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3/19/2012. 2. The skull is divided into two parts:Neurocranium- which forms a protective case or

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1. OSTEOLOGY The Skull

2. 3/19/2012 2 The skull is divided into two parts: Neurocranium- which forms a protective case or “vault” around the brain Viscerocranium- which forms the anterior part of the skull including the orbits, nasal cavities and upper/lower jaw bones

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5. 3/19/2012 5 Squamous (flat) portion forms the skeleton of the forehead Fontal bone forms the roof of the orbit Nasion is an area where the frontal bone intersects with the nasal bones Glabella- smooth, slightly depressed area located just superior to the nasion

6. 3/19/2012 6 Supraorbital margin- marks the boundary between the squamous and orbital portions Supraorbital notch or foramen is for the passage of the supraorbital nerve and vessels A prominent ridge just superior to the supraorbital margin is the superciliary arch (more pronounced in males) Zygomatic process of the frontal bone articulates with the zygomatic bone

7. 3/19/2012 7 Cheek bones Forms a portion of the lateral wall of the orbit Frontal Process of the zygomatic bone articulates with the frontal bone Temporal process of the zygomatic bone articulates with the temporal bone Zygomaticofacial foramen- small foramen for passage of the zygomaticofacial nerve

8. 3/19/2012 8 Forms the upper jaw Alveolar processes of the maxillae includes the sockets and supporting bone for the maxillary teeth Maxillae form the floor of the orbit Large infraorbital foramen for passage of the infraorbital nerve & vessels Surrounds most of the pear-shaped piriform aperture

9. 3/19/2012 9 Frontal processes of the maxillae articulates with the frontal bone Zygomatic processes of the maxillae articulates with the zygomatic bones Anterior nasal spine- sharp prominence at inferior aspect of the piriform aperture Intermaxillary suture- site where the two maxilla are united in the median plane

10. 3/19/2012 10 Seen within the piriform aperture are the scrolled middle nasal conchae (part of the ethmoid bone) & the inferior nasal conchae Vomer bone along with the perpendicular plate of the ethmoid bone which together form the bony nasal septum can also be identified with the piriform aperture

11. 3/19/2012 11 U-shaped bone with alveolar process that houses the mandibular teeth Mental foramen- located inferior to 2nd premolar for passage of the mental nerve and vessels Mental protuberance- a triangular elevation of bone that forms the prominence of the chin Mental tubercle- located just lateral to the protuberance Body is the horizontal portion Ramus is the vertical portion

12. Osteology Lateral Aspect of the Skull

13. 3/19/2012 13 Parietal bone Frontal bone Occipital bone Temporal bone Sphenoid bone Mandible Zygomatic bone Maxillae Lacrimal bone Nasal bone

14. 3/19/2012 14 Paired bones that form the lateral & superior cranium Temporal Lines- mark the attachment site of the temporalis muscle & fascia Articulates with frontal bone via coronal suture Articulates with occipital bone via lambdoid suture Pterion-site where 4 cranial bones articulate-important clinical implications

15. 3/19/2012 15 Paired bones that form the inferior lateral aspect of skull Temporal bone is described as having a flat squamous portion and a mastoid process (site of attachment of several muscles) Zygomatic arch extends anteriorly to articulate with the zygomatic bone

16. 3/19/2012 16 External acoustic meatus (ear canal) and the pointed styloid process are considered to be located the tympanic portion of the temporal bone Styloid process serves as the attachment site for several muscles and the stylohyoid ligament

17. 3/19/2012 17 Mandible and a portion of the zygomatic arch removed in this view Located on the inferior aspect of the arch is a small bony protrusion- articular tubercle that is important in the mechanics of the TMJ Mandibular fossa- deep recess that accepts the condyle of the mandible-also important region of the TMJ

18. 3/19/2012 18 Forms major portion of the cheek Temporal process that articulates with the the zygomatic arch Frontal process that articulates with the frontal bone Zygomaticofacial foramen – small foramen generally visible

19. 3/19/2012 19 Forms the posterior aspect of the skull Articulates with the parietal bone via the lambdoid suture Prominent palpable elevation located posteriorly is the external occipital protuberance

20. 3/19/2012 20 Irregular shaped bone that forms a portion of the orbit, lateral aspect of skull and a portion of the cranial base Sphenoid can be divided into 4 parts: Greater wing Lesser wing Pterygoid processes Body Some portions of the sphenoid can only be seen inside the cranial cavity

21. 3/19/2012 21 Portion of zygomatic arch and mandible removed in this view Greater wing articulates with the temporal, parietal & frontal bones at the pterion Pterygoid processes are two thin plates of bone that serve as attachment sites for muscles Pterygoid hamulus-small hook of bone extending from the medial pterygoid plate- tensor veli palatini tendon courses around this

22. 3/19/2012 22 Portion of zygomatic arch and mandible removed in this view Posterior aspect of the maxillae is referred to as the tuberosity of maxillae Small alveolar foramina for the posterior superior alveolar nerves & vessels Pterygomaxillary fissure-tear-drop shaped fissure between the sphenoid and tuberosity of the maxillae Pterygopalatine fossa is a small but important space located medial to the fissure

23. 3/19/2012 23 Lateral Aspect of Skull Nasal bone can also identified as it articulates with the frontal bone and the maxillae Lacrimal bone- which houses the lacrimal sac van be identified within the orbit Prominent anterior nasal spine at the inferior aspect of the piriform aperture

24. 3/19/2012 24 Mandible Condylar process is located at the superior part of the ramus and involved in the articulation of the mandible with the temporal bone (TMJ) Coronoid process is located just anterior and serves as the attachment site for the temporalis muscle Angle of mandible is between the ramus and body

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27. 3/19/2012 27 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 & coronal sutures Lambda-is the landmark formed by the intersection of the sagittal & lambdoid sutures

28. 3/19/2012 28 Calvaria Inferior aspect of the skull cap presents several features: Vascular grooves for branches of the middle meningeal artery Granular Foveolae- pits formed by arachnoid granulations (site of CSF transfer) Groove for the superior sagittal sinus-large venous channel within the dura mater Diploe- cancellous bone containing red marrow

29. Infant Skull Superior & Lateral Aspects

30. 3/19/2012 30 Infant Skull Bones forming the calvaria & some parts of the cranial base develop by intramembranous ossification Whereas-most parts of the cranial base develop by endochondral ossification Bones in the infant skull are separated by areas of fibrous tissue membranes- the fontanelles: Anterior Posterior Mastoid sphenoidal

31. 3/19/2012 31 Infant Calvaria Anterior Fontanelle (soft spot) is the future site of the bregma By about 18-24 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 12 months

32. 3/19/2012 32 Infant Skull Mastoid & sphenoidal fontanelles fuse early in infancy Palpation of fontanelles during infancy enables physicals to determine: Growth progress of the frontal & parietal bones Degree of hydration of the infant (a depressed fontanelle indicates dehydration) Level of intracranial pressure-bulging fontanelle indicates increased pressure on the brain

33. Osteology External Aspect of the Cranial Base

34. 3/19/2012 34 Cranial Base Inferior aspect of the skull presents six different bones: Palatine processes of the maxillae Palatine bone Sphenoid bone Vomer Temporal Occipital bone Numerous foramina can also be identified

35. 3/19/2012 35 Cranial Base- Palate Hard palate is formed by the palatine processes of the maxillae and the horizontal plates of the palatine bone Small prominence projecting posteriorly form the hard palate in the median plane is the posterior nasal spine

36. 3/19/2012 36 Cranial Base- Palate Posterior to the central incisors is a small depression-incisive fossa with a pair of canals- incisive canals for the passage of the nasopalatine nerves Posterolaterally are the greater & lesser palatine foramen for passage of the nerves & vessels of the same name

37. 3/19/2012 37 Cranial Base-Vomer Vomer-thin, flat unpaired bone in the midline that forms a major portion of the bony nasal septum On either side of the vomer are two large openings- choanae (posterior nasal apertures)

38. 3/19/2012 38 Cranial Base- Sphenoid Three parts of the sphenoid bone can be appreciated on the inferior aspect of skull: Greater wing Medial pterygoid plate Lateral pterygoid plate Pterygoid fossa is between the two pterygoid plates

39. 3/19/2012 39 Cranial Base- Sphenoid Foramen ovale for passage of the mandibular division (V3) of the trigeminal nerve Foramen spinosum- for passage of the middle meningeal artery Groove for the pharyngotympanic (auditory) tube lies medial to spinosum

40. 3/19/2012 40 Cranial Base- Temporal Mastoid process- prominence located posteriorly on the temporal bone Mastoid serves as the attachment site for the SCM and posterior belly of the digastric muscles External acoustic meatus (EAM) is located just anterior to the mastoid

41. 3/19/2012 41 Cranial Base- Temporal Styloid process- thin bony process extending inferior & anteriorly Styloid serves as attachment site for numerous muscles & ligaments Mandibular fossa- articular surface that accepts the condyle of the mandible forming the TMJ

42. 3/19/2012 42 Cranial Base- Temporal Two important foramen can be identified on the inferior aspect of the temporal bone: Stylomastoid foramen- located between the mastoid & styloid processes is a small foramen for the passage of the facial nerve (CN VII) Carotid canal- passage for the internal carotid artery into the cranial cavity

43. 3/19/2012 43 Cranial Base- Occipital Occipital bone forms the posterior and inferior aspects of the skull Foramen Magnum- a large foramen for passage of the spinal cord Foramen magnum divides the occipital bone into 3 parts: Basilar Region Condylar Region Squamous Region

44. 3/19/2012 44 Cranial Base- Occipital Basilar portion presents a small tubercle- pharyngeal tubercle for attachment of the pharyngeal constrictors Foramen lacerum (jagged-shaped) is located lust lateral to the basilar portion

45. 3/19/2012 45 Cranial Base- Occipital Condylar portion presents the occipital condyles that articulate with the atlas Jugular foramen- large foramen between the occipital & temporal bones for passage of cranial nerves: IX, X, XI and the internal jugular vein Hypoglossal canal for passage of the hypoglossal nerve (CN XII)

46. 3/19/2012 46 Cranial Base- Occipital Squamous portion presents the palpable external occipital protuberance Superior & inferior nuchal lines project laterally and are sites for muscular attachments

47. Osteology Internal Aspect of the Cranial Base

48. 3/19/2012 48 Cranial Base Internal aspect of the cranial base is divided into three major regions or fossae: Anterior cranial fossa Middle cranial fossa Posterior cranial fossa These three fossae lie at different levels and form the bowl-shaped floor of the cranial cavity

49. 3/19/2012 49 Anterior Cranial Fossa Frontal lobes of the brain occupies the anterior cranial fossa Fossa is formed by the: Orbital portion of the frontal bone Ethmoid bone in the middle Lesser wing of the sphenoid

50. 3/19/2012 50 Anterior Cranial Fossa Frontal crest- a median bony extension from the frontal bone Foramen cecum is located at the base of the crest and is a small foramen for passage a vessels during development Crista galli- ridge of bone projecting superiorly from the ethmoid bone and serves as the attachment for the cerebral falx

51. 3/19/2012 51 Anterior Cranial Fossa On either side of the crista galli is a “sievelike” Cribriform plate for passage of the olfactory axons into the cranial cavity Optic canal for passage of the optic nerve (CN II) and the ophthalmic artery can be appreciated within the lesser wing of the sphenoid

52. 3/19/2012 52 Middle Cranial Fossa Temporal lobes of the brain occupy the middle cranial fossa Fossa is formed by the: Greater wing of the sphenoid Squamous portion of the temporal bone Petrous portion of the temporal bone

53. 3/19/2012 53 Middle Cranial Fossa Sella turcica- the saddle-like bony formation located on the superior aspect of the body of the sphenoid Sella turcica is surrounded by anterior & posterior clinoid processes

54. 3/19/2012 54 Middle Cranial Fossa Sella turcica is composed of three parts: Hypophyseal fossa (pituitary fossa) Tuberculum sellae (saddle horn) Dorsum Sellae (back of the saddle) Sella turcica- essentially houses and guards the pituitary gland

55. 3/19/2012 55 Middle Cranial Fossa Middle cranial fossa presents five important foramina: Superior orbital fissure for passage of CN’s III, IV, V1 & VI & ophthalmic veins Foramen rotundum which transmits the maxillary nerve (V2) Foramen ovale- which transmits the mandibular nerve (V3)

56. 3/19/2012 56 Middle Cranial Fossa Foramen spinosum which transmits the middle meningeal artery Foramen lacerum- nothing is transmitted vertically thru this foramen although the internal carotid artery and some nerves pass across the foramen horizontally Grooves for the greater & lesser petrosal nerves are located along the anterior slope of the petrous portion of the temporal bone

57. 3/19/2012 57 Middle Cranial Fossa Petrous portion of the temporal bone houses the middle and inner ear cavities Arcuate eminence- marks the roof of the anterior semicircular canal of the inner ear cavity Trigeminal impression is located just anteromedial the eminence-which marks the location of the sensory ganglion of the trigeminal nerve

58. 3/19/2012 58 Posterior Cranial Fossa The largest & deepest of the three fossae Cerebellum, pons and medulla occupy the posterior fossa Formed mainly by the occipital bone and the petrous & mastoid portions of the temporal bone

59. 3/19/2012 59 Posterior Cranial Fossa Clivus marks the anterior portion of the occipital bone Foramen magnum- large foramen that marks the transition from the medulla to the spinal cord Posterior to the foramen magnum is the internal occipital crest and internal occipital protuberance

60. 3/19/2012 60 Broad grooves show the horizontal course of the transverse and S-shaped sigmoid sinuses (both dural venous sinuses) Sigmoid sinus empties into the large jugular foramen which also transmits several cranial nerves: Glossopharyngeal (CN IX) Vagus (CN X) Accessory (CN XI) Posterior Cranial Fossa

61. 3/19/2012 61 Posterior Cranial Fossa Internal acoustic meatus is located just anterosuperior to the jugular foramen Internal acoustic meatus transmits the facial nerve (CN VII) and vestibulochochlear nerve (CN VIII) along with the labyrinthine artery Hypoglossal canal for the hypoglossal nerve (CN XII) lies superior to the margin of the foramen magnum

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63. 3/19/2012 63 Osteology of the Orbit Seven bones articulate to make each orbit: Frontal Zygomatic Maxillary Lacrimal Ethmoid Palatine Sphenoid

64. 3/19/2012 64 Osteology of the Orbit Optic canal- transmits the optic nerve and ophthalmic artery Superior orbital fissure- transmits CN III, IV, V1 & VI Inferior orbital fissure & groove- transmits the infraorbital vessels & nerve Anterior & posterior ethmoidal foramina- transmits vessels & nerves with same name

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