The Three Big Processes

1. Of Life The Three Big Processes

2. Menstrual Cycle • The Menstrual cycle is a cycle that happens in females approximately every 28 days, but depends on the individual. This cycle begins on the first day of a female’s menstrual period. During this, tissue and blood from the uterus lining will come out through the vagina, which is called menstruation. It follows by the releasing of hormones, which tells the uterus to get ready for a new egg, and hormones prepare the egg to be released. The lining of the uterus grows with nutrients and blood, in the case that an egg is fertilized. The egg would attach itself to the lining and the lining would provide an environment that nurtures the egg, so it can grow to become an embryo, and then a fetus. At about 14 days into the cycle, the egg moves from the ovary and for seven days, the egg travels down the fallopian tubes, which is the ideal time that an egg should be fertilized. This is the process called ovulation. If the egg is not fertilized by sperm, the egg will dissolve. The uterus no longer needs extra blood, so the blood supply to the uterus is cut off temporarily, and because of this the blood, nutrients, and egg in the uterus linings are bleed out. And then the cycle happens again. This is the process that allows fertilization to happen, so without it we wouldn’t be alive right now Egg gets ready to be released into fallopian tubes A mature egg is released into fallopian tubes (ovulation) Beginning of Menstrual cycle Egg in fallopian tubes, heading to uterus Egg is not fertilized, so it is shed

3. Fertilization • The Process of Fertilization • Fertilization is where a sperm can fertilize the ready egg in the fallopian tube during a 6-12 hour period. Fertilization starts when a sperm enters the egg (conception) and the embryo starts to form. Two cells divide and become four, then the four cells divide and become eight, and so on until the cells form the structure of the eventual human body. • By the time the cluster of cells reaches the uterus and settles down into the lining of the uterus, it has become an embryo. This process (from fertilization to implantation) takes about 7 days. From now on, the female body concentrates on the growth of the embryo and stops the menstral cycle until a few weeks after the baby is born. That is why women can’t conceive again while in pregnancy. But this does not exclude the possibility of having more than one embryo or fetus at a time while pregnant e.g. twins. This is the process of fertilization. • Definition of fertilization: The process of combining the male sperm with the female ovum. The product of this combination is a cell called a zygote.

4. Sperm entering egg. Sperm entering egg, diagram. Developing fetus.

5. Spermatogenesis • Spermatogenesis is the process by which sperm develop to become mature sperm, which are capable of fertilizing a female egg or ovum. Spermatogenesis starts so happen from the age of around 13, when most boys hit puberty but occasionally immature sperm form earlier on, and continues on throughout a male’s whole life, at a rate of millions of sperm per day. Spermatogenesis occurs in the testicles and the epididymis. First sperm forms in the testicles, then they swim to the epididymis using their tails, and complete their development, this takes approximately 70 days. When the development is complete the sperm move into the vas deferens. The prostate gland and seminal vesicles then make seminal fluid that mixes with sperm to produce semen. This process allows fertilization to happen there for allowing the cycle of life happen, for if spermatogenesis did not happen in a male that male would not be able to create sperm, meaning that he could not fertilize an egg and create a child.

6. Process diagram Process diagram 2