Norma basalis

Anatomy

1. Class 2 3/28/2019 1 Norma Basalis Dr.Devi

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

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4. Anterior part of the norma basalis Alveolar arch Hard palate Incisive fossa Greater palatine foramen Lesser palatine foramen Posterior nasal spine 4

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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

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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 posterior border, begins behind greater palatine foramen and runs medially . 9

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11. Extends from the posterior border of the hard palate to the transverse line passing through the a nterior 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 the occipital bone; marked in the median plane by the pharyngeal tubercle 12

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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

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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 posterior border is prolonged downward and laterally to form the pterygoid hamulus 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 Mandibular fossa 20

21. Posterior part of norma basalis Median area – Foramen magnum External occipital crest External occipital protuberance Superior nuchal lines 21

22. 22 Lateral area : Condylar part of occipital bone Squamous part of occipital bone Jugular foramen between occipital and petrous temporal bones Styloid process of temporal bone 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 Post border of the hard palate- palatine aponurosis Post nasal spine- musculus uvulae Palatine crest- tensor veli palatine muscle 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, middle meningeal vein 25

26. Foramen spinosum – middle meningeal artery, meningeal branch of mandibular nerve ( nervus spinosus ) Canalis innominatus - lesser petrosal nerve Carotid canal- internal carotid artery 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 Lowest part of medulla oblongata Three meninges Through the subarachnoid space Spinal accessory nerves Vertebral artery Sympathetic plexus around the vertebral arteries Posterior spinal arteries Anterior spinal artery Through the narrow anterior part Apical ligament of dens Vertical band of cruciate ligament Membrana tectoria 28

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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 Foramen caecum- veins from nose to superior sagittal sinus Posterior ethmoidal canals- posterior ethmoidal vessels Optic canal- optic nerve, ophthalmic artery 32

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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 ICA 34

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36. Jugular foramen Through anterior part Through middle part 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

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39. FEOTAL SKULL 39 Dimensions  Larger in proportion to other parts of skeleton  The facial skeleton is 1/8 th 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 7 th 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 7 th 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 4 th yr.  Differentiation reaches maximum by about 35 yrs., when diploic vein produce characteristic arking in radiographs  Mastoid process appear during 2 nd yr, and mastoid air cells during 6 th 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. CRANIOMET R Y 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- Dolichocephalic or long headed ( when C.I is 75 or less) Mesaticephalic ( when C.I is between 75 and 80) 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 larger – in lower races 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 Thank you !