During Week 5 of pregnancy, or 3 weeks after conception, the dividing cells of the embryo form a disk, which folds into 3 layers. These layers are the beginnings of the organization of cells that will develop into all of the organs and tissues of the human body. A groove forms down the center of the disk, which now has a top and bottom, front and back, and left and right side. This neural groove deepens and then forms a tube, which will develop into the brain and spinal cord. An early circulatory system develops from tubes on the left and right side of the groove. The tubes merge, kink, and fuse together to form the chambers of the heart, which will begin to beat and pump blood. The central nervous system is also developing and the gastrointestinal tract begins to form. Simultaneously, the surrounding environment is also changing to nourish, protect, and support this development.
Did you know?
You're likely to need the loo more often, even during your first trimester, as your uterus expands onto your bladder. Higher progesterone levels and the fact that tubes from your kidneys are dilated may mean more trips to the loo for small amounts of wee.