By the end of the 5th week, 42 to 44 pairs of somites are formed, lying on either side of the developing neural tube. The first occipital and the last 5 - 7 coccygeal somites disappear. The remainder contribute to the development of the axial skeleton, the skull and vertebral column and related muscles.

What is the fate of somites?

The somites eventually diverge into sclerotome (cartilage), syndotome (tendons), myotome (skeletal muscle), dermatome (dermis), and endothelial cells, each corresponding to different regions within the somite itself.

At what stage do the somites first appear?

In the human embryo it arises in the third week of embryogenesis. It is formed when a dermamyotome (the remaining part of the somite left when the sclerotome migrates), splits to form the dermatome and the myotome.