1. The document describes the parts and structures of the norma basalis of the human skull. It is divided into anterior, middle, and posterior parts. 2. The anterior part contains the alveolar arch, hard palate, incisive fossa, and palatine foramina. The middle part contains the median area with the vomer bone and lateral areas with the sphenoid and temporal bones. 3. The posterior part contains the foramen magnum and occipital bone laterally. Various structures like nerves and vessels pass through skull foramina.

1. CLASS 2
5/28/2019 1
Dr.De
vi

2. NORMA BASALIS
2
It is subdivided into 3 parts
:
Anterior
Middle
Posterior
Imaginary
transverse line
passing through
the anterior
margin of the
foramen
magnum

3. 3

4. ANTERIOR PART OF THE
NORMA BASALIS
• Alveolar arch
• Hard palate
• Incisive fossa
• Greater palatine foramen
• Lesser palatine foramen
• Posterior nasal spine
4

5. 5

6. 6
Hard palate
Sutures : palate is crossed by cruciform
suture; intermaxillary , interpalatine ,
palatomaxilary
Dome: arched in all directions, shows pits
for the palatine glands

7. 7

8. Incisive fossa : deep fossa situated anteriorly
in the median plane
Two incisive canals: rt & lt pierce the walls of
the incisive fossa , one on each side
8

9. Greater palatine foramen
: on each side, situated
just behind the lateral
part of the
palatomaxillary suture
lesser palatine foramen :
two or three in number ,
lie behind the greater
palatine foramen ,
perforate pyramidal
process of palatine bone.
Posterior nasal spine :
posterior border of hard
palate .
Palatine crest : curved
ridge near the posterior9

10. 10

11. Extends from the posterior border of the hard palate to the
transverse line passing through the anterior border of
foramen magnum
•Median area
•Lateral area 11

12. Median area :
Posterior border of
vomer, vomer separates
the two posterior nasal
apertures, inferior
border articulates with
the bony palate.
superior border splits
into two alae and
articulates with the
rostrum of the sphenoid
bone.
Broad bar of bone
formed by fusion of the
posterior part of the
body of the sphenoid
and basilar part of the12

13. 13

14. 14

15. Lateral area :
Two parts of sphenoid bone- pterygoid
process and greater wing
Pterygoid process- medial $ lateral
plate ; pterygoid fossa
Anterior border articulate with palatine
bone
Separated laterally from post surface
of the body of the maxilla by
pterygomaxillary fissure
15

16. 16

17. •Medial pterygoid
plate-directed
backwards
•Medial and lateral
surfaces & free
posterior border
•Upper end of this
border divided to
enclose a triangular
depression called the
scaphoid fossa
•Medial to this fossa
there is a small
pterygoid tubercle
•Lower end of the 17

18. Sulcus tubae- groove between the
postromedial margin of the greater wing of
sphenoid bone and petrous temporal
bone. It lodges the cartilaginous part of
the auditory tube 18

19. Three parts of temporal
bone :
19

20. •Inferior surface of the
petrous part of
temporal bone is
triangular in shape
• lies between the
greater wing of
sphenoid and
basioocciput
•Apex is perforated by
the upper end of the
carotid canal and is
separated from the
sphenoid by foramen
lacerum
•Carotid canal runs
forwards and medially
within the petrous
temporal bone
20

21. POSTERIOR PART OF NORMA
BASALIS• Median area –
1. Foramen magnum
2. External occipital crest
3. External occipital protuberance
4. Superior nuchal lines
21

22. 22
Lateral area :
a)Condylar part of occipital bone
b)Squamous part of occipital bone
c)Jugular foramen between occipital and
petrous temporal bones
d)Styloid process of temporal bone
e)Mastoid process of temporal bone

23. 23
• Occipital condyles : on
each side of the anterior
part of the FM, articulates
with the superior articular
facets of the atlas vertebra
to form atlanto-occipital
joint
• Hypoglossal canal/ant
condylar canal: directed
laterally and forwards
• Jugular foramen: forwards
$medially, placed at the
posterior end of the petro-
occipital suture
• Jugular fossa :ant wall of
the foramen is hollowed
out , lodges internal
jugular vein

24. ATTACHMENTS ON EXTERIOR
OF SKULL
1. Post border of the hard palate-
palatine aponurosis
2. Post nasal spine-musculus uvulae
3. Palatine crest- tensor veli palatine
muscle
4. Pharyngeal tubercle- superior
constrictor muscle
24

25. STRUCTURES PASSING THROUGH
FORAMINA
• Incisive foramen –
greater palatine
vessels, nasopalatine
nerve
• Greater palatine
foramen – greater
palatine vessels ,
anterior palatine
nerve
• Lesser palatine-
middle and posterior
palatine
• Foramen ovale –
mandibular nerve,
accessory meningeal
artery, lesser petrosal
nerve, emissary vein,
25

26. • Foramen
spinosum –
middle
meningeal
artery,
meningeal
branch of
mandibular
nerve (nervus
spinosus)
• Canalis
innominatus-
lesser petrosal
nerve
26

27. • Foramen
lacerum-
meningeal
branch of
ascending
pharyngeal
artery , emissary
veins
• Pterygotypanic
fissure- chorda
tympanic nerve,
anterior
tympanic artery 27

28. • FORAMEN MAGNUM
• Through wider posterior part
a. Lowest part of medulla oblongata
b. Three meninges
• Through the subarachnoid space
a. Spinal accessory nerves
b. Vertebral artery
c. Sympathetic plexus around the vertebral arteries
d. Posterior spinal arteries
e. Anterior spinal artery
• Through the narrow anterior part
a. Apical ligament of dens
b. Vertical band of cruciate ligament
c. Membrana tectoria
28

29. 29

30. • Hypoglossal / anterior condylar canal-
hypoglossal nerve , its meningeal branch ,
meningeal branch of ascending pharyngeal
artery, emissary vein (sigmoid sinus and
internal jugular vein )
30

31. INTERIOR OF THE
SKULL
31

32. STRUCTURES PASSING THROUGH
FORAMINA
1. Foramen caecum- veins
from nose to superior
sagittal sinus
2. Posterior ethmoidal
canals- posterior
ethmoidal vessels
3. Optic canal- optic nerve,
ophthalmic artery
32

33. 33

34. 4. Superior orbital fissure
 Lateral part
lacrimal nerve, frontal nerve,
trochlear nerve, superior
ophthalmic vein, meningeal
branch of the lacrimal artery
 Middle part
Upper and lower divisions of the
oculomotor nerve, nasociliary
nerve, abducent nerve
 Medial part
inferior ophthalmic vein,
sympathetic plexus around ICA34

35. 35

36. • Jugular foramen
1. Through anterior part
2. Through middle part
3. Through posterior part
36

37. • Mastoid canaliculus –in the lateral
wall of the jugular fossa auricular
branch of vagus
• Stylomastoid foramen- facial nerve ,
stylomastoid branch of the
posterior auricular artery
37

38. 38

39. FEOTAL SKULL
39
Dimensions
 Larger in proportion to other parts of skeleton
 The facial skeleton is 1/8th of calvaria whereas it
is ½ of calvaria
 Base of skull is short & narrow
 Internal ear is of same size as in adult
Structure of bones :
 Bones in cranial vault are smooth & unilamellar,
 There is no diploe
 Tables and diploe appear by fourth year of age

40. Bony Prominences
 Frontal & Parietal tubera are prominent
 Glabella, superciliary arches and mastoid
processes are not developed
paranasal air sinuses- rudimentary or
absent
orbits are large- germs of the developing
teeth lies close to the orbital floor
40

41. 41
Ossification of Bones
 Two halves of frontal bone are separated by
metopic suture.
 Mandible is also present in two halves
 Occipital bone is in 4 parts ( (1)squamous, (2)
condylar, and (1) basilar)
 Unossified membranous gap a total of 6
frontanelle at the angles of parietal bones are
present.

42. POST NATAL GROWTH OF SKULL
42
 It proceeds at different rate and over different
periods
 Growth of calvaria related to - growth of brain
 Grwoth of facial skeleton related to -
development of dentition, muscle of
mastication & tongue

43. GROWTH OF VAULT
43
Rate – rapid during first yr.
slow upto 7th yr.
Growth in breadth : occurs at saggital suture
sutures bordering greater wings, Occipito
mastoid suture Petro- occipital suture at base

44. Growth in Height - occurs at
Frontozygomatic suture
Pterion
Squamous suture
Asterion
Growth in Anteroposterior Diameter - occurs at
coronal & lambdoid sutures
44

45. GROWTH OF BASE
45
It grows in antero-posterior diameter at 3
cartilaginous plates situated between –
Occipital & sphenoid bones
Pre & post sphenoid bones
Sphenoid & ethmoid bones

46. GROWTH OF FACE
 Growth of orbits and ethmoid is
complete by 7th yr.
 Growth occurs mostly during first
year, although continues till puberty
n even later
46

47. CLOSURE OF FRONTANELLES
47
 Anterior – by 18 months
 Posterior – by 2-3 months
 Mastoid – by 12 months

48. THICKENING OF BONES
48
 Two tables and diploe appear by 4th yr.
 Differentiation reaches maximum by about 35
yrs., when diploic vein produce characteristic
arking in radiographs
 Mastoid process appear during 2nd yr, and
mastoid air cells during 6th yr.

49. OBLITERATION OF SUTURES OF VAULT
49
 It begins on inner surface between 30-40 yrs. & on
outer surface between 40-50 yrs.
 Occurs first in lower part of coronal suture
Posterior part of saggital suture
Lambdoid suture

50. AGE RELATED CHANGES
50
 Skull becomes thinner & lighter
 Reduction in size of maxilla and mandible
 Decrease in vertical height of face
 Angle of mandible becomes more obtuse

51. CRANIOMETRY
51
1. Cephalic Index
it expresses shape of head,& is the proportion of
breadth to length of skull
cephalic index = breadth x 100
length
Length/ longest diameter – measured from
glabella to occipital point
Breadth / widest diameter – measured a little
below parietal tubera

52. Human races may be-
a. Dolichocephalic or long headed ( when C.I
is 75 or less)
b. Mesaticephalic ( when C.I is between 75
and 80)
c. Brachycephalic or Short headed (when C.I
is above 80)
52

53. FACIAL ANGLE
 Is the angle between 2 lines drwan
from the nasion to th basion or
anterior margin of foramen magnum
and the prosthion or central point
on upper incisor alveolus
 It is a rough index of degree of
devlopment of brain because it is
angle between facial skeleton and
calvaria, which are inversely
propotional to each other.
 Angle – smallest-
evolved races of man 53

54. ABNORMAL CRANIA
 Oxycephaly or Acrocephaly – tower
like skull or steeple skull is a
abnormally tall skull.
- Occurs due to premature closure of
suture between presphenoid and
postsphenoid and coronal suture
 Scaphocephaly or boat shaped
skull is due to premature synostosis
in saggital suture
54

55. 55