A dermatome also refers to the part of an embryonic somite. The mouth is between somite 1 and 2 (chelicerae and pedipalps). The cells within each somite are specified based on their location within the somite. Noggin function is required for correct nervous system, somite, and skeletal development. There is a yellow sub-basal mark found on 4th somite. This phenomenon allows neural crest cells to funnel through the rostral portion of each somite. The myotome is that part of a somite that forms the muscles of the animal. Many kinds of tissue derive from the segmented paraxial mesoderm by means of the somite. The prosoma and opisthosoma are connected by the pedicel, or pregenital somite. From their initial location within the somite, the sclerotome cells migrate medially towards the notochord. Somite formation can be induced by "Noggin"-secreting cells. On the thorax and abdomen somite, they measure . The 7th and last somite do not bear appendages or any other significant external structures. The word "somite" is sometimes also used in place of the word "metamere".