The Skull

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The Skull
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• The cranial bones house the brain.
• The facial bones determine facial features.
• Included within the skull are the AUDITORY
  OSSICLES.
• 1. Malleus (hammer)
• 2. Incus (anvil)
• 3. Stapes (stirrup)
• The hyoid bone does not articulate with the skull.

Cranial bones
Facial bones
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• The bones of the skull are joined by SUTURES.
• The names of the sutures are determined by the
  bones that come together.
• The names of the sutures are also determined by
  the plane that it is in.

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• The sutures are remnants of the suture lines
  found on the infant skull.
• On the infant skull, a FONTANELLE (soft spot) is
  found at the junction of two sutures.
• There are three fontanelles on the infant skull
  anterior, anterolateral, and posterolateral.

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• SAGITTAL SUTURE is a line over the top of the
  skull between the PARIETAL BONES. It separates
  the skull into right and left halves.
• The CORONAL SUTURE runs up the side and over the
  top of the skull. It separates the skull into
  anterior and posterior halves. Its name means
  crown. The coronal suture looks like a crown
  worn by royalty.

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• The SQUAMOSAL SUTURE runs anterior to posterior
  along the flat sides of the skull.
• The LAMBDOIDAL SUTURE is a horseshoe shape along
  the OCCIPITAL BONE. If you use your imagination,
  it looks like the Greek letter lambda.

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Sinuses

• 4 of the bones of the skull contain SINUSES.
• These are hollow areas within the bone that can
  be seen by X-ray.
• All the sinuses are PARANASAL, or next to the
  nasal bones.
• They are named for the bones they are in.

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• FRONTAL SINUS
• - superior to the nose, deep to the FRONTAL
  NOSE.
• MAXILLARY SINUS
• - deep to the surface of the MAXILLARY
  BONES, inferior to the ORBITS, and lateral to the
  central line of the nose.

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• ETHMOID SINUSES
• - within the ETHMOID BONE.
• - very difficult to see as the ethmoid bone
  are deep.
• SPHENOID SINUS
• -can be seen only with X-rays.
• - in the center of the skull, superior to
  the line of the CORONOID PROCESS and the
  MANDIBULAR NOTCH.

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• The skull foramina are very important. They are
  where the blood vessels and cranial nerves leave
  the skull and enter the body proper.
• We will only study the foramina for nerves.

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Are we there yet?
Are we there yet?
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• The OCCIPITAL BONE has a PROTUBERANCE that is
  central. This bone also has CONDYLES that
  articulate with the ATLAS (C1).
• The FRONTAL BONE has SINUSES.
• The TEMPORAL BONE has a ZYGOMATIC PROCESS (which
  connects to the PROCESS of the ZYGOMA to form the
  ZYGOMATIC ARCH (CHEEK)

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• The temporal bone also has a MANDIBULAR FOSSA
  that articulates with the mandible, and a MASTOID
  and STYLOID PROCESS. The PETROUS RIDGE houses
  the middle ear bones.
• The SPHENOID BONE has the SELLA TURCICA which is
  where the HYPOPHYSIS (PITUITARY GLAND) sits.

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• The PTERYGOID PROCESS are wing-like processes
  that are inferior to most of the skull and the
  SPHENOID SINUSES as well as the GREAT and SMALL
  WINGS.
• The GREAT WINGS (posterior) can be seen from the
  cranial chamber and from an interior view. The
  SMALL WINGS can be seen within the cranial
  chamber.

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• The ETHMOID BONE has the CRISTA GALLI. This can
  be seen from a superior/interior position. The
  crista galli separates the frontal lobes. This
  structure also serves as a point of attachment of
  the FALX CEREBRI, or dura mater of the brain.

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• The crista galli sits on the CRIBIFORM PLATE
  which contains many foramina for the OLFACTORY
  BULBS. These olfactory bulbs pick up sensory
  stimuli from the nose and then combine to form
  the OLFACTORY NERVE (CN I)
• The ethmoid bone also contains the PERPENDICULAR
  PLATE that extends inferiorly from the cribiform
  plate and is perpendicular to it. This structure
  runs in an anterior-posterior direction. It
  forms the cranial portion of the nasal septum.

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• The sinuses are lateral to the perpendicular
  plate. The SUPERIOR and MIDDLE CONCHA of the
  ethmoid are shaped like shells. The INFERIOR
  CONCHA is part of the inferior half of the nasal
  septum formed from the VOMER bone.
• One of the functions of the nasal passages is to
  warm and moisten the air that passes through it.
  Another function is to filter particles. By
  having the concha, the air flow becomes turbulent
  over a greater surface area. This accomplishes
  both warming and filtering effects.

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• The MAXILLARY BONE has sinuses that have been
  already discussed. The ALVEOLAR PROCESSES are
  the bulges that are associated with the
  depressions that hold teeth.
• The PALATINE PROCESS is the part of the hard
  palate. It is a horizontal plate associated with
  the maxilla.

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• The MANDIBLE has 2 RAMI. These are inferior to
  the mandibular notch on each side and are where
  the external jaw muscles (masseter and
  temporalis) insert.
• The mandible also has ALVEOLAR PROCESSES that
  hold the teeth.

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• The CORONOID PROCESS is the anterior process and
  the CONDYLOID PROCESS is the spool shaped process
  where the jaw forms a hinge joint with the skull.
• The MANDIBULAR NOTCH is between the coronoid and
  condyloid processes.

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• The PALATINE BONE has HORIZONTAL PLATES that form
  the remainder of the hard palate that is not
  formed by the maxillary bone.
• The VOMER is like a plow. It joins from the
  inferior side of the perpendicular plate of the
  ethmoid to form the NASAL SEPTUM. This bone
  forms the right and left NARES.

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The Bones of the Skull

• Frontal Forehead. Forms part of the
  cranial floor and roof of the orbits (horizontal
  plates)
• Ethmoid Medial wall of the orbit socket,
  the cribiform plate, and crista galli.
• Sphenoid Greater and lesser wings, pterygoid
  plates.
• Maxilla floor of the eye socket and
  part of hard palate.

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Bones of the Cranium
Bone How Many? Landmarks
Occipital 1 Nuchal lines, protuberance, condyles
Parietal 2
Frontal 1 Sinues
Temporal 2 Zygomatic arch, mandibular fossa, mastoid and styloid process, petrous ridge
Sphenoid Ethmoid 1 1 Sella turcica, pterygoid processes,, sinuses, wings Crista galli, cribiform plate, perpendicular plates, sinuses, conchae
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Bones of the Face
Bone How many? Landmarks
Nasal 2
Maxillary 2 Sinuses, alveoli, palatine process (hard palate)
Zygomatic 2 Temporal process
Mandible 1 Rami, alveoli, coronoid, condyloid process, sigmoid notch
Lacrimal 2
Palatine 2
Vomer 1
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Identify the following
Frontal Bone Superciliary Ridge Glabella Lacrimal
Bone Maxilla Mandible Nasal Bones Nasal
Conchae Alveolar Ridges Parietal Bones Temporal
Bones Sphenoid Bones
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FRONTAL BONE
SUPERIOR and INFERIOR TEMPORAL LINES
PARIETAL BONE
TEMPORAL BONE
NASAL BONES
INFRAORBITAL FORAMEN
ZYGOMA
MAXILLA
OCCIPITAL BONE
STYLOID PROCESS
EXTERNAL AUDITORY MEATUS
MENTAL FORAMEN
MANDIBLE
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IDENTIFY THE FOLLOWING
Frontal Bone Jugular Foramen Frontal
Sinus Occipital bone Sphenoid Bone
Temporal Bone Crista Galli Greater
Wing Cribiform Plate Lesser Wing Olfactory
Foramen Sella Turcica Foramen Magnum Foramen
Ovale Foramen Rotundum Foramen Spinale
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The Cranial Nerves
Number Name Exit
Function
I Olfactory Cribiform
Plate SENSORY smell
II Optic Optic
Foramen SENSORY vision
III Oculomotor Sup. Orbital
Fissure MOTOR external muscles of the eye
except lateral rectus and superior oblique
levator palpebrae superioris. PARASYMPATHETIC
sphincter of pupil and ciliary muscle of lens.
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Number Name Exit
Function
IV Trochlear Sup. Orbital
Fissure MOTOR superior oblique muscle of the
eye
V Trigeminal
V1 Ophthalmic Branch Sup. Orb.
Fissure SENSORY cornea, nasal mucosa, skin
of face
V2 Maxillary Branch Foramen
rotundum SENSORY skin of face, oral cavity,
anterior two-thirds of tongue, teeth
V3 Mandibular Branch Foramen ovale
MOTOR muscles of mastication SENSORY Skin of
face
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Number Name Exit
Function
VI Abducens Sup. Orb.
Fissure MOTOR lateral rectus muscle of the
eye.
VII Facial
Stylomastoid Foramen PARASYMPATHETIC
lacrimal, submandibular, and sublingual glands
MOTOR muscles of facial expression SENSORY
taste, anterior two-thirds of tongue
VIII Vestibulocochlear
VIII 1 Vestibular Int. auditory
meatus SENSORY equilibrium
VIII 2 Cochlear Int. auditory
meatus SENSORY hearing
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Number Name Exit
Function
IX Glossopharyngeal Jugular
foramen MOTOR stylopharyngeus muscle
SENSORY posterior one-third of tongue, taste,
pharynx, branch to the carotid sinus
PARASYMPATHETIC parotid gland
X Vagus
Jugular Foramen SENSORY external
meatus, pharynx, and larynx MOTOR pharynx,
and larynx PARASYMPATHETIC thoracic and
abdominal viscera
XI Spinal Accessory Jug.
Foramen MOTOR trapezius and
sternocleidomastoid muscle
XII Hypoglossal
Hypoglossal Canal MOTOR Muscles of the
tongue
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Neumonic for Cranial Nerves

• On Old Olympic Towering Top, A Frenchman and a
  German View Some Hops.

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Olfactory bulbs
Olfactory tracts
Optic nerve
Occulomotor nerve
Trigeminal nerve
Trochlear nerve
Abducens nerve
Vestibulocochlear nerve
Glossopharyngeal nerve
Hypoglossal nerve
Facial nerve
Vagus nerve
Spinal accessory
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Cranial Nerves (inferior view)
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Trigeminal Nerve Branches
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Cranial Fossae

• There are three distinct regions within the
  cranium that are separated by anatomical
  structures.
• ANTERIOR FOSSA includes the frontal bone, the
  cribiform plate, and crista galli of the ethmoid
  bone. The lesser wings of the sphenoid bone are
  also in the anterior fossa. This is the area
  where the frontal lobe of the brain rests.

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• MIDDLE FOSSA has the temporal bone and the
  greater wings of the sphenoid. The petrous
  portion of the temporal bone serves as the
  posterior boundary of the middle fossa. The
  temporal lobe of the brain rests here.
• POSTERIOR FOSSA includes a small part of the
  temporal bone and the occipital bone. This is
  where the cerebellum, pons, and medulla are
  found.

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Location of Cranial Foramina

• Cribiform Plate anterior fossa
• Optic Foramen juncture between the anterior and
  middle fossa.
• Superior Orbital Fissure seen in the orbit (for
  the lacrimal nerve, frontal nerve, trochlear
  nerve, upper division of occulomotor nerve, and
  nasociliary nerve.)
• Inferior Orbital Fissure seen in the orbit and
  is for the abducents and lower division of the
  occulomotor nerve.

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• Foramen Rotundum (maxillary branch of trigeminal)
  and Foramen Ovale (mandibular nerve) are in the
  middle fossa. Both are located in the sphenoid
  bone.
• Auditory Canal located in the posterior fossa.
  The auditory and facial nerves use this canal.
• Stylomastoid Foramen at juncture of occipital
  and temporal bones which meet in the posterior
  fossa.

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Functional Areas of the Cerebral Cortex
Primary Sensory Cortex
Motor Association Area
Primary Motor Cortex
Wernikes Area
Prefrontal Area
Primary Visual Cortex
Associative Visual Cortex
Brocas Area
Associative Auditory Cortex
Primary Auditory Cortex
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Foramina of the Cranial Bones
Foramina
Associated Nerve
Olfactory Foramen Olfactory N. (I)
Optic Foramen Optic N. (II)
Superior Orbital Fissure Oculomotor (III), Trochlear (IV), Ophthalmic N. (V1), Abducens N. (VI)
Foramen Rotundum Maxillary N. (V2)
Foramen Ovale Mandibular N. (V3)
Internal Acoustic Meatus Facial N. (VII), Acoustic N. (VIII)
Jugular Foramen Glossopharyngeal N. (IX), Vagus N. (X), Accessory (XI)
Hypoglossal Canal Hypoglossal N. (XII)
Stylomastoid Foramen Facial N. (VII)
Foramen Magnum Medulla Oblongata, Accessory N. (XI)
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Foramina of Facial Bones
Foramina
Associated Nerve
Supraorbital Foramen Ophthalmic N. (V1)
Infraorbital Foramen Maxillary N. (V2)
Mental Foramen Mandibular N. (V3)
Mandibular Foramen Mandibular N. (V3)
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Gender Differences in Skull Morphology and Anatomy
Male Trait Female
Large, heavy Size Small, light
Rugged, rigid Character Smooth, delicate
Steep, flat Forehead rounded
squared Orbit Shape Rounded
Large, heavy Cheekbone size Small, delicate
Laterally arched Cheek shape Compressed arch
Large, square chin Mandible Small, pointed chin
Large, broad Occipital condyles Small, narrow
large Mastoid process small
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Racial Differences in Skull Anatomy
Caucasian Oriental/American Indian African
Narrow nasal opening Wide nasal opening
Retreating cheeks Forward cheeks
Strong overbite Edge to edge bite Moderate overbite
Wide oval skull Wide oval skull Long oval skull
Flat, slanted forehead Flat, high forehead Round, high forehead
Bone is a dense, ivory texture