

## Sphenoid
<ul>
  <li>A complex bone comprising part of the skull base:</li>
  <ul>
    <li>
      Embryologically: the skull base begins as cartilaginous precursors which then ossify,
      including the sphenoid
    </li>
    <li>
      Note: the other bones of the orbit form by membranous ossification (no cartilaginous
      precursor)
    </li>
  </ul>
</ul>
<p>Components&nbsp;</p>
<ul>
  <li>Body: containing the deep depression of the sella turcica</li>
  <li>Lesser wing</li>
  <li>Greater wing</li>
  <li>Pterygoid processes with pterygoid hamulus on the ends</li>
  <li>Foramen ovale which transmits numerous structures (see later)</li>
  <li>The optic canal passes through the lesser wing</li>
  <li>The superior orbital fissure is formed between the lesser and greater wings</li>
  <li>The foramen rotundum passes through the pterygoid process</li>
  <li>Foramen spinosum transmits the middle meningeal artery</li>
  <li>The small pterygoid canal lies medially</li>
</ul>

## Temporal
<ul>
  <li>Squamous part connects with the greater wing of the sphenoid and parietal bones</li>
  <li>Zygomatic process forms part of the zygomatic arch</li>
  <li>Petrous part contains the middle ear, labyrinth and the carotid canal</li>
  <li>Mastoid part connects with the parietal and occipital bones and contains air cells.</li>
  <ul>
    <li>This contains the stylomastoid foramen, which transmits the facial nerve</li>
  </ul>
  <li>Tympanic part forms the wall of the external auditory meatus</li>
</ul>

## Maxilla
<ul>
  <li>So-called membranous bone (compare with sphenoid above)</li>
  <li>Forms part of the orbital floor, lateral wall of the nose and hard palate</li>
  <li>Contains the pyramidal maxillary sinus</li>
  <li>The roof of the sinus is indented by the infraorbital canal</li>
  <li>The sinus drains the middle meatus of the nasal cavity</li>
</ul>
<HotTopic>
<div>
    <p>The walls of the nasolacrimal duct are formed by:</p>
    <ul>
      <li>Maxilla</li>
      <li>Lacrimal bone&nbsp;</li>
      <li>Inferior nasal concha.</li>
    </ul>
</div>

</HotTopic>

## Connections from cranial fossa (and contents)

### Middle cranial fossa
<ul>
  <li>Foramen ovale to the infratemporal fossa</li>
  <ul>
    <li>OVALE</li>
    <li>V3: mandibular division of trigeminal</li>
    <li>Accessory meningeal artery</li>
    <li>Lesser petrosal nerve</li>
    <li>Emissary vein</li>
  </ul>
  <li>Foramen spinosum connects to infratemporal fossa</li>
  <ul>
    <li>Middle meningeal artery and vein</li>
    <li>Meningeal branch of the mandibular nerve</li>
  </ul>
  <li>Foramen lacerum</li>
  <ul>
    <li>
      Parasympathetic fibres via the greater petrosal nerve travelling to the pterygopalatine
      ganglion
    </li>
    <li>The ICA passes over the surface</li>
  </ul>
  <li>Foraman rotundum</li>
  <ul>
    <li>Maxillary nerve&nbsp;</li>
    <li>Small veins of the cavernous sinus</li>
  </ul>
  <li>Pterygoid canal</li>
  <ul>
    <li>Deep petrosal nerve</li>
    <li>Greater petrosal nerve</li>
  </ul>
  <li>Stylomastoid foramen (part of the temporal bone)</li>
  <ul>
    <li>Facial nerve (excluding chorda tympani)</li>
  </ul>
  <li>Pterygotympanic fissure</li>
  <ul>
    <li>Transmits the chorda tympani to the infratemporal fossa</li>
  </ul>
</ul>

### Posterior cranial fossa
<ul>
  <li>Jugular foramen (formed by petrous temporal and occipital bones)</li>
  <ul>
    <li>Glossopharyngeal</li>
    <li>Vagus</li>
    <li>Accessory (cranial part)</li>
    <li>Internal jugular vein</li>
  </ul>
  <li>Foramen magnum</li>
  <ul>
    <li>Accessory (spinal part)</li>
  </ul>
  <li>Hypoglossal canal</li>
  <ul>
    <li>Hypoglossal nerve</li>
  </ul>
</ul>

## Cervical vertebrae
<ul>
  <li>Seven in total</li>
  <li>Atlas and axis (C1 and C2) are unique</li>
  <li>C7 is unique</li>
  <ul>
    <li>Transverse process occasionally enlarged to form a so-called &lsquo;cervical rib&rsquo;</li>
  </ul>
  <li>C3-C6 are &lsquo;typical&rsquo;</li>
  <ul>
    <li>Triangular shaped canal</li>
    <li>Bifid spinal processes</li>
    <li>Kidney shaped body</li>
    <li>Small transverse processes</li>
  </ul>
  <li>Foramen transversarium is within the transverse processes of all vertebrae</li>
</ul>

## Infratemporal fossa
<ul>
  <li>Found behind the maxilla and the zygomatic arch</li>
  <li>Roof: greater wing of sphenoid and squamous part of the temporal bone</li>
  <li>Medial wall: lateral pterygoid plate</li>
  <li>Anterior wall: maxilla</li>
  <li>Posterior wall: styloid apparatus</li>
  <li>Lateral wall: mandibular ramus</li>
  <li>Middle meningeal artery exits the fossa through the foramen spinosum</li>
  <li>
    Maxillary artery leaves via the pterygomaxillary fissure and enters the pterygopalatine fossa
  </li>
  <li>Mandibular division of the trigeminal enters through the foramen ovale</li>
  <li>
    Otic ganglion lies in the fossa and immediately below the foramen ovale: receives preganglionic
    parasympathetic supply from the lesser petrosal nerve (component of the glossopharyngeal bound
    for the parotid gland) and communicates with the facial nerve
  </li>
</ul>
<p>
  <strong>Trivia</strong>: the vomer (which forms the nasal septum) and the mandible are the only
  unpaired facial bones.
</p>


Sphenoid A complex bone comprising part of the skull base: Embryologically: the skull base begins as cartilaginous precursors which then ossify, including…

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