THE%20SKULL

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THE SKULL

• SIMPLY, AMAZING!

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• Most complex bony structure
• 22 bones in all
• Mostly flat bones, but not all!

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Functions of Cranial Bones

• Enclose and protect the fragile brain and furnish
  attachment sites for head and neck muscles

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Functions of Facial Bones

• 1. form framework of face
• 2. contain cavities for special sense organs
• 3. openings for food/air passage
• 4. secure the teeth
• 5. anchor the facial muscles of expression

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• ALL BONES OF THE SKULL ARE FIRMLY LOCKED IN PLACE
  BY JOINTS CALLED SUTURES
• Four major sutures

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THE CRANIUM (8)

• 1 frontal bone
• 2 parietal bones
• 2 temporal bones
• 1 occipital bone
• 1 sphenoid bone
• 1 ethmoid bone

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THE FRONTAL BONE
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Parietal Bones Form most of the superior and
lateral aspects of the skull
Figure 7.3a
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Parietal Bones and Major Associated Sutures

• Four sutures mark the articulations of the
  parietal bones
• Coronal suture articulation between parietal
  bones and frontal bone anteriorly
• Sagittal suture where right and left parietal
  bones meet superiorly
• Lambdoid suture where parietal bones meet the
  occipital bone posteriorly
• Squamosal or squamous suture where parietal and
  temporal bones meet

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Occipital Bone and Its Major Markings

• Forms most of skulls posterior wall and base
• Major markings include the posterior cranial
  fossa, foramen magnum, occipital condyles, and
  the hypoglossal canal

Figure 7.2b
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Temporal Bones

• Form the inferolateral aspects of the skull and
  parts of the cranial floor
• Divided into four major regions squamous,
  tympanic, mastoid, and petrous
• Major markings include the zygomatic, styloid,
  and mastoid processes, and the mandibular and
  middle cranial fossae

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Temporal Bones

• Major openings include the stylomastoid and
  jugular foramina, the external and internal
  auditory meatuses, and the carotid canal

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Temporal Bones
Figure 7.5
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Sphenoid Bone

• Spans the width of the middle cranial fossa. Has
  a butterfly like shape.
• Articulates with all other cranial bones.

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• Markings and regions to know
• Sphenoid sinuses
• Hypophyseal fossa a snug enclosure for the
  pituitary gland.
• Greater and Lesser Wings
• Optic Canals (opening for optic nerves)
• Superior Orbital fissures long slit between
  greater and lesser wings, allows cranial nerves
  to control eye movement.
• Pterygoid processes anchors muscles used in
  chewing
• Foramen rotundum and Foramen ovale

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Ethmoid Bone

• Lies between the sphenoid and nasal bones of the
  face. Most deeply situated.
• Markings/Regions
• Cribriform plates help form roof of nasal
  cavities and cranial fossa.
• Olfactory foramina allow olfactory nerves to
  pass from nasal cavities to the brain.
• Crista galli
• Ethmoid sinuses

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Maxillary Bones

• Medially fused bones that make up the upper jaw
  and the central portion of the facial skeleton
• Facial keystone bones that articulate with all
  other facial bones except the mandible
• Their major markings include palatine, frontal,
  and zygomatic processes, the alveolar margins,
  inferior orbital fissure, and the maxillary
  sinuses

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Maxillary Bone
Figure 7.8b
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Zygomatic bones

• Paired bones aka Cheek bones
• Form prominences of the cheeks and parts of the
  inferolateral margins of orbits.
• Articulates with temporal, frontal, and maxillary
  bones.

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Nasal Bones

• Form bridge of nose
• Articulates with frontal, maxillary, and ethmoid
  bones.

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Lacrimal Bones

• Located in the medial wall of the orbits.
• Articulates with the frontal, ethmoid, and
  maxillary bones.

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Palatine Bones

• Complete the posterior part of the hard palate.
• Forms part of the posterolateral walls of the
  nasal cavity.
• Small part of the orbits.

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The Vomer

• Forms part of the nasal septum dividing the nasal
  cavity in left and right halves.

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The Inferior Nasal Conchae

• Thin curved bones in the nasal cavity.
• Forms the lateral wall of the nasal cavity.

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Application Question

• Mr. and Mrs. Walkabots have recently given birth
  to a beautiful baby girl, Zeplin. After a few
  months of great joy they notice that their
  daughter vomits often, sleeps a lot, is irritable
  all the time and cannot look them in the eye.
  Zeplin does not meet developmental milestones
  over the next six months. HELP!