Development ofCNS, Derivatives ef Ectodermand Endoderm.docx

1-Derivatives of Ectodermand ? 1)Central nervous system. 2)Neural crest. 3)Otic and lens placodes. 4)Other Derivatives of ectoderm. 2-Formation of CNS (neurulation) ?.is induced by growth factors secreted by the developing notochord. 3-CNS develops through the following steps ? 1)Neural plate...

1-Derivatives of Ectodermand ? 1)Central nervous system. 2)Neural crest. 3)Otic and lens placodes. 4)Other Derivatives of ectoderm. 2-Formation of CNS (neurulation) ?.is induced by growth factors secreted by the developing notochord. 3-CNS develops through the following steps ? 1)Neural plate:is formed as a result of change of the flat ectodermal cells into columnar cells. 2)Neural folds, neural groove and neural crest: ·Lateral edges of the neural plate elevate to form \"neural folds\". ·The neural folds continue to elevate and become separated from each other by the \"neuralgroove\". ·The cells at the margin of the neural fold become specialized to form 2 stripscalled \"neuralcrests\".The 2 neural crests fuse dorsal to the developing neural tube, then split into 2 columns that lie dorsolateral to the neural tube. 3)Neuraltube: ·The cranial end of the tube is called \"cranial neuropore\", which closes at the 25th day. ·The caudal end of the tube is called \"caudal neuropore\" which closes at the 27h day. The remaining ectoderm of both sides fuses dorsal to the neural crests and neural tube to form the surface ectoderm. 4-Derivatives of neural crest ? 1)Neural cells:-.Cells of sensory, parasympathetic and sympathetic ganglia ·Adrenal medulla.Schwann cells ·Glial cells 2)Pigment cells; melanocytes of skin and iris. 3)Secretory cells; parafollicular C-cells of thyroid gland. 4)Mesenchymal cells:-.Chondroblasts and osteoblasts of facial skeleton.Myoblasts ·Fibroblasts ·Odontoblasts (form dentin of teeth) 5)Arachnoid and pia mater. 6)Aortico-pulmonary septum (between ascending aorta and pulmonary trunk) 5-Otic and lens placodes consist of ? ·Lens placode gives rise to lens of the eye. ·Otic placode gives rise to the internal ear. 6-Other derivatives of ectoderm consist of ? 1)Peripheral nerves. 2)Sensory epithelium of eye, ear, nose and tongue. 3)Sensory nerve endings of epidermis of skin. 4)Pituitary gland. 5)Anterior part of oral cavity. 6)Lower part of anal canal. 7-Derivatives of endoderm consist of ? 1)Lining epithelium of:- ·Digestive system, except anterior part of oral cavity and lower part of anal canal. ·Respiratory tract. ·Most ofthe urinary bladder and urethra..Tympanic cavity (middle ear) and Eustachian tube. 2)Glandular epithelium (parenchyma) of:- ·Tonsils (palatine and nasopharyngeal). ·Thymus. ·Thyroid and parathyroid glands. ·Liver. ·Pancreas.