the cranial bone

8/3/2019 The Cranial Bone

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Dr. Rashed

Weam Al RahamnehSondos Majdi Harbieh

9 feb-2012

Skull (1 ) : Cranial bones


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skull

Cranial

bone

Facial

bone

Frontal

bone

parietal

boneOccipital

bone

Temporal

bone

Sphenoid

bone

Ethmoid

bone

Todays lecture is about the skull:

The Skull is an easy subject and its made of several bones , as usual

we always have a classification to make things easier.The Skull is traditionally studying of the following words >> we look atit from frontal view then we see some bones and we dont see theothers .

some parts of the skull we study it from lateral view, posterior view ,inferior view and so on.Skull is defined into two parts>

The part we discovering with the brain is the cranial part.


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What are the bones that make the cranial part?1-Frontal bone >why we call it frontal bone ?because it is in the front.Theres a sutures that make the joint between two bones .Sutures :The process of joining two surfaces or edges together along

aline

2-lateral bone >briefly bone that surrounding the brain.

3-occipital bone.

4- temporal bone.

5- sphenoid bone.

6- ethmoid bone.

*These are cranial bones , we will study each of them in details .

The second part of the skull is the face >so there are facial bone and there are cranial bone .

You as a dentist have to have a good knowledge about theskull

Note:mandible is not a part of the skull , it is a separate one articulate withthe temporal bone .The doctor used a mind map and he said that it is one of the easiestway to study anatomy.

Temporal bone > we call it temporal because when somebodybecome older the most white hair grow there .


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From WiKi :temporal bone either of the two irregular bones forming part of thelateral surfaces and base of the skull, and containing the organs ofhearing. It is divided anatomically into four parts: the mastoid, petrous,squamous, and tympanic parts

- at frontal view you dont see any part of parietal bone but if you lookat the back of the skull you will see the two parietal bone .

*Cranial vault :1- sagital sutures : articulates the two parietal bones.

2- coronal sutures :articulates the frontal bone with the two parietalbones.

3- lambdiod sutures :articulates the two parietal bones with theoccipital bone.

Parietal bones :

form the sides and the roof of the cranium and as we said that they

articulate with each other in the mid line at the sagittal suture andthey articulate with the occipital bone behind, at the lambdoidsuture.

* lambda: is an intersection of sagittal and lambdoid sutures.

-Why parietal bone is simple?

Because when you look at it you will not see any process or foramen.

- Coronal suture lies in the coronal section and it is located betweenparietal bone and frontal bone and it is articulate with the greater wingof sphenoid bone.


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**When we look >

- anteriority > we will not able to see the parietal bones only we cansee the frontal bone.

- superiorly > frontal and parietal bones and a very little part of the

temporal bone

- laterally > parietal bones.

-Inferiorly > temporal bones.

*Note :-- You will find two lines in the temporal bones we call it temporal lines>the lower one is inferior temporal line which begin as a single from the

posterior margin of the zygmotic process of the frontal bone.

These lines give the origin to attach the muscles to the coronoidprocess of mandible and it is called temporalis.

So : The over view of the parietal bone > it is large and quadrangularin shape that has 4 sites, and it forms greater part of the skull (sides

and roof of the cranial cavity).Pariatal bones articulate with 5 bones one of them is the frontal boneby a sagittal sutures.

What are the surface features of the parietal bone?

External and internal surfaces.

Quadrangular has an external surface ( convex) and internal surface.And it has a superior and inferior temporal lines > these temporal linesreceive the origin of the temporal muscles which is the muscles ofmastications.

In the internal surface of the parietal bone ( which is concave) there isa depressions and elevations.


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The frontal bone:

- when we look at the frontal bone we will not able to see all the parts

so the frontal bone , so to be able to see all the parts you must look atdifferent parts of the skull.

- There is a foramen in the frontal bone called :orbit.

From WikipediaencyclopediaThe orbits are conical or four-sided pyramidal cavities, which open into

the midline of the face and point back into the head. Each consists of abase, an apex and four walls. They are intended to protect the eyefrom mechanical injury.[4]

The base, which opens in the face, has four borders. The followingbones take part in their formation:

1. Superior margin: frontal bone2. Inferior margin: maxilla and zygomatic3. Medial margin: frontal, lacrimal and maxilla4. Lateral margin: zygomatic and frontal

The apex lies near the medial end ofsuperior orbital fissure andcontains the optic canal which communicates with middle cranial

fossa.The roof (superior wall) is formed by the orbital plate frontal bone andthe lesser wing of sphenoid. The orbital surface presents medially bytrochlear fovea and laterally by lacrimal fossaThe floor (inferior wall) is formed by the orbital surface ofmaxilla, theorbital surface ofzygomatic bone and the orbital process ofpalatinebone. Medially near the orbital margin is located the groovefor nasolacrimal duct. Near the middle of the floor, located infraorbital
http://encyclopedia.thefreedictionary.com/Orbit+(anatomy)#cite_note-3http://encyclopedia.thefreedictionary.com/Superior+orbital+fissurehttp://encyclopedia.thefreedictionary.com/Middle+cranial+fossahttp://encyclopedia.thefreedictionary.com/Middle+cranial+fossahttp://encyclopedia.thefreedictionary.com/Frontal+bonehttp://encyclopedia.thefreedictionary.com/Maxillahttp://encyclopedia.thefreedictionary.com/Zygomatic+bonehttp://encyclopedia.thefreedictionary.com/Palatine+bonehttp://encyclopedia.thefreedictionary.com/Palatine+bonehttp://encyclopedia.thefreedictionary.com/Nasolacrimal+ducthttp://encyclopedia.thefreedictionary.com/Orbit+(anatomy)#cite_note-3http://encyclopedia.thefreedictionary.com/Superior+orbital+fissurehttp://encyclopedia.thefreedictionary.com/Middle+cranial+fossahttp://encyclopedia.thefreedictionary.com/Middle+cranial+fossahttp://encyclopedia.thefreedictionary.com/Frontal+bonehttp://encyclopedia.thefreedictionary.com/Maxillahttp://encyclopedia.thefreedictionary.com/Zygomatic+bonehttp://encyclopedia.thefreedictionary.com/Palatine+bonehttp://encyclopedia.thefreedictionary.com/Palatine+bonehttp://encyclopedia.thefreedictionary.com/Nasolacrimal+duct


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groove, which leads to the infraorbital foramen. The floor is separatedfrom the lateral wall by inferior orbital fissure, which connects the orbittopterygopalatine and infratemporal fossa.The medial wall is formed by the frontal process of maxilla, lacrimalbone, orbital plate of ethmoid and a small part of the body of thesphenoid.

From the book:- The lateral wall is the thickest wall of the orbit and the thinnest partof it is where the anterioinferior corner of the parietal bone articulateswith the greater wing of the sphenoid : this point is referred to as thepterion

- The frontal bone have a process ( bony projection or sth protrudingout of the bones) this process goes towards maxilla and formsmaxillary process of the frontal bone.

If you look a little bit more in details and see the frontal bone its alsomaking the roof of the orbit and this is what we are going to see in theskull:- supraorbital margin.- supraorbital notch or foramen.- the roof of the orbit.

- Again when you look laterally you can see that there is a frontal bonearticulating with the parietal bone by coronary suture, anteriorly youcan see that the frontal bone articulates with zygomatic bone thatmake side of the face and the suture between them is calledzygomaticfrontal suture and you can feel it ..

But we still have another parts of frontal bone and we need to look tothe cranial view to see it . there is a part of the frontal bone goes
http://encyclopedia.thefreedictionary.com/Inferior+orbital+fissurehttp://encyclopedia.thefreedictionary.com/Pterygopalatine+fossahttp://encyclopedia.thefreedictionary.com/Infratemporal+fossahttp://encyclopedia.thefreedictionary.com/Lacrimal+bonehttp://encyclopedia.thefreedictionary.com/Lacrimal+bonehttp://encyclopedia.thefreedictionary.com/Inferior+orbital+fissurehttp://encyclopedia.thefreedictionary.com/Pterygopalatine+fossahttp://encyclopedia.thefreedictionary.com/Infratemporal+fossahttp://encyclopedia.thefreedictionary.com/Lacrimal+bonehttp://encyclopedia.thefreedictionary.com/Lacrimal+bone


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inside to make the roof above our eyes and a floor of the interiorcranial fossa .

Interior cranial fossa is a depression in the floor of the cranialvault which houses the projecting frontal lobes ( fromwikipidia )

So this part will make the roof of the orbit and there for we will call it

orbital plate of frontal bone ..

Also as the frontal bone comes down from ( sorry I can`t hear ) itbecomes thick and there is a cavity .That will open to the nose and this is one of paranasal sinuses

Paranasal sinuses are a group of four paired air-filledspacesthat surround the nasal cavity (maxillary sinuses),above and between the eyes (ethmoid sinuses and frontalsinuses), and behind the ethmoids (sphenoid sinuses)

And now lets see the mind map of frontal bone
http://en.wikipedia.org/wiki/Skeletal_pneumaticityhttp://en.wikipedia.org/wiki/Skeletal_pneumaticityhttp://en.wikipedia.org/wiki/Maxillary_sinuseshttp://en.wikipedia.org/wiki/Ethmoid_sinushttp://en.wikipedia.org/wiki/Frontal_sinuseshttp://en.wikipedia.org/wiki/Frontal_sinuseshttp://en.wikipedia.org/wiki/Sphenoid_sinuseshttp://en.wikipedia.org/wiki/Skeletal_pneumaticityhttp://en.wikipedia.org/wiki/Skeletal_pneumaticityhttp://en.wikipedia.org/wiki/Maxillary_sinuseshttp://en.wikipedia.org/wiki/Ethmoid_sinushttp://en.wikipedia.org/wiki/Frontal_sinuseshttp://en.wikipedia.org/wiki/Frontal_sinuseshttp://en.wikipedia.org/wiki/Sphenoid_sinuses


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Note in the figure :* sguama mean thin* roof of the orbit is also the floor of interior cranial fossa

the sphenoid boneit is a central bone that is very important and if it become destroyedthe skull will become weak and useless

it is like the butterfly .. why? because it has body , wings and legs

NOW lets start from the center

* There is a depression ( fosaa ) that is called a pituitary fossa( because the pituitary gland is there )

* also there are two elevations just like a horse saddle there for this depression is called sellae turse ( also pituitary fossa )

NOW let`s see the wings

* it has 2 wings one lesser and the another is greater wing1- the lesser wings ( 2 in number ) in its root there is a foramen (

the optic nerve enter from it so we call it optic foramen )this lesser wings articulate with frontal bone

2- 2 greater wings that join the body

There is an area between lesser and greater wings , this area opensinto the orbit there for its called superior orbital fissure

Greater wind has 3 foramen :1- foramen rotandum maxillary nerve is going through thisforamen ,its gonna supply skin , upper teeth and a part of the nose


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2- at the back there is an oval foramen called foreman ovale mandibular nerve comes down to supply the lower teeth ..

3- posterior and lateral there is foramen spinosum

why spinosum ??? because in the last part of the greater wing ( basal

part ) there is a spine middle meningeal artery goes through it

NOW let`s see the greater wing from below ( basal view)

(note : we can`t see the lesser wing from below )

There is a spine that is called spine of sphenoid .. there is a ligamentfrom this spine to the mandible called sphenomandibular ligament( I can`t hear)

We must also see the sphenoid from sagittal viewAND from the sagittal view we can see that :* The body of the sphenoid is not solid it has sinuses that are calledsphenoid air sinuses ..

Sphenoid air sinuses (They are lined with mucous membraneand communicate with the nasal cavity , ther serve as voise

resonater) ( from the book )

NOW let`s move to the legs of the sphenoid bone ( we are still in thesagittal view )

* The two legs are called pteregoid process

- They give attachment to two heads of medial pteregoid muscle- The legs are 2 plates lateral one and medial one


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We have :

lateral pteregoid muscle ( two parts) . One of them areattached to pteregoid process

medial pteregoid muscle ( two parts) both of them areattached to pteregoid process

NOW let`s go to the mind map and this will be the final part of ourlecture


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Forgive us if u find any mistake and good luck in you new semester

Done by :

SONDOS MAJDI

WEAM AL RAHAMNEH

the cranial bone

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