Changes

[[File:Figure 3 Negative feedback loop.jpg|thumb|Figure 3: Negative feedback loop]]

[[File:Figure 3 Negative feedback loop.jpg|thumb|Figure 3: Negative feedback loop]]

Spermatogenesis is controlled by a complex feedback mechanism involving the hypothalamus, anterior pituitary and testes. Gonadotrophic releasing hormone (GnRH)is released by the hypothalamus in a pulsatile manner and travels through portal vessels to the anterior pituitary, where it acts of the gonadotrophic cells. These cells respond to the stimulation by producing either follicle stimulating hormone (FSH) or luteinising hormone (LH) depending on the pattern of GnRH secretion.  

Spermatogenesis is controlled by a complex feedback mechanism involving the hypothalamus, anterior pituitary and testes. '''Gonadotrophic releasing hormone (GnRH)''' is released by the hypothalamus in a pulsatile manner and travels through portal vessels to the anterior pituitary, where it acts of the gonadotrophic cells. These cells respond to the stimulation by producing either '''follicle stimulating hormone (FSH)''' or '''luteinising hormone (LH)''' depending on the pattern of GnRH secretion.  

LH and FSH travel in the bloodstream to the testes, where LH acts on the Leydig cells to stimulate them to convert steroids to testosterone and other androgens, which in turn contribute to the stimulation of Sertoli cells.

LH and FSH travel in the bloodstream to the testes, where LH acts on the Leydig cells to stimulate them to convert steroids to '''testosterone''' and other androgens, which in turn contribute to the stimulation of Sertoli cells.

FSH acts on the receptors of Sertoli cells and, in combination with testosterone, stimulates many functions, including synthesis and secretion of oestrogen, inhibin and many other products, meiosis, spermatocyte maturation and Leydig cell function.

FSH acts on the receptors of Sertoli cells and, in combination with testosterone, stimulates many functions, including synthesis and secretion of '''oestrogen''', '''inhibin''' and many other products, meiosis, spermatocyte maturation and Leydig cell function.

Inhibin, testosterone and oestrogen feedback negatively on the anterior pituitary and hypothalamus to suppress secretion of gonadotrophic hormones (Figure 3).

Inhibin, testosterone and oestrogen feedback negatively on the anterior pituitary and hypothalamus to suppress secretion of gonadotrophic hormones (Figure 3).