Ovulation
Ovulation is the development and release of an egg from a women’s ovary. This occurs once in the menstrual cycle usually about 14 days before the end of the cycle. This is the fertile time for a woman.
The whole process is controlled by two glands in the brain, the hypothalamus and pituitary, which tell hormones in your body to trigger certain physical responses. The egg is released from a mature follicle on the ovary (either one, it’s random) and travels down the fallopian tube. Fertilisation may occur in the fallopian tube if sperm are present. The egg survives for about 12 – 24 hours.
Sperm
Sperm take about 70 days to develop and are produced in the testes. Sperm is expelled in seminal fluid on ejaculation. There may be 100’s million sperm produced at ejaculation though relatively few, several hundred, will reach the fallopian tubes.
The 'fertilising capacity' of the sperm can be dependant on the number of sperm produced and the quality of the sperm. By quality we mean such things as the sperm’s motility (ability to move forward) and shape. The sperm are capable of fertilization for about 72 hours.