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A spermatogonium (plural: spermatogonia) is an undifferentiated male germ cell. Spermatogonia undergo spermatogenesis to form mature spermatozoa in the seminiferous tubules of the testicles. There are three subtypes of spermatogonia in humans: Type A (dark) cells, with dark nuclei.
The stem cells involved are called spermatogonia and are a specific type of stem cell known as gametogonia. Three functionally separate spermatogonia cell types are recognized on the basis of the appearance of the nuclei : type A dark spermatogonia (Ad), type A pale spermatogonia (Ap), and type B spermatogonia (B).
A d spermatogonia are reserve stem cells. These cells can divide to produce more SSCs but usually do not. A p spermatogonia are actively dividing to maintain the stem cell pool. B1-B4 spermatogonia encompass the differentiating spermatogonia and are no longer considered to be stem cells. Most research into SSCs has been carried out in rodents.
Each cell division from a spermatogonium to a spermatid is incomplete; the cells remain connected to one another by bridges of cytoplasm to allow synchronous development. Not all spermatogonia divide to produce spermatocytes; otherwise, the supply of spermatogonia would run out.
Spermatogonia going through mitosis to form primary spermatocytes in Grasshopper testes. Spermatocytogenesis. At puberty, spermatogonia located along the walls of the seminiferous tubules within the testis will be initiated and start to divide mitotically, forming two types of A cells that contain an oval shaped nucleus with a nucleolus attached to the nuclear envelope; one is dark (Ad) and ...
Gonocytes are the precursors of spermatogonia that differentiate in the testis from primordial germ cells around week 7 of embryonic development and exist up until the postnatal period, when they become spermatogonia. [1] Despite some uses of the term to refer to the precursors of oogonia, it was generally restricted to male germ cells.
Germinal epithelium of the testicle. 1 basal lamina, 2 spermatogonia, 3 spermatocyte 1st order, 4 spermatocyte 2nd order, 5 spermatid, 6 mature spermatid, 7 Sertoli cell, 8 tight junction (blood testis barrier)
Appearance of first spermatogonia: 16 100 Appearance of first ovarian follicles: 17 120 Numerous Leydig cells. Peak of testosterone secretion 20 150 Regression of Leydig cells. Diminished testosterone secretion 24 200 First multilayered ovarian follicles. Canalisation of the vagina 28 230 Cessation of oogonia multiplication 28 230 Descent of testis