1. Bones of Skull and cranial cavity
DR.CHANDRALEKHA

4. Cranial bones There are 8 cranial bones 1 frontal bone.
1 occipital bone.
1 sphenoid bone
1 Ethmoid bone
2 parietal bones
2 Temporal bones

6. cranium The cranium consists of two major parts
The calvaria (skull cap) forms the roof and the walls
The base of the cranial cavity is divided into three regions.
1. Anterior cranial fossa
2. Middle cranial fossa
3. Posterior cranial fossa

9. The skull Cranial cavity Orbital cavity Nasal cavity Buccal cavity
Middle ear cavity
Inner ear cavity
Paranasal air sinuses

13. Frontal bone Frontal bone forms the forehead.
It forms anterior wall and about one – third of the roof of the cranial cavity.
Frontal tuber
Superciliary arch
Glabella
Supra orbital margin
Nasion
Coronal suture
Frontal air sinus

16. Frontal bone

17. Parietal bones There are 4 borders 4 angles. Sutures: sagittal suture
Coronal suture
Lambdoid suture
Squamous suture
Lines: superior temporal and inferior temporal lines.
Parietal foramen

20. Temporal bones This bone has 4 different parts
1. Squamous part which has two prominent features
zygomatic process and mandibular fossa
2. Tympanic part
is a small ring of bone that borders the external acoustic meatus
The styloid process

21. Temporal bones 3. Mastoid part– has mastoid air sinus
infection and inflammation of this air sinus is known as Mastoiditis
Mastoid notch -- medial to the mastoid process
Stylomastoid foarmen
Mastoid foarmen—at its posterior end
4. Pterous part: anterior surface forms part of the middle cranial fossa
The posterior surface forms the part of posterior cranial fossa
Posteromedial surface has Internal acoustic meatus
The carotid canal--- a passage of internal carotid artery
Jugular foramen: IJV,9,10,11 NERVES, SIGMOID SINUS

23. Occipital bone It has three parts 1. Squamous part 2. condylar part.
3. basilar part
Foramen magnum---transmits spinal cord to the cranial cavity
Hypoglossal canal---anterior to the occipital condyle
Condylar canal--- posterior to the occipital condyle

24. Occipital bone External occipital protruberance Superior nuchal line
Inferior nuchal line

26. Sphenoid bone Body of sphenoid Pair of greater wings
Pair of lesser wings
Optic foramen
Anterior clinoid process
Superior orbital fissure
Sella turcica

28. Foramens in the sphenoid bone
Foramen rotundum
Forman ovale
Foramen spinosum
Foramen lacerum--- occurs at the junction of sphenoid, temporal, and occipital bones

29. Sphenoid bone
Sphenoidal air sinus occur within the body of the sphenoid bone.
At the junction of the body and the greater wing there is a pair of pterygoid process which has medial pterygoid and lateral pterygoid plate . Between the two pterygoid plate is the Pterygoid fossa.

31. Ethmoid bone Crista galli Cribriform plate of ethmoid
Perpendicular plate of ethmoid bone
Superior and middle conchae are the extension of ethmoid bone
On each side of the perpendicular plate of ethmoid bone, anterior, middle and posterior ethmoidal air sinuses are seen

33. Facial bones There are 14 facial bones 2 maxillae 2 nasal bones
2 palatine bones
2 inferior nasal conchae
2 zygomatic bones
2 lacrimal bones
1 vomer
1mandible

35. Maxillae Has body, palatine process,
Frontal process, zygomatic process
Alveolar process
Palatine process forms the roof of the mouth cavity, and floor of the nasal cavity (hard palate)
Near the anterior margin of palatine process, just behind the incisors , is an incisive foramen
Body– infra orbital foramen transmits infra orbital vessels and nerves

36. MAXILLA

37. Palatine bones
horizontal plate of Palatine bones form the posterior part of the hard palate
Orbital plate of palatine bones form part of the floor of the orbital cavity.
Perpendicular plate of palatine bone forms the lateral wall of the nasal cavity
Posterolateral corner of the hard palate--- two large greater palatine foramina.

39. NASAL BONE
Two small rectangular bones form the bridge of the nose and support cartilages that give shape to the nose.
NASAL
BONE

40. Lacrimal bones This bone forms the medial wall of the orbit
Lacrimal fossa- depression in it , lodges the lacrimal sac.

41. INFERIOR NASAL CONCHA
The inferior nasal conchae are the largest of the three conchae in the lateral wall of the nasal cavity.

42. VOMER
The vomer forms the inferior half of the nasal septum.

43. Zygomatic bones Has maxillary process Frontal process Temporal proces
This bones from the prominence of cheek
Zygomatico facial foramen and zygomatico temporal foramen

45. Mandible Mandible is the strongest bone of the skull.
It forms the lower jaw
Provides attachments of muscles of facial expression and muscles of mastication
It has body, ramus, and angle
The point of chin is the mental protruberance.
Mental foramen

48. Bones associated with the skull
There are 7 bones associated with the skull but not considered part of it.
Three ear ossicles on each side namely malleus, incus and stapes (6bones)
The hyoid bone between the chin and the larynx

49. Incudo malleolar joint Incudostapedial joint
Ear ossicles
Malleus consists of head, neck, anterior process, lateral process & handle.
Incus has a body & long process.
Stapes smallest and medially placed ossicle consists of the head, neck two limbs or crura, footplate or base.
Joints are incudo malleolar joint (a saddle joint) & incudostapedial joint ( a ball & socket joint).
Incudo malleolar joint
Incus
Malleus
Stapes
Incudostapedial joint

50. Hyoid bone
The hyoid bone is suspended from the styloid process of the skull by stylohyoid ligament and stylohyoid muscles.
It has body pair of greater horn and pair of lesser horn

52. The skull in the infancy and childhood
The spaces between the unfused cranial bones are called fontanels
The bones are joined at these points only by fibrous membranes.
The anterior, posterior, sphenoid (2)and mastoid fontanels(2)
In total there are 6 fontanels
Anterior fontanels fuse between 18 to 24 months after birth.
All the other fontanels ossify before the infant is a year old.

54. The skull in the infancy and childhood
The frontal bone and the mandible are separate bones at birth but fuse medially in early childhood
The frontal bones usually fuse by 6 year but in some children the metapic suture persists between them.
Traces of these sutures are evident in some adult skull

55. The skull in the infancy and childhood
The face of the new born is flat and the cranium is large.
To accommodate the growing brain, the skull grows more rapidly than the rest of the skeleton during childhood.