Human Life Cycle

The human life cycle is essential to the world's population. It allows individuals to create families that can change society in multiple ways and all those individuals that has the capacity to change the world has a mother. Every soon to be mother wants an easy pregnancy but most importantly hopes and prays for a healthy baby. Understanding pregnancy is important soley due to the fact its a major factor in the cycle of life. Pregnancy involves growth, development and a new beginning.

A women that is becoming pregnant with a child is also known as conceiving, this process carried out by having sexual intercourse with a male. A female ovulate an egg cell, oocytes goes down a uterine tube. During sexual intercourse male sperm moves into the vagina, which is near the female's cervix, this occurs in the reproductive system. The sperm cell swims up the uterus and meets up with the oocyte and the process of fertilization occurs. During sexual intercourse many sperms swim towards the oocyte but only one sperm cell has the ability to fertilize the egg.

During beginning fertilization of the egg the cytoplasm triggers lysosomes vesicles that release enzymes that hard the zona pellucida so that it reduces the chance of more than one sperm can penetrates the oocytes. The egg divided then undergoes meiosis ends. The nuclei of the egg and nuclei of the sperm unite the membrane falls apart and the chromosome mingles which complete fertilization. The sperm cell and egg cell each has 23 chromosomes and during fertilization it 46 somatic cell this cell is called a zygote the first cell of the future offspring.

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The Zygotes undergoes mitosis 30 hours after forming, cells division occurs rapidly. The rapid cell division is called cleavage. During cleavage tiny cells move through the uterine tubes during the time of implantation cells in the interface of the blastocyst. The cell surrounding the embryo is called the placenta this organ attaches to the embryo and uterine wall exchanges of nutrients ,gasses ,waste between maternal blood and embryo blood. The beginning of the embryonic stage the of the offspring is called an embryo. Embryonic stage ends at eight week of the prenatal development . During this ime the placenta form and major organ develops and the major external body structure appears. The cell in the inner cell mass flatten embryonic disc with two distinct layers the connection stalk attached to the embryonic disc to developed placenta farther . Ectodermic cell gives the nervous system and portions of special sensory organ ,epidermis ,hair, nail, glands of the skin. Mesodermal cell form all type of muscle tissue, bone tissue, bone marrow . blood, blood vessel, lymphatic vessel, connective tissues internal reproductive e organ , kidney and epithelial lining of body cavities.

Endodermal cells produced the epithelial lining of the digestive tract ,respiratory tract, urinary bladder and urethra . When the chronrionic villi develops the embryonic blood vessel appears. During the 4th week of development the flat embryonic disc is a cylindrical structure and head and jaws develops the hearts starts to beats and tiny buds which will become upper and lower limbs forms. At 5th to 7 week the head grow rapidly and become more rounded and face begins to develop showing eyes nose mouth and more human like.

The upper and lower limbs elongate and figure and toes appears . By the end of the seventh week all the main internal organs are present ,the structure in enlarges and the embryonic become more human like appearance . End of 8 week until birth the offspring s called a fetus. Fetal stage is the end of the eighth week of the development and last until the birthing process during this time the fetus is growing very rapidly the body proportion enlarge at a considerable rate. The beginning of the fetal stage the head is larger than the limbs are short.

During the third month the body length accelerates and the head growth slows. During the twelve week the external reproductive organ are distinguishable male or female. At the 4th month the body grows 20 cm the skeleton beginnings to ossify. The following month the skeleton muscles contracts and the pregnant woman may fell fetal movement, hair begins to appears on the head . During the 6 month the fetus gains weight and eyebrow and eyelash appear and the blood vessel in the skin give a red appearance in the fetus.

During the last trimester the fetal brain cell develops rapidly . At the end of the ninth month 266 day the fetus is full term. The fetus is around 50 center meter and weight around 2. 7kg to 3. 6 kilogram everything is well develop and the fetus head is toward the cervix. Pregnancy ends with the birthing process, during this period rapid changed occurs. Progesterone starts to decline and it suppress the uterine to contracts, this stimulated synthesis of prostanglandin the uterine contracts.

The cervix begins to thin and opens ,stretching of the uterine and vaginal tissues occurs. The nerves impulses to the hypothalamus which signals the posterior glands to release the oxytocin hormones this stimulates powerful contraction. During labor the rhythmic contraction begins ,the fetus is positioned head downward and labor contraction forces the head towards the cervix. The cervix begins to dilate and increase in oxytocin is release. As labor continues the abdominal muscles contracts and forces the fetus through the cervix and the vagina to the outside.

After the delivery of the neonatal the placenta separates the uterine walls and is expelled the birth canals. Bleeding occur after the expelling which is called the after birth. Pregnancy involves a lot of different change in the body for the mother and the baby. This occurs from unite of the male and female and a miracle of life begins. The changes happen in a very rapid speed each day different development occurs . The beginning of a new family occurs between the individuals mother, father, child. This is only the beginning of the life journey, for the child. 1002 words

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