====== FOURTH VENTRICLE ======

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Fourth Ventricle

  * floor
    * rhomboid fossa (diamond shaped)
    * formed by
      * posterior (dorsal surface)
        * lower or closed part of pons
        * open or upper part of medulla oblongata
    * structural layers
      * ependyma
      * thin layer of neuroglia
        * beneath ependyma
      * layer of grey matter forming various nuclei
    * parts
      * upper triangular part
        * dorsal surface of pons
      * lower triangular part
        * dorsal surface of medulla
      * intermediate part
        * junction of pons and medulla
        * prolonged laterally over inferior cerebellar peduncle
          * as floor of lateral recess
          * marked by transverse fibres of striae medullaris
          * arcuate nucleus to cerebellum
    * features
      * dorsal median sulcus
        * sulcus limitans
          * divides each half
            * median eminence
              * wider above
              * narrow below
              * facial colliculus
                * deep to it is genu of facial nerve
                  * formed by looping around abducent nucleus
            * lateral vestibular area
          * depression at cranial end
            * superior fovea
          * depression at caudal end
            * inferior fovea
              * sulcus limitans runs obliquely
                * two triangle
                  * hypoglossal triangle
                  * vagal triangle
          * upper part is locus ceruleus
            * bluish in colour
            * pigmented neurons
              * substantia ferruginea
            * help in paradoxical sleep
              * rich in noradrenaline
      * lowest part resembles tip of writing pen
        * calamus scriptorius
      * between vagal triangle and gracile tubercle
        * area postrema
          * function as chemoreceptor
        * ependymal thickening
          * funiculus separans
            * separates both
  * tela choroidea
    * double layer of piamater
    * covered by secretory ependyma
      * forms choroid plexus
  * lateral boundaries
    * each side bounded by
      * inferolaterally by
        * tubercles
          * gracile tubercle
          * cuneate tubercle
      * superolaterally by
        * superior cerebellar peduncle
  * roof
    * parts
      * superior
        * formed by superior cerebellar peduncle and
        * superior medullary velum
          * fills the gap between superior cerebellar peduncle
          * covered on dorsal syrface by lingula of superior vermiss (cerebellum)
      * inferior
        * very thin
        * devoid of nervous tissue
        * tela choroidea of fourth ventricle covers it posteriorly
        * caudally median aperture
          * communicate with subarachnoid space in
             * cerebello medullary cistern
        * inferior medullar velum
          * forms a part of roof in region of nodule of cerebellum
        * superior to inferior medullar velum
          * tela choroidea
            * reaches floor
              * marked by a ridge tenia
    * opening in roof
      * median aperture or foramen of magendie
        * situated caudal to nodule
        * communication between csf and subarachnoid space
      * foramen of luschka
        * present on lateral recess
          * subarachnoid space
  * communication
    * inferiorly with central canal
    * superiorly with cerebral aqueduct