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Embryonic Development and Organization of the Brain

Explore the intricate stages of embryonic brain development, including primary and secondary brain vesicles. Learn about the structures of the adult brain derived from these vesicles and the organization of different brain regions. Discover the brain stem components and ventricles of the brain, vital for cerebrospinal fluid circulation and protection. Understand the blood-brain barrier and its essential role in preventing harmful substances from entering the brain.

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Embryonic Development and Organization of the Brain

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  1. The Central Nervous System • Central nervous system – the brain and spinal cord • Directional terms unique to the CNS • Rostral – toward the nose • Caudal – toward the tail

  2. Embryonic Development of the Brain Figure 13.2a-e

  3. Embryonic Development of the Brain Figure 13.2a-e

  4. Embryonic Development of the Brain Figure 13.2a-e

  5. Embryonic Development of the Brain Figure 13.2a-e

  6. Embryonic Development of the Brain • Brain arises from the rostral part of the neural tube • Three primary brain vesicles in 4-week embryo • Prosencephalon – the forebrain • Mesencephalon – the midbrain • Rhombencephalon – the hindbrain

  7. Embryonic Development of the Brain • Secondary brain vesicles • Prosencephalon • Divides into telencephalon and diencephalon • Mesencephalon – remains undivided • Rhombencephalon • Divides into metencephalon and myelencephalon

  8. Embryonic Development of the Brain • Structures of the adult brain • Develop from secondary brain vesicles • Telencephalon the cerebral hemispheres • Diencephalon thalamus, hypothalamus, and epithalamus • Metencephalon pons and cerebellum • Myelencephalon medulla oblongata

  9. Embryonic Development of the Brain • Brain stem includes: • The midbrain, pons, and medulla oblongata • Ventricles • Central cavity of the neural tube enlarges

  10. Embryonic Development of the Brain • Brain grows rapidly, and changes occur in the relative position of its parts • Cerebral hemispheres envelop the diencephalon and midbrain • Wrinkling of the cerebral hemispheres • More neurons fit within limited space

  11. Brain Development from Week 5 to Birth Figure 13.3a-d

  12. Basic Parts and Organization of the Brain • Divided into four regions • Cerebral hemispheres • Diencephalon • Brain stem: midbrain, pons, and medulla • Cerebellum

  13. Basic Parts and Organization of the Brain Figure 13.4

  14. Basic Parts and Organization of the Brain • Organization • Centrally located gray matter • Externally located white matter • Additional layer of gray matter external to white matter • Due to groups of neurons migrating externally • Cortex – outer layer of gray matter • Formed from neuronal cell bodies • Located in cerebrum and cerebellum

  15. Basic Parts and Organization of the Brain Figure 13.5

  16. Ventricles of the Brain • Expansions of the brain’s central cavity • Filled with cerebrospinal fluid • Lined with ependymal cells • Continuous with each other • Continuous with the central canal of the spinal cord

  17. Ventricles of the Brain • Lateral ventricles – located in cerebral hemispheres • Horseshoe-shaped from bending of the cerebral hemispheres • Third ventricle – lies in diencephalon • Connected with lateral ventricles by interventricular foramen

  18. Ventricles of the Brain • Cerebral aqueduct – connects 3rd and 4th ventricles • Fourth ventricle – lies in hindbrain • Connects to the central canal of the spinal cord

  19. Ventricles of the Brain Figure 13.6a, b

  20. Protection of the Brain – Cerebrospinal Fluid (CSF) • Provides a liquid cushion for the brain and spinal cord • The brain “floats” in CSF • Formed in choroid plexuses in the brain ventricles

  21. Protection of the Brain – Cerebrospinal Fluid (CSF) Figure 13.27a

  22. Protection of the Brain – Cerebrospinal Fluid (CSF) Figure 13.27b

  23. Protection of the Brain – Blood-Brain Barrier • Prevents most blood-borne toxins from entering the brain • Impermeable capillaries • Not an absolute barrier • Nutrients such as oxygen pass through • Allows alcohol, nicotine, and anesthetics through

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