Spermatocyte
Spermatocytes are precursor cells of sperm in spermatogenesis . There are two types: 1st and 2nd order spermatocytes.
Spermatocytes I arise from the spermatogonia by entering the first meiosis of meiosis . In doing so, they replicate their DNA so that each chromosome consists of two sister chromatids . During prophase I of meiosis, these are superimposed on one another and parts of the chromosomes are exchanged ( crossing-over ).
The subsequent completion of the first meiosis (meiosis I) creates two daughter cells from spermatocyte I, spermatocytes II , by separating the homologous chromosome pairs. They are now significantly smaller than the spermatocytes I and after the division only contain half the amount of DNA. Type II spermatocytes are haploid, they divide in the course of spermiogenesis (final phase of spermatogenesis ) through meiosis II to form spermatids which are the precursors of the actual sperm . During meiosis II the sister chromatids are separated.
Various tissues, including testicular tissue, have a form of immune privilege .
literature
- Johannes W. Rohen, Elke Lütjen-Drecoll: Functional embryology: the development of the functional systems of the human organism . Schattauer Verlag, 2012, ISBN 9783794528233 , p. 17.
Individual evidence
- ↑ S. Zhao, W. Zhu, S. Xue, D. Han: Testicular defense systems: immune privilege and innate immunity. In: Cellular & Molecular Immunology. Volume 11, number 5, September 2014, pp. 428-437, doi : 10.1038 / cmi.2014.38 , PMID 24954222 , PMC 4197207 (free full text).