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Chapter 7:The Axial Skeleton

part 1

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Structures of Bones

Articulations:

contacts with other bones

Marks:

areas of muscle and ligament attachment

Foraminae:

openings for nerves and blood vessels

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The Axial Skeleton - longitudinal axis

Supports and protects organsin body cavities

Attaches to muscles of:

head, neck, and trunk

respiration

appendicular skeleton

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Bones of the Axial Skeleton - 80 The skull:

8 cranial bones

14 facial bones

Bones associated

with the skull: 6 auditory ossicles

the hyoid bone

The vertebral column:

24 vertebrae

the sacrum

the coccyx

The thoracic cage:

24 ribs the sternum

Th Sk ll

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The Skull The skullprotects:

the brain

entrances torespiratory system

entrance to digestive

system

Has 22 bones:

8 cranial bones:

form the braincase or cranium

14 facial bones:

protect and support entrances

to digestive and respiratory

tracts

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Cranial Bones Enclose the cranial cavity

Which contains the brain:

and its fluids, blood vessels, nerves, membranes

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The Facial Bones Superficial facial bones

for muscle

attachment Maxillary

Lacrimal

Nasal

Zygomatic Mandible

Deep facial bones

separate the oral and

nasal cavities & form thenasal septum Palatine bones

Inferior nasal conchae

Vomer

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1. The Occipital Bone

Cranial Bones - 8

Function

Forms posterior/inferior surfaces of

cranium

Articulations

Parietal bones

Temporal bones

Sphenoid First cervical vertebra (atlas)

Marks

Occipital condyles -articulate with neck

Inferior and superior nuchal lines-to attach ligaments

External occipital protuberance

External occipital crest -to attach ligaments Foramina

Foramen magnum-connects cranial and spinal cavities

Jugular foramen-for jugular vein

Hypoglossal canals-for hypoglossal nerves

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2. The Parietal Bones Functions

forms part of the superior and

lateral surfaces of the cranium

Articulations Other parietal bone

Occipital bone

Temporal bone

Frontal bone Sphenoid

Marks Superior and inferior temporal lines to attach temporalis

muscle

Grooves for cranial blood vessels

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3. The Frontal Bone

Figure 76

Functions

Forms the anterior cranium and upper eyesockets Contains frontal sinuses

Articulations -8

Parietal bone

Sphenoid

Ethmoid

Nasal bone

Lacrimal bone

Maxillary bone

Zygomatic bone

Metopic suture

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Marks

Frontal squama

(forehead)

Supraorbital margin

(protects eye)

Lacrimal fossa(for tearducts)

Frontal sinuses

3. The Frontal Bone-cont

Foramina Supraorbital foramen for blood vessels of

eyebrows, eyelids, and frontal sinuses

Supraorbital notchan incomplete supraorbitalforamen

4 Th T l B

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4. The Temporal Bones

Figure 77

Functions Part of lateral walls

of cranium andzygomatic arches

Surround and

protect inner ear

Attach muscles of

jaws and head

Articulations

Zygomatic bone Sphenoid

Parietal bone

Occipital bone

Mandible

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M k

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Marks

Squamous part-borders

the squamous suture

Mandibular fossa-articulates with the

mandible

Zygomatic process: inferior to the

squamous portion

articulates with

temporal process ofzygomatic bone

forms zygomatic arch

(cheekbone)

d

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Petrous part: encloses structures of the

inner ear

Auditory ossicles: 3 tiny bones in tympanic

cavity (middle ear)

transfer sound from

tympanic membrane toinner ear

Mastoid process:

for muscle attachment

contains mastoid air cells

connected to middle ear Styloid process:

to attach tendons and

ligaments of the hyoid,

tongue and pharynx

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Foramina

Carotid canal:

for internal carotid artery

Foramen lacerum:

for carotid and small arteries

hyaline cartilage

auditory tube

E l i l

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External acoustic canal:

ends at tympanic membrane

Stylomastoid foramen:

for facial nerve

Internal acoustic canal:

for blood vessels and nerves of the inner ear

facial nerve

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6 Th S h id

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6. The Sphenoid

Figure 78

Functions Part of the floor of the cranium

Unites cranial and facial bones

Strengthens sides of the skull

Contains sphenoidal sinusesArticulations

Ethmoid

Frontal bone

Occipital bone

Parietal bone

Temporal bone Palatine bones

Zygomatic bones

Maxillary bones

Vomer

M k

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Marks Sphenoid body:

at the central axis of the sphenoid

Sella turcica:

saddle-shaped enclosure on the superior surface of the body

Lesser wings:

anterior to the sella turcica

Greater wings:

form part of the cranial floor

sphenoidal spine

posterior wall of the orbit

Hypophyseal fossa:

a depression within the sellaturcica

holds the pituitary gland

Sphenoidal sinuses:

either side of the body

inferior to the sella turcica

Pterygoid processes:

form pterygoid plates

to attach muscles of the

lower jaw and soft palate

Foramina

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Foramina Optic canals:

for optic nerves

Superior orbital fissure: For blood vessels and nerves

of the orbit

Foramen rotundum:

for blood vessels and nervesof the face

Foramen ovale:

for blood vessels and nerves

of the face

Foramen spinosum:

for blood vessels and nerves

of the jaws

7 The Ethmoid

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7. The Ethmoid

Figure 79

Functions

Forms anteromedial floor of the cranium

Roof of the nasal cavity

Part of the nasal septum and medial orbital wall

Contains ethmoidal air cells(sinuses)

Articulations Frontal bone

Sphenoid

Nasal bone

Lacrimal bone Palatine bone

Maxillary bones

Inferior nasal conchae

Vomer

3 Parts of the Ethmoid

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3 Parts of the Ethmoid The cribriform plate is the floor of the cranium

roof of the nasal cavity

The 2 lateral massescomposed of the ethmoidallabyrinth, superior nasal conchae, & middle nasal

conchae The perpendicular plateis part of the nasal septum

Foramina

Olfactory

foraminain

thecribriform

plate for

olfactory

nerves

Facial Bones 14

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Facial Bones - 14 Maxillary (2)-

Figure 710a

Functions Support upper teeth

Form inferior orbital rim

Form lateral margins of external

nares

Form upper jaw and hard palate

Contain maxillary sinuses(largest

sinuses)

Articulations Frontal bones Ethmoid

Other maxillary bone

All other facial bones except the mandible

Marks

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Marks Orbital rim-protects eye and

orbit

Anterior nasal spine-attaches cartilaginousanterior nasal septum

Alveolar processes-borders

the mouth supports upper teeth

Palatine processes -form the hard palate (roof of

mouth)

Maxillary sinuses-to lighten bone

Nasolacrimal canal-protects lacrimal sac and

nasolacrimal duct

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Foramina

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Foramina

Infraorbital foramen:

for sensory nerve to brain (viaforamen rotundumof

sphenoid)

Inferior orbital fissure:

for cranial nerves and blood vessels

Th P l ti B (2)

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The Palatine Bones (2)

Figure 710b,c

Functions

Form the posterior portionof the hard palate

Contribute to the floors of

the orbits

Articulations With other palatine bone

Maxillary bones

Sphenoid Ethmoid

Inferior nasal conchae

Vomer

Divisions of the Palatine Bones

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Divisions of the Palatine Bones

Horizontal plate-posterior part of hard palate

Perpendicular plate-from horizontal plate to

orbital processof orbit floor

Foramina

Many in the lateralportion of the horizontal

plate

For small blood vessels

and nerves of the roof ofthe mouth

Nasal Bones 2

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Nasal Bones- 2 Functions

Support the bridge of the nose

Connect to cartilages of the distal part of the nose

(external nares)

Articulations

With other nasal bones

Ethmoid

Frontal bones

Maxillary bones

Vomer (1)

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Vomer (1) Functions

Forms the inferior portion of the bony nasalseptum

Articulations

Sphenoid

Ethmoid

Palatine bones

Maxillary bones

Cartilaginous part of

the nasal septum

Inferior Nasal Conchae (2)

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Inferior Nasal Conchae (2) Functions

To create air turbulence in the nasal cavity

To increase the epithelial surface area

To warm and humidify inhaled air

Articulations

Ethmoid

Maxillary bones

Palatine bones

Lacrimal bones

Zygomatic Bones (2)

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Zygomatic Bones (2) Functions

Contribute to the rim and lateral wall of the orbit

Form part of the zygomatic arch Articulations

Sphenoid

Frontal bone

Temporal bones

Maxillary bones

Foramina

Zygomaticofacial foramen:

for sensory nerves of cheeksMarks

Temporal process meets the zygomatic process of the

temporal bone

L i l B (2) ( ll t f i l b )

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Lacrimal Bones (2) (smallest facial bones)

Functions

Form part of the medial wall of the orbit Articulations

Frontal bone

Maxillary bones Ethmoid

Marks

Lacrimal sulcus:

location of the lacrimal sac

leads to the nasolacrimal canal (between orbit

and nasal cavity)

The Mandible (1)

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The Mandible (1)

Figure 712a,b

Functions Forms the lower jaw

Articulations Mandibular fossae of the

temporal bones

Marks

Bodyof the mandible - horizontalportion

Alveolar processes- support the lower

teeth

Mental protuberance- attaches facialmuscles

Mylohyoid line - for insertion of the

mylohyoid muscle (floor of mouth)

Ramus- ascending from the mandibular

angle on either side

Parts of the Ramus

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Parts of the Ramus Condylar process:

articulates with

temporal bone attemporomandibular

joint

Coronoid process: insertion point for

temporalis muscle(closes the jaws)

Mandibular notch: separates condylar

and coronoidprocesses

F i

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Foramina

Mental foramina-for sensory nerves of lips

and chin

Mandibular foramen-entrance to the

mandibular canal; for blood vessels and

nerves of lower teeth

Th H id B ( /f i l b )

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The Hyoid Bone (assoc w/facial bones) Functions

Supports the larynx

Attaches muscles of thelarynx, pharynx, and tongue

Articulations Connects lesser hornsto

styloid processes of

temporal bones

Marks Bodyof the hyoid-attaches muscles of larynx, tongue, and

pharynx

Greater horns(greater cornua)-support larynx & attach muscles

of the tongue

Lesser horns(lesser cornua)-attach stylohyoid ligaments &

support hyoid and larynx

The Infant Skull

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The Infant Skull

Figure 715

Grows rapidly Is large compared to the body

Has many ossification centers

Fusion is not complete at birth: 2 frontal bones

4 occipital bones

several sphenoid and temporal elements

Fontanels

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Fontanels Are areas of fibrous connective tissue (soft spots)

Cover unfused sutures in the infant skull

Allow the skull to flex during birth

Anterior fontanel-frontal, sagittal, and coronal

sutures

Occipital fontanel-lambdoid and sagittal sutures