How old are you? 21? 39? 80?
Like everybody else, your estimate was based on when you were born. Right? Well, what if we told you you're almost a year (9 months) older than your conventional age?
A baby has already lived nine crucial months by the time it is born. Now, traditionally, these months aren’t considered when calculating our ages, but that doesn’t mean they’re less significant. These nine months play a crucial role in shaping our development and health.
Below, we look at what happens during the germinal stage of prenatal development, review its significance, and answer a few frequently asked questions.
What Is the Germinal Stage of Prenatal Development?
The nine months of a normal pregnancy generally has three prenatal stages:
Prenatal Stage | Timeline | Major Events |
Germinal Stage | 8 - 9 Days | Conception - Formation of the blastocyst |
Embryonic Stage | 3rd - 8th Week | Formation of distinct human characteristics (structures and organs) |
Fetal Stage | 9th Week - Birth | The transformation from an embryo to a mature fetus |
What Occurs During the Germinal Stage of Prenatal Development?
The germinal stage of prenatal development begins with the joining of a sperm and an egg in the fallopian tube and ends with the formation of a blastocyst. It's the shortest of the three prenatal stages and usually takes about nine days in normal pregnancies.
Let's look at this process:
Fertilization & Conception
The total volume of semen for each ejaculation averages between 2 and 5 ml with about 200-300 million sperms. However, only one sperm succeeds in fertilizing the ovum.
Before fertilization, the ovum (egg) releases chemicals known as chemoattractants. Chemoattractants attract sperm to the unfertilized egg in the fallopian tube. The entire journey takes about 30-45 minutes.
The chemoattractants are also responsible for choosing the sperm that will eventually penetrate the ovum’s membrane. Once "the chosen one" has entered the ovum and deposited its genetic components, the egg immediately becomes resistant to further penetration. The ovum and sperm's nuclei then combine to form a single-celled zygote, which stays in the fallopian tube for approximately 72 hours.
Cleavage
This stage within the germinal period of prenatal development begins two to three days after fertilization. It involves several mitotic divisions known as cleavage. First, the zygote divides into two daughter cells. This process recurs every 12-24 hours for about four days to form 16 daughter cells.
The resulting cells form a solid ball known as a morula. Ultrasounds might not detect any noticeable changes at this stage. This is because while the mitotic divisions produce more daughter cells, the resulting morula is always the same size as the initial zygote.
Blastulation
In this stage, the morula transforms into a blastocyst. Blastocyst is a fancy word for a hollow fluid-filled ball with many cells. It consists of three major parts:
- Embryoblast – Mass of cells inside the blastocyst that will eventually become the embryo.
- Trophoblast – Mass of cells outside the blastocyst that will ultimately form the placenta.
- Blastocoel – A cavity that forms when the embryoblast cells move to the blastocyst's north pole.
Like cleavage, this germinal stage of prenatal development takes 2-3 days. It usually occurs between the 5th and 7th day after fertilization.
Implantation
The fourth and last stage of the germinal period is implantation. It often begins on the 8th or 9th day after conception. Implantation is the embedment of the blastocyst into the endometrium (the inner lining of the uterus).
When the blastocyst comes into contact with the endometrium, the trophoblast cells immediately begin multiplying. During this proliferation, the cells also secrete enzymes that digest the endometrium's outer layer (mucosa). This process weakens the mucosa, enabling the trophoblast villi (finger-like projections) to penetrate it.
After penetration, the villi gradually pull the blastocyst (known as embryo after implantation) into the endometrium. By the time the implantation ends, the embryo should be fully covered by the endometrial epithelium.
Significance and Outcomes of the Germinal Stage
Below, we look at the significance of the germinal stage of prenatal development.
- The mitotic divisions during cleavage establish the baby's foundational cellular structure.
- The blastocyst implantation into the uterine walls ensures the continuation of the expectancy by offering sustenance and shock absorption.
- The baby's genetic setup formulates during the cell divisions in the germinal stage.
- The mother's health and environment can enhance or affect the baby's future development during this stage.
- The initial cell differentiation creates the basic cellular framework that dictates the formulation of various organs and tissues.
Frequently Asked Questions (FAQ)
What Is the Germinal Stage of Prenatal Development?
The germinal stage of prenatal development is the first stage of fetal development. It involves fertilization, cleavage, blastulation, and implantation, all of which happen within the first week of conception.
What Occurs During the Germinal Stage of Prenatal Development?
First, a sperm penetrates the ovum to form a zygote. The ovum then undergoes cellular transformations to form a blastocyst, which moves down the fallopian tube and is implanted in the uterine walls as an embryo.
When Does the Germinal Stage of Prenatal Development Occur?
The germinal stage occurs within the first 7-9 days of conception.
Can You Describe the Germinal Stage of Prenatal Development Using Its Key Processes?
The germinal stage has four key processes: fertilization, cleavage (mitotic divisions to form a morula), blastulation (cellular development to form a blastocyst), and implantation into the uterine walls.
What Is the Importance of the Germinal Stage?
The germinal stage is essential in the baby's development and health foundation. Any error in this phase can affect the baby's growth.
Conclusion
The germinal stage of prenatal development only takes about nine days. However, its impacts are lifelong. Therefore, the mother should always ensure they are in a safe and harmless environment during this period.
Successful fertilization, cellular differentiation, and implantation set the groundwork for a healthy pregnancy. And the opposite is true — exposing the embryo to harmful substances or environments during this stage can lead to irreversible cellular complications.
