Parenchyma of testis

Parenchyma testis

Definition

The parenchyma of testis is the specific tissue of testis comprising the seminiferous tubules.

Within the basement membrane are epithelial cells arranged in several irregular layers, which are not always clearly separated, but which may be arranged in three different. Among these cells may be seen the spermatozoa in different stages of development.

  • Lining the basement membrane and forming the outer zone is a layer of cubical cells, with small nuclei; some of these enlarge to become spermatogonia. The nuclei of some of the spermatogonia may be seen to be in process of indirect division, and in consequence of this daughter cells are formed, which constitute the second zone.
  • (2) Within this first layer is to be seen a number of larger polyhedral cells, with clear nuclei, arranged in two or three layers; these are the intermediate cells or spermatocytes. Most of these cells are in a condition of karyokinetic division, and the cells which result from this division form those of the next layer, the spermatoblasts or spermatids. 

(3) The third layer of cells consists of the spermatoblasts or spermatids, and each of these, without further subdivision, becomes aspermatozoön. The spermatids are small polyhedral cells, the nucleus of each of which contains half the usual number of chromosomes. In addition to these three layers of cells others are seen, which are termed the supporting cells (cells of Sertoli). They are elongated and columnar, and project inward from the basement membrane toward the lumen of the tube. As development of the spermatozoa proceeds the latter group themselves around the inner extremities of the supporting cells. The nuclear portion of the spermatid, which is partly imbedded in the supporting cell, is differentiated to form the head of the spermatozoön, while part of the cell protoplasm forms the middle piece and the tail is produced by an outgrowth from the double centriole of the cell. Ultimately the heads are liberated and the spermatozoa are set free..


Comparative anatomy in animals

Translations

Translations