Animal breeding / by Laurence M. Winters.

  • Winter, Laurence Merriam, 1891-
Date:
1925
Catalogue details

Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Animal breeding / by Laurence M. Winters. Source: Wellcome Collection.

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    SPERMATOGENESIS 25 phatics, encloses the testis and posteriorly protracts into the interior of the testis in the form of a mass of fibrous tissue called mediastinum testis. (3) Other fibrous processes project inward and divide the glandular substance into lobules. (4) This glandular substance of the testis is composed of the convoluted seminiferous tubules (tubules producing or carrying semen), two or three of which unite to form a straight tubule which passes into the body of the medias¬ tinum. (5) The spermatogonia (sperm-producing cells) are sit¬ uated within the seminiferous tubules; they, the sperma¬ togonia, constitute part of the outermost layer comprising the seminiferous tubules. (6) Between the tubules is a loose connective tissue con¬ taining numerous yellow epithelioid interstitial (situated in) cells and numerous lymphatics, blood vessels and nerves. (7) The straight tubules, when within the mediastinum, unite, giving rise to a network of vessels called the rete testis. (8) The rete testis leds into the efferent ducts (ducts leading out). (9) The efferent ducts open into a single convoluted tube, the epididymis, situated at the posterior margin of the testis and attached to the mediastinum. (10) The loAver extremity of the epididymis runs into a thick-walled muscular tube, which is the vas deferens. 21. Spermatogenesis.—Spermatogenesis is the matura¬ tion, or production, of spermatozoa. By cell division, a spermatogonium divides into two parts, one of which continues to be a spermatogonium; the other passes into the second layer of the seminal epithelium, there increases in size and becomes a spermatocyte. Then, by a process of reduction, each spermatocyte divides and two secondary spermatocytes are formed; both of these also divide and four spermatids are produced, each of which develops into a mature spermatozoon.