By the seventh week, the embryo is around 18 mm (3/4 inch) in length; the nipples and the foetus's hair follicles start to form. The location of both the elbows and toes can be seen. At this point of time, spontaneous limb movements can be detected by ultrasound. For a seven week old foetus, all essential organs at least begin formation. By this week the foetus has individual fingerprints. Thus even in uterus the embryo has unique characteristics. The outer ear is present, while the inner ear is well established along with its hearing and its balancing mechanisms.
However, technically speaking, it is generally from the 8th week until birth that the developing human is actually termed as a foetus. A foetus is less sensitive to injury from environmental exposures as compared to the embryo. While most structures have already formed in the foetus, they continue to become functional and grow.
However, technically speaking, it is generally from the 8th week until birth that the developing human is actually termed as a foetus. A foetus is less sensitive to injury from environmental exposures as compared to the embryo. While most structures have already formed in the foetus, they continue to become functional and grow.