Three Cell-Producing Layers

All the cells of the body are produced from the fertilized single-celled ovum. Although all the cells carry the same genetic information, different genes operate to produce each of the three cell types--ectoderm, mesoderm and endoderm---of which the entire human body is composed. The embryo has an ectodermal, mesodermal and endodermal layer, and each layer produces particular kinds of tissue. The endoderm, for example, produces the surface of the alimentary canal and associated glands, and surface of the lungs, trachea and larynx.. The Mesoderm produces tissue specific to bone, cartilage, muscle, the lining of blood vessels and the lining of the ureters. Ectoderm produces tissue for the brain, nerves, epidermis, hair, nails, the lining of the nose and anus, and the sensory organs.