our little man

3.01.2006

growth and development: week 4

"your developing baby is still tiny. its size varies from 0.014 inch to about 0.04 inch in length.

fetal development is still in the very early stages, but many great changes are taking place! the implanted blastocyst is embedded more deeply into the lining of your uterus, and the amniotic cavity, which will be filled with amniotic fluid, is starting to form. the placenta, which plays an important role in hormone production and transport of oxygen and nutrients, is forming. vascular networks that contain maternal blood are establishing.

different layers of cells are developing. these germ layers develop into specialized parts of your baby's body, such as various organs. there are three germ layers - the ectoderm, endoderm and mesoderm.

the ectoderm will become the nervous system (including the brain), the skin and the hair. the endoderm develops into the lining of the gastrointestinal tract, the liver, pancreas, and thyroid. from the mesoderm comes the skeleton, connective tissues, blood system, urogenital system and most of the muscles."

--your pregnancy week by week

posted at 9:20 PM by aimee // 0 comments