GENERAL ANATOMY 2
COLLEGE OF DENTISTRY
NORMA OCCIPITALIS
This is the horse-shoe-shaped back of the skull. It extends from the tip of one mastoid process, over the
vault, to the tip of the other. The bones that take part in its formation are parts of the two parietal bones,
the occipital bone and the mastoid portions of the temporal bone.
THE NORMA OCCIPITALIS PRESENTS THE FOLLOWING FEATURES:
1. External occipital protuberance or INION- well-marked median projection situated between
the lambda and posterior margin of the foramen magnum.
2. External occipital crest- median vertical ridge extending from the INION to the foramen
magnum.
3. Superior nuchal line- well-marked and prominent curved ridge extending laterally from the
INION. It marks the division between the back of the head and the back of the neck.
4. Highest nuchal line- less-marked curved ridge above and parallel to the superior nuchal line.
5. Inferior nuchal line- curved ridge found below and parallel to the superior nuchal line.
6. Occipito-mastoid suture- union of occipital and mastoid part of the temporal bone.
7. Mastoid process of the temporal bone
8. Mastoid foramen- found in the mastoid process of the temporal bone; passage of emissary veins.
NORMA BASALIS EXTERNA
This view is obtained when the skull is turned upside down, thus exposing the external surface of
its base, divided into anterior and posterior region by an imaginary line drawn between the two
articular tubercles.
ANTERIOR REGION
1. Hard palate- combined palatine processes of maxillae and horizontal plates of the palatine bones.
2. Alveolar process- crescentic ridge of maxilla, lined with cavities –alveoli –into which upper teeth
are received.
3. Alveolar margin- protruding inferior border of alveolar process.
4. Maxillary tuberosity- prominent posterior angle of alveolar margin, made distinct by the
eruption of wisdom tooth; roundness behind the last upper molar.
5. Incisive foramen- shallow depression on anterior limit of the median palatine suture of the hard
palate, just posterior to the incisor tooth. It transmits the nasopalatine nerve of Scarpa.
6. Palatine crest- horizontal ridge found anterior to posterior border of the horizontal plate of the
palatine bone.
7. Greater palatine foramen- passageway of greater palatine nerves and vessels.
8. Lesser palatine foramen- smaller openings immediately behind the greater palatine foramen;
passageway of lesser palatine nerves and vessels.
9. Posterior nasal spine- backward median projection arising from the union of two horizontal
plates of palatine bones.
10. Choanae or posterior nares- two oval apertures representing the posterior openings of the nasal
cavities. It is bounded by:
a. Above- ala of vomer and body of sphenoid
b. Laterally- medial pterygoid process
c. Posteriorly- perpendicular plate of palatine bone
, GENERAL ANATOMY 2
COLLEGE OF DENTISTRY
d. Inferiorly- posterior border of the hard palate
e. Medially- vomer
11. Pterygoid process- vertical projection directed downwards from junction of body of great wing
of the sphenoid, provided with two laminae (lateral and medial, enclosing the pterygoid fossa).
12. Pterygoid hamulus- slender, curved or hook-like prolongation of the inferior extremity of medial
pterygoid lamina.
13. Scaphoid fossa- depression enclosed by diverging posterior margin of the medial pterygoid
lamina superiorly.
14. Pterygoid tubercle- well-marked prominence above and postero-medial to scaphoid fossa.
15. Foramen ovale- oval aperture behind and lateral to upper end of lateral pterygoid lamina
(passageway of mandibular nerve)
16. Foramen spinosum- round opening immediately lateral and behind foramen ovale (passageway
of middle meningeal vessels and the nervus spinosus).
POSTERIOR REGION:
1. Foramen magnum- largest bony opening of the skull; oval opening on anterior and inferior part
of the occipital bone. Passageway of the spinal cord, covered by three layers of meninges (dura
mater, arachnoid mater, pia mater), cerebro-spinal fluid, spinal accessory nerve and vertebral
vessels.
2. Basilar portion- thickened plate of bone, projecting anteriorly from the foramen magnum.
3. Pharyngeal tubercle- small median elevation on the inferior surface of basilar portion, midway
between basilar suture and foramen magnum.
4. Foramen lacerum- irregular, large aperture with jagged margins situated between the
basi-occipital and petrous temporal posteriorly and great wing of the sphenoid anteriorly. Covered
by fibrous tissue in life.
5. Mandibular or glenoid fossa- large depression, immediately behind the articular tubercle and
anterior to the external acoustic meatus.
6. Occipital condyles- large, smooth, oval and convex processes slightly converging anteriorly and
found at the anterior and lateral margins of the foramen magnum.
7. Condylar fossa- depression immediately behind the condyles.
8. Posterior condylar canal- when present, extends from the condylar fossa to the posterior cranial
fossa (passageway of emissary vein).
9. Anterior condylar canal or hypoglossal canal- short canal just above the condyles, perforating
the bone in lateral and forward directions (passageway of hypoglossal nerve).
10. Jugular process- well-marked quadrilateral eminence immediately lateral to the occipital
condyles.
11. Jugular foramen- the large aperture, bounded by jugular process of the occipital bone posterior
and petrous temporal anteriorly, medial to the base of the styloid process. Passageway of the
internal jugular vein, the glossopharyngeal nerve, the vagus nerve, and the spinal accessory nerve.
12. Jugular fossa- a deep concavity on the lateral anterior part of the jugular foramen.
13. Mastoid process- blunt downward projection of the mastoid portion of the temporal bone.
COLLEGE OF DENTISTRY
NORMA OCCIPITALIS
This is the horse-shoe-shaped back of the skull. It extends from the tip of one mastoid process, over the
vault, to the tip of the other. The bones that take part in its formation are parts of the two parietal bones,
the occipital bone and the mastoid portions of the temporal bone.
THE NORMA OCCIPITALIS PRESENTS THE FOLLOWING FEATURES:
1. External occipital protuberance or INION- well-marked median projection situated between
the lambda and posterior margin of the foramen magnum.
2. External occipital crest- median vertical ridge extending from the INION to the foramen
magnum.
3. Superior nuchal line- well-marked and prominent curved ridge extending laterally from the
INION. It marks the division between the back of the head and the back of the neck.
4. Highest nuchal line- less-marked curved ridge above and parallel to the superior nuchal line.
5. Inferior nuchal line- curved ridge found below and parallel to the superior nuchal line.
6. Occipito-mastoid suture- union of occipital and mastoid part of the temporal bone.
7. Mastoid process of the temporal bone
8. Mastoid foramen- found in the mastoid process of the temporal bone; passage of emissary veins.
NORMA BASALIS EXTERNA
This view is obtained when the skull is turned upside down, thus exposing the external surface of
its base, divided into anterior and posterior region by an imaginary line drawn between the two
articular tubercles.
ANTERIOR REGION
1. Hard palate- combined palatine processes of maxillae and horizontal plates of the palatine bones.
2. Alveolar process- crescentic ridge of maxilla, lined with cavities –alveoli –into which upper teeth
are received.
3. Alveolar margin- protruding inferior border of alveolar process.
4. Maxillary tuberosity- prominent posterior angle of alveolar margin, made distinct by the
eruption of wisdom tooth; roundness behind the last upper molar.
5. Incisive foramen- shallow depression on anterior limit of the median palatine suture of the hard
palate, just posterior to the incisor tooth. It transmits the nasopalatine nerve of Scarpa.
6. Palatine crest- horizontal ridge found anterior to posterior border of the horizontal plate of the
palatine bone.
7. Greater palatine foramen- passageway of greater palatine nerves and vessels.
8. Lesser palatine foramen- smaller openings immediately behind the greater palatine foramen;
passageway of lesser palatine nerves and vessels.
9. Posterior nasal spine- backward median projection arising from the union of two horizontal
plates of palatine bones.
10. Choanae or posterior nares- two oval apertures representing the posterior openings of the nasal
cavities. It is bounded by:
a. Above- ala of vomer and body of sphenoid
b. Laterally- medial pterygoid process
c. Posteriorly- perpendicular plate of palatine bone
, GENERAL ANATOMY 2
COLLEGE OF DENTISTRY
d. Inferiorly- posterior border of the hard palate
e. Medially- vomer
11. Pterygoid process- vertical projection directed downwards from junction of body of great wing
of the sphenoid, provided with two laminae (lateral and medial, enclosing the pterygoid fossa).
12. Pterygoid hamulus- slender, curved or hook-like prolongation of the inferior extremity of medial
pterygoid lamina.
13. Scaphoid fossa- depression enclosed by diverging posterior margin of the medial pterygoid
lamina superiorly.
14. Pterygoid tubercle- well-marked prominence above and postero-medial to scaphoid fossa.
15. Foramen ovale- oval aperture behind and lateral to upper end of lateral pterygoid lamina
(passageway of mandibular nerve)
16. Foramen spinosum- round opening immediately lateral and behind foramen ovale (passageway
of middle meningeal vessels and the nervus spinosus).
POSTERIOR REGION:
1. Foramen magnum- largest bony opening of the skull; oval opening on anterior and inferior part
of the occipital bone. Passageway of the spinal cord, covered by three layers of meninges (dura
mater, arachnoid mater, pia mater), cerebro-spinal fluid, spinal accessory nerve and vertebral
vessels.
2. Basilar portion- thickened plate of bone, projecting anteriorly from the foramen magnum.
3. Pharyngeal tubercle- small median elevation on the inferior surface of basilar portion, midway
between basilar suture and foramen magnum.
4. Foramen lacerum- irregular, large aperture with jagged margins situated between the
basi-occipital and petrous temporal posteriorly and great wing of the sphenoid anteriorly. Covered
by fibrous tissue in life.
5. Mandibular or glenoid fossa- large depression, immediately behind the articular tubercle and
anterior to the external acoustic meatus.
6. Occipital condyles- large, smooth, oval and convex processes slightly converging anteriorly and
found at the anterior and lateral margins of the foramen magnum.
7. Condylar fossa- depression immediately behind the condyles.
8. Posterior condylar canal- when present, extends from the condylar fossa to the posterior cranial
fossa (passageway of emissary vein).
9. Anterior condylar canal or hypoglossal canal- short canal just above the condyles, perforating
the bone in lateral and forward directions (passageway of hypoglossal nerve).
10. Jugular process- well-marked quadrilateral eminence immediately lateral to the occipital
condyles.
11. Jugular foramen- the large aperture, bounded by jugular process of the occipital bone posterior
and petrous temporal anteriorly, medial to the base of the styloid process. Passageway of the
internal jugular vein, the glossopharyngeal nerve, the vagus nerve, and the spinal accessory nerve.
12. Jugular fossa- a deep concavity on the lateral anterior part of the jugular foramen.
13. Mastoid process- blunt downward projection of the mastoid portion of the temporal bone.
