Under the epididymis ( epididymis ) ( ancient Greek ἐπί epi "on, at, on" and δίδυμος didymos "double twins") is meant a the testicles resting sexual organ , which is mainly a total of 4 long from the confined space tortuous, to 6 m Epididymal duct ( ductus epididymidis ).
Each epididymis is connected to the associated testicle via the efferent ducts , serves for the maturation and storage of the sperm cells produced by the testes and passes into the spermatic duct . The epididymis and vas deferens are descendants of the urinary duct .
Macroscopically, the epididymis is divided into a head ( caput epididymidis ), body ( corpus epididymidis ) and tail or tail ( cauda epididymidis ). It rests on the back of the testicle in the longitudinal direction, with the head of the epididymis resting on the upper pole of the testicle. In addition to the efferent ducts, this also contains the initial stretch of the epididymal duct ( ductus epididymidis ). However, the main part of the epididymis lies in the epididymis body and tail, the latter also containing the beginning of the vas deferens . The epididymis is closely connected to the testicle itself via a mesentery , the mesepididymis .
Both epididymis and testicles are covered by a double peritoneal covering, the tunica vaginalis testis , due to the descensus testis . An extension of the peritoneal covering descends next to the testicles. Both sheets of the envelope - the outer periorchium and the inner epiorchium - are connected to one another, enclose the slit-shaped cavitas peritonealis scroti , an exclave of the abdominal cavity.
Embryologically, the epididymal duct arises from the urnal duct (Wolff duct), which is greatly elongated directly below the confluence of the efferent ducts, which originate from the urnal duct . In the further course, the Wolff duct forms the spermatic duct ( ductus deferens ).
In the vicinity of the head of the epididymis, three relics of embryonic development can often be found: As a continuation of the head of the epididymis, a vesicle-shaped, stalked appendage extends over the testicle pole, the appendix epididymidis , the upper end of the urinary duct. Next to the head of the epididymis, the connective tissue of the spermatic cord contains the paradidymidis or epididymis, short, closed tubules, remnants of the tubules of the urnus. On the upper pole of the testis, near the head of the epididymis, is further usually takes one of the appendix epididymis similar but ungestielter Annex, the appendix testis ( Hydatid of Morgagni ), the upper end of the Müller gangs represents, from which the in women develop internal genital organs .
The ductuli efferentes is a system of around 10 to 20 individual passages that pass the immature sperm from the rete testis into the epididymis. In addition, they have many myofibroblasts under their epithelium , since the immature sperm are still completely unable to move. For the same reason, the epithelial cells that line the efferent ducts sometimes carry kinocilia that help transport sperm. Others have microvilli to draw fluid from the sperm suspension and thus increase the sperm concentration. In general, the epithelium of the efferent ducts can be described as "wavy", as high prismatic and low epithelial cells alternate with one another.
Each of the efferent ducts is about four inches long and coiled to about one inch. They open into the epididymal duct.
The corridor, which is up to 6 m long, is curled up to 6 cm. This is where the sperm mature. In contrast to the ductuli efferentes, it has a uniform, double-row, highly prismatic epithelium consisting of main cells and lower basal cells, which is densely covered with stereocilia . The main cells serve to further reduce fluid and have proton pumps with which they keep the environment acidic. This leads to “acid rigidity” in the sperm and prevents premature activation. They also stage the epididymosomes . Here, too, there is contractile tissue around the epithelium, consisting of myofibroblasts, which slowly push the sperm further towards the cauda equina. The total transit time from the head of the epididymis to the tail of the epididymis is approx. 12 days. In a microscopic section, there are usually collections of immature sperm in the lumen of the duct.
Here are mature sperm that are stored here. In response to neural stimulation, the smooth muscle cells located here contract and press the sperm suspension into the seminal duct, where it is transported on.
The sperm cells only acquire their motility through a variety of processes through their intensive contact with the wall of the epididymis, the epithelial epithelium, and the substances formed by it , but not yet their ability to fertilize, which they only achieve with the capacitation in the female genital tract as the final phase of sperm maturation .
The cells of the epithelial epithelium resorb fluid and secrete, among other things, glycoproteins that are adsorbed on the surface of the sperm . The spermatozoa are transported over the head and body into the tail of the epididymis over a period of about two weeks by contraction of the myofibroblasts. The head and body are used for maturation, the tail for storing mature sperm cells ( sperm cells ). The smooth muscles of the tail are innervated and, like the vas deferens, contract during emission to carry the sperm into the urethra.
New studies show that the epigenetics of the sperm is adjusted as it passes through the epididymis, depending on the current state of health and the physical and mental state of the wearer.
By far the most common disease of the epididymis is inflammation of the epididymis , known as epididymitis . This leads to a very painful, often massive, enlargement of the epididymis. Benign tumors such as cystadenomas of the epididymis in Von Hippel-Lindau disease and adenomatoid tumors rarely occur .
- Renate Lüllmann-Rauch: pocket textbook histology. 5th edition. Thieme, Stuttgart / New York 2015, ISBN 978-3-13-129245-2 , p. 529f.
- Katherine J. Wu: Dads Pass On More Than Genetics in Their Sperm . In: Smithsonian . ( smithsonianmag.com [accessed August 3, 2018]).