Ectoderm Surface ectoderm adenohypophysis lens of the eye sensory organs ear olfactory epithelium epithelial linings oral cavity lower anal canal external auditory meatus epidermis, hair, and nails mammary, sweat, and salivary glands Neuroectoderm - CNS and brain brain - all neurons within brain and spinal cord/CNS neurohypophysis oligodendrocytes astrocytes ependymal cells pineal gland retina Neural Crest - PNS and nearby non-neural structures ANS enteric nervous system ganglia (dorsal root, cranial, and autonomic) cranial nerves celiac ganglion melanocytes chromaffin cells of adrenal medulla enterochromaffin cells Schwann cells pia and arachnoid bones of the skull odontoblasts aorticopulmonary septum Endoderm Epithelium lining of respiratory: trachea, bronchi, and lungs urinary: urinary bladder, female urethra, and majority of male urethra GI tract biliary system lower 2/3 of vagina middle ear cavity and auditory tube Liver Parathyroid Thyroid follicular cells Thymus Pancreas Parafollicular (C) cells of thyroid Mesoderm Muscle (smooth, cardiac, and skeletal) Dermis and subcutaneous layers of skin Bone, cartilage, and connective tissue Dura mater Serous linings of body cavities peritoneum Spleen Cardiovascular structures Lymphatics Laryngeal cartilage Blood: RBCs, WBCs, Kupffer cells, and microglia Urogenital structures male:testes, epididymis, ductus deferens, seminal vesicle, and ejaculatory duct female: ovaries, uterus, uterine tubes, and upper 1/3 of vagina Kidneys Adrenal cortex Defects Types of errors malformation vs. deformation malformation is intrinsic embryological disruption during the embryonic period deformation is extrinsic disruption, occurs after embryonic period agenesis vs. hypoplasia vs. aplasia agenesis = organ is absent because of absent primordial tissue e.g., renal agenesis - failure of one or both kidneys to develop hypoplasia = organ develops incompletely with remnant primordial tissue e.g., microorchidism in Klinefelter syndrome aplasia = organ absent but primordial tissue present e.g., thymic aplasia in DiGeorge syndrome Craniopharyngioma benign Rathke's pouch tumor containing cholesterol crystals and calcifications, tends to compress the optic chiasm Mesodermal defects VACTERL Vertebral defects: usually small hypoplastic vertebrae or hemivertebrae, only half of the bone is formed Anal atresia/imperforate anus Cardiac defects: ventricular septal defect, atrial septal defect, and Tetralogy of Fallot Tracheo-Esophageal fistula Renal defects: incomplete formation of one or both kidneys Limb defects: absent or displaced thumbs, polydactyly, and syndactyly