BIOL-242 Lecture Notes - Lecture 63: Seminiferous Tubule, Spermatocyte, Spermatid
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Mitosis of spermatogonia (stem cell) forms two spermatocytes. Most body cells have 46 chromosomes - diploid chromosomal number (2n) One maternal, one paternal homologous chromosomes. Gametes have 23 chromosomes - haploid chromosomal number (n) Stem cells in contact with epithelial basal lamina. Each mitotic division one type a daughter cell and one type b daughter cell. Type a cells maintain germ cell line at basal lamina. Type b cells move toward lumen and develop into primary spermatocytes. Primary spermatocyte (2n) two secondary spermatocytes(n) Each secondary spermatocyte (n) two spermatids (n) Spermatid small, nonmotile cells close to lumen of tubule. Spermatids elongate; lose excess cytoplasm; form a tail spermatozoon (sperm) Figure 27. 9 spermiogenesis: transformation of a spermatid into a functional sperm. Head - genetic region; nucleus and helmet like acrosome containing hydrolytic enzymes that enable sperm to penetrate egg. Midpiece - metabolic region; mitochondria atp to move tail.