (hierarchy), something which is higher in a hierarchical structure of any kind Places *Superior (proposed U.S. state), an unsuccessful proposal for the Upper Peninsula of Michigan to form a separate state *Lake ...

(sometimes

inferior Inferior may refer to: * Inferiority complex * An Anatomical terms of location#Superior and inferior, anatomical term of location * Inferior angle of the scapula, in the human skeleton *Inferior (book), ''Inferior'' (book), by Angela Saini * ''The ...

) vesical artery, a branch of the

internal iliac artery 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 comp ...

Innervation

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

inferior hypogastric plexus The inferior hypogastric plexus (pelvic plexus in some texts) is a network () of nerves that supplies the organs of the pelvic cavity. The inferior hypogastric plexus gives rise to the prostatic plexus in males and the uterovaginal plexus in female ...

. The vas deferens is innervated by a variety of different types of nerve ending. Adrenergic synapses are found in 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 ...

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, along with epithelial tissue, muscle tissue, and nervous tissue. It develops from the mesenchyme derived from the mesoderm the middle embryonic germ layer. Connective tissue ...

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 is ...

. Noradrenergic synapses may also be present in the vas deferens.

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 reprod ...

; 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 Stereocilia (or stereovilli or villi) are non-motile apical cell modifications. They are distinct from cilia and microvilli, but are closely related to microvilli. They form single "finger-like" projections that may be branched, with normal cell ...

). The vas deferens has the greatest muscle-to-lumen ratio of any hollow organ.

Function

During

, 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 radially symmetrical contraction and relaxation of muscles that propagate in a wave down a tube, in an anterograde direction. Peristalsis is progression of coordinated contraction of involuntary circular muscles, which ...

. The sperm is transferred from each vas deferens into the urethra, partially mixing with secretions from the male accessory sex glands such as the

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

and the

bulbourethral gland The bulbourethral glands or Cowper's glands (named for English anatomist William Cowper) are two small exocrine glands in the reproductive system of many male mammals (of all domesticated animals, they are absent only in dogs). They are homolo ...

s, which form the bulk of

semen Semen, also known as seminal fluid, is an organic bodily fluid created to contain spermatozoa. It is secreted by the gonads (sexual glands) and other sexual organs of male or hermaphroditic animals and can fertilize the female ovum. Semen ...

Clinical significance

Contraception

vasectomy Vasectomy, or vasoligation, is an elective surgical procedure for male Sterilization (medicine), sterilization or permanent contraception. During the procedure, the male vas deferens, vasa deferentia are cut and tied or sealed so as to prevent sp ...

is a method of

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

in which the vasa deferentia are permanently cut, though in some cases it can be reversed. A modern variation,

vas-occlusive contraception Vas-occlusive contraception is a form of male contraception that blocks sperm transport in the vas deferens, the tubes that carry sperm from the epididymis to the ejaculatory ducts. Various vas-occlusive contraceptive methods have been researche ...

, 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 rare genetic disorder that affects mostly the lungs, but also the pancreas, liver, kidneys, and intestine. Long-term issues include difficulty breathing and coughing up mucus as a result of frequent lung infections. ...

), causing

male infertility Male infertility refers to a sexually mature male's inability to impregnate a fertile female. In humans it accounts for 40–50% of infertility. It affects approximately 7% of all men. Male infertility is commonly due to deficiencies in the semen, ...

. 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

enkephalin An enkephalin is a pentapeptide involved in regulating nociception in the body. The enkephalins are termed endogenous ligands, as they are internally derived and bind to the body's opioid receptors. Discovered in 1975, two forms of enkephalin ...

s, 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 In physics, a quantum (plural quanta) is the minimum amount of any physical entity ( physical property) involved in an interaction. The fundamental notion that a physical property can be "quantized" is referred to as "the hypothesis of quantizat ...

Other animals

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

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 testostero ...

to the

urethra The urethra (from Greek οὐρήθρα – ''ourḗthrā'') is a tube that connects the urinary bladder to the urinary meatus for the removal of urine from the body of both females and males. In human females and other primates, the urethra c ...

. In

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

and amphibians, sperm is carried through the archinephric duct, which also partially helps to transport urine from the kidneys. In

teleost Teleostei (; Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts ), is, by far, the largest infraclass in the class Actinopterygii, the ray-finned fishes, containing 96% of all extant species of fish. Tel ...

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

ureter The ureters are tubes made of smooth muscle that propel urine from the kidneys to the urinary bladder. In a human adult, the ureters are usually long and around in diameter. The ureter is lined by urothelial cells, a type of transitional e ...

s, and often called the vas deferens, although probably not truly

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 ...

with that in humans. The vas deferens loops over the ureter in

placental mammal Placental mammals ( infraclass Placentalia ) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguish ...

s, but not in marsupial mammals. In cartilaginous fishes, the part of the archinephric duct closest to the testis is coiled up to form an

. 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 amniotes, however, 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 (, Ancient Greek 'without jaws') is an infraphylum of jawless fish in the phylum Chordata, subphylum Vertebrata, consisting of both present (Cyclostomata, cyclostomes) and extinct (conodonts and ostracoderms) species. Among recent animal ...

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 Mammal male reproductive system Scrotum