The nervous system begins as a simple structure and becomes increasingly complex through a sequence of developmental changes. This lesson introduces the germ layers and follows the ectoderm as it forms the neural tube, the foundation of the central nervous system.
By about 16 days after fertilization, the embryo has three layers of cells. Each layer contributes to different tissues and organs.
All flashcards
What are the three embryonic germ layers?
Endoderm is the inner layer, mesoderm the middle layer, and ectoderm the outer layer; each gives rise to different tissues.
How does the neural tube form?
Neuroectoderm forms the neural plate, which bends into a groove; the neural folds then meet and fuse to enclose the tube.
What do neural crest cells contribute to?
They form parts of the peripheral nervous system and tissues such as craniofacial cartilage and bone, and melanocytes.
What do the five secondary brain vesicles develop into?
Telencephalon forms the cerebrum; diencephalon forms structures including the thalamus and hypothalamus; mesencephalon forms the midbrain; metencephalon forms the pons and cerebellum; myelencephalon forms the medulla.
What are the three forms of spina bifida described here?
Occulta, meningocele, and myelomeningocele; they differ in whether and how much nervous tissue is involved.
Quiz questions
Which primary brain vesicle remains a single division and develops into the midbrain?Answer: Mesencephalon.
Which adult structures develop from the metencephalon?Answer: The pons and cerebellum.
In the developing spinal cord, which functional association is characteristic of dorsal and ventral regions?Answer: Dorsal regions are sensory-associated; ventral regions are motor-associated.
Which embryonic brain region is associated with the third ventricle?Answer: The diencephalon.
Which description best characterizes myelomeningocele?Answer: The meninges and spinal nerves protrude through the spinal column.
Based on Anatomy and Physiology 2e by J. Gordon Betts, Kelly A. Young, James A. Wise, Eddie Johnson, Brandon Poe, Dean H. Kruse, Oksana Korol, Jody E. Johnson, Mark Womble, Peter DeSaix (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.