Human Reproduction

Human reproduction is an Essential process of life that result in producing new life and maintains the transmission of genetics material from one generation to another and this process continues. In human reproduction, the new individual results from the coming together of two cells (gametes) an ovum produced by the female, and a sperm produced by the male. The fusing of the two gametes is called a zygote. Each gamete contributes half the genetic material present in the zygote, and the genetic material present in zygote are contributed half from mother and father.

Sperm are produced in the testes, the male reproductive organs. The male gonads are Testes and they are contained in Scrotum which produce the male hormone called Testosterone. Boys start producing sperm at puberty (approximately 15 years of age) and most men have mature sperm well into old age. Sperm are made at the rate of about 300 million per day, and live about 48 hours after being deposited in the women’s vagina. Male sperms have a tail which helps propels them forward and then to be carried by fluid movement which finally takes it upto female reproduction system. The sperm once in female reprocution tract, penetrates the ovum. The sperm pass out of the testes into the male reproductive ducts which they are suspended in secretions which form semen. The average volume of semen for each ejaculation is 2.5 to 6 million. Around 40-100 million per ML sperms are Ejaculate.

All females have a monthly Menstrual Cycle which is part of their reproductive cycle, Which is of 28 Days in length but it does vary from one individual to another.

Under action of FSH (A hormone secreted by the brain), It stimulates the growth of follicle each month which contains an egg and there can be around 5-6 follicles stimulated to Grow. The steroid hormone Oestradiol is secreted within the follicle and provides a nurturing environment for the developing egg.

As development proceeds the biggest follicle becomes the dominant follicle and other sister follicle subsequently die.  This process is complete by Day 10 to the menstrual cycle.

Luteinizing hormone is released from the brain once the dominant follicle reaches maturity, LH hormone than initiate the ovulation and the follicle ruptures within next 40-48 hours. Once the follicle is ruptured, Egg is released and it goes into the fallopian tubes.

If intercourse occurs within 48 hours of ovulation, then the sperm need to complete the long arduous swim from the vagina, through the uterus and into the fallopian tube, Where only several thousand sperms survive when Egg arrives but only one sperm finally penetrates the outer Egg membrane and it is trapped by female Egg cytoplasm. This is the process of fertilization and within 24 hours cell division occurs. The journey down the Fallopian tube takes 6 days in which time the fertilized egg has become a 130+160 cell structure known as a blastocyst.

The remains of the original ovulated follicle become the corpus luteum and secrete a steroid hormone called progesterone. Progesterone helps prepare the uterus for when the blastocyst arrives, 6-8 days after fertilization.

The blastocyst finds a suitable area, hatches out of its shell (zone pellucid) and buries itself into the uterine lining. This is the process of implantation. The blastocyst secretes a hormone (chorionic gonadotrophin) that signals the mother that the egg is implanted and is growing. This hormone stimulates the corpus luteum to continue to secrete progesterone.

If the blastocyst does not implant or is not viable this stimulation does not occur. The Progesterone levels start to Fall and corpus luteum begins to shrink by day 21 or 22 of Menstrual cycle. in five cycles in which fertilization has occurred will result in implantation and ongoing pregnancy.

Males semen always has Sex hormones and sperms but its different with females Menstrual Cycle Since their Sex hormones and release of Ovum is cycle. As a new cycle of Menstruation begins, its length is 28 days but it can be variable from 21 days to 36 days or even More. Ovulation occurs at approximately Day 14 in a 28 day cycles, but occurs earlier in a short cycle and later in longer cycles.

(Note that some women menstruate but do not ovulate. i.e. no ovum is released from the ovary) When an ovum is present, there is relatively short period of approximately 24 to 48 hours when the women is fertile. During this fertile period, sperm but be present in the fallopian tube and be able to reach the egg. Only one sperm is required to fertilize the ovum but in order for this to occur there must be a minimum of 40 million sperm per ml in the semen deposited in the women’s vagina if the ovum is not fertilized it dies.