The cranial bones


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The cranial bones

  1. 1. Dr. Lorena C. Balacanao
  2. 2. The Skull <ul><li>Function </li></ul><ul><li>Protect the brain and its processes </li></ul><ul><li>Framework of the head </li></ul><ul><li>Provides attachment of the cranial and facial muscles </li></ul>
  3. 3. Subdivisions <ul><li>Cranial Bones </li></ul><ul><li>Facial Bones </li></ul>
  4. 4. The Cranial Bones <ul><li>It forms the roof and the base of the skull </li></ul><ul><li>It houses and protects the brain </li></ul><ul><li>It is also called neurocranium </li></ul><ul><li>It consists of paired and unpaired bones </li></ul><ul><li>It consists of 8 bones </li></ul>
  5. 5. Cranial bones <ul><li>Frontal 1 </li></ul><ul><li>Parietal 2 </li></ul><ul><li>Temporal 2 </li></ul><ul><li>Occipital 1 </li></ul><ul><li>Sphenoid 1 </li></ul><ul><li>Ethmoid 1 </li></ul><ul><li>Total 8 </li></ul><ul><li>Types of Development occur are: </li></ul><ul><li>Intramembranous ossification and </li></ul><ul><li>Endochondral ossification </li></ul>
  6. 6. Neurocranium <ul><li>Cranial vault </li></ul><ul><li>Cranial base </li></ul><ul><li>Parietal, frontal, squamous temporal and squamous part occipital bone. </li></ul><ul><li>Bone formation in this region occurs primarily by way of intramembranous ossification . </li></ul><ul><li>basilar and lateral portions of the occipital, sphenoid, ethmoid, and the petrous and mastoid part of the temporal bone </li></ul><ul><li>These bones are formed through endochondral ossification , and for this reason the cranial base is sometimes referred to as the chondrocranium . </li></ul>
  7. 7. During fetal life/ Infancy
  8. 8. <ul><li>The cranial bones are separated by a fibrous joint </li></ul><ul><li>This is called sutures </li></ul><ul><li>Sutures are immovable fibrous joint </li></ul>
  9. 9. Serrate suture Lap Suture Plane suture Samples on the different sutures
  10. 10. <ul><li>Synchondrosis </li></ul><ul><li>Is another type of immovable joint that joins the bone by a hyaline cartilage in between </li></ul><ul><li>Between the sphenoid and ethmoid </li></ul><ul><li>Between the sphenoid and occipital bone </li></ul>
  11. 11. <ul><li>Anterior fontanelle- 12-18 mos </li></ul><ul><li>Posterior fontanelle- 2-3 mos </li></ul><ul><li>Bregma </li></ul><ul><li>Lambda </li></ul>
  12. 12. <ul><li>Pterion </li></ul><ul><li>Asterion </li></ul><ul><li>Vertex </li></ul>
  13. 14. The frontal bone <ul><li>resembles a cockle shell </li></ul><ul><li>The vertical part has 2 surfaces: </li></ul><ul><li>The external and internal surface </li></ul><ul><li>1 . Frontal eminence/ tuber - asymmetrical </li></ul><ul><li>2 . Superciliary arches - 2 arch elevations serves as the attachment of corrugators supercili </li></ul>
  14. 15. <ul><li>3. Glabella - a smooth flat surface between the arches; beneath is the major part of the frontal sinus </li></ul><ul><li>4. Supraorbital foramen/ notch - passage way of supraorbital nerve, artery and vein </li></ul>
  15. 17. <ul><li>internal surface are the ff: </li></ul><ul><li>1. Groove for superior sagittal sinus </li></ul><ul><li>2. Frontal crest- linear elevation below the GFSSS </li></ul><ul><li>3. Foramen cecum - transmit vein to superior sagittal sinus </li></ul><ul><li>4. Ethmoidal crest- articulates with the cribriform plate of ethmoid bone </li></ul><ul><li>  </li></ul>
  16. 19. The Parietal bone - <ul><li>forms the roof of the cranium; </li></ul><ul><li>Bounded by the four sutures </li></ul><ul><li>1. Sagittal suture - between the parietal bones </li></ul><ul><li>2. Coronal suture - between frontal and parietal bones </li></ul>
  17. 20. <ul><li>BREGMA is the junction between sagittal and coronal sutures and it correspond to anterior fontanel le during infancy </li></ul><ul><li>Anterior fontanelle is a diamond shaped fontanel about 2 inches in its widest part and </li></ul><ul><li>- Closes at 12-18 months </li></ul>
  18. 21. <ul><li>3. Lambdoid suture- The suture between the occipital bone and parietal bone </li></ul><ul><li>4. Squamous suture- between the parietal and squamous temporal bones </li></ul><ul><li>  </li></ul>
  19. 22. <ul><li>LAMBDA is the junction between sagittal and lambdoid sutures and it correspond to posterior fontanelle during infancy stage </li></ul><ul><li>Posterior fontanel is a triangular in shaped fontanel, which about .5 inch in its widest part and; </li></ul><ul><li>- closes at 2 months </li></ul>
  20. 23. <ul><li>Internal- </li></ul><ul><li>1. Groove for sagittal sinus </li></ul><ul><li>2. Pacchionian granulations or Arachnoid villi or granulations are major sites of absorption of CSF into superior sagittal sinus </li></ul><ul><li>3. Groove for middle meningeal artery </li></ul>
  21. 25. <ul><li>External- </li></ul><ul><li>1. Parietal foramen- transmits a vein to the superior sagittal sinus and sometimes it also transmit small branch to occipital artery. </li></ul><ul><li>2. Temporal lines - a pair of slight thickenings that form an arc across the parietal and frontal bones. Serves as the superior attachment for Temporalis muscles </li></ul>
  22. 27. <ul><li>A. Squamous part : external surface consists of; </li></ul><ul><li> 1. Nuchal lines -located at the lower part of the squama; it has three parts </li></ul><ul><li>Highest - attachment of epicranial aponeurosis </li></ul><ul><li>Superio r- trapezuis, scm, occipito-frontalis </li></ul><ul><li>I nferior - rectus capitis posticus, major and minor </li></ul>
  23. 28. <ul><li>2. External occipital protuberance and crest - attachment for the ligamentum nuchae </li></ul><ul><li>3. Foramen magnum - an oval aperture midway between the squama and base; serves as the passageway of </li></ul><ul><li>Medulla oblongata </li></ul><ul><li>Meninges and spinal roots accessory nerve, Vertebral arteries </li></ul><ul><li>Meningeal branches of vertebral arteries </li></ul>
  24. 29. The Occipital bone <ul><li>-the bone of the occiput or back </li></ul><ul><li>It has 2 parts and 2 surfaces </li></ul><ul><li>Parts Surfaces: </li></ul><ul><li>1. Squamous part </li></ul><ul><li>2. Basilar part </li></ul><ul><li>1. External </li></ul><ul><li>2. Internal </li></ul>
  25. 30. <ul><li>1. Occipital condyle - located on either side of the Foramen magnum where the skull rest on the vertebral column </li></ul><ul><li>2. Hypoglossal canal- lies antero-lateral to the occipital condyle serves as the passageway for the XIICN </li></ul><ul><li>3. Condylar canal- located postero-lateral to the occipital condyle- it transmit </li></ul><ul><li>a. emissary vein and b. meningeal branch of ascending pharyngeal artery </li></ul>
  26. 32. <ul><li>Squamous part - Internal aspect consists of  </li></ul><ul><li>1. Cruciate Eminence - divides the internal part into: </li></ul><ul><li>Upper two fossae which are triangular-shaped and the occipital lobes of the cerebrum lodged; </li></ul><ul><li>Lower two fossae which are quadrilateral and accommodate the hemispheres of the cerebellum. </li></ul><ul><li>2. Internal occipital protuberance - it is located at the point of intersection of the four divisions of the cruciate eminence </li></ul>
  27. 33. <ul><li>2. Basilar part: external surface </li></ul><ul><li>It is a thick quadrilateral shaped bone that articulates with the sphenoid bone by means of clivus. </li></ul><ul><li>1 . Pharyngeal tubercle - serves as the attachment of superior constrictor muscle </li></ul><ul><li>Internal surface- smooth </li></ul><ul><li>  </li></ul>
  28. 35. The Temporal bone <ul><li>- it forms lateral wall of the cranial cavity. It separates the middle cranial fossa to posterior cranial fossa and houses the ear ossicles and the part of the internal ear. </li></ul><ul><li>It has 4 parts: </li></ul><ul><li>1. Squamous part - relatively flat and vertical </li></ul><ul><ul><li>zygomatic process : extends anteriorly to form part of the zygomatic arch. </li></ul></ul>
  29. 37. <ul><ul><li>Mandibular fossa : a depression where the mandible articulates with the cranium. </li></ul></ul><ul><li>2. Tympanic Part - a small ring of bone that borders the external acoustic meatus, the opening into the ear canal. </li></ul><ul><ul><li>Styloid process : a pointed spine on its inferior surface that provides attachment to the muscles of the tongue, pharynx and hyoid bone. </li></ul></ul>
  30. 38. <ul><li>3. Mastoid Part - lies posterior to the tympanic part. </li></ul><ul><ul><li>Mastoid process : it is filled with small air sinuses that communicate with the middle-ear cavity. </li></ul></ul><ul><ul><li>Mastoid notch : lies to the mastoid process and give rise to the digastric muscle. </li></ul></ul>
  31. 39. <ul><li>4. Petrous part- can be seen in the cranial floor, separating the middle cranial fossa from the posterior fossa. The strongest bone that contains the ear ossicles </li></ul>
  32. 41. <ul><li>Two prominent foramina </li></ul><ul><li>Carotid canal: passage for the internal carotid artery. </li></ul><ul><li>Jugular foramen: large irregular opening just medial to the styloid process between the temporal and occipital bone. </li></ul>
  33. 42. The Sphenoid bone <ul><li>it resembles a bat </li></ul><ul><li>It has 4 processes namely: </li></ul><ul><li>Lesser wing </li></ul><ul><li>Greater wing </li></ul><ul><li>Body </li></ul><ul><li>Pterygoid process </li></ul>
  34. 44. <ul><li>1. Lesser wing - two triangular plates and It forms the boundary between the anterior and middle cranial fossa. And also the upper boundary of the superior orbital fissure </li></ul>
  35. 46. <ul><li>a. Superior orbital fissure - located between the lesser wing and the greater wing of the sphenoid bone. It transmits the following: </li></ul><ul><li>Oculomotor nerve (III), </li></ul><ul><li>Trochlear nerve (IV), </li></ul><ul><li>Lacrimal, Frontal and Nasocilliary branches of Opthalmic nerve, </li></ul><ul><li>Abducent nerve (VI), </li></ul><ul><li>Superior opthalmic vein </li></ul>
  36. 47. <ul><li>2. Greater wing – two strong processes that arises from the body and extends lateral-ward anteriorly </li></ul><ul><li>It forms the postero-lateral boundary of the orbit) and curved upward forming the infratemporal fossa </li></ul>
  37. 49. <ul><li>It contains the following </li></ul><ul><li>1. Foramen rotundum- Maxillary nerve </li></ul><ul><li>2 . Foramen ovale-Mandibular nerve (V 3 ), Accessory meningeal artery, Lesser petrosal nerve (occasionally) </li></ul><ul><li>3. Foramen spinosum- Middle meningeal artery and vein, Meningeal branch of mandibular nerve </li></ul>
  38. 50. <ul><li>The body - located at the mid part of the bone, containing the sphenoidal sinus and above is a shallow depression that houses the pituitary gland. </li></ul><ul><li>Part of the body of the sphenoid are: </li></ul><ul><li>1. The chiasmatic groove , it where the optic chiasma lies and it ends laterally to the optic canal. </li></ul>
  39. 52. <ul><li>2. Optic canal-passage way of CN2. </li></ul><ul><li>3. Posterior to it is a shallow depression called the Sella Turcica or the Hypophyseal Fossa that houses the Pituitary Gland </li></ul><ul><li>4. The Sella turcica is bounded </li></ul><ul><li>Anteriorly by the Tuberculum sellae </li></ul><ul><li>Posteriorly by the dorsum sellae . </li></ul>
  40. 53. <ul><li>5. Beneath the sellae are the sphenoidal air sinuses. </li></ul><ul><li>6. Clivus- articulates with occipital bone </li></ul>
  41. 54. <ul><li>4. Pterygoid process - It consists of: </li></ul><ul><li>a. medial plate is continuous to hamulus that serves as the attachment of tensor veli palati </li></ul><ul><li>b. lateral plate serve as the attachment of the pterygoid muscles </li></ul>
  42. 55. <ul><li>Pterygoid process articulates with: </li></ul><ul><li>a. antero-inferiorly to the maxillary tuberosity and </li></ul><ul><li>b. supero-medially to the pyramidal process of the palatine bone ; </li></ul><ul><li>c. Antero-superiorly it has an angular cleft known as the pterygoid fissure- </li></ul><ul><li>pterygopalatine groove . It is where the Sphenopalatine ganglion rest/ located (SPG). </li></ul>
  43. 56. The Ethmoidal bone <ul><li>is cuboidal spongy bone that separates the nasal cavity from the brain . </li></ul><ul><li>It consists of three parts: </li></ul><ul><li>The horizontal &quot; cribriform&quot; plate part of the anterior cranial base- </li></ul><ul><li>It serves as the foramen of exit of the olfactory nerve and roof of the nasal cavity </li></ul>
  44. 58. <ul><li>The vertical &quot; perpendicular&quot; plate , which is part of the nasal septum and consider to be as the supero-medial border of the nasal septum </li></ul><ul><li>The two lateral masses, labyrinths – contains the ethmoidal air sinuses </li></ul>
  45. 60. <ul><li>Other parts: </li></ul><ul><li>1. Critsa galli- the extension of the perpendicular plate at the anterior cranial fossa which serves as the attachment of the falx cerebri </li></ul><ul><li>2. The middle and superior nasal concha of the nasal cavity are part of the ethmoidal bone </li></ul><ul><li>3. Uncinate process- part of the middle nasal concha </li></ul><ul><li>  </li></ul>
  46. 62. The Lateral view of the skull
  47. 66. The Frontal View of the skull