Giving an overview of the two different processes, compare and contrast the processes of spermatogenesis and oogenesis.

In spermatogenesis, germline epithelium in the seminiferous tubules of the testes divides by mitosis and then a period of cell growth occurs, changing them from spermatogonia to primary spermatocytes. These then develop into 2 secondary spermatocytes and then 4 spermatids by meiosis I and II. The 4 spermatids undergo differentiation to become sperm cells. Oogenesis is more complicated and involves more steps. Oogonia are formed during foetal development and undergo mitosis and cell growth to become primary oocytes. These are then ‘arrested’ in prophase I of meiosis I, and then once the menstrual cycle starts at puberty, the FSH produced triggers meiosis I to continue and two cells are produced (one keeps the cytoplasm and becomes the secondary oocyte, and the other forms a polar body). This is now arrested in metaphase II, until fertilisation by a sperm cell triggers meiosis II to continue. The egg is now mature and becomes an ovum; its nucleus then fuses with the sperm’s nucleus to form a zygote.
The differences are that spermatogenesis produces 4 functional sperm, whereas oogenesis only produces 1 functional egg (and 2 to 3 polar bodies). The 4 sperm produced are all of equal size, but the egg retains the cytoplasm and the polar bodies are thus much smaller. Spermatogenesis is also continuous from puberty to death, but oogenesis occurs in distinct stages, beginning prenatally and continuing according to the monthly menstrual cycle, and ending at menopause.