Osteology of Human Skull

1. Osteology of the SKULL
By: Dr Prasanna Kumar P

2. Content
1. Introduction
2. Functions
3. Divisions-
• Norma frontalis—the anterior view
• Norma lateralis—the lateral view
• Norma occipitalis—the posterior
view
• Norma basalis—the inferior view
• Norma verticalis—the superior
view

3. The Skull
• The skull is composed of several separate bones (28 bones) united at
immobile joints called sutures.
• The connective tissue between the bones is called a sutural ligament
Introduction

4. • The upper part of the cranium is The vault
• The base of the skull is the lowest part of the cranium
• The skull bones are made up of External and internal tables of compact bone separated
by a layer of spongy bone called the diploic bones
• The bones are covered on the outer and inner surfaces with periosteum.
• Only one moveable bone, the mandible which is united to the skull by the
mobile Temporomandibular Joint
The bones of the skull can be divided into:
• Bones of the cranium (contain the brain)
• Bones of the face (facial skeleton)

5. Cranial skeleton, consisting of 8
bones:
Paired bones
• Parietal
• Temporal
• Incus
• Malleus
• stapes
Unpaired bones
• Frontal
• Occipital
• Sphenoid
• Ethmoid
Facial skeleton, consisting of 14 bones:
Paired bones
• Maxilla
• Zygomatic
• Nasal
• Lacrimal
• Palatine
• Inferior nasal concha
Unpaired bones
• Mandible
• Vomer
The skull
The skull is made up of 28 bones.

6. Skull Joints
• The joints in the skull are mostly sutures, a
few primary cartilaginous joints and three
pairs of synovial joints.
• Sutures are:
1. Plane – internasal suture
2. Serrate – coronal suture
3. Denticulate – lambdoid suture
4. Squamous – parietotemporal suture

7. Anatomical position of the skull
1. Reid’s base line is a horizontal
line obtained by joining the
infraorbital margin to the center
of external acoustic meatus, i.e.
auricular point.
2. The Frankfurt’s horizontal
plane of orientation is obtained
by joining the infraorbital
margin to the upper margin of
the external acoustic meatus

8. Bones of skull
• Frontal bone
• Parietal bone
• Occipital bone
• Temporal bone
• Sphenoid bone
• Lacrimal bone
• Nasal bone
• Zygomatic bone
• Ethimoid bone
• Vomer
• Inferior nasal concha
• Palatine bone
• Maxilla
• Mandible

9. FRONTAL BONE

11. Parietal bone

12. Occipital bone

13. TEMPORAL BONE

16. Sphenoid bone

18. Lacrimal bone

19. Nasal bone

21. Zygomatic bone

22. Ethimoid bone

23. Vomer

24. Inferior nasal concha

25. Palatine bone

26. • Superior – Norma verticalis
• Posterior – Norma occipitalis
• Anterior – Norma frontalis
• Lateral – Norma lateralis
• Inferior – Norma basalis
Exterior of the skull
The external features of the skull are studied from five different aspects
Methods of study of the skull

27. Exterior of the skull
The external features of the skull are studied from five different aspects

28. Exterior of the skull
The external features of the skull are studied from five different aspects
Inferior – Norma basalis

29. Study of skull as a whole from inside after removing skull cap

30. Study of skull as a whole

31. NORMA VERTICALIS

32. NORMA VERTICALIS
• Oval in shape
• Wider posteriorly than anteriorly
• Bones
1. Upper part of frontal bone -anteriorly.
2. Uppermost part of occipital bone-
posteriorly.
3. A parietal bone-on each side.
• Sutures – coronal, sagittal, lambdoid,
metopic

33. Norma Verticalis
Superior aspect of the skull
Frontal:
Frontal
eminences
Parietals:
• parietal
foramens
• parietal
eminences
Sutures:
- Coronal
↓Bregma
- Sagittal
- Lambdoid
↓Lambda
Occipital
Norma Verticalis

34. Bones and Sutures
The bones are frontal, parietal, and occipital
• Frontal bone (squamous part) anteriorly.
• Parietal bones (paired) on each side of midline.
• Occipital bone (squamous part) posteriorly.
These bones are united by three sutures.
• Coronal suture (L. = a crown), between frontal and two parietal bones. It
crosses the cranial vault from side-to side.
• Sagittal suture (L. = an arrow), between two parietal bones. It lies in the median
plane.
• Lambdoid suture, between occipital and two parietal bones. It is shaped like
the letter lambda.
Norma Verticalis

35. Anatomical Features
• Bregma: It is the point at which the coronal and sagittal sutures meet. It is the site
of anterior fontanelle in new born skull.
• Parietal eminence: It is the area of maximum convexity of parietal bone, seen on
each side.
• Vertex: It is the highest point of the skull. It lies on the sagittal suture, near its
middle and is situated a few centimeters behind the bregma.
• Lambda: Point at which the sagittal and lambdoid sutures meet is named as
lambda.
• Parietal foramen: A small foramen is seen in each parietal bone near the sagittal
suture, 3 to 4 cm in front of lambda.
• Temporal lines: A pair of temporal lines, one superior and one inferior are seen.
They are present antero posteriorly on lateral side of each parietal emenience. They
are better described in norma lateralis.
Norma Verticalis

36. Norma Verticalis

37. Norma Verticalis

38. Calvaria
• Emissary foramen: small,
inconsistent (not always present)
foramina for passage of emissary
veins.
• Bregma: is the landmark formed by
the intersection of the sagittal and
coronal sutures.
• Lambda: is the landmark formed by
the intersection of the sagittal and
lambdoid sutures.
Norma Verticalis

39. Infant calvaria
• Anterior Fontanelle: (soft spot) is
the future site of the bregma
• By about 18 months the
surrounding bones fuse together
and is no longer palpable.
• Posterior Fontanelle: is triangular
and marks the future site of the
lambda
• Fusion of surrounding bones
occurs by about 6 months
Fontanelles- membranous gaps (soft spots) in skull that permit growth
Norma Verticalis

40. Inner calvaria
• Frontal bone
• Parietal bone
• Coronal suture
• Sagittal suture
• Frontal sinus
• Groove for superior sagittal sinus
• Groove for middle meningeal artery
• Granular foveolae
Norma Verticalis

41. NORMA OCCIPITALIS

42. Norma Occipitalis
(Post. Aspect)
Bones:
• Occipital
• Parietals
• Mastoid
process
Landmarks:
• External occipital
protuberance
• Superior and
inferior nuchal
lines
• External occipital
• Mastoid foramen
Sutures:
• Lambdoid suture
• Occipitomastoid
suture
• Parietomastoid
suture
Norma Occipitalis

43. Bones and sutures
The back of skull is composed of posterior part of parietal bones,
occipital bone and mastoid part of temporal bones.
• Parietal bones, superiorly one on each side.
• Occipital bone (squamous part), inferiorly.
• Mastoid part of temporal bone, inferolaterally on each side.
The sutures which unite these bones are:
• Lambdoid suture, between occipital and two parietal bones.
• Occipitomastoid suture, between occipital and mastoid part of
temporal bone.
• Parietomastoid suture, between parietal and mastoid part of temporal
bone.
Norma Occipitalis

44. • Lambda: It is the point at which sagittal and lambdoid sutures meet.
• External occipital protuberance: It is a median bony projection seen midway
between the lambda and the foramen magnum. The most prominent point of
the prominence is called inion.
• Superior nuchal lines: These are curved bony ridges passing laterally, on each
side, from the external occipital protuberance.
• External occipital crest: Is a median, vertical ridge passing vertically
downwards from the external occipital protuberance to the posterior margin of
foramen magnum.
• Inferior nuchal lines: These are curved bony ridges passing parallel to and
below the superior nuchal lines, laterally on each side from the middle of
external occipital crest.
Anatomical Features
Norma Occipitalis

45. Norma Occipitalis

46. Norma Occipitalis

47. Norma Frontalis
(Anterior aspect of the skull)
Regions (cavities):
- Nasal
- Orbit
- Oral
Bones:
- Frontal
- Zygomatic
- Maxillae
- Mandible
- Nasal
Norma frontalis

48. NORMA FRONTALIS

49. It presents:
• Frontal bone, forms the forehead.
• Right and left nasal bones, form the bridge of nose.
• Right and left maxillae, form the upper jaw.
• Right and left zygomatic bones, form the malar prominences.
• Mandible, forms the lower jaw.
Bones and sutures
Norma frontalis

50. • Forehead: It is formed by the frontal bones. On each side of median plane, the
frontal bone articulates with the nasal bone at the root of nose.
• Frontal prominence: It is a low, rounded elevation seen above each of the
supraciliary arch.
• Supraciliary arches: These are rounded bony elevations forming an arch above
each of the superior orbital margins.
• Glabella: It is a median elevation between the supraciliary arches.
• Orbits: These are two bony cavities in which the eyes are located.
• Bony external nose: Is formed by the nasal bones above and the maxillae
laterally.
• Anterior nasal aperture: It is a piriform shaped aperture seen in the center of
norma frontalis.
Anatomical Features
Norma frontalis

51. • Anterior nasal aperture: It is a piriform shaped aperture seen in the center of
norma frontalis. It is bounded by nasal bones above and maxillary bones
laterally and inferiorly.
• Root of nose: It is a slightly depressed area seen above the nasal bones where
they meet the frontal bone at the frontonasal sutures.
• Nasion: It is a median point at the root of nose where the internasal and
frontonasal sutures meet.
• Prominence of the cheek: It is formed by the body of zygomatic bone.
• Anterior surface of maxilla: It presents on each side (Nasal notch, medially,
Infraorbital foramen, 1 cm below the infraorbital margin, Incisive fossa above
the incisor teeth, Canine fossa lateral to canine eminence produced by the root
of canine tooth).
Anatomical Features
Norma frontalis

52. • Upper jaw: It is formed by the alveolar processes of the two maxillae and bears
the upper teeth.
• Lower jaw: The lower jaw is formed by mandible. The upper border, also called
alveolar arch of mandible, carries the lower teeth.
• Anterior surface of body of mandible: (Symphysis menti, Mental protuberance,
Mental point (gnathion), Mental foramen, Oblique line on body of mandible).
Norma frontalis Anatomical Features

53. Norma frontalis

54. Norma frontalis

55. Norma frontalis

56. NORMA LATERALIS

57. Norma Occipitalis
(Post. Aspect)
Bones:
• frontal
• parietal
• occipital
• temporal
• sphenoid
• zygomatic
• mandible
• Maxilla
• nasal
Sutures:
• Coronal suture
• Parietosquamosal
suture
• Lambdoid suture
Norma lateralis

58. It presents:
• Above: Nasal, frontal, parietal and occipital bones.
• In middle: Maxilla, zygomatic, sphenoid and temporal bones.
• Below: Body and ramus of mandible.
The sutures which unite these bones are:
• Coronal suture
• Parieto-squamosal suture, between parietal bone and squamous part of
temporal bone.
• Parietomastoid suture, between parietal bone and mastoid part of temporal b.
• Occipitomastoid suture, between occipital bone and mastoid part of temporal
bone.
• Lambdoid suture
Bones and sutures
Norma lateralis

59. • Temporal lines: These are two in number, one superior and one inferior
temporal line.
• Zygomatic arch: A horizontal bar of bone formed by the union of temporal
process of zygomatic bone and zygomatic process of temporal bone is seen in
centre anteriorly.
• Temporal fossa: It is the area bounded above and posteriorly by the temporal
line and below by the zygomatic arch and frontal process of zygomatic bone.
• Pterion: It is the region in the anterior part of temporal fossa where the 4 bones
forming floor of temporal fossa meet.
• Infratemporal fossa: It is the region on the side of skull below the zygomatic
arch.
• Lateral or external surface of ramus of mandible: The ramus projects upwards
from posterior part of body of mandible.
Anatomical Features
Norma lateralis

60. • External acoustic meatus: It is the external aperture of bony ear canal.
• Suprameatal triangle (triangle of McEven): It is a small depression present
postero-superior to the external auditory meatus.
• Tympanic plate of temporal bone: It is a thin plate of bone forming the anterior
and inferior wall of external acoustic meatus.
• Mastoid process: It is a conical process seen extending down from the
mastoid part of temporal bone, behind the external acoustic meatus.
• Styloid process: It is a thin long bony process of temporal bone lying
anteromedial to the mastoid process.
• Asterion: It is the meeting point of parietomastoid, occipitomastoid and
lambdoid sutures.
Anatomical Features
Norma lateralis

61. Norma lateralis

62. Osteology of the head
Norma lateralis

63. Norma lateralis

64. Norma lateralis

65. Norma lateralis

66. Norma lateralis

67. NORMA BASALIS

68. Norma Basalis
• Norma basalis or inferior surface of cranium extends from alveolar
arch in front to the superior nuchal lines behind.
• It is studied in three parts namely, anterior, middle and posterior.
• Anterior part is formed by the alveolar arch and hard palate.
• The middle part extends from posterior margin of hard palate to
anterior margin of foramen magnum and the posterior part lies behind
a transverse line passing through the anterior margin of the foramen
magnum.

69. Norma Basalis

70. • Alveolar arch
• Hard palate
Anatomical features in the anterior part of norma basalis
Norma Basalis

71. Norma Basalis - Anterior
• Alveolar process of
maxilla
• Palatine process of
maxilla
• Horizontal plate of
palatine bone
• Incisive foramen
• Greater palatine
foramen
• Lesser palatine
foramen

72. The median area
•Posterior border of vomer
•Broad bar of bone
The lateral area
•Pterygoid process
•Infratemporal surface of the greater wing of sphenoid
•Sulcus tubae (groove for auditory tube)
•Inferior surface of the petrous temporal bone
•Downward edge of tegmen tympani
Anatomical features in the middle part of norma basalis
Norma Basalis

73. Norma Basalis - Middle
• Vomer
• Pharyngeal tubercle
• Pterygoid process of
sphenoid bone
Medial & Lateral plates /
Fossa / Hamulus

74. Norma Basalis - Middle
• Foramen ovale
• Foramen
spinosum / Spine
of sphenoid
• Foramen lacerum
• Carotid canal

75. The median area
•Foramen magnum
•External occipital crest
•External occipital protuberance
The lateral area
•Occipital condyles
•Hypoglossal canal
•Condylar fossa
•Jugular process of occipital bone
•Jugular foramen
•Tympanic canaliculus
•Stylomastoid foramen
Anatomical features in the posterior part of norma basalis
Norma Basalis

76. Norma Basalis - Posterior
• Occipital condyles
• Styloid process of
temporal bone
• Mastoid process
• External occipital
protuberance
(inion)
• Nuchal lines
• Superior
• Inferior

77. • Foramen magnum
• Jugular foramen
• Stylomastoid
foramen
• Condylar canal
• Mastoid foramen
Norma Basalis - Posterior

78. Female
Male
Thinner and lighter
Thicker and heavier
Bones
Less
More
Cranial capacity
Not well-marked
Well-marked, hence
seen prominently
Muscular markings
and ridges
Not prominent
Prominent
Superciliary arches
Less prominent
Prominent
Mastoid process
Prominent
Less prominent
Frontal and parietal tubers
Differences between male and female skulls

79. Mandible
• The mandible, or the lower jaw, is the
largest and the strongest bone of the face.
• It develops from the first pharyngeal arch.
• It has a horseshoe-shaped body which
lodges the teeth, and a pair of rami which
project upwards from the posterior ends of
the body.

80. MANDIBLE: ANTERIOR VIEW

81. MANDIBLE: LATERAL VIEW

82. MANDIBLE: POSTERIOR VIEW

83. Maxilla

84. • Maxilla (cheek) is the second
largest bone of the face, the first
being the mandible
• The two maxillae form the whole of
the upper jaw, and each maxilla
forms a part each in the formation
of face, nose, mouth, orbit, the
infratemporal and pterygopalatine
fossae
• Each maxilla has a body and four
processes—the frontal, zygomatic,
alveolar and palatine.

86. References
• B d chaurasia’s human anatomy (volume
3)
• Netter’s head and neck anatomy for
dentistry
• Human osteology for dental students
inderbir singh
• Gray’s Atlas of Anatomy 3rd edition

87. Thank you