Abstract
The epithelium of the sex cords and the seminiferous tubules is described from the foetal state to maturity. The basal supporting cells were observed to proliferate actively at and soon after birth, but their division ceased by the age of 16 weeks. Some of the new cells were observed to be located towards the centre of the sex cords by the age of four weeks. By the age of 28 weeks some of the supporting cells, which never give rise to spermatogonia, become transformed to typical Sertoli cells. By the age of 44 weeks all the supporting cells have been transformed into Sertoli cells. Many gonocytes show degenerative changes shortly after birth. The gonocytes which do not degenerate, proliferate from the eighth week and give rise to spermatogonia. Spermatogonia increase in number and by the age of 20 weeks primary spermatocytes are produced. Spermatids and sperm appear by the age of 28 weeks. En beskrivning lamnas av sadesstrangarnas resp. sadeskanalernas epitel fran sent fosterstadium till full utveckling baserad pa en under-sokning av testiklar fran 50 SRB-tjurar och ett foster. Proliferation iakttogs hos de basala odifferentierade stodjecellerna fore och efter fodeisen samt fram till 16 veckors alder. Som ett resultat av denna proliferation iakttogs fran 4 veckors alder odifferentierade stodjeceller aven centralt i sadesstrangarna. De odifferentierade stodjecellerna omvandlades till Sertoliceller men gav icke upphov till spermatogonier. Typiska Sertoliceller observerades fran och med 28 veckors alder. Alla odifferentierade stodjeceller voro omvandlade till Sertoliceller vid 44 veckors alder. Kort tid efter fodeisen observerades hos manga gonocyter degenerativa forandringar. Gonocyter, som icke degenererade, visade proliferation och gav upphov till spermatogonier med borjan vid 8 veckors alder. Antalet spermatogonier okade under de foljande veckorna successivt. Primara spermatocyter observerades fran 20 veckors alder samt spermatider och spermier fran 28 veckors alder.
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