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Anatomy of the Nervous System

  1. PROSENCEPHALON = forebrain
    forms from process of ventral induction (ie, 3 closely interconnected sequential events of formation + cleavage + midline development)
    • cerebrum, lateral ventricles, choroid, thalami, cerebellum sonographically visible at 12 weeks MA
    1. Telencephalon = cerebrum

      = cerebral hemispheres, putamen, caudate nucleus
    2. Diencephalon
      = thalamus, hypothalamus, epithalamus (= pineal gland + habenula), globus pallidus, optic vesicles
  2. MESENCEPHALON = midbrain
    = short segment of brainstem above pons; traverses the hiatus in tentorium cerebelli; contains cerebral peduncles, tectum, colliculi (corpora quadrigemina)
  3. RHOMBENCEPHALON = hindbrain
    • posterior cystic space of 4th ventricle sonographically detectable between 8 and 10 weeks MA
    1. Metencephalon = cerebellar hemispheres, vermis
    2. Myelencephalon = medulla oblongata, pons
  4. BRAINSTEM = midbrain + pons + medulla contains
    1. cranial nerve nuclei
    2. sensory and motor tracts between thalamus, cerebral cortex, and spinal cord
    3. reticular formation controlling respiration, blood pressure, gastrointestinal function, centers for arousal and wakefulness