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My Pregnancy Week 5
Even though this may be the first week a home pregnancy test confirms your pregnancy, it is incredible how many changes your little one has already gone through. By week five, the embryo, now securely nestled in your uterine wall, will begin dividing into three layers of cells: the ectoderm, the mesoderm, and the endoderm.
Ectoderm
The top layer of cells is called the ectoderm. The neural tube, which will eventually form the spinal cord and the brain, will begin to develop this week. Skin, hair, nails, and sweat glands will all develop from this layer.
Mesoderm
The most impressive changes this week take place in the middle layer, called the mesoderm. Though your baby is only about the size of a grain of rice, the heart has divided into chambers and will begin pumping blood this week! Muscles, cartilage, bone, placenta, and the umbilical cord will also all develop from this layer.
Endoderm
Your baby's lungs, intestines, thyroid, and pancreas will eventually develop from the endoderm.
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