- How human fertilization happens
- In vitro fertilization
- Fertilization symptoms
- How embryonic development happens
- How Placenta is formed
- When the baby can be born
Fertilization is the name of the moment when the sperm is able to penetrate the egg, giving rise to an egg or zygote, which will develop and form the embryo, which after developing will form the fetus, which after birth is considered a baby.
Fertilization occurs in the fallopian tubes and the egg or zygote begins to divide as it moves until it reaches the uterus. When it arrives in the uterus, it is implanted in the uterine endometrium and here nesting officially takes place (nest site) about 6-7 days after fertilization.
How human fertilization happens
Human fertilization occurs when a sperm enters the egg, in the first portion of the fallopian tube, causing the woman to become pregnant. When a sperm can penetrate the egg, its wall immediately prevents other sperm from entering.
A single sperm crosses its membrane, carrying 23 chromosomes from man. Immediately, these isolated chromosomes combine with the other 23 chromosomes of the woman, forming a normal complement of 46 chromosomes, arranged in 23 pairs.
This starts the cell multiplication process, the end result of which is the birth of a healthy baby.
In vitro fertilization
In vitro fertilization is when the doctor inserts the sperm into the egg, inside a specific laboratory. After the doctor observes that the zygote is developing well, it is implanted in the inner wall of the woman's uterus, where it can continue to develop until it is ready for birth. This process is also called IVF or artificial insemination. Find out more details about artificial insemination here.
Fertilization symptoms
The signs and symptoms of fertilization are very subtle, and are usually not noticed by the woman, but they can be mild colic, and a small bleeding or pink discharge, which is called nesting. In most cases, the woman does not notice the symptoms of pregnancy until two weeks after the nest. See all the symptoms of fertilization and how to confirm the pregnancy.
How embryonic development happens
The embryonic development occurs from the nesting until the 8th week of gestation, and in this phase the formation of the placenta, the umbilical cord, and an outline of all the organs takes place. From the 9th week of gestation the small being is called an embryo, and after the 12th week of gestation it is called a fetus and here the placenta has developed enough so that, from then on, it can supply all the nutrients that are necessary for the development of the fetus.
How Placenta is formed
The placenta is formed by a maternal component of large and multiple layers, called placental sinuses, through which the maternal blood flows continuously; by a fetal component that is mainly represented by a large mass of placental villi, which protrude into the placental sinuses and through which the fetal blood circulates.
The nutrients diffuse from the maternal blood through the placental villus membrane to the fetal blood, passing through the umbilical vein to the fetus.
Fetal excreta such as carbon dioxide, urea and other substances, diffuse from fetal blood to maternal blood and are eliminated to the outside by the mother's excretory functions. The placenta secretes extremely high amounts of estrogen and progesterone, about 30 times more estrogen than is secreted by the corpus luteum and about 10 times more progesterone.
These hormones are very important in promoting fetal development. During the first weeks of pregnancy, another hormone also secreted by the placenta, chorionic gonadotropin, which stimulates the corpus luteum, causing it to continue to secrete estrogen and progesterone during the first part of pregnancy.
These hormones in the corpus luteum are essential for the continuation of pregnancy during the first 8 to 12 weeks. After this period, the placenta secretes sufficient amounts of estrogen and progesterone to ensure the maintenance of pregnancy.
When the baby can be born
The baby is ready to be born after 38 weeks of gestation, this being the most common time of a healthy pregnancy. But the baby can be born after 37 weeks of gestation without being considered pre-mature, but pregnancy can also last up to 42 weeks, being a normal situation.
