All life begins at conception, when the sperm from males swims and fertilizer the eggs released within the females. This newly created embryo starts growing within the uterus of its mother and is protected by a sac known as the placenta. The systems which sustain life begin developing, but they are not at their strongest until later on in the child's life. After this period of approximately nine months, the new human is born into the word during the process of childbirth and must immediately start surviving from the first breath, which is a critical life or death moment.
If all goes well and the child is born unharmed, the new person enters the stage of infancy. Infancy is the period of life that our bodies grow and adapt to life outside of the mother's womb. We must now rely on our bodies to carry out basic functions for life such as breathing, pumping blood, heating, eating, etc. The most critical parts of our bodies develop and mature such as the hole in the cranium closing, the holes in our heart which protected the lungs from blood sealing, and the cartilage skeleton turning into stronger bone.
The immune system learns to recognize infections and protect the body from the ten billion bacteria we come into contact with everyday. New connections between brain cells are made and we begin to evolve, especially when beginning to speak. Another key moment during infancy is the ability to walk which is held responsible for by balance which is located in the inner ear. Infancy is just the beginning of the life we are about to encounter and all the new experiences we will undertake. The next critical point in life is puberty which begins when a child approximately reaches the age of 11.
For all people, puberty begins within the brain when proteins are released. Our bodies begin to produce hormones such as estrogen and testosterone, and the sexual organs and reproductive system begin working. Women normally undergo menstruation and a change in body form such as wider hips, breasts, and a more womanly and attractive figure. Men start producing sperm and their bodies change also with a steep increase in height and the formation of more masculine muscles. Both sexes experience an interest in their sexuality when it comes to attracting partners and many have extraordinary experiences such as their first kiss.
These moments stay them forever and play a major role in the next stage of life: adulthood. The stage of adulthood begins at the age of twenty-one and is when most people's lifestyles are chosen. Many graduate from college and go onto lifelong careers, and some even choose to settle down, get married, and begin a family which results in a the beginning of a new generation! There are also many physical changes that occur such as the slowing down of our metabolism which results in weight gain, wrinkles due to aging, women go through menopause, stress levels increasing, etc.
Our bodies are still working incredibly amazing, but they are slowly starting to slow down and not always work with us. The next stage of life begins at age 60 and is considered old age. At this point, the body slows down at a dramatic rate and people are at dangerous risks. For example, many older people suffer from osteoporosis, which is when the density in bones lessens and they are at a great risk of breaking with one wrong move. Many do not have the energy they used to and are vulnerable to excessive weight gain from an almost nonexistent metabolism.
Their bodies are shutting down little by little each year and it is almost time for the next and last stage of life. The last and final stage of life is death. Death is a biological process that is determined by the DNA we carry. The average age of death at the moment in America is around 77 to 80 years old. Our bodies shut down and the last brain impulses are sent. It is a depressing moment, but it is the circle of life and it allows for traditions and customs to be passed down throughout future generations. This is the mystery of the incredible human body and it is an amazing machine that carries us throughout our wonderful lives.