· web viewthe main features of the viscerocranial part are the zygomatic arch, and lateral...

SKULL BONESNEUROCRANIM & VISCEROCRANIUM

5. 10. 2012

Kaan YücelM.D., Ph.D.

http://yeditepeanatomy1.org

Dr.Kaan Yücel http://yeditepeanatomy1.org Skull bones

http://www.youtube.com/yeditepeanatomy

The skeleton of the head is the skull. We rather use the ancient Greek term “cranium”, e.g. the cranial nerves. The skull has 22 bones, excluding the ossicles of the ear. Except for the mandible, which forms the lower jaw, the bones of the skull are attached to each other by sutures, are immobile, and form the cranium.

The part that is covering the cranial cavity and the brain in it is called neurocranium. The skeleton of the face is called viscerocranium or facial skeleton. It is the lower part of the cranium.

Out of the 22 bones in the skull, 8 of them are in the neurocranium. They are:• 1 Frontal bone; the bone in the front of the head• 1 Occipital bone; the bone at the back of the head• 2 Parietal bones; “paries” means wall, and these though bones are on the lateral sides of the skull.• 2 Temporal bones; “temple” has two meanings “time” and “temple”. Time can make more sense for

the temporal bones, as where they are the hair becomes grey first.• 1 Sphenoid bone in the middle (Greek sphēnoeidēs wedge-shaped) • 1 Ethmoid bone again in the middle (In Moore’s textbook it is part of the facial skeleton,though)The skeleton of your face is made up by the remaining 14 bones of the cranium.They are:• Two Nasal bones• Two Maxillæ• Mandible• Two Lacrimal bones• Two Zygomatic bones• Two Palatines• Two Inferior Nasal Conchæ• VomerThe inferior and anterior parts of the frontal lobes of the brain occupy the anterior cranial fossa, the

shallowest of the three cranial fossae. The fossa is formed by the frontal bone anteriorly, the ethmoid bone in the middle, and the body and lesser wings of the sphenoid posteriorly. The butterfly-shaped middle cranial fossa has a central part composed of the sella turcica on the body of the sphenoid and large, depressed lateral parts on each side. The bones forming the lateral parts of the fossa are the greater wings of the sphenoid and squamous parts of the temporal bones laterally and the petrous parts of the temporal bones posteriorly. The posterior cranial fossa, the largest and deepest of the three cranial fossae is formed mostly by the occipital bone, but the dorsum sellae of the sphenoid marks its anterior boundary centrally and the petrous and mastoid parts of the temporal bones contribute its anterolateral “walls.”

Sutura is that form of articulation where the contiguous margins of the bones are united by a thin layer of fibrous tissue; it is met with only in the skull. The major suturae in the skull are; coronal, lambdoid, and sagittal suturues.

Important landmarks in the skull are: Bregma: The midline point where the coronal and sagittal sutures intersect Lambda: The midline point where the sagittal and lambdoid sutures intersect. Glabella: The most forward projecting point in the midline of the forehead at the level of the supra-orbital

ridges and above the nasofrontal suturePterion: The point of intersection between the frontal, sphenoid, parietal and the temporal bonesNasion: The point of intersection between the frontonasal suture and the midsagittal plane.Gnathion: The most anterior and lowest median point on the border of the mandibleThe bones of the calvaria of a newborn infant are separated by membranous intervals. They include the

anterior and posterior fontanelles and the paired sphenoidal and mastoid fontanelles.

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The skeleton of the head is the skull. We rather use the ancient Greek term “cranium”, e.g. the

cranial nerves. The skull has 22 bones, excluding the ossicles of the ear. Except for the mandible, which

forms the lower jaw, the bones of the skull are attached to each other by sutures, are immobile, and form

the cranium. Suture is also a term used in surgical practices as “surgical stitching of a wound”. Actually

suture in anatomy is a type of articulation where two articulation surfaces come together along a line, just

like you sew them with a needle.

We can divide the cranium into two or three parts. Generally into two!

Let’s see, there is one part enclosing the brain; protecting the brain, and there is another part which

makes the skeleton of your face. The part that is covering the cranial cavity and the brain in it is called

neurocranium. The skeleton of the face is called viscerocranium or facial skeleton. It is the lower part of

the cranium. Here the viscera means organ, and on your face there is a list of organs; your mouth, your

nose, your eyes. The prefix neuro in the term neurocranium just refers to the “nerve” telling you that this

part of the skeleton of the head covers the brain and meninges (the membrane covering the brain) within

the cranial cavity.

A third part of the skeleton of the head? The part that covers the upper part of the head; calvaria

(skullcap) “kafatası” in Turkish might be considered as a third part. If you add it into the neurocranium,

then the cranium has two parts. Ok? So the neurocranium has one roof (calvaria) and one floor; the base

(base of the skull) basicranium.

Question: which bones make up the neurocranium? Out of the 22 bones of the cranium, 8 of them

belong to the neurocranium. Some of them are paired which means you can find one on the right side, and

one on the left side, and some of them are single.

1 Frontal bone; the bone in the front of the head

1 Occipital bone; the bone at the back of the head

2 Parietal bones; “paries” means wall, and these though bones are on the lateral sides of the skull.

2 Temporal bones; “temple” has two meanings “time” and “temple”. Time can make more sense for the

temporal bones, as where they are the hair becomes grey first.

1 Sphenoid bone in the middle (Greek sphēnoeidēs wedge-shaped)

1 Ethmoid bone again in the middle (In Moore’s textbook it is part of the facial skeleton,though)

http://twitter.com/yeditepeanatomy3

1.SKULL


As you see only the temporal bones and the parietal bones above them are paried (bilateral), and

the other four bones are single (unilateral) which make the eight bones of the neurocranium.

The neurocranium has a dome-like roof, the calvaria (skullcap), and a floor or cranial base (basicranium).

The bones making the calvaria are primarily flat bones (frontal, parietal, and occipital). The bones

contributing to the cranial base are primarily irregular bones with substantial flat portions (sphenoidal and

temporal). The ethmoid bone is an irregular bone that makes a relatively minor midline contribution to the

neurocranium but is also part of the viscerocranium. Watch out! Although there is only a minor

contribution of the ethmoid bone to the neurocranium, it is counted under the bones of the neurocranium.

The skeleton of your face is made up by the remaining 14 bones of the cranium.

They are:

Two Nasal bones

Two Maxillæ

Mandible

Two Lacrimal bones

Two Zygomatic bones

Two Palatines

Two Inferior Nasal Conchæ

Vomer

The viscerocranium forms the anterior part of the cranium and consists of the bones surrounding the

mouth (upper and lower jaws), nose/nasal cavity, and most of the orbits (eye sockets or orbital cavities).

The viscerocranium consists of 14 irregular bones: 2 singular bones centered on or lying in the midline

(mandible and vomer) and 6 bones occurring as bilateral pairs (maxillae; inferior nasal conchae; and

zygomatic, palatine, nasal, and lacrimal bones).

The maxillae and mandible house the teeth—that is, they provide the sockets and supporting bone for the

maxillary and mandibular teeth. The maxillae contribute the greatest part of the upper facial skeleton,

forming the skeleton of the upper jaw, which is fixed to the cranial base. The mandible forms the skeleton

of the lower jaw, which is movable because it articulates with the cranial base at the temporomandibular

joints.

Several bones of the cranium (frontal, temporal, sphenoid, and ethmoid bones) are pneumatized

bones, which contain air spaces (air cells or large sinuses), presumably to decrease their weight. The total

volume of the air spaces in these bones increases with age.

What we have to do now is to see what each bone has: bone markings & formations. The

information on each bone can be presented in two ways. The textbooks (Moore’s, Gray’s, and Snell’s)

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present the information on cranial bones by talking about the views from anterior, inferior and lateral

aspects. Another way might be talking about each bone one by one.I will do it that way. On the other hand,

I will also give you the perspective of “what you see when you look at the anterior part of the skull or from

an inferior view” at the end. Remember! To remember “repeating” is the best way! So you will have both

the regional (bones one by one) perspective and also the views perspective (that of the textbooks).

Figure 1. Skull bones (lateral view)http://images.tutorvista.com/content/locomotion-animals/human-skull-structure.jpeg

2.1. FRONTAL BONE (OS FRONTALE)Figure 2. Frontal bonehttp://www.bleaching-dental.com/img/news/126.jpg

The frontal bone consists of two portions:

squama (etymology: Latin, squama: scale; squama frontalis)- vertical portion

corresponding with the region of the foreheadorbital portion (frontal orbit; orbita frontalis)– horizontal partion

enters into the formation of the roofs of the orbital and nasal cavities


2.BONES OF THE NEUROCRANIUM

The biggest part of the brain (one third of a brain

hemisphere); the frontal lobe mostly resides on the frontal lobe.

The frontal bone forms the forehead. It also contributes to the

formation of two cavities; the orbital cavity where the eyes are

located and the nasal cavity (the cavity inside your nose).

http://www.bleaching-dental.com/img/news/126.jpg

http://images.tutorvista.com/content/locomotion-animals/human-skull-structure.jpeg


Figure 3. Frontal bone, squamous parthttp://virtual.yosemite.cc.ca.us/rdroual/Lecture%20Notes/Unit%202/chapter_6_axial_skeleton_copy%20with%20figures.htm

So you should take the frontal bone as two pieces; one flat surface (squama) and one horizontal

surface forming the roof of the orbit (the nest for the eye). From now on, if a cranial bone has a flat,

smooth surface, it will be named as squamous part (just like the one in the occipital bone, back of the

head).

Anterior viewThe supra-orbital margin of the frontal bone, the angular boundary between the squamous and

the orbital parts, has a supra-orbital foramen or notch in some crania for passage of the supra-orbital

nerve and vessels. Just superior to the supra-orbital margin and the rim of the orbit there is a ridge, the

superciliary arch. The prominence of these ridges, deep to the eyebrows, is generally greater in males.

Between the superciliary arches is a small depression (glabella). The superciliary arches extend laterally on

each side from the glabella. In some people, frontal eminences are also visible, giving the calvaria an

almost square appearance.

Medially, the frontal bone projects inferiorly forming a part of the medial rim of the orbit. Laterally,

the zygomatic process of the frontal bone projects inferiorly forming the upper lateral rim of the orbit.

This process articulates with the frontal process of the zygomatic bone.

In some adults a metopic suture, a persistent frontal suture or remnant of it, is visible in the midline

of the glabella, the smooth, slightly depressed area between the superciliary arches. The estimated

prevalence is 1 in 15,000 live births with a 3:1 male:female ratio.


http://virtual.yosemite.cc.ca.us/rdroual/Lecture%20Notes/Unit%202/chapter_6_axial_skeleton_copy%20with%20figures.htm


Figure 4. Frontal bone (anterior view)http://www.csuchico.edu/anth/Module/frontal.html

The internal surface of the squama frontalis of the frontal bone is concave and presents in

the upper part of the middle line a vertical groove, the sagittal sulcus, the edges of which unite below to

form a ridge, the frontal crest. The frontal crest is a median bony extension of the frontal bone. At its base

is the foramen cecum (blind hole) of the frontal bone, which gives passage to vessels during fetal

development. Nasal process is the downward projection of the nasal part of the frontal bone which

terminates as the nasal spine.

Figure 5. Frontal bone (inner surface)http://www.bartleby.com/107/illus135.html


http://www.bartleby.com/107/illus135.html

http://www.csuchico.edu/anth/Module/frontal.html


2.2. PARIETAL BONESThe two parietal bones unite and form the sides and roof of the cranium. Each bone is irregularly

quadrilateral in form. The external surface is convex, smooth, and marked near the center by an eminence,

the parietal eminence (tuber parietale). Crossing the middle of the bone in an arched direction are two

curved lines, the superior and inferior temporal lines. The parietal foramen is a small, inconstant aperture

located posteriorly in the parietal bone near the sagittal suture. Paired parietal foramina may be present.

Figure 6. Parietal bone (lateral view)http://medical-dictionary.thefreedictionary.com/parietal+bone

Figure 7. Parietal bones (anterior view)http://aftabphysio.blogspot.com/2010/09/bones-of-skull.html

2.3. TEMPORAL BONESThe temporal bones are situated at the sides and base of the skull. The temporal bone has the

temporal lobe on which is important for a long list of functions including memory, emotional memory,

hearing. It has the canal that goes to the ear.

The temporal bone contributes most of the lower portion of the lateral wall of the cranium.

Each temporal bone has five parts:

1) Squamous part

2) Tympanic part

3) Mastoid parthttp://www.youtube.com/yeditepeanatomy 8

http://aftabphysio.blogspot.com/2010/09/bones-of-skull.html

http://medical-dictionary.thefreedictionary.com/parietal+bone


4) Petrous part

5) Styloid process

The squamous part has the appearance of a large flat plate, forms the anterior and superior parts of

the temporal bone, contributes to the lateral wall of the cranium, and articulates anteriorly with the

greater wing of the sphenoid bone at the sphenosquamous suture, and with the parietal bone superiorly

at the squamous suture. The zygomatic process is an anterior bony projection from the lower surface of

the squamous part of the temporal bone that initially projects laterally and then curves anteriorly to

articulate with the temporal process of the zygomatic bone to form the zygomatic arch.

The squamous part lies just lateral to the greater wing of the sphenoid. It participates in the

temporomandibular joint. It contains the mandibular fossa, which is a concavity where the head of the

mandible articulates with the base of the skull. An important feature of this articulation is the prominent

articular tubercle, which is the downward projection of the anterior border of the mandibular fossa.

The tympanic part of the temporal bone is immediately below the origin of the zygomatic process

from the squamous part of the temporal bone. The external acoustic opening (pore) is the entrance to the

external acoustic meatus (canal), which leads to the tympanic membrane (eardrum). The external acoustic

opening is clearly visible on the surface of this part.

The mastoid part is the most posterior part of the temporal bone. It is continuous with the

squamous part of the temporal bone anteriorly, and articulates with the parietal bone superiorly, and with

the occipital bone posteriorly.

On the lateral edge of the mastoid part lies the cone-shaped mastoid process projecting from its

inferior surface. The mastoid process is a prominent structure and is the point of attachment for several

muscles. On the medial aspect of the mastoid process is the deep mastoid notch, which is also an

attachment point for a muscle.

Immediately lateral to the basilar part of the occipital bone is the petrous part of the temporal

bone. Wedge-shaped in its appearance the petrous part of the temporal bone is between the greater

wing of the sphenoid anteriorly and the basilar part of the occipital bone posteriorly. The apex forms one

of the boundaries of the foramen lacerum, an irregular opening filled in life with cartilage. Posterolateral

from the foramen lacerum along the petrous part of the temporal bone is the large circular opening for the

carotid canal.

The large opening between the occipital bone and the petrous part of the temporal bone is the

jugular foramen.This foramen is very important as major structures pass through this foramen. The vein



draining the brain exits the skull through the jugular foramen. Later on, in the second year you will learn

the 12 cranial nerves. Three of them pass through the jugular foramen and go to their destinations exiting

the cranium. Anterosuperior to the jugular foramen is the internal acoustic meatus for the passage of two

other cranial nerves. One of them is the nerve for the muscles of the face, and the other is good for the

hearing and balance.

The styloid process is needle-shaped bone marking. It projects from the lower border of the

temporal bone anteromedial to the mastoid process. The styloid process is a point of attachment for

numerous muscles and ligaments. The stylomastoid foramen, transmitting the nerve for the muscles of

the face lies posterior to the base of the styloid process; between the styloid process and the mastoid

process.

Figure 8. Temporal bonehttp://medicinembbs.blogspot.com/2011/02/skull-anatomy.html

2.4. SPHENOID BONEThe sphenoid bone is situated at the base of the skull in front of the temporal bones and basilar

part of the occipital bone. It somewhat resembles a bat with its wings extended, and is divided into a

median portion; body, two great and two small wings extending outward from the sides of the body, and

two pterygoid processes which project from it below.

The greater and lesser wings of the sphenoid spread laterally from the lateral aspects of the body

of the bone. The pterygoid processes, consisting of lateral and medial pterygoid plates, extend inferiorly

on each side of the sphenoid from the junction of the body and greater wings. Pterygoid fossa is between

the two plates. Each medial plate of the pterygoid process ends inferiorly with a hook-like projection, the

pterygoid hamulus.


http://medicinembbs.blogspot.com/2011/02/skull-anatomy.html


The sphenoidal crests are formed mostly by the sharp posterior borders of the lesser wings of the

sphenoid bones. The sphenoidal crests end medially in two sharp bony projections, the anterior clinoid

processes.

The sella turcica (L. Turkish saddle) is the saddle-like bony formation on the upper surface of the

body of the sphenoid, which is surrounded by the anterior and posterior clinoid processes. Clinoid means

“bedpost,” and the four processes (two anterior and two posterior) surround the hypophysial fossa, the

“bed” of the pituitary gland, like the posts of a four-poster bed.

The sella turcica is composed of three parts:

1) The tuberculum sellae (horn of saddle): a variable slight to prominent median elevation forming the

posterior boundary of the prechiasmatic sulcus and the anterior boundary of the hypophysial fossa. It lies

behind the chiasmatic groove. On both ends of the tuberculum sellae are middle clinoid processes.

2) The hypophysial fossa (pituitary fossa): a median depression (seat of saddle) in the body of the

sphenoid that accommodates the pituitary gland (L. hypophysis).

3) The dorsum sellae (back of saddle): a square plate of bone projecting superiorly from the body of the

sphenoid. It forms the posterior boundary of the sella turcica, and its prominent superolateral angles make

up the posterior clinoid processes.

On each side of the body of the sphenoid, four foramina perforate the roots of the cerebral surfaces of the

greater wings of the sphenoids:

Superior orbital fissure : Located between the greater and the lesser wings, it opens anteriorly into the

orbit.

Foramen rotundum (round foramen) : Located posterior to the medial end of the superior orbital

fissure.

Foramen ovale (oval foramen) : A large foramen posterolateral to the foramen rotundum.

Foramen spinosum (spinous foramen) : Located posterolateral to the foramen ovale.

The foramen lacerum (lacerated or torn foramen) is not part of the crescent of foramina. This

ragged foramen lies posterolateral to the hypophysial fossa and is an artifact of a dried cranium. In life, it is

partly closed by a cartilage plate.

Figure 9. Sphenoid bone (anterior view)http://virtual.yosemite.cc.ca.us/rdroual/Lecture%20Notes/Unit%202/chapter_6_axial_skeleton_copy%20with%20figures.htm


http://virtual.yosemite.cc.ca.us/rdroual/Lecture%20Notes/Unit%202/chapter_6_axial_skeleton_copy%20with%20figures.htm


Figure 10. Foramina in the sphenoid bone (superior view) and other openings http://medchrome.com/wp-content/uploads/2011/05/skull-superior.jpg

2.5. OCCIPITAL BONE


http://medchrome.com/wp-content/uploads/2011/05/skull-superior.jpg


The occipital bone is situated at the back and lower part of the cranium. It is trapezoid in shape and

curved on itself. It is pierced by a large oval aperture, the foramen magnum, through which the cranial

cavity communicates with the vertebral canal.

The foramen magnum is the most prominent feature of the cranial base. The major structures

passing through this large foramen:

spinal cord (where it becomes continuous with the medulla oblongata of the brain)

meninges (coverings) of the brain and spinal cord

vertebral arteries

anterior and posterior spinal arteries

spinal accessory nerve (CN XI).

The four parts of the occipital bone are arranged around the foramen magnum:

1) The curved, expanded plate behind the foramen magnum is named the squama.

2) The thick, quadrilateral piece in front of the foramen is called the basilar part.

3) On either side of the foramen is the lateral portion of the occipital bone.

The cranial base is formed posteriorly by the occipital bone, which articulates with the sphenoid bone

anteriorly.

The external occipital protuberance, is usually easily palpable in the median plane; however,

occasionally (especially in females) it may not be prominent. The external occipital crest descends from

the protuberance toward the foramen magnum.

The superior nuchal line marks the superior limit of the neck. It extends laterally from each side of

the protuberance. The inferior nuchal line is less distinct.

On the lateral parts of the occipital bone are two large protuberances, the occipital condyles. The

cranium articulates with the vertebral column by the occipital condyles.

The clivus is a shallow depression, incline (Latin for "slope") behind the dorsum sellæ that slopes

obliquely backward. Posterior to foramen magnum, the posterior cranial fossa is partly divided by the

internal occipital crest into bilateral large concave impressions, the cerebellar fossae. The internal

occipital crest ends in the internal occipital protuberance. Actually, the internal occipital crest is the lower

division of a cross called as cruciate eminence. The cruciate eminence divides the interior surface of the

occipital bone into four fossae. The superior two fossae are triangular and lodge the occipital lobes of the

cerebrum (cerebral fossae). The inferior two are quadrilateral and accommodate the hemispheres of the



cerebellum (cerebellar fossae). The internal occipital protuberance is the prominent elevation in the

centre of the cruciate eminence.

The hypoglossal canal for the hypoglossal nerve (CN XII) is superior to the anterolateral margin of

the foramen magnum.

Figure 11. Occipital bone (inner surface)

2.6. ETHMOID BONEGk, ethmos, sieve sifter, eidos, form

The etmoid bone is exceedingly light and spongy, and cubical in shape; it is situated at the anterior

part of the base of the cranium, between the two orbits, at the roof of the nose, and contributes to each of

these cavities. It consists of four parts: a horizontal or cribriform plate, forming part of the base of the

cranium; a perpendicular plate, constituting part of the nasal septum; and two lateral ethmoidal

labyrinths. The crista galli (L. crest of the cock) is a thick, median ridge of bone posterior to the foramen

cecum (frontal bone), which projects superiorly from the ethmoid. On each side of the ridge called crista

galli, located in the frontal bone, is the sieve-like cribriform plate of the ethmoid. Its numerous tiny

foramina transmit the olfactory nerves (CN I) from the olfactory areas of the nasal cavities to the olfactory

bulbs of the brain, which lie on this plate.



Figure 12. Ethmoid Bonehttp://medical-dictionary.thefreedictionary.com/ethmoid+bone

Figure 13. Ethmoid bone’s location in the skullhttp://www.daviddarling.info/images/ethmoid_bone.jpg

3.1. ANTERIOR CRANIAL FOSSAThe inferior and anterior parts of the frontal lobes of the brain occupy the anterior cranial fossa, the

shallowest of the three cranial fossae. The fossa is formed by the frontal bone anteriorly, the ethmoid bone

in the middle, and the body and lesser wings of the sphenoid posteriorly. The greater part of the fossa is

formed by the orbital parts of the frontal bone, which support the frontal lobes of the brain and form the

roofs of the orbits. This surface shows sinuous impressions (brain markings) of the orbital gyri (ridges) of

the frontal lobes.

3.2. MIDDLE CRANIAL FOSSAThe butterfly-shaped middle cranial fossa has a central part composed of the sella turcica on the

body of the sphenoid and large, depressed lateral parts on each side. The middle cranial fossa is

posteroinferior to the anterior cranial fossa, separated from it by the sharp sphenoidal crests laterally. The


3.CRANIAL FOSSAE

http://www.daviddarling.info/images/ethmoid_bone.jpg

http://medical-dictionary.thefreedictionary.com/ethmoid+bone


bones forming the lateral parts of the fossa are the greater wings of the sphenoid and squamous parts of

the temporal bones laterally and the petrous parts of the temporal bones posteriorly. The lateral parts of

the middle cranial fossa support the temporal lobes of the brain. The boundary between the middle and

the posterior cranial fossae is the superior border of the petrous part of the temporal bone laterally and a

flat plate of bone, the dorsum sellae of the sphenoid, medially.

3.3. POSTERIOR CRANIAL FOSSAThe posterior cranial fossa, the largest and deepest of the three cranial fossae, lodges the

cerebellum, pons, and medulla oblongata. The posterior cranial fossa is formed mostly by the occipital

bone, but the dorsum sellae of the sphenoid marks its anterior boundary centrally and the petrous and

mastoid parts of the temporal bones contribute its anterolateral “walls.” Posterior to foramen magnum,

the posterior cranial fossa is partly divided by the internal occipital crest into bilateral large concave

impressions, the cerebellar fossae.

Figure 14. Cranial fossaehttp://tmjc.com.ne.kr/tmj/info/drinfo/images/tm6-6.jpg

4.1. NASAL BONESThe nasal bones are two small oblong bones, varying in size and form in different individuals; they

are placed side by side at the middle and upper part of the face, and form, by their junction, “the bridge”

of the nose. Each has two surfaces and four borders.


4.BONES OF THE VISCEROCRANIUM

http://tmjc.com.ne.kr/tmj/info/drinfo/images/tm6-6.jpg


Figure 15. Nasal bone and other facial boneshttp://upload.wikimedia.org/wikipedia/commons/thumb/7/77/Illu_facial_bones.jpg/250px-Illu_facial_bones.jpg

4.2. MAXILLÆ (UPPER JAW)The maxillae are the largest bones of the face, excepting the mandible, and form, by their union,

the whole of the upper jaw. Each assists in forming the boundaries of three cavities: the roof of the mouth,

the floor and lateral wall of the nose and the floor of the orbit. It has two fissures, the inferior orbital and

pterygomaxillary fissures.

Each bone consists of a body and four processes—zygomatic, frontal, alveolar, and palatine. The

maxillae form the upper jaw; their alveolar processes include the tooth sockets (alveoli) and constitute the

supporting bone for the maxillary teeth. The two maxillae are united at the intermaxillary suture in the

median plane. The maxillae surround most of the piriform aperture and form the infra-orbital margins

medially. They have a broad connection with the zygomatic bones laterally and an infraorbital foramen

inferior to each orbit for passage of the infra-orbital nerve and vessels.

Figure 16. Maxillahttp://www.probertencyclopaedia.com/E_MAXILLA.HTM


http://www.probertencyclopaedia.com/E_MAXILLA.HTM

http://upload.wikimedia.org/wikipedia/commons/thumb/7/77/Illu_facial_bones.jpg/250px-Illu_facial_bones.jpg


4.3. MANDIBLE (LOWER JAW)The mandible is the largest and strongest bone of the face, serves for the reception of the lower

teeth. It is a U-shaped bone with an alveolar process that supports the mandibular teeth. Dentoalveolar

syndesmosis (gomphosis or socket) is a fibrous joint in which a peglike process fits into a socket

articulation between the root of the tooth and the alveolar process of the jaw (mandile or maxilla).

The mandible consists of a head, a curved, horizontal portion, the body, and two perpendicular

portions, the rami (sing. ramus, which means branch). The two rami of the mandible unite with the ends

of the body nearly at right angles. Just below the head of the mandible, is the neck of the mandible.

The body of mandible is arbitrarily divided into two parts: the lower part is the base of mandible;

the upper part is the alveolar part of mandible. On the superior part of the ramus a condylar and coronoid

process extend upward. The condylar process is involved in articulation of the mandible with the temporal

bone, and the coronoid process is the point of attachment for the temporalis muscle. The head of the

mandible enters the fossa mandibularis in the temporal bone when it comes to the temporomandibular

joint.

Mandibular notch is a deep concavity between the condylar and coronoid processes.

Inferior to the second premolar teeth are the mental foramina for the mental nerves and vessels.

Continuing past this foramen is a ridge (oblique line) passing from the front of the ramus onto the body of

mandible. The oblique line is a point of attachment for muscles that depress the lower lip.

The incisive canal is a continuation forward of the mandibular canal beyond the mental foramen and

below the incisor teeth.

The mental protuberance, forming the prominence of the chin, is a triangular bony elevation inferior to

the mandibular symphysis (L. symphysis menti), the osseous union where the halves of the infantile

mandible fuse. Just lateral to the mental protuberance, on either side, are slightly more pronounced

bumps (mental tubercles).

Interior viewMedial to the condylar process is the pterygoid fossa. Mandibular foramen lies inferior to this fossa.

Lingula is a tongue-like bony process over the mandibular foramen. The internal surface of the body bears

an oblique ridge, the mylohyoid line, which begins a short distance below the last molar tooth as a

prominent crest. Below the mylohyoid line is a concave area, termed the submandibular fossa, which

lodges the submandibular salivary gland. Running forward from the ramus into the submandibular fossa is

the shallow mylohyoid groove which fades out anteriorly. Immediately above the line is the shallow

sublingual fossa for the salivary gland of the same name. The inferior border of the body is marked, a little



to each side of the midline, by the small, roughened digastric fossa for attachment of the anterior belly of

the digastric muscle. The digastric fossa is on either on either side of the symphysis menti.

Figure 23. Mandible (Lat., mandibula)http://facialfractures.blogspot.com

4.4. LACRIMAL BONEThe lacrimale bone is the smallest and most fragile bone of the face is situated at the front part of the

medial wall of the orbit.

Figure 17. Lacrimal bonehttp://www.upstate.edu/cdb/education/grossanat/hnskullantlb.shtml

4.5. ZYGOMATIC BONES cheek bones, malar bones

The zygomatic bones are quadrilateral bones. The zygomatic bones form the prominence of the

cheeks, and that is why we also call them as “the cheek bones”. They are located on the maxillae on each


http://www.upstate.edu/cdb/education/grossanat/hnskullantlb.shtml

http://facialfractures.blogspot.com/


side and inferolateral sides of the orbits. The walls, floor and much of the infra-orbital margins of the orbits

are formed by the zygomatic bones.

A small zygomaticofacial foramen pierces the lateral aspect of each bone. The zygomatic bones

articulate with the frontal, sphenoid, and temporal bones and the maxillae.

Figure 18. Zygomatic bone’s location in the skull Figure 19. Zygomatic bonehttp://medical-dictionary.thefreedictionary.com/zygomatic+bone http://www.upstate.edu/cdb/education/grossanat/hnskullantzb2.shtml

4.6. PALATINE BONEThe palatine bone is situated at the back part of the nasal cavity between the maxilla and the

pterygoid process of the sphenoid. It contributes to the walls of three cavities: the floor and lateral wall of

the nasal cavity, the roof of the mouth, and the floor of the orbit. It has one horizontal plate, and a vertical

(perpendicular) plate. It also three prolongations; orbital, maxillary (pyramidal) and sphenoidal

processes.

The hard palate (bony palate) is formed by the palatine processes of the maxillae anteriorly and the

horizontal plates of the palatine bones posteriorly. The free posterior border of the hard palate projects

posteriorly in the median plane as the posterior nasal spine. Posterior to the central incisor teeth is the

incisive foramen, in the midline of the bony palate where blood vessels and nerves pass.

Superior to the posterior edge of the palate are two large openings: the choanae (posterior nasal

apertures), which are separated from each other by the vomer (L. plowshare), a flat unpaired bone of

trapezoidal shape that forms a major part of the bony nasal septum.

Figure 20. Palatine bonehttp://medical-dictionary.thefreedictionary.com/os+palatinum


http://medical-dictionary.thefreedictionary.com/os+palatinum

http://www.upstate.edu/cdb/education/grossanat/hnskullantzb2.shtml

http://medical-dictionary.thefreedictionary.com/zygomatic+bone


Figure 21. Hard palatehttp://www.gla.ac.uk/ibls/US/cal/anatomy/cleftpalate/final/hardp975.htm

4.7. INFERIOR NASAL CONCHAConcha Nasalis Inferior; Inferior Turbinated Bone

The inferior nasal concha extends horizontally along the lateral wall of the nasal cavity. The anterior

and middle nasal conchae are not separate bones but parts of the ethmoid bone.

Figure 22. Inferior nasal conchahttp://www.bcnlp.ac.th/Anatomy/page/apichat/bone/page/inferior-concha.html


http://www.bcnlp.ac.th/Anatomy/page/apichat/bone/page/inferior-concha.html

http://www.gla.ac.uk/ibls/US/cal/anatomy/cleftpalate/final/hardp975.htm


4.8. VOMERVomer is a small bone in the midline, resting on the sphenoid bone. It contributes to the formation

of the bony nasal septum separating the two choanae.

Figure 24. Vomerhttp://www.ask.com/wiki/Vomer

Sutura is that form of articulation where the contiguous margins of the bones are united by a thin layer of

fibrous tissue; it is met with only in the skull.

5.1. CORONAL SUTUREParietal bones articulate with the frontal bone in their front, forming the coronal suture.

5.2. LAMBDOID SUTUREParietal bones articulate with the occipital in their behind, forming the lambdoid suture.

5.3 .SAGITTAL SUTUREParietal bone articulates with its the opposite side, forming the sagittal suture. Vertex, the most superior

point of the calvaria, is near the midpoint of the sagittal suture.

The coronal suture separates the frontal and parietal bones, the sagittal suture separates the parietal

bones, and the lambdoid suture separates the parietal and temporal bones from the occipital bone.

Figure 26. Suturaehttp://upload.wikimedia.org/wikipedia/commons/thumb/0/0d/Human_skull_side_suturas.svg/524px-Human_skull_side_suturas.svg.png


5.SUTURA

http://upload.wikimedia.org/wikipedia/commons/thumb/0/0d/Human_skull_side_suturas.svg/524px-Human_skull_side_suturas.svg.png

http://www.ask.com/wiki/Vomer


Bregma: The midline point where the coronal and sagittal sutures intersect

Lambda: The midline point where the sagittal and lambdoid sutures intersect.

Glabella: The most forward projecting point in the midline of the forehead at the level of the supra-

orbital ridges and above the nasofrontal suture

Pterion: The point of intersection between the frontal, sphenoid, parietal and the temporal bones

Nasion: The point of intersection between the frontonasal suture and the midsagittal plane.

Gnathion: The most anterior and lowest median point on the border of the mandible.

Figure 27. Landmarks of the skullhttp://chestofbooks.com/health/anatomy/Human-Body-Construction/Craniocerebral-Topography.html


7. FONTANELLES

6. IMPORTANT LANDMARKS

http://chestofbooks.com/health/anatomy/Human-Body-Construction/Craniocerebral-Topography.html


The bones of the calvaria of a newborn infant are separated by membranous intervals. They include

the anterior and posterior fontanelles and the paired sphenoidal and mastoid fontanelles. Palpation of the

fontanelles during infancy, especially the anterior and posterior ones, enables physicians to determine the:

• Progress of growth of the frontal and parietal bones.

• Degree of hydration of an infant (a depressed fontanelle indicates dehydration).

• Level of intracranial pressure (a bulging fontanelle indicates increased pressure on the brain).

The anterior fontanelle, the largest one, is diamond or star shaped; it is bounded by the halves of the

frontal bone anteriorly and the parietal bones posteriorly. Thus it is located at the junction of the sagittal,

coronal, and frontal sutures, the future site of bregma. By 18 months of age, the surrounding bones have

fused and the anterior fontanelle is no longer clinically palpable.

The posterior fontanelle is triangular and bounded by the parietal bones anteriorly and the occipital bone

posteriorly. It is located at the junction of the lambdoid and sagittal sutures, the future site of lambda. The

posterior fontanelle begins to close during the first few months after birth; and by the end of the 1st year,

it is small and no longer clinically palpable.

The sphenoidal and mastoid fontanelles fuse during infancy and are less important clinically than the

midline fontanelles.

The resilience of the cranial bones of infants allows them to resist forces that would produce fractures in

adults. The fibrous sutures of the calvaria also permit the cranium to enlarge during infancy and childhood.

The increase in the size of the calvaria is greatest during the first 2 years, the period of most rapid brain

development. The calvaria normally increases in capacity for 15-16 years. After this, the calvaria usually

increases slightly in size for 3-4 years as a result of bone thickening.

Figure 28. Fontanelleshttp://medical-dictionary.thefreedictionary.com/fontanelle

HEAD INJURIEShttp://www.youtube.com/yeditepeanatomy 24

CLINICAL ANATOMY

http://medical-dictionary.thefreedictionary.com/fontanelle


Head injuries are a major cause of death and disability. The complications of head injuries include

hemorrhage, infection, and injury to the brain and cranial nerves.

FRACTURES OF THE CRANIAL FOSSAEIn fractures of the anterior cranial fossa, the cribriform plate of the ethmoid bone may be damaged.

Fractures of the middle cranial fossa are common, because this is the weakest part of the base of the skull.

Anatomically, this weakness is caused by the presence of numerous foramina and canals in this region; the

cavities of the middle ear and the sphenoidal air sinuses are particularly vulnerable.

How the bones are located in the skull?



Which bones/anatomical features do you see in each view (anterior, lateral, posterior,superior views)?

Anterior view of the skull (Facial- frontal aspect of the cranium)Figure 29. Anterior view of the skullhttp://img.medscape.com/pi/emed/ckb/clinical_procedures/834279-835401-23.jpg


http://img.medscape.com/pi/emed/ckb/clinical_procedures/834279-835401-23.jpg


The anterior view of the skull includes the forehead superiorly, and, inferiorly, the orbits, the nasal region, the part of the face between the orbit and the upper jaw, the upper jaw, and the lower jaw. Features of the anterior or facial (frontal) aspect of the cranium are the frontal and zygomatic bones, orbits, nasal region, maxillae, and mandible.

The frontal bone, specifically its squamous (flat) part, forms the skeleton of the forehead,

articulating inferiorly with the nasal and zygomatic bones.

The zygomatic bones (cheek bones, malar bones), forming the prominences of the cheeks,

lie on the inferolateral sides of the orbits and rest on the maxillae. The anterolateral rims, walls,

floor, and much of the infra-orbital margins of the orbits are formed by these quadrilateral bones.

The zygomatic bones articulate with the frontal, sphenoid, and temporal bones and the maxillae.

Inferior to the nasal bones is the pear-shaped piriform aperture, the anterior nasal opening

in the cranium. The bony nasal septum can be observed through this aperture, dividing the nasal

cavity into right and left parts. On the lateral wall of each nasal cavity are curved bony plates, the

nasal conchae.



The maxillae form the upper jaw; their alveolar processes include the tooth sockets (alveoli)

and constitute the supporting bone for the maxillary teeth. The two maxillae are united at the

intermaxillary suture in the median plane. The maxillae surround most of the piriform aperture and

form the infra-orbital margins medially. They have a broad connection with the zygomatic bones

laterally and an infraorbital foramen inferior to each orbit for passage of the infra-orbital nerve and

vessels.

The mandible is a U-shaped bone with an alveolar process that supports the mandibular

teeth. It consists of a horizontal part, the body, and a vertical part, the ramus. Inferior to the

second premolar teeth are the mental foramina for the mental nerves and vessels. The mental

protuberance, forming the prominence of the chin, is a triangular bony elevation inferior to the

mandibular symphysis (L. symphysis menti), the osseous union where the halves of the infantile

mandible fuse.

Lateral view of the skullFigure 30. Skull, lateral viewhttp://www.arthursclipart.org/medical/skeletal/skull%20lateral%20view.gif

The lateral aspect of the cranium is formed by both the neurocranium and the viscerocranium .The

main features of the neurocranial part are the external acoustic opening, and the mastoid process

of the temporal bone. The main features of the viscerocranial part are the zygomatic arch, and

lateral aspects of the maxilla and mandible.

The zygomatic arch is formed by the union of the temporal process of the zygomatic bone and the

zygomatic process of the temporal bone.


http://www.arthursclipart.org/medical/skeletal/skull%20lateral%20view.gif


The external acoustic opening (pore) is the entrance to the external acoustic meatus (canal),

which leads to the tympanic membrane (eardrum). The mastoid process of the temporal bone is

posteroinferior to the external acoustic opening. Anteromedial to the mastoid process is the styloid

process of the temporal bone, a slender needle-like, pointed projection.

Posterior view of the skull (Occipital aspect of the cranium)Figure 30. Skull, posterior viewhttp://www.infovisual.info/03/016_en.html

The posterior or occipital aspect of the cranium is composed of the occiput (L. back of head, the

convex posterior protuberance of the squamous part of the occipital bone), parts of the parietal

bones, and mastoid parts of the temporal bones. The external occipital protuberance, is usually

easily palpable in the median plane; however, occasionally (especially in females) it may be

inconspicuous. A craniometric point defined by the tip of the external protuberance is the inion (G.

nape of neck). The external occipital crest descends from the protuberance toward the foramen

magnum, the large opening in the basal part of the occipital bone. The superior nuchal line,

marking the superior limit of the neck, extends laterally from each side of the protuberance; the

inferior nuchal line is less distinct. In the center of the occiput, lambda indicates the junction of the

sagittal and the lambdoid sutures . Lambda can sometimes be felt as a depression. One or more

sutural bones (accessory bones) may be located at lambda or near the mastoid process.

Superior view of the skull (Superior aspect of the cranium)Figure 31. Skull bones, superior view


http://www.infovisual.info/03/016_en.html


http://www.becomehealthynow.com/images/organs/bones/skull_bones_top_view.png

The superior (vertical) aspect of the cranium, usually somewhat oval in form, broadens

posterolaterally at the parietal eminences. In some people, frontal eminences are also visible,

giving the calvaria an almost square appearance.

The coronal suture separates the frontal and parietal bones, the sagittal suture separates the

parietal bones, and the lambdoid suture separates the parietal and temporal bones from the

occipital bone. Bregma is the craniometric landmark formed by the intersection of the sagittal and

coronal sutures. Vertex, the most superior point of the calvaria, is near the midpoint of the sagittal

suture.

The parietal foramen is a small, inconstant aperture located posteriorly in the parietal bone near

the sagittal suture; paired parietal foramina may be present.

CRANIAL BASE (BASE OF THE SKULL, BASICRANIUM, KAFA TABANI)The cranial base (basicranium) is the inferior portion of the neurocranium (floor of the cranial cavity) and

viscerocranium minus the mandible. The external surface of the cranial base features the alveolar arch of

the maxillae (the free border of the alveolar processes surrounding and supporting the maxillary teeth);

the palatine processes of the maxillae; and the palatine, sphenoid, vomer, temporal, and occipital bones.

The hard palate is a part of the external surface of the cranial base.

The internal surface of the cranial base (L. basis cranii interna) has three large depressions that lie at

different levels: the anterior, middle, and posterior cranial fossae, which form the bowl-shaped floor of the

cranial cavity. The anterior cranial fossa is at the highest level, and the posterior cranial fossa is at the

lowest level.

Figure 32. Cranial base https://www2.aofoundation.org/AOFileServerSurgery/MyPortalFiles?FilePath=/Surgery/en/_img/surgery/01-Diagnosis/93/Skull-base/93_SB-

D_i520_L.gif


https://www2.aofoundation.org/AOFileServerSurgery/MyPortalFiles?FilePath=/Surgery/en/_img/surgery/01-Diagnosis/93/Skull-base/93_SB-D_i520_L.gif

https://www2.aofoundation.org/AOFileServerSurgery/MyPortalFiles?FilePath=/Surgery/en/_img/surgery/01-Diagnosis/93/Skull-base/93_SB-D_i520_L.gif

http://www.becomehealthynow.com/images/organs/bones/skull_bones_top_view.png

· web viewthe main features of the viscerocranial part are the zygomatic arch, and lateral...

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