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Introduction
When a woman becomes pregnant, the baby inside her womb goes through several stages of development. They convert from a fertilised egg to blastocyst and then a foetus, ready to take birth after nine months.
Embryo development is a crucial topic of Biology, NEET UG syllabus. If you’ve studied Biology in your 10th and 12th, you must be acquainted with the basis of embryo development definition, embryo development classification and other related topics. Today, we are going to discuss embryo development in detail. Let’s get started!
What is Embryo Development?
Embryo development in humans is a journey of life that begins when the single-cell gets divided into several cells together. After the egg fertilisation, the zygote is formed. The egg fertilisation process starts in the fallopian tube. This egg divides itself into compartments such as 2, 4, 6, 8, and so on, which later appear as a ball-like structure known as a morula. Later, the morula gets converted into Blastula, where they form a hollow structure. The open system will later be filled with fluid.
The next stage in embryo development is termed the blastocyst. In this stage, the cells get differentiated, and it further keeps on differentiating. As these cells keep growing further, the embryo’s body starts to grow. The embryo’s body requires adequate nutrients from the mother’s body for complete development. It is the essential stage as blastocyst attaches itself from the mother’s body and takes a fixed position inside the mothers’ uterus, where the baby starts growing.
The next stage is the placenta. In simple terms, the placenta is the only pathway that connects the baby to the mother’s womb. It allows the exchange of nutrients that helps babies to grow and flourish till the time they are born. The placenta is also responsible for collecting the waste material and the carbon dioxide from the foetus to avoid complications.
In appearance, the placenta is a nearly 22 cm long disk-shaped tube that holds the baby in the correct position. The placenta is extremely rich in blood vessels. The umbilical cord plays a significant role by connecting the foetus to the placenta, allowing the easy transfer of materials. Mainly, the placenta is attached at the bottom, sides, top, front and back of the uterus. In some cases, the placenta also gets attracted to the uterus’s lower part. This condition is termed placenta previa.
It is responsible for performing several important tasks, including releasing hormones such as progesterone, placental lactogen, oestrogen, relaxin and human chorionic gonadotropin, which helps in the overall development of the foetus.
- Removing the waste material left by the foetus.
- The umbilical cord responsible for connecting the placenta and the foetus transport substances essential for the growth of the foetus.
- Proving essential nutrients and oxygen to the foetus in the womb.
The next step is the foetal stage. In this stage, the organs inside the baby’s body develop. In this stage, the doctors can spot the organs and they keep on growing till the baby is fully ready for the birth or parturition phase.
What is Parturition?
Parturition can be defined as the labour and the delivery of the baby. During the parturition process, the cervix dilates and relaxes with time. Also, the cortisol, oxytocin and oestrogen hormones activities and starts to produce milk and labour. Once the parturition phase begins, the uterus starts to contract and push the foetus into the cervix, after which the foetus gets pushed towards the birth canal. The process continues until and unless the baby comes out.
Human Embryonic Development And Various Stages
Weeks after fertilisation | Embryonic development |
Week three | During week three, Notochord is developed during week three. Also, Neurulation follows gastrulation. |
Week four | During week four, the heart starts to beat as it is the first organ that develops. Optic pits, arm buds become visible |
Week five | Size ~ 4 mm. During week five, the baby starts to look like C in shape. Pharyngeal arches, inner ear, pancreas, liver, gallbladder and spleen develop. |
Week six | Size ~ 8 mm. During week six, hands, feet, eyes, nose, leg buds, kidney and stomach develop. |
Week seven | Size ~ 13 mm. During week seven, primary sex organs, lymphatic system and lungs develop. |
Week eight | Size ~ 20 mm. During week eight, nipples, External ear and hair follicles develop. During this time, most of the organs start developing. |
After the first few weeks, the development process accelerates and it completes till eight or nine months. The baby starts to respond to lights, sound and touch in the last month. At this stage, the baby begins to hold firmly, turn around their head, blink and even position themselves for labour. The baby’s head needs to be down; else, C-section is suggested. By the end of the nine months, the baby weighed nearly 7 pounds and was 18-20 inches long.
Conclusion
Today, people, especially women, have started to take proper care during pregnancy which contributes to the complete growth and development of the embryo during the nine months. In India, several private and public hospitals offer top-notch services to provide adequate guidance during the pregnancy phase and even after that.
Till now, we studied embryo development in detail. We hope things are clear to you now. It can be said that embryo development is a vast topic that requires extra attention to score high marks.
