Editing Mesoderm (section)

==Paraxial mesoderm==
{{Main|Paraxial mesoderm}}
During the third week, the paraxial mesoderm is organized into segments. If they appear in the cephalic region and grow with cephalocaudal direction, they are called somitomeres. If they appear in the cephalic region but establish contact with the neural plate, they are known as [[neuromere]]s, which later will form the mesenchyme in the head. The somitomeres organize into somites which grow in pairs. In the fourth week, the somites lose their organization and cover the notochord and spinal cord to form the backbone. In the fifth week, there are 4 occipital somites, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 8 to 10 coccygeal that will form the axial skeleton.  Somitic derivatives are determined by local signaling between adjacent embryonic tissues, in particular the neural tube, notochord, surface ectoderm and the somitic compartments themselves.<ref name="Yusuf-2006">{{Cite journal |last=Yusuf |first=Faisal |year=2006 |title=The eventful somite: Patterning, fate determination and cell division in the somite |journal=Anatomy and Embryology |volume=211 Suppl 1 |pages=21–30 |doi=10.1007/s00429-006-0119-8 |pmid=17024302 |s2cid=24633902 |id={{ProQuest|212010706}}}}{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref>  The correct specification of the deriving tissues, skeletal, cartilage, endothelia and connective tissue is achieved by a sequence of morphogenic changes of the paraxial mesoderm, leading to the three transitory somitic compartments: dermomyotome, myotome and sclerotome. These structures are specified from dorsal to ventral and from medial to lateral.<ref name="Yusuf-2006" /> Each somite will form its own sclerotome that will differentiate into the tendon cartilage and bone component. Its myotome will form the muscle component and the dermatome that will form the dermis of the back. The myotome and dermatome have a nerve component.<ref name="RFB2004Mesoderm" /><ref name="Langman's Medical Embryology 2010" />