Fertilization and the Key Changes in Human Pregnancy - Assignment Example

Secondary oocytes are formed after the primary oocyte during ovulation. Oocytes contain yolk granules that nurture the cell in the early development of the embryo. Fertilization occurs during the union of the male sperm and the secondary oocyte producing a zygote. A zygote is a fertilized egg that develops into a fetus. The secondary oocyte has the female chromosome X whereas the sperm has both female (X) chromosome and the Male (Y) chromosome. Oocytes must be supplied with various molecules needed for the growth of the embryo.

A female undergoes various changes during pregnancy. These are known as trimesters consisting of three stages over the 9-month or 40-week pregnancy period. The fetus undergoes different changes in each of the three stages until it fully develops. The first trimester is the period of up to 13 weeks of pregnancy. It is the most crucial stage of pregnancy. The female body undergoes many changes. The body structure and organs of the fetus begin to develop. This includes the eyes, mouth, ears, throat, and skin. The fetus is surrounded by the amniotic sac. The placenta is developed and transfers nutrients from the mother to the baby and waste from the baby to the mother. The body of the pregnant mother undergoes changes signified by certain symptoms. These symptoms include nausea also known as morning sickness, fatigue, frequent urination, and softness of breasts. Spotting or normal bleeding is common as the fetus is implanted firmly in the uterus. The experiences at this stage vary with different women. Some women are very tired during this stage whereas others are full of energy. It is at this stage that miscarriages, birth defects, or ectopic pregnancies can occur (Tortora & Derrickson, 2009).

The second trimester is from 14 to 26 weeks. This is a pleasurable time of the pregnancy. All the symptoms experienced in the first trimester are gone. There is no morning sickness or fatigue. Most pregnant mothers start planning for the birth of their baby at this stage. They sleep better and have more energy. Different symptoms develop; back pain and abdominal pain due to the increase in weight of the fetus. Other symptoms include constipation and heartburn. The baby starts moving from 16 to 20 weeks. From 18 to 22 weeks the pregnant mother can undergo an ultrasound to see the development of the baby and know the sex of the child (Tortora & Derrickson, 2009).

The third trimester is from 27 to 40 weeks. This is the final stage of the pregnancy and the mother is ready to give birth. Different symptoms develop; shortness of breath, hemorrhoids, and sleep. The uterus has increased in weight and it is difficult for the pregnant woman to move around. The baby’s eyes can open, and fingernails, toenails, hair, and bones are developed. The baby can breathe as the lungs are fully developed. The baby has a heartbeat, and the liver and kidneys start functioning at this stage. The body is capable of storing minerals and develops antibodies to survive once it is born. The fetus starts developing once fertilization has taken place. The fetus develops in the female over 40 weeks in three stages where it fully develops. The mother finally gives birth after the full term of the pregnancy (Tortora & Derrickson, 2009).