define different stages of unborn baby after fertilisation in human body?
Answers
when a fertilized sperm made with a ova a zogyote is formed this lead to exterinal fertilisation
Explanation:
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Explanation:
Fetal Development: Stages of Growth
Pregnancy begins with the first day of your last menstrual period. Find out what happens to your fetus month by month.
The start of pregnancy is actually the first day of your last menstrual period. This is called the 'menstrual age' and is about two weeks ahead of when conception actually occurs.
Here's a primer on conception
Each month a group of eggs (called oocytes) is recruited from the ovary for ovulation (release of the egg). The eggs develop in small fluid-filled cysts called follicles. Normally, one follicle in the group is selected to complete maturation. This dominant follicle suppresses all the other follicles in the group, which stop growing and degenerate.
The mature follicle opens and releases the egg from the ovary (ovulation). Ovulation generally occurs about two weeks before a woman's next menstrual period begins.
After ovulation, the ruptured follicle develops into a structure called the corpus luteum, which secretes progesterone and estrogen. The progesterone helps prepare the endometrium (lining of the uterus) for the embryo to implant.
On average, fertilization occurs about two weeks after your last menstrual period. When the sperm penetrates the egg, changes occur in the protein coating around it to prevent other sperm from entering. At the moment of fertilization, your baby's genetic make-up is complete, including its sex.
If a Y sperm fertilizes the egg, your baby will be a boy; if an X sperm fertilizes the egg, your baby will be a girl.
Human chorionic gonadotrophin (hCG) is a hormone present in your blood from the time of conception. It is produced by cells that form the placenta and is the hormone detected in a pregnancy test. However, it usually takes three to four weeks from the first day of your last period for the hCG to increase enough to be detected by pregnancy tests.
Within 24 hours after fertilization, the egg begins dividing rapidly into many cells. It remains in the fallopian tube for about three days. The fertilized egg (called a blastocyte) continues to divide as it passes slowly through the fallopian tube to the uterus where its next job is to attach to the endometrium (a process called implantation). Before this happens, the blastocyte breaks out of its protective covering. When the blastocyte establishes contact with the endometrium, an exchange of hormones helps the blastocyte attach. Some women notice spotting (or slight bleeding) for one or two days around the time of implantation. The endometrium becomes thicker and the cervix is sealed by a plug of mucus.
Within three weeks, the blastocyte cells ultimately form a little ball, or an embryo, and the baby's first nerve cells have already formed. Your developing baby is called an embryo from the moment of conception to the eighth week of pregnancy. After the eighth week and until the moment of birth, your developing baby is called a fetus.
The development stages of pregnancy are called trimesters, or three-month periods, because of the distinct changes that occur in each stage.
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