testis


testis
/tes"tis/, n., pl. testes /-teez/. Anat., Zool.
the male gonad or reproductive gland, either of two oval glands located in the scrotum.
[1675-85; < L]

* * *

plural  testes,  also called  testicle 
 in animals, the organ that produces sperm (q.v.), the male reproductive cell. In humans the testis is either of the paired, oval-shaped organs that produce sperm and the male hormones, the androgens (androgen). They are contained within the scrotal sac, which is located directly behind the penis and in front of the anus. Each testis weighs about 25 grams (0.875 ounce) and is 4 to 5 centimetres (1.6 to 2.0 inches) long and 2 to 3 centimetres (0.8 to 1.2 inches) in diameter. Each is covered by a fibrous capsule called the tunica albuginea and is divided by partitions of fibrous tissue from the tunica albuginea into 200 to 400 wedge-shaped sections, or lobes. Within each lobe are 3 to 10 coiled tubules, called seminiferous tubules, which produce the sperm cells. Both the partitions between lobes and the seminiferous tubules converge in one area near the anal side of each testis to form what is called the mediastinum testis. Sperm cells produced in the seminiferous tubules migrate, by short contractions of the tubules, to the mediastinum testis; they are then transported through a complex network of canals (rete testis and efferent ductules) to the epididymis (see epididyme) for temporary storage. The epididymis partially surrounds the top and anal side of each testis.

      In the embryo, the testes originate in the lower body cavity near the kidneys. They migrate to their position within the scrotum (q.v.) in about the seventh or eighth month of development in the unborn child. Descent is controlled by the androgen testosterone. The production of testosterone by the fetal testes is stimulated by chorionic gonadatropin, a hormone secreted by the placenta. Testosterone secretion ceases a few weeks after birth, and the cells within the testes remain undeveloped during early childhood; during adolescence, gonadotropic hormones from the pituitary gland at the base of the brain stimulate the development of tissue, so that it becomes capable of producing sperm and androgens.

      The seminiferous tubules, in which the sperm are produced, comprise about 90 percent of the testicular mass. In the young male, the tubules are simple and composed of undeveloped sperm-producing cells (spermatogonia) and the Sertoli cells. In the older male, the tubules become branched, and spermatogonia are changed into the fertile sperm cells after a series of transformations called spermatogenesis (q.v.). The Sertoli cells found in both young and adult males mechanically support and protect the spermatogonia.

      Cells known as interstitial cells, or Leydig cells, located beneath the tunica albuginea, in the septal walls, and between the seminiferous tubules, are thought to secrete androgens. The Leydig cells are irregularly shaped and commonly have more than one nucleus. Frequently they contain fat droplets, pigment granules, and crystalline structures; the Leydig cells vary greatly in number and appearance among the various animal species. They are surrounded by numerous blood and lymphatic vessels, as well as by nerve fibres. The secretion of androgens is controlled by the pituitary hormones.

      In animals that breed seasonally, such as sheep and goats, the testes regress completely during the nonbreeding season and the spermatogonia return to the state found in the young, sexually immature males. Frequently in these animals the testes are drawn back into the body cavity except in the breeding season, when they again descend and mature; this process is known as recrudescence.

* * *


Universalium. 2010.

Look at other dictionaries:

  • TESTIS — Isidoro, a quo quaeritur veritas in iudicio, quem quisque ante iudicium sibi placitis alligat, ne ei sit postea liberum, aut dissunulare aut subtrahere se: Unde alligatus quoque Cicer. l. 2. ad Q. Fratr. Ep. 3. Nerius index edidit ad alligatos,… …   Hofmann J. Lexicon universale

  • testis — (pl. testes), 1704, from L. testis testicle, usually regarded as a special application of testis witness (see TESTAMENT (Cf. testament)), presumably because it bears witness to virility (Cf. Gk. parastates, lit. one that stands by; and Fr. slang… …   Etymology dictionary

  • Testis — Tes tis, n.; pl. {Testes}. [L.] (Anat.) A testicle. [1913 Webster] …   The Collaborative International Dictionary of English

  • testis — testis. См. семенник. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Testis — (lat.), 1) der Zeuge; T, ocularis, der Augenzeuge; 2) s. Testes …   Pierer's Universal-Lexikon

  • testis — index witness Burton s Legal Thesaurus. William C. Burton. 2006 …   Law dictionary

  • Testis — ⇒ Hoden …   Deutsch wörterbuch der biologie

  • tèstis — m anat. muška spolna žlijezda; mudo, jaje, sjemenik ✧ {{001f}}lat …   Veliki rječnik hrvatskoga jezika

  • testis — ► NOUN (pl. testes) Anatomy & Zoology ▪ an organ which produces sperm. ORIGIN Latin (see TESTICLE(Cf. ↑testicular)) …   English terms dictionary

  • testis — [tes′tis] n. pl. testes [tes′tēz΄] [L] TESTICLE …   English World dictionary

  • Testis — Der Hoden [ˈhoːdn̩] oder (seltener) der/die Hode [ˈhoːdə] (v. mittelhochdt.: hode, v. althochdt.: hodo, v. idg.: *skeu(t) „bedecken, verhüllen“) oder der Testikel (v. lat.: testiculus, Vkl. von testis Zeuge [der Virilität], Hode, Plural:… …   Deutsch Wikipedia


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.