How a baby is made. The first 10 weeks

How a baby is made.

So let’s answer the question how a baby is made. The early fetal development of a baby involves 10 weeks of development. Some developmental processes take weeks while others take days. The weeks 3-8 of the development period are called embryogenesis. The baby is most susceptible to environmental changes, radiation and drugs during this period. In this article we will discuss the early development up until week 10.

Timeline of how a baby is made

Day 0

The egg aka oocyte is released from the ovary following a luteinizing hormone surge that causes the Graafian follicle to rupture. The ovary is the female reproductive organ and produces oocytes. Learn more about how oocytes are made by reading a medical textbook here.

The sperm has already arrived at the ampulla. Learn more about sperm production and their arrival at the ampulla here.

The oocyte is taken up by the fimbriae which are hair like projections at the end of the fallopian tube to take up the oocyte.

Once the oocyte is pushed into the fallopian tube by the fimbriae it then moves along the fallopian tube being pushed by the cilia (small projections of cells lining the fallopian tube).

The oocyte arrives in the ampulla and it is fertilized by the sperm. Learn more about fertilization here.

The oocyte gets converted into a zygote post fertilization. A zygote is where the baby’s sex is determined. If the egg gets fertilized by a sperm containing XX genome, a baby girl will be born. If the genome contains XY chromosomes a baby boy will be formed. Y is the male chromosome containing the SRY gene.

Day 2-3-4

The zygote then divides every eight hours to form a ball of cells. On day 4 a ball of 16 cells is formed and is called a morula. The morula keeps on moving through the fallopian tubes and arrives at the fundus of the uterus.

Day 5

The cells continue to divide. A cavity starts appearing in the ball of cells known as the blastocoele and now the ball of cells is called a blastocyst.

Day 6-10

The blastocyst now implants onto the walls of the uterus. Most commonly it is the posterior superior internal surface of the uterus.

Week 2

The embryo now grows to form a bilaminar disc (two layered disc) by continuous dividing of cells. The bilaminar disc is composed of epiblast, the layer above, and hypoblast, the layer below.

Week 3

Week 3-8 is the embryonic period. Most mothers become aware of their pregnancy by this time. Week 3 starts with the process called gastrulation. Gastrulation is the formation of a trilaminar disc from a bilaminar disc that was formed in week 2. Cells from the epiblast migrate to form the three embryonic layers.

  • Ectoderm (the outermost layer)
  • Mesoderm (the middle layer)
  • Endoderm (the lower most layer)

The ectoderm will then form a primitive streak and lead to the formation of notochord (This forms the intervertebral disc in adult) from the underlying mesoderm. It also forms the neural plate and folds which will form the brain and spinal cord of the baby. Neural tube is formed from the neural folds. The folds close up during the third week to form the neural tube.

Week 4

The heart of the baby is formed from the mesoderm and it starts beating during the fourth week. The limb buds begin to form which will form the arms and legs.

Week 6

The heart of the baby starts beating by the fourth week but its activity only starts appearing on the transvaginal ultrasound by the sixth week.

Week 8

By the eight week mark the baby starts moving. At this stage the embryo has come out of the embryonic period and has now entered the fetal period.

Week 10

By the tenth week the baby’s genitalia have developed and it is easily recognizable whether it is a boy or a girl.

Learn more about other pregnancy and female reproductive topics by visiting other articles here. Or Read a good book to learn the entire topic.

Or watch a video below.

Finally here is a picture that we drew in med school. 🙂

How a baby is made.

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