• parietal
  • There are usually three lacunae on either side of the sinus: a small frontal, a large parietal, and an occipital, intermediate in size between the other two. (wikipedia.org)
  • Skull fractures occur more easily at the thin squamous temporal and parietal bones, the sphenoid sinus, the foramen magnum (the opening at the base of the skull that the spinal cord passes through), the petrous temporal ridge, and the inner portions of the sphenoid wings at the base of the skull. (wikipedia.org)
  • veins
  • The sinus receives some cerebellar and inferior cerebral veins, and veins from the tympanic cavity. (wikipedia.org)
  • present
  • The ethmoidal cells (sinuses) are present at birth, however by 2 years of age they are recognisable through the use of Computerised Tomography (CT) scanning. (wikipedia.org)