The Skull Its bones can be divided into : Its bones can be divided into : 1. NEUROCRANIUM 1. NEUROCRANIUM It forms a protective case around the brain

The SkullThe Skull•Its bones can be divided Its bones can be divided

intointo: : •11 . .NEUROCRANIUMNEUROCRANIUM

•It forms a protective case It forms a protective case around the brain around the brain..

•22 . .VISCEROCRANIUMVISCEROCRANIUM•It forms the skeleton of It forms the skeleton of

the facethe face..

NEUROCRANIUMNEUROCRANIUM

•Is divided into two Is divided into two portionsportions::

•((AA)) MembranousMembranous partpart : :•It consists of It consists of FlatFlat

bones bones ((CalvariaCalvaria) ) or or Cranial Vault,Cranial Vault, which which

surround the brainsurround the brain . .

NEUROCRANIUMNEUROCRANIUM

•((BB)) Cartilaginous Cartilaginous part part ChondrocraniumChondrocranium

•It forms the bones of the It forms the bones of the basebase of the skull of the skull..

MEMBRANOUS MEMBRANOUS NEUROCRANIUMNEUROCRANIUM

Intra membranousIntra membranous ossification of ossification of mesenchyme at the mesenchyme at the top and most of the top and most of the sides of the brain forms sides of the brain forms a number of Flat, a number of Flat, membranous bonesmembranous bones..


•The mesenchymal cells The mesenchymal cells are derived are derived mostlymostly from the from the Neural CrestNeural Crest and and partlypartly from the from the Para Axial mesodermPara Axial mesoderm..


At birth, the neural crest At birth, the neural crest cells form condensed cells form condensed Fibrous jointsFibrous joints between between the flat bones of the skull the flat bones of the skull ((SuturesSutures))..

At the meeting of more At the meeting of more than two sutures, they than two sutures, they become wide to form become wide to form FontanellesFontanelles..


The fontanelles are The fontanelles are (6)(6) in number in number..

The The AnteriorAnterior FontanelleFontanelle is the is the most prominentmost prominent..

Its palpation gives Its palpation gives an idea about the an idea about the intracranial pressure intracranial pressure and the process of and the process of ossification of the ossification of the skullskull..

MOLDINGMOLDING

•It is It is adaptation adaptation of of the the shapeshape of the of the fetal skull to the fetal skull to the pelvic cavity during pelvic cavity during birth. It depends on birth. It depends on the softness of the the softness of the bones and their loose bones and their loose connections at the connections at the sutures to allow the sutures to allow the overlapping of the overlapping of the bones of the skullbones of the skull..

MOLDINGMOLDING•11.. The Frontal bone The Frontal bone

becomes flatbecomes flat..•22.. The Occipital The Occipital

bone is drawn outbone is drawn out..•33 . .Slight overriding Slight overriding

of one Parietal of one Parietal bone on the otherbone on the other..

•Restoration of the Restoration of the normal shape is normal shape is within few days within few days after birthafter birth..

CHONDROCRANIUMCHONDROCRANIUM

It is formed by It is formed by fusion of several fusion of several separate separate cartilagescartilages..

((11 ) )PARACHORDALPARACHORDAL CARTILAGECARTILAGE )BASAL( )BASAL( PLATEPLATE

It is the cartilage in It is the cartilage in front of the rostral limit front of the rostral limit of the notochord of the notochord (center of sella turcica)(center of sella turcica) . .

It is derived from the It is derived from the Neural Crest cellsNeural Crest cells..

PARACHORDAL PARACHORDAL )BASAL( )BASAL( PLATEPLATE

It fuses with the It fuses with the cartilages derived cartilages derived from the from the SclerotomesSclerotomes of of the occipital the occipital somitessomites..

PARACHORDAL PLATEPARACHORDAL PLATE

•It forms the It forms the Base Base of of the Occipitalthe Occipital bonebone..

•It extends around It extends around the cranial end of the cranial end of the spinal cord to the spinal cord to form the form the boundaries of boundaries of the foramen the foramen magnummagnum..

CARTILAGENOUS CARTILAGENOUS NEUROCRANIUMNEUROCRANIUM

•Ossification begins Ossification begins in thein the::

•Occipital boneOccipital bone. . •BasisphenoidBasisphenoid

(body of(body of sphenoid) sphenoid) bonebone..

•Ethmoid boneEthmoid bone.. •In thatIn that orderorder..

((22 ) )HYPOPHYSEAL CARTILAGEHYPOPHYSEAL CARTILAGE

It is formed around It is formed around the developing the developing pituitary pituitary gland,rostral to the gland,rostral to the occipital basal occipital basal plateplate..

Its cartilage fuses Its cartilage fuses to form the to form the Body Body of theof the sphenoid sphenoid bonebone..


TRABECULAETRABECULAE CRANIICRANII•They fuse to form the They fuse to form the

bodybody of the ethmoid of the ethmoid..•ALA ORBITALISALA ORBITALIS

•It forms the It forms the lesser winglesser wing of the sphenoidof the sphenoid..

•ALA TEMPORALISALA TEMPORALIS•It forms the It forms the greater greater

wingwing of the sphenoid of the sphenoid..


OTIC CAPSULESOTIC CAPSULES•They surround the They surround the

otic vesicles otic vesicles (primordia of the (primordia of the internal ear) and will internal ear) and will form the form the petrous petrous and and mastoidmastoid parts of parts of the temporal bonethe temporal bone..


NASAL CAPSULESNASAL CAPSULES•They surround the They surround the

nasal sacs and nasal sacs and contribute to the contribute to the formation of the formation of the ethmoidethmoid bone bone..


•An elongated median An elongated median plate of cartilage is plate of cartilage is formed between the formed between the nasal region and the nasal region and the anterior border of the anterior border of the foramen magnumforamen magnum..

VISCEROCRANIUMVISCEROCRANIUMThe mesenchyme The mesenchyme

forming the bones of the forming the bones of the face including the nasal face including the nasal and lacrimal bones is and lacrimal bones is derived from the derived from the Neural Neural Crest cells Crest cells that migrate that migrate into the into the first twofirst two pharyngeal archespharyngeal arches..

CARTILAGENOUS CARTILAGENOUS VISCEROCRANIUMVISCEROCRANIUM

•The The DorsalDorsal end of the end of the first archfirst arch ( (Meckel’Meckel’ cartilage) forms the cartilage) forms the bony ossicles of the bony ossicles of the middle earmiddle ear::

•Malleus Malleus andand IncusIncus ..•Its remnant is the Its remnant is the

SphenomandibularSphenomandibular ligamentligament..

•..


•The The DorsalDorsal end of end of thethe SecondSecond arch arch ((ReichertReichert’ ’ cartilage) forms : cartilage) forms : 1.1. StapesStapes of the of the middle earmiddle ear . .

• 22 . .StyloidStyloid process process of the temporal of the temporal bonebone..


•The The VentralVentral end of end of the the 22ndnd arch arch forms : forms : 1.1.Lesser hornLesser horn

•22.. Superior Superior part of the part of the body of hyoid bonebody of hyoid bone..

•The The VentralVentral part of part of the the 33rdrd arch arch forms: 1. forms: 1. Greater hornGreater horn.. 2.2.InferiorInferior part of the part of the body of hyoidbody of hyoid..


•TheThe 4 4thth andand 6 6thth arches arches fusefuse toto form theform the LaryngealLaryngeal cartilages cartilages Except Except the the EpiglottisEpiglottis..

MEMBRANOUS MEMBRANOUS VISCEROCRANIUMVISCEROCRANIUM

•Intramembranous Intramembranous ossification of the ossification of the MaxillaryMaxillary prominence prominence (dorsal portion of the (dorsal portion of the first arch ) gives the first arch ) gives the following bonesfollowing bones::

•11 . .SquamotemporalSquamotemporal ((becomes part of the becomes part of the neurocranium)neurocranium). .

•22 . .MaxillaMaxilla.. •33 . .ZygomaticZygomatic..

MEMBRANOUS MEMBRANOUS VISCEROCRANIUMVISCEROCRANIUM

•Intramembranous Intramembranous ossification of the ossification of the MandibularMandibular prominence (ventral prominence (ventral portion of the first arch) portion of the first arch) forms the forms the MandibleMandible..

•EndochondralEndochondral ossification occurs in the ossification occurs in the mandibular condyles mandibular condyles and the median planeand the median plane

NEW BORN SKULLNEW BORN SKULLIt is It is largelarge in proportion to in proportion to

the rest of the skeletonthe rest of the skeleton..The small face compared The small face compared

to the calvaria is due toto the calvaria is due to::11.. SmallSmall size of the jaws size of the jaws..

22 . .AbsenceAbsence of the Para of the Para nasal sinusesnasal sinuses..

33 . .UnderdevelopedUnderdeveloped facial bones at birthfacial bones at birth . .

POST NATAL GROWTH OF THE POST NATAL GROWTH OF THE SKULLSKULL

The greatest increase of The greatest increase of size of the calvaria is during size of the calvaria is during the first the first two yearstwo years.. This is This is the period of most rapid the period of most rapid increase of size of the brainincrease of size of the brain..

The calvaria normally The calvaria normally increases in capacity until increases in capacity until about about 16 16 yearsyears of age of age..

A slight increase of its size A slight increase of its size for 3 to 4 years because of for 3 to 4 years because of increase thickening of the increase thickening of the bonebone..

CRANIOSYNOSTOSISCRANIOSYNOSTOSIS

It is It is prematurepremature closure of the skull closure of the skull suturessutures..

Its cause is unknown Its cause is unknown but genetic factors are but genetic factors are important it is more important it is more common in common in malesmales..

SCAPHOCEPHALYSCAPHOCEPHALY

Premature closure Premature closure of the of the SagittalSagittal suturesuture..

The skull becomes The skull becomes long, narrow and long, narrow and wedge- shapedwedge- shaped..

OXYCEPHALYOXYCEPHALY

Premature closure of Premature closure of the the CoronalCoronal suture suture..

The skull is high and The skull is high and tower liketower like..

PLAGIOCEPHALYPLAGIOCEPHALY

Premature closure Premature closure of the of the Coronal Coronal or or LambdoidLambdoid suturessutures..

The skull is twisted The skull is twisted and asymmetricand asymmetric..

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GOOD LUCKGOOD LUCK

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The Skull Its bones can be divided into : Its bones can be divided into : 1. NEUROCRANIUM 1. NEUROCRANIUM It forms a protective case around the brain