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 Anatomy of the Nervous System

Third Ventricle  !!navigator!!

Position: in midline of diencephalon

Walls:

  • inferiorly: curving floor of 3rd ventricle formed
    • anteriorly by median eminence and tuber cinereum
    • posteriorly by mammillary bodies + midbrain posterior to tuber cinereum
  • superiorly: curving roof with 5 layers:
    1. body of fornix
    2. superior layer of tela choroidea
    3. vascular layer = velum interpositum containing bathed in CSF:
      1. internal cerebral veins
      2. medial posterior choroidal arteries
    4. inferior layer of tela choroidea
    5. choroid plexus of 3rd ventricle
  • superior lateral wall: formed by medial aspects of thalami
  • inferior lateral wall: formed by hypothalamus anteriorly + subthalamus posteriorly
  • massa intermedia = band of gray matter as a communication between 2 thalami across midline
  • anteriorly: lamina terminalis
    • anterosuperior border: anterior commissure
    • anteroinferior border: optic chiasm
  • posteriorly: pineal gland

Recesses: 2 anterior + 2 posterior recesses

  1. optic recess superiorly
  2. infundibular recess inferiorly = pars cava infundibuli formed by funnel-shaped proximal hypothalamic infundibulum (pituitary stalk)
    • median eminence at base of infundibulum = raised portion of hypothalamic gray matter
  3. pineal recess in deep aspect of pineal gland
    • posterior commissure in inferior wall of pineal recess
    • habenular commissure in superior wall of pineal recess
  4. suprapineal recess above habenular commissure and below splenium of corpus callosum

Tela choroidea ventriculi tertii

= ependymal + glial layers forming choroid plexus (= richly vascularized tela) that projects into 3rd ventricle

  1. upper layer attached to lower surface of fornix
  2. lower layer attached anteriorly to stria medullaris thalami + posteriorly to superior surface of the pineal body

[tela, Latin = web], [khorion, Greek = membrane enclosing fetus, afterbirth] [chorioeides, Greek = membrane-like] [plexus, Latin = braid, network]

Interventricular Foramen of Monro  !!navigator!!

= Y-shaped communication between 2 lateral ventricles and 3rd ventricle

Location: posterior to anterior columns of fornix

Aqueduct of Sylvius  !!navigator!!

= opening at posterior aspect of 3rd ventricle below posterior commissure

 Outline