Derivatives of the endoderm
Most cells originating from the primitive node migrate cranially. They give rise to the prechordal plate, the material for the axial structures (notochordal process and later the notochord), and the intra-embryonic endoderm. The endodermal cells lie laterally from the notochordal process. They firstly displace the hypoblast cranio-laterally, and then later caudally. This forms the endoderm as the ventral germ layer.
Many authors consider the human prechordal plate to be of endodermal origin. It gives rise, amongst other things, to the endodermal layer of the oropharyngeal membrane and to the endodermal lining of the foregut. Furthermore, the prechordal plate is an important source of the mesenchyme of the head.
The following structures derive from the endoderm: the epithelium of the whole digestive tract (except the oral and anal depressions), the epithelium of the middle ear (tympanic cavity, auditory tube), the epithelium and the glands of trachea and bronchial tree, the alveolar cells of the lung, and the epithelium of urinary bladder, prostate, urethra and of the lower part of the vagina. Futhermore, the endoderm gives rise to the parenchyma of many intrinsic organs: submandibular and sublingual glands, tonsils, thyroid gland, parathyroid gland, thymus, liver and pancreas.