the anatomy fourth lec..pdf

7/29/2019 the anatomy fourth lec..pdf

1/14

1


2/14

2

The SKULL

Air Sinuses: means the rooms or spaces filled with air within the bones of the skullthose which we refer to as Paranasal sinuses. Paranasal sinuses actually is not a correct

scientific term because when we look to its meaning para means around. The correct

scientific name is air sinuses because those are spaces filled with air but since most of

them are located around the nasal area and opening into the nose, they refer to them as

paranasal sinuses. The only exception is one of them which is para acoustic orpara

auditory that is located around the ear and it opens into the middle ear (the mastoid air

cells). If you put your finger and palpate behind the auricle of the ear, you will feel the

bony prominence themastoid process of temporal bone if you fracture it from inside it

opens usually into the middle ear .

So these are air sinuses, all of them are paranasal except one which ispara acoustic.

In general they started to use the term paranasal to describe them all including the

mastoid air cells.

The word itself comes from that these sinuses are around the nose and they open there

, so their definition is they are air containing spaces within the skull bones more

accurate or within the cranial bones . They are lined with the same epithelium lining the

respiratoy system which is Psudostratified columnar epithelium.

The function of these air sinuses:

Until now theres no 100% sure function for these sinuses

1) To reduce the skull weight: (the most speculated expected function)

the skull is based on the vertebral column and the vertebral column has intervertebral

disks , so to reduce the pressure on the vertebral column we empty the skull bones

from inside and fill them with air.


3/14

3

2) Voice modification: They consider them sometimes () Thisfunctions comes from the idea that when you have an inflammation in these

sinuses sinusitis () you will see that the sound of the speakerbecomes different . So they have something related to the voice production and the

tone of the voice.

3) Thermal Insulation effect : During the winter, when you exhale you exhale a hotair so you lose its temperature and then you inhale a cold air, so whats happening

there that is when you exhale part of this warm air will get into these sinuses and

keep the area of the head warm thats how you keep the temperature .

The sinuses are :

The maxillary sinuses (the biggest one) :

They are two sinuses (left & right) found within the body of the maxillary bones. They

are pyramidal in shape. They open into the middle meatus which is an area on the lateral

wall of the nasal cavity.


4/14

4

The frontal air sinuses:

Found within the frontal bone above the orbit. They open into the middle meatus in the

nasal cavity

Sphenoid sinuses:

Found within the sphenoid body. They open into sphenoethmoidal recess in the superior

corner of the nasal cavity. Look at the picture in the previous page.

Ethmoidal air cells:

These are group of small spaces; they arent sinuses anymore , theyre like small cells

Those air cells are classified into groups :

1-Anterior air cells: they are arranged in an oblique way inside the body of the

ethmoid bone. They are four in number. It opens into the middle meatus in the nasal

cavity

2-Middle air cells: it opens into the middle meatus in the nasal cavity

3-Posterior air cells: It opens into the superior meatus in the nasal cavity

Mastoid air cells:

Within the mastoid process behind

the middle ear in the temporal bone,

they gather in the mastoid antrum

() and they open into themiddle ear

All of the air sinuses open into the nasal cavity with exception of mastoid air

cells which o en into the middle ear


5/14

5

Skull fractures:

We are speaking clinically now. The skull fractures we classify them according to the

classification of the skull (facial bones and neurocranial bones):

If the fracture was in one of the eight cranial bones >>> CRANIAL or

NEUROCRANIAL fracture

Since the cranial bones are classified into cranial vault and cranial base so there are also

cranial vault fractures and cranial base fractures

If the fracture was in one of the fourteen facial bones >>> FACIAL fracture

There are two types :

I.

Complicated fracture: involving more than one bone (more complicated

because the bones are smaller. They were classified into three sub classifications

by ReneLe Fort who is a French surgeon. E.g. the fracture of the two maxillary

bones

II. Single facial fracture: involving only one bone. The most common single facial

fracture is the fracture of the nasal bones and the second most common is the

fracture of the mandible.

lets talk In more details :

cranial vault fractures or fractures of the calvaria:

There are two ways or two mechanisms for the cranial vault to resist fractures or to

resist the force of blows or hits:

1. The convexity of the skull: always the convex surface is stronger than the flat

surface. WHY?? Because when you have a blow or a hit affecting a convex

surface the waves of force can be distributed all the way around into all bones so

that it will reduce the effects of this blow.

2.

The diploid bone:its also called diploic which means double or two layers ofbone. The skull bones which are formed by intermembranous ossification in the

cranial vault ( parietal , frontal, the squamous of occipital and temporal ) when you


6/14

6

look at them in a cross section or in a sagittal view you will see that they are made

of two layers (an outer and inner layers) which are called two tables of compact

bone.

You will first see an external table of compact bone then you will see the

trabeculae (the spongy bone) and between these trabeculae is the bone marrow

then you have another table called the internal table of compact bone. So if you have a

blow or a hit on one of these diploic bones it can produce a fracture on the outer table

then theres another table to resist this fracture. If the blow was very strong it might

fracture the two layers.

The fractures were classified according to the nature of the fracture

itself:

I. Linear fractures : for example if you have a hit with a very small stone in a very

fast speed it will hits on the skull directly , this force will be directly radiated into

two directions forming a linear fracture from the centre of the blow. They are the

most frequent type of fractures to the cranial vault.

II. Comminuted fractures: comminuted means multiple pieces .if the subject was

large when it hits it makes many centers for the fracture so it will produce manyfracture segments or pieces of skull bones. The fracture doesnt produce only one

line INSTEAD it produces a network of lines that producing fractured separated

segments.

These two types of fractures (mentioned above) are common in brittle skulls in

adults which are hard enough to be fractured.

III. Depressed fracture (thin areas): if this large object is pressuring over the skull

of a child, its still not that much ossified, so when you produce pressure on them

there will not be a fracture there will be a depression because the bones areresilient. When the stone hits the skull of a child the bone will be pressured inside

not fractured and pressuring into the brain.

You know that there are two types of bones: compact bone and spongy bone

its trabeculae which runs between the com act bone


7/14

7

IV. Pterion fractures :

Its the most dangerous onebecause: The pterion is located 2-3 fingers above the

mid of the zygomatic arch on the lateral wall demarcated by H-shaped suture. Its the

weakest point of the skull and the anterior arch of the middle meningeal artery is

passing there. So any fracture in this area or separation of this suture will lead to

epidural hemorrhage. 80% of epidural hemorrhage happens in the pterion region

because of fractures there affecting the anterior branch of the middle meningeal

artery.

The cranial base fractures :

The cranial base have three depressions from inside: anterior cranial fossa , middle

cranial fossa and posterior cranial fossa . We have anterior cranial fossa fracture,

middle cranial fossa fracture and posterior cranial fossa fracture; so we classify

the fractures here according to the location NOT to the nature of the fracture

.

Anterior cranial fossa fractures:

1) Fracture of the cribriform plate: One of the weakest areas is the cribriform plateof ethmoid; always when there are perforations or spaces in the bone this is an

area of weakness because there arent enough ossification (not enough calcium inthese areas) to provide strength.

Usually if you have a fracture in the anterior cranial fossa the cribriform plate will

be easily fractured. The cribriform plate of ethmoid is the roof of the nasal cavity and

the floor of the anterior cranial fossa and through it passes the olfactory nerve and the

olfactory nerve fibers decends into the nasal cavity. When this area is fractured crista

galli is fractured also and there will be tearing of the meningis which is attached to

crista galli, the fracture of the cribriform plate of ethmoid has two representations:

NASAL BLEEDINGepistaxis: the blood comes down from the cribriform

plate in the anterior cranial fossa into the nose and then to the outside, this happens

when theres an injury to an artery or a vein.


8/14

8

Leakage of the cerebrospinal fluid into the nose cerebrospinal rhinorrhea ()

In these fractures affecting the cranial base usually the patient is going into a coma.

2) Fracture of orbital plate of frontal bone: If its fracturing it there will be ableeding or cerebrospinal fluid leakage into the area of the orbit , because the

orbital plate of frontal bone is the roof of the orbits so if its fractured the bleeding

wont go into the nose it goes into the orbits, as soon as it gets into the orbit it will

increase the pressure of fluids there , this pressure will push the eyeball to outside.

because the orbit has a limited area and the fluid enters it so where this fluid is

going to settle down , it can do nothing but pressing , behind it theres bone it

cant push it , anteriorly theres the eyeball it can easily push it to the outside

exophthalmos

Middle cranial fossa fractures:

They are the most common fractures in the cranial base because its the weakest part

in the cranial base due to numerous openings there; foramina and canals which mean that

the least amount of bone is there. Its possible that a fracture in this area produces a

fracture in one of these foramina and any structure passing through these foramina will be

affected. E.g. in the foramen rotundum passes the maxillary nerve which supplies the

upper teeth, if the fracture radiating across foramen rotundum it will lead to injury of themaxillary nerve and you will lose sensation of the upper teeth and in the area of the face

over the maxilla paresthesia

Cerebrospinal fluid is a clear colorless fluid which results by the

filtration of blood so its plasma. Cerebro means cerebrum ()

& spinal means the spinal cord because this fluid is located around

the brain and the spinal cord. From outside theres the meningis,

from inside the brain and spinal cord, in between there is this

liquid or aqueous environment to protect the brain as a cushion.


9/14

9

If the fracture is over the ovale, the mandibular nerve will be affected and so on .

Now if you look to the foramina here in the middle cranial fossa usually the nerves

passing across them which can be injured are the CRANIAL NERVES (3rd

-6th

)

according to the area of fracture : foramen ovale>>> mandibular , foramen

rotundum>>>maxillary , foramen spinosum>>> middle meningeal artery which leads to

epidural hemorrhage .

If the fracture going more posteriorly in the middle cranial fossa and fracturing the

petrous part of temporal bone which is the border between the middle cranial fossa and

posterior cranial fossa. The petrous part has anterior and posterior walls, the anterior is

much thinne. If its fractured there will be leakage of blood or CSF through external

auditory meatus () into inside petrous part of temporal bone which contains themiddle ear then to the external ear and to the outside eventually .

Posterior cranial fossa fractures :

Its kind of a strong area so the fractures are not that much there unless the blow

comes from the back and there will be bleeding into the post vertebral muscles. The

bleeding will decends through the foramen magnum and goes into the neck posteriorly.

Now the area of the muscles in the posterior neck is tough and very thick. The most

common one of these muscles is the trapezius. so the bleeding will get stuck between the

vertebral column and the post vertebral muscles , it usually takes 1-2 days to discover thisleakage by finding a bulge there especially if the fracture and the leakage is not that

severe .

Some of the fractures in the posterior cranial fossa affect one of the large foramina:

jugular and magnum.

What will happen if the fracture passes through the foramen magnum where the medulla

oblongata ends and the spinal cord starts??

Medulla oblongata contains two important centers controlling two vital structures

in the body: the respiratory centre and the cardiovascular centre, so its controlling


10/14

10

the heart beating, the rate of the heartbeat and the process of respiration. If

medulla oblongata was injured it leads to direct death.

If the damage goes a little bit downward into the spinal cord it leads to

quadriplegia () : paralysis of the upper and lower limbs.

What will happen if the fracture is passing in the jugular area?

The internal jugular vein will be damaged which will lead to hemorrhage

Damage to one or all of the cranial nerves from the 9th

to the 11th

.

Facial fractures :Complicated fractures : The most common type of fractures in the face is

COMPLICATED involving more than one bone . It has been classified by a

French surgeon calledRen Le Fort.He used to go to thecemetery, dig the

graves take the skulls and goes over a high building and throws them from there.

Then he studies the patterns of fractures.

He finally concluded that these kinds of fractures if its complicated it will go in

three patterns from the simplest to the most complicated:

A. Le fort I: called transmaxillary (Trans means cross) involving the two maxillary

bones. It usually involves the fracture or the separation of the alveolar processes of

the maxillary bones or the separation of the alveolar processes from the palatineprocesses which produces the floating palate. sometimes it extends more

posteriorly to affect the pterygoid processes of the sphenoid bone
http://en.wikipedia.org/wiki/Ren%C3%A9_Le_Forthttp://en.wikipedia.org/wiki/Ren%C3%A9_Le_Forthttp://en.wikipedia.org/wiki/Ren%C3%A9_Le_Fort


11/14

11

B. Le fort II : called pyramidal or the scientific name is subzygomatic because it

doesnt involve the zygomatic bone; the zygomatic bone is still attached . It

involves the maxillary bones, the lacrimal bones and the nasal bones.

C.

Le fort III: called suprazygomatic or craniofacial fracture because the facial

skeleton separates from the cranial one. This time the zygomatic bone is involved.

You are supposed to memorize the name of the fracture, its classification and the involved

bones for each of these

Any fracture in the bone means that there also will be damage to the soft tissue overlying;

the skin, the muscles, there will be edema, hemorrhage, pain.


12/14

12

Single fractures :

1) The nasal bones fracture is the most common fracture because of prominence ofthe nose. Most of the professional boxers dont have the nasal bones because

when they are fractured they are too small to be treated so surgeons remove theminstead. This fracture has complications: fracture of orbital margin and injury to

frontal or ethmoidal sinuses.

2) The mandibular fractures are classified according to the location (the area offracture):

1. Condylar fractures: The most common reason for condylar fractures is that you

have a blow to the chin anteriorly, this blow will push the mandible posteriorly

and since the mandible cant be pushed back because of the presence ofTrusses() in the mandibular fossa then the neck of

the condyle fractures which is the weakest area there. This is common in car

accidents when the driver is not putting the seat belt.

2. Body fractures: usually happens in the canine region, why? For two reasons:

A) The mandible is a ring bone U shaped when the bone becomes convex andangular it becomes weaker and easier to be fractured and the most angular region

is in the canine region. B) The canine has the largest root from all lower teeth.


13/14

13

When the root is large, its socket is large and the socket of the canine is the largest

socket indicating the least amount of bone. Body fractures results from lateral

blows side to side fractures

Condylar and body fractures are the most common types of the mandibular

fractures with a percentage of 30% for the condylar and 25% for the body fractures.

3. Angular and ramus fractures are not clinically significant.

4. Coronoid process fractures:its the least common one (1-2%).When its

fractured the coronoid segment will be pushed superiorly because its attached to

the temporalis muscle which raises the mandible and in that side of the mandible

you see kind of a mandibular drop. Some muscles (the medial pterygoid and

the Masseter) will be still supporting the mandible so its not a complete drop.

Three important rules to distinguish mandibular fractures :

The mandible is one bone from side to side .If you see a fracture in one side of the

mandible expect another fracture, this rule is called Ring Bone Rule. That is the

difference between a dentist and an excellent one , hes not always looking in the

area of complain but he goes comprehensively all the way around , so you always

have to look in both sides and if you see a fracture or dislocation in the mandible

look for another one on the opposite side.

The hyoid bone is another example of the bones that follow the ring bone rule.

Panoramic X-Ray is the best to diagnose mandibular fractures. NOTHING else

will be better than panoramic x-ray. Panoramic means comprehensive view.

Look for cortical margins and mandibular canal discontinuity. In the mandible

there are two cortical margins: the lower cortical margin and the border of the

alveolar process. In the area of the mandibular canal you see a translucency which indicates a space containing air , its the canal in which the mandibular

nerve passes through to supply the root of the lower teeth. You look along with

the mandibular canal also because sometimes the fracture is inside only anddoesnt reach into the cortical margins. So follow these three areas: the margin

of the alveolar bone , the lower cortical margin and the mandibular canal.


14/14

14

Whats the difference between a symptom and a sign ???

The symptom is what the patient is complaining of. E.g. when a patient comes to the

doctor and says Ive blood coming out from my nose.

The signis what the doctor discovers and the patient isnt aware of. E.g. the doctor

measures the temperature of a patient and sees that hes fevered.

Made and

Reviewed by :

AREEJ KLAIB

the anatomy fourth lec..pdf

Documents

Transcript of the anatomy fourth lec..pdf