Norma Basalis

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Norma Basalis
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Inferior Aspect of Skull

• Formed by
• Palatine processes of maxilla
• Horizontal plate of palatine bones
• Vomer
• Pterygoid processes, inferior surfaces of great
  wings, spinous processes part of body of
  sphenoid
• Inferior surfaces of squamae petrous portions
  of temporals
• Inferior surface of occipital bone

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Anterior Part

• Formed principally by hard palate, which is
  bounded anteriorly laterally by alveolar arch
• Incisive fossa
• Lateral incisive foramina (of Stenson) which
  continue as incisive canals transmit terminal
  branches of greater palatine vessels
  nasopalatine nerves from nasal cavity
• Median incisive foramina (of Scarpa) transmit
  nasopalatine nerves when present
• Depressions for palatine glands
• Cruciate suture

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Anterior Part

• Greater palatine foramen
• For transmission of greater palatine vessels
  nerve, which descend in greater palatine canal
  from pterygopalatine fossa
• Lesser palatine foramina
• Pyramidal process of palatine bone, perforated by
  one or more foramina through which course lesser
  palatine vessels nerve to soft palate
• Transverse ridge for attachment of tendinous
  expansion of tensor veli palatini muscle
• Posterior nasal spine, on which attaches musculus
  uvulae

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Middle Part

• Commences just behind hard palate extends to
  level of anterior border of foramen magnum.
• Choanae
• Medial pterygoid plate
• Scaphoid fossa for origin of tensor veli palatini
  muscle
• Pterygoid hamulus, around which tendon of tensor
  veli palatini muscle turns
• Lateral pterygoid plate
• Its lateral surface affords attachment to
  pterygoideus lateralis muscle

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Middle Part

• Pharyngeal tubercle
• Near center of basilar portion of occipital bone
• For attachment of fibrous raphe of pharynx
• Depressions on each side for insertions of rectus
  capitis anterior longus capitis
• Foramen ovale
• At base of lateral pterygoid plate
• Through which passes mandibular nerve, accessory
  meningeal artery, lesser petrosal nerve
• Sphenoidal spine
• Lateral to foramen ovale
• Attachment to sphenomandibular ligament tensor
  veli palatini

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Middle Part

• Foramen spinosum
• Posterior somewhat lateral to foramen ovale
• Transmits middle meningeal vessels small
  meningeal branch of mandibular nerve
• Mandibular fossa
• Lateral to sphenoidal spine
• Divided into 2 parts by petrotympanic fissure
• Anterior portion - concave, smooth, bounded in
  front by articular tubercle - articulates with
  condyle of mandible.
• Posterior portion is rough bounded behind by
  tympanic part of temporal bone.

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Middle Part

• Foramen lacerum
• At base of medial pterygoid plate in dried skull
• Irregular in shape variable in size
• Not complete foramen in intact body, because its
  inferior part is covered over by
  fibrocartilaginous plate, across superior (inner
  or cerebral) surface of which passes internal
  carotid artery.
• Boundary
• - In front by great wing of sphenoid
• - Behind by apex of petrous portion of temporal
  bone
• - Medially by body of sphenoid basilar portion
  of occipital bone

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Middle Part

• Carotid canal
• Inferior surface of petrous temporal bone is
  pierced by round opening.
• Internal carotid artery, coursing within canal,
  immediately takes right angle turn to reach side
  of foramen lacerum.
• Quadrilateral surface
• Rough surface near apex of petrous portion of
  temporal bone, lateral to which is orifice or
  entrance of carotid canal.
• Attachment to levator veli palatini

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Middle Part

• Sulcus tubae auditivae
• Lateral to foramen lacerum, between petrous part
  of temporal great wing of sphenoid
• Lodges cartilaginous part of auditory tube which
  is continuous with bony part within temporal bone
• Petrosphenoidal fissure at bottom of this sulcus

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Posterior Part

• Formed principally by occipital bone
• Mastoid process
• Mastoid notch on medial side of each process, for
  posterior belly of digastricus
• Occipital groove medial to mastoid notch, for
  occipital artery
• Styloid process
• Medial slightly anterior to mastoid processes
• Stylomastoid foramen
• At base of styloid process
• Facial nerve exits toward side of face,
  stylomastoid artery enters to tympanic cavity.

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Posterior Part

• Jugular foramen
• Medial to styloid process posterior to carotid
  canal
• Anterior compartment inferior petrosal sinus
• Intermediate glossopharyngeal, vagus,
  accessory nerves
• Posterior sigmoid sinus which leads to internal
  jugular vein, some meningeal branches from
  occipital ascending pharyngeal arteries
• Petro-occipital fissure
• Extending anteriorly from jugular foramen to
  foramen lacerum

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Posterior Part

• Foramen magnum
• Posterior to basilar portion of occipital bone
• Transmit
• - Medulla oblongata its membranes
• - Accessory nerves
• - Vertebral arteries
• - Anterior posterior spinal arteries
• - Ligaments connecting occipital bone with axis
• Basion
• Opisthion

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Posterior Part

• Occipital condyles
• By which foramen magnum is bounded laterally
• On medial surfaces of which attach alar ligaments
• Articulate with superior articular surfaces
  overlying lateral masses of atlas
• Jugular process
• Lateral to each occipital condyle
• Attachment for rectus capitis lateralis muscle
  lateral atlanto-occipital ligament

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Posterior Part

• Hypoglossal canal
• Courses forward laterally from inner aspect of
  occipital bone within cranium just above foramen
  magnum to opening that perforates occipital bone
  externally at lateral part of base of occipital
  condyle
• Transmits hypoglossal nerve a branch of
  posterior meningeal artery
• Condyloid fossa
• Posterior to each occipital condyle
• Perforated on one or both sides by condyloid
  canal, for transmission of a vein from sigmoid
  sinus to vertebral veins in upper cervical region

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Posterior Part

• External occipital crest
• External occipital protuberance
• Superior inferior nuchal lines

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