Surfaces

• The inferior surface of each orbital plate is smooth and concave, and presents, laterally, under cover of the zygomatic process
  Zygomatic process of frontal bone
  The zygomatic process of frontal bone is the part of the zygomatic process consisting of the frontal bone.The supraorbital margin of the frontal bone ends laterally in the zygomatic process, which is strong and prominent, and articulates with the zygomatic bone...
  
  , a shallow depression, the lacrimal fossa, for the lacrimal gland
  Lacrimal gland
  The lacrimal glands are paired almond-shaped glands, one for each eye, that secrete the aqueous layer of the tear film. They are situated in the upper, outer portion of each orbit, in the lacrimal fossa of the orbit formed by the frontal bone. Inflammation of the lacrimal glands is called...
  
  ; near the nasal part is a depression, the fovea trochlearis, or occasionally a small trochlear spine, for the attachment of the cartilaginous pulley of the obliquus oculi superior.
• The superior surface is convex, and marked by depressions for the convolutions of the frontal lobes of the brain
  Brain
  The brain is the center of the nervous system in all vertebrate and most invertebrate animals—only a few primitive invertebrates such as sponges, jellyfish, sea squirts and starfishes do not have one. It is located in the head, usually close to primary sensory apparatus such as vision, hearing,...
  
  , and faint grooves for the meningeal branches of the ethmoidal vessels
  Ethmoidal vessels
  Ethmoidal vessels can refer to:* Anterior ethmoidal artery* Posterior ethmoidal artery...
  
  .
  • The ethmoidal notch
    Ethmoidal notch
    The ethmoidal notch separates the two orbital plates; it is quadrilateral, and filled, in the articulated skull, by the cribriform plate of the ethmoid....
    
     separates the two orbital plates; it is quadrilateral, and filled, in the articulated skull, by the cribriform plate
    Cribriform plate
    The cribriform plate of the ethmoid bone is received into the ethmoidal notch of the frontal bone and roofs in the nasal cavities....
    
     of the ethmoid.
    • The margins of the notch present several half-cells which, when united with corresponding half-cells on the upper surface of the ethmoid, complete the ethmoidal air cells.
  • Two grooves cross these edges transversely; they are converted into the anterior and posterior ethmoidal canals by the ethmoid, and open on the medial wall of the orbit
    Orbit
    In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
    
    .
    • The anterior canal transmits the nasociliary nerve
      Nasociliary nerve
      The nasociliary nerve is a branch of the ophthalmic nerve. It is intermediate in size between the two other main branches of the ophthalmic nerve, the frontal nerve and the lacrimal nerve, and is more deeply placed.-Path:...
      
       and anterior ethmoidal vessels,
    • the posterior, the posterior ethmoidal nerve and vessels.

• In front of the ethmoidal notch
  Ethmoidal notch
  The ethmoidal notch separates the two orbital plates; it is quadrilateral, and filled, in the articulated skull, by the cribriform plate of the ethmoid....
  
  , on either side of the frontal spine, are the openings of the frontal air sinuses.
  • These are two irregular cavities, which extend backward, upward, and lateralward for a variable distance between the two tables of the skull; they are separated from one another by a thin bony septum, which often deviates to one or other side, with the result that the sinuses are rarely symmetrical.
  • Absent at birth, they are usually fairly well-developed between the seventh and eighth years, but only reach their full size after puberty
    Puberty
    Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...
    
    .
  • They vary in size in different persons, and are larger in men than in women.
  • They are lined by mucous membrane
    Mucous membrane
    The mucous membranes are linings of mostly endodermal origin, covered in epithelium, which are involved in absorption and secretion. They line cavities that are exposed to the external environment and internal organs...
    
    , and each communicates with the corresponding nasal cavity
    Nasal cavity
    The nasal cavity is a large air filled space above and behind the nose in the middle of the face.- Function :The nasal cavity conditions the air to be received by the other areas of the respiratory tract...
    
     by means of a passage called the frontonasal duct
    Frontonasal duct
    The frontal air sinuses are lined by mucous membrane, and each communicates with the corresponding nasal cavity by means of a passage called the frontonasal duct....
    
    .