✅ PRIMERA SEMANA | EMBRIOLOGÍA [2023] 📚 DESARROLLO EMBRIONARIO | GESTACIÓN | EMBARAZO

Summary

This video explains the key stages of human prenatal development during the first week of gestation, focusing on fertilization and implantation. It covers the fusion of male and female gametes, the formation of the zygote, and the subsequent cell divisions that lead to the development of the blastocyst. The video also highlights the crucial events of implantation, including the interaction between the trophoblast and endometrium, and the formation of the bilaminar germinative disc. The content is presented in a simple and engaging way, perfect for beginners studying human embryology.

Takeaways

• 😀 Fertilization is the first step of human prenatal development, occurring when the male sperm and female secondary oocyte fuse to form a zygote.
• 😀 The zygote contains 46 chromosomes, with 23 from the sperm and 23 from the oocyte, making it a diploid cell.
• 😀 Fertilization usually happens in the ampulla of the fallopian tube and lasts for approximately 24 hours.
• 😀 On Day 2 after fertilization, segmentation occurs, where the zygote undergoes mitotic divisions to form blastomeres.
• 😀 By Day 3, the zygote becomes a 16-cell Morula. The cells inside are called the inner cell mass, which will become the embryo.
• 😀 The outer cell mass of the Morula will develop into the trophoblast, which forms the placenta.
• 😀 On Day 4, the Morula becomes a blastocyst, with the embryoblast at one pole and the trophoblast forming the blastocyst wall.
• 😀 On Day 5, the zona pellucida is removed, allowing the blastocyst to join the endometrium of the maternal uterus.
• 😀 On Day 6, the blastocyst attaches to the endometrium through its embryonic pole, marking the beginning of implantation.
• 😀 On Day 7, the endometrium is eroded by the syncytiotrophoblast, and the embryoblast forms two layers: the epiblast and hypoblast, forming the bilaminar germinative disc.

Q & A

What is the process of fertilization in human prenatal development?

Fertilization is the process by which the male and female gametes, sperm and secondary oocyte, fuse. This typically occurs in the ampulla of the uterine tube or fallopian tube, and results in the formation of a zygote with 46 chromosomes.

How long does fertilization last, and where does it typically occur?

Fertilization lasts for approximately 24 hours and typically occurs in the ampulla of the uterine tube.

What is the significance of the zygote in human development?

The zygote is the result of fertilization and marks the beginning of human life. It is a diploid cell with 46 chromosomes, 23 from the sperm and 23 from the secondary oocyte, and is surrounded by the Zona Pellucida.

What happens on the second day of gestation after fertilization?

On the second day, segmentation occurs, where the zygote undergoes mitotic divisions to increase its number of cells. The first division results in two blastomeres, and subsequent divisions lead to more blastomeres forming a compact structure.

What is compaction and when does it occur in human prenatal development?

Compaction is the process where blastomeres, the cells resulting from the zygote's divisions, form a tightly packed spherical structure. This occurs around the third day after fertilization when the blastomeres make maximum contact with each other.

What is the morula, and when does it form?

The morula is formed around the third day after fertilization and consists of 16 cells. The cells inside the morula form the inner cell mass, which will become the embryo, and the outer cell mass, which will become the trophoblast, the precursor to the placenta.

What is the blastocyst, and how does it form?

Around day 4, the morula forms a blastocyst when fluid enters through the Zona Pellucida and creates a space called the Blastocele. The inner cell mass becomes the embryonic pole, while the trophoblast forms the wall of the blastocyst.

What happens on the fifth day after fertilization?

On the fifth day, the Zona Pellucida is shed, allowing the blastocyst to contact and implant into the maternal uterine lining, specifically the endometrium.

What occurs on the sixth day of gestation?

On the sixth day, implantation occurs when the blastocyst attaches to the endometrium, specifically at the embryonic pole. The trophoblast divides into two layers: the inner cytotrophoblast and the outer syncytiotrophoblast.

How does the endometrium interact with the trophoblast during implantation?

During implantation, the syncytiotrophoblast secretes enzymes that erode the endometrium, facilitating the embedding of the blastocyst. The trophoblast produces human chorionic gonadotropin (hCG), which is essential for maintaining pregnancy.

What are the two layers formed by the epiblast and hypoblast in the embryo?

On the seventh day, the embryoblast forms two layers: the epiblast, a cylindrical layer, and the hypoblast, a cubic layer. Together, these layers form the bilaminar germinative disc, which gives rise to the embryo.