You've most likely heard some story as a kid of how you came to be. The stork flew from the sky with you wrapped warmly in a blanket. Softly given to your parents, the stork left you as a fresh newborn to your parents. The End. We all know that is not the case. How do we develop in our mother's belly? What is prenatal physical development?
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How do we develop in the womb of our mother? What many physical changes must a baby human endure before birth?
Prenatal development is also referred to as antenatal development. Prenatal development is the process from the point of forming an embryo, through the fetus' development, to the baby's birth.
Let's look at this process much like following a map. Where do we begin in the process? Your development into the person reading these words begins before your existence.
Conception happens with an egg from the mother is fertilized by sperm from the father. Specifically, in humans, conception begins with ovulation. Ovulation occurs when the egg that has been stored in the mother's two ovaries matures and is then released into the fallopian tubes.
Ovulation happens when a female is halfway through the menstrual cycle, and the other is a combination of hormones that aid in the ovulation process.
But conception is just the tipping point of the amazing changes and developments for a child to be born.
Three specific physical characteristics of prenatal development occur inside the human female's body as it begins the fantastic creation of life -- the zygote, the embryo, and the fetus.
Within several hours of conception, there are 23 chromosomes from the egg and 23 chromosomes from the sperm that fuse. The fusion of these chromosomes then creates the zygote (or a fertilized egg). Once chromosomes have been fused, the zygote will travel down the fallopian tubes to the uterus.
This travel is quite the journey for this microscopic organism. Less than half of the zygotes making the journey will survive. If the zygote completes this journey from the fallopian tubes to the uterus, it will attach to the wall of the female's uterus.
What if the zygote gets lost on the journey and does not complete the travel? The zygote will be flushed away in the female's menstrual cycle.
The cells within the zygote will begin to divide until there are eventually trillions of cells. Shortly after, these cells will soon transform and take a separate function. At the earliest stages of transformation, the changes happening inside the zygote begin the earliest stages of a human being. The cells on the outside? These cells will begin to create a protective environment, supporting new life throughout the pregnancy.
When the zygote attaches to the uterus wall, it is referred to as the embryo. The embryonic phase will last about six weeks as the major internal and external organs form. The embryo's appearance will rapidly change from this point until being birthed.
As stated previously, the embryo's outer layer forms a protective layer or environment so that the embryo will survive throughout the pregnancy. So what does this protective environment look like?
There are three major structures that the environment is made up of:
The amniotic sac- is a fluid-filled container that the embryo will live inside until birth. The amniotic sac will act as a cushion against outside pressure and regulates temperature.
The placenta- this organ allows for the transfer of nutrients between the mother and the embryo. The placenta can also filter harmful materials in an attempt to protect the embryo.
The umbilical cord- this cord links the embryo to the placenta and transfers the material to the fetus which protects the embryo that could be a threat to its health.
Fig. 1 The appearance of the embryo will go through many changes.
Nine weeks after conception, the embryo becomes a fetus. Becoming a fetus is a defining characteristic of growth. Major aspects of growth for this organism will happen in the embryonic phase. Now, the fetus has about six months of growth, starting from a weight of less than an ounce to weighing six to eight pounds at birth.
The fetus stage is where there are more defined characteristics of being a human -- moving, sleeping, and forms of swallowing and breathing. Also, the fetus will have developed its senses and; now be able to distinguish tastes and sounds.
The normal prenatal development process is about 38 weeks long but there is a timeline of events that makes up the three stages of development.
Stage (Weeks) | Changes and Developments |
Germinal Stage (Weeks 1-2) | Time of conception where the sperm fertilizes the egg (where DNA is passed). A zygote (a one-cell structure) is then created. The sex of the baby and the genetic makeup of the baby are determined. The process of mitosis occurs here. |
Embryonic Stage (Weeks 3-8) | After the zygote has 150 cells it will then travel down the Fallopian tubes and implant into the uterus (becoming an embryo). During this stage, the heart begins to beat, and organs will form as well as function. |
Fetal Stage (Weeks 9-40) | At this stage, the embryo becomes a fetus. |
Fetal Stage (Weeks 9-12) | The fetus, at this period, is the size of a kidney bean and takes a more human form. The sex organs begin to distinguish. |
Fetal Stage (Week 16-28) | Fingers and toes begin to develop and the fetus is about 4.5 inches long. The brain is doubling in size at this time. |
Fetal Stage (Weeks 36-40) | The fetus was around six pounds and are about 18.5 inches long. In this period, the organs are developed enough to survive outside the womb. |
As humans in our mother's bellies, we are going through complex and fast-paced changes. While we are generating a human form, the inner workings of our cognition are also being produced. What do prenatal cognitive developmental stages look like?
During the third week of pregnancy, there are cells that are rapidly multiplying to form the neural plate. The neural plate will eventually fold to become the neural tube. Later this structure will become the forebrain, midbrain, hindbrain, and spinal cord.
In the fifth week of pregnancy, neurons are forming and multiply in these regions of the prenatal brain.
During the second trimester of pregnancy (about the sixth week), the brain is at its most active period as about 250,000 neurons are being created every minute! In this period, neurons will also begin to move to different areas of the prenatal brain. These neurons will begin to perform specific functions (like storing memories and understanding sounds) and connect with other neurons to create information passages.
In the sixth month of pregnancy, the prenatal brain is still rapidly developing new functions. The cerebral cortex is growing faster compared to the other portions of the brain. The cerebral cortex is in charge of language and thought processes.
Before birth, the prenatal brain and nerves are already developed enough to control basic reflexes and functions that are vital such as swallowing, breathing, and sleeping. Even physical reflexes have developed early in the development of prenatal cognition. Have you ever felt the belly of a pregnant woman and the baby moved or kicked once you touched the belly? That's the baby reacting to the stimulus of touch!
During the seventh month, the neurons get another update. A process called myelination begins when a fat-based substance forms with the connections between neurons. Because of the newly made myelin sheath, the signals that are sent by the neurons are now able to move much faster.
By the seventh month, the prenatal brain is functioning with about 70 percent of neural processes!
As birth approaches, the eighth month is the period in which the auditory cortex (sound), the visual cortex (sight), and the Broca's area (the area that helps produce speech) start to function. Why is this important? The baby yet to be born is able to understand sight and sounds and even differentiate between languages! These are the beginning functions of cognitive development.
Before birth, the prenatal brain and nerves are already developed enough to control basic reflexes and functions that are vital such as swallowing, breathing, and sleeping. Even physical reflexes have developed early in the development of prenatal cognition. Have you ever felt the belly of a pregnant woman and the baby moved or kicked once you touched the belly? That's the baby reacting to the stimulus of touch!
One of the first neurons to go through myelination are those located in the brain regions responsible for motor development (the brainstem and spinal cord) and they’ll be the most fully developed by that period.
The development of the fetus from conception to birth seems like a well-orchestrated process. But could something cause this process to have problems or delays?
Genetic and environmental factors are crucial factors that can affect the prenatal physical development of a child. The child is dependent upon the mother to help monitor proper development. Prenatal care is highly effective at ensuring the best-case scenario for prenatal development and life after birth. Prenatal care monitors the health of the fetus and the mother throughout the stages of pregnancy. This care can reduce the risk of possible complications. Often, there is the monitoring of vitamins such as folic acid to help prevent birth defects.
Fig. 2 Prenatal care can lead to a healthy baby.
There are other environmental agents to consider during physical development in the womb such as biological, chemical, or physical. These agents are known as teratogens and there are different types that could cause issues.
Alcohol is not safe to consume while pregnant no matter the amount. Alcohol has the ability to cross the placenta and directly affect the fetus. There is a direct correlation between intellectual deficiencies and disorders related to consuming alcohol while pregnant. If there is heavy consumption of alcohol during pregnancy leads to Fetal Alcohol Spectrum Disorder or FASD. But what are the physical effects on the fetus from FASD? Physically speaking, children affected by FASD will have a small head size and abnormal facial features.
Nicotine can also pass through the placenta and directly affect the fetus. If, for example, the mother of the fetus smokes, the developing fetus will have a reduction in blood oxygen levels. Smoking while pregnant can lead to premature birth, stillbirth, low birth weight, or sudden infant death syndrome (SIDS).
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What is prenatal physical development?
Prenatal development is also referred to as antenatal development. Prenatal development is the process from the point of forming an embryo, through the fetus' development, to the baby's birth.
What are the three phases of prenatal development?
Three specific physical characteristics of prenatal development occur inside the human female's body as it begins the fantastic creation of life -- the zygote, the embryo, and the fetus.
What is the cognitive development of prenatal development?
During the third week of pregnancy, there are cells that are rapidly multiplying to form the neural plate. The neural plate will eventually fold to become the neural tube. Later this structure will become the forebrain, midbrain, hindbrain, and spinal cord.
What are the factors of prenatal development?
Factors of prenatal development are genetic and environmental such as prenatal care and the consumption of nicotine and alcohol.
Why is it important to study prenatal physical development?
It is important to study prenatal physical development to ensure that the baby will successfully be born and also develop properly in it's lifetime.
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