Third-arch cells form bones, muscles, and nerves in the throat that are used to swallow. Cells from the second arch form the third ear bone, a throat bone, and facial muscles. Specific cells in each arch form bone, muscle, and blood vessels.Ĭells from the first arch form the upper and lower jaws and two of the ear bones. Four swellings called arches develop in the area that will be the throat. The human head begins forming at the base of the embryo at about three weeks. The complicated assemblage of bones, tissue, muscles, arteries, and nerves that comprises our head is based on a simple plan found in sharks, with echoes of even earlier structures in headless worms.
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