several components which develop into tissues: intermediate mesoderm, paraxial mesoderm, lateral plate mesoderm, and chorda-mesoderm. The chorda-mesoderm develops into the notochord. The intermediate mesoderm develops into kidneys and gonads. The paraxial mesoderm develops into cartilage, skeletal muscle, and dermis. The lateral plate mesoderm develops into the circulatory system (including the heart and spleen), the wall of the gut, and wall of the human body. Through cell signaling cascades and interactions with the ectodermal and endodermal cells, the mesodermal cells begin the process of differentiation. The mesoderm forms: muscle (smooth and striated), bone, cartilage, connective tissue, adipose tissue, circulatory system, lymphatic system, dermis, Dentine of teeth, genitourinary system, serous membranes, spleen and notochord. Ectoderm The ectoderm generates the outer layer of the embryo, and it forms from the embryo's epiblast. The ectoderm develops into the surface ectoderm, neural crest, and the neural tube. The surface ectoderm develops into: epidermis, hair, nails, lens of the eye, sebaceous glands, cornea, tooth enamel, the epithelium of the mouth and nose. The neural crest of the ectoderm develops into: peripheral nervous system, adrenal medulla, melanocytes, facial cartilage. The neural tube of the ectoderm develops into: brain, spinal cord, posterior pituitary, motor neurons, retina. Note: The anterior pituitary develops from the ectodermal tissue of Rathke's pouch. Neural crest Because of its great importance, the neural crest is sometimes considered a fourth germ layer. It is, however, derived from the ectoderm. See also Germ cell Histogenesis Neurulation List of human cell types derived from the germ layers References Embryology Developmental biology Gastrulation