Anatomy 1

• Head and Neck


  A complicated region with clinical relevance
• Cranium


  The skeleton of the head
• Neurocranium


  • The bony case of the brain and its membranous coverings
  • Has a dome-like roof (calvaria) and a floor (cranial base/basicranium)
  • Formed by intramembranous ossification of head mesenchyme from the neural crest
• Viscerocranium


  • The facial skeleton
• Skull bones


  • Made up of external and internal tables of compact bone separated by a layer of spongy bone called the diploë
  • The internal table is thinner and more brittle than the external table
  • Some bones are pneumatized, containing air spaces to decrease weight
• Anterior view of the skull

  1. Structures passing through foramina in the anterior cranial fossa

  2. Structures passing through foramina in the middle cranial fossa

  3. Structures passing through foramina in the posterior cranial fossa
• Neonatal skull


  • Skull is made of several major bones connected by fibrous sutures
  • Sutures are important for trauma and growth
  • Fontanelles are membranous gaps between the bones
• Difference between adult and neonatal skull

  • Neonates have a disproportionately large cranium relative to the face
  • Bones are smooth and unilaminar, without diploë
  • Most skull bones are incompletely ossified at birth
  • Tympanic part of temporal bone is C-shaped ring, not curved plate
  • External auditory meatus is almost entirely cartilaginous
  • Tympanic membrane is nearer the surface
  • Mastoid process is not present
  • Mandible has right and left halves united by fibrous tissue
  • Angle of mandible is more obtuse
• Fractures of the anterior cranial fossa can damage the cribriform plate of the ethmoid bone, leading to epistaxis and cerebrospinal rhinorrhea
• Fractures involving the orbital plate of the frontal bone can result in hemorrhage beneath the conjunctiva and into the orbital cavity, causing exophthalmos
• Fractures of the middle cranial fossa are common due to numerous foramina and canals in this region, and can lead to leakage of cerebrospinal fluid and blood from the external auditory meatus
• Fractures of the posterior cranial fossa can lead to blood escaping into the nape of the neck, tracking between the muscles and appearing in the posterior triangle
• Bone damage


  • Resulting in damage of overlying meninges and underlying mucoperiosteum
• Bone damage


  Patient will have bleeding from the nose (epistaxis) and leakage of cerebrospinal fluid into the nose (cerebrospinal rhinorrhea)
• Fractures involving the orbital plate of the frontal bone

  Hemorrhage beneath the conjunctiva and into the orbital cavity, causing exophthalmos
• Fractures involving the orbital plate of the frontal bone

  The frontal air sinus may be involved, with hemorrhage into the nose
• Fractures of the Middle Cranial Fossa


  • Common because it is the weakest part of the base of the skull because of numerous foramina and canals in this region; the cavities of the middle ear and the sphenoidal air sinuses are particularly vulnerable
• Fractures of the Middle Cranial Fossa

  The leakage of cerebrospinal fluid and blood from the external auditory meatus is common
• Fractures of the Middle Cranial Fossa

  The 7th and 8th cranial nerves may be involved as they pass through the petrous part of the temporal bone
• Fractures of the Middle Cranial Fossa

  The 3rd, 4th, and 6th cranial nerves may be damaged if the lateral wall of the cavernous sinus is torn
• Fractures of the Middle Cranial Fossa

  Blood and cerebrospinal fluid may leak into the sphenoidal air sinuses and then into the nose
• Fractures of the Posterior Cranial Fossa

  Blood may escape into the nape of the neck deep to the postvertebral muscles
• Fractures of the Posterior Cranial Fossa


  Some days later, it tracks between the muscles and appears in the posterior triangle, close to the mastoid process
• Fractures of the Posterior Cranial Fossa

  The mucous membrane of the roof of the nasopharynx may be torn, and blood may escape there
• Fractures involving the jugular foramen


  The 9th, 10th, and 11th cranial nerves may be damaged
• The strong bony walls of the hypoglossal canal usually protect the hypoglossal nerve from injury
• Maxillofacial fractures


  Dr. Léon-Clement Le Fort (a Paris surgeon and gynecologist, 1829–1893) classified three common variants
• Le Fort I fracture

  • Wide variety of horizontal fractures of the maxillae, passing superior to the maxillary alveolar process (i.e., to the roots of the teeth), crossing the bony nasal septum and possibly the pterygoid plates of the sphenoid
• Le Fort II fracture

  • Passes from the posterolateral parts of the maxillary sinuses (cavities in the maxillae) superomedially through the infra-orbital foramina, lacrimals, or ethmoids to the bridge of the nose. As a result, the entire central part of the face, including the hard palate and alveolar processes, is separated from the rest of the cranium
• Le Fort III fracture

  • Horizontal fracture that passes through the superior orbital fissures and the ethmoid and nasal bones and extends laterally through the greater wings of the sphenoid and the frontozygomatic sutures. Concurrent fracturing of the zygomatic arches causes the maxillae and zygomatic bones to separate from the rest of the cranium
• Contrecoup (counterblow) fracture


  • No fracture occurs at the point of impact, but one occurs on the opposite side of the cranium
• Craniosynostosis


  Premature closure of the sagittal suture, in which the anterior fontanelle is small or absent, results in a long, narrow, wedge-shaped cranium, a condition called scaphocephaly
• Plagiocephaly


  When premature closure of the coronal or the lambdoid suture occurs on one side only, the cranium is twisted and asymmetrical
• Oxycephaly or turricephaly


  Premature closure of the coronal suture results in a high, tower-like cranium
• Oxycephaly is more common in females
• Premature closure of sutures usually does not affect brain development
• Cervical spine


  The most superior portion of the vertebral column, lying between the cranium and the thoracic vertebrae
• Cervical vertebrae


  • Consists of seven distinct vertebrae, two of which are given unique names: The first cervical vertebrae (C1) is known as the atlas, and the second cervical vertebrae (C2) is known as the axis
• Typical cervical vertebra


  • The transverse processes possess a foramen transversarium for the passage of the vertebral artery and veins (note that the vertebral artery passes through the transverse processes C1 to 6 and not through C7), the spines are small and bifid, the body is small and broad from side to side, the vertebral foramen is large and triangular, the superior articular processes have facets that face posteriorly and superiorly; the inferior processes have facets that face inferiorly and anteriorly
• Atypical cervical vertebrae


  • The 1st, 2nd, and 7th cervical vertebrae are atypical