Sertoli cells are much larger than germ cells, which are found nearby, and have less prominent nuclei. These cells are characterized by their relation to germ cells or primitive spermatogonia. They bind together to form a blood-testis barrier to keep germ cells contained in the seminiferous tubules and connect with each other through tight junctions. They promote spermatogenesis, which begins at the periphery of the tubules. Sertoli cells are found in the periphery of the seminiferous tubules. They produce testosterone, a steroid hormone that exerts its effects by binding intracellular receptors of different tissues and regulating protein expression. On histology, they have pink cytoplasm and can be identified by pink crystals of Reinke. Leydig cells are found in the interstitium of the testes adjacent to the seminiferous tubules. įunctional cells of the male reproductive system primarily consist of Leydig and Sertoli cells found in the testes. Together, these hormones form the hypothalamic-pituitary-gonadal axis that promotes and maintains sexual development and function in the male. Important hormones that modulate these include follicle-stimulating hormone (FSH) and luteinizing hormone (LH), which are released from the anterior pituitary gland and are regulated by gonadotropin-releasing hormone (GnRH), produced by the hypothalamus. Other key hormones include inhibin B and Mullerian inhibiting substance (MIS) hormone, both produced by the Sertoli cells in the testes. Testosterone can be converted in the periphery to a more active form, dihydrotestosterone via 5-alpha-reductase, or estradiol via aromatase. The major male androgen is testosterone, which is produced from Leydig cells in the testes. These structures are well-vascularized with many glands and ducts to promote the formation, storage, and ejaculation of sperm for fertilization, and to produce important androgens for male development. The male reproductive system consists of the internal structures: the testes, epididymis, vas deferens, prostate, and the external structures: the scrotum and penis.
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