Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

An Introduction to the Axial Skeleton

Terms: Structures of Bones

Articulations: Contacts with other bones

Landmarks (Bone Markings; Marks): Areas

of muscle and ligament attachment

Foramina: Openings for nerves and blood

vessels

All bones possess distinctive landmarks that are

designed for specific functions, e.g. certain

landmarks are used as articulating surfaces to form

a joint (an articulation) with another bone on the

skeleton.

Examples of these include condyles, heads, and

facets.

A complete list of bony landmarks is shown in your

activities packet pg 89 Table 7.1

In your lab activities study sheet, it is suggested that

you create online study cards using “Quizlet”

The Axial Skeleton

The axial skeleton Has 80 bones & forms the vertical axis of

the body. It can be divided into three parts: the skull, the

vertebral column, & the bony thorax.

The skull: 8 cranial bones & 14 facial bones

– Bones associated with skull: 6 auditory ossicles & hyoid bone

The vertebral column: 24 vertebrae (singular = vertebra),

The sacrum, & The

coccyx

The thoracic cage:

24 ribs & The sternum

The axial skeleton forms the vertical

axis of the body

Functions of the Axial Skeleton

Supports and protects organs in body cavities

Attaches to muscles of:

Head, neck, &

trunk

Respiration

Appendicular

skeleton

The Skull

The skull is composed of two sets of bones:

8 cranial bones:

Forms the walls and floor of the cranial cavity

Most of the bones are flat or slightly curved

14 facial bones:

Have irregular shapes. These bones form the face & the walls of orbital

and nasal cavities and provide bony sockets for the teeth.

Learning the bones of the skull can be challenging, thus you

must examine it’s 3-D. In addition to your drawings, note your

3-D paper skull and the iPad App.

All but one of the bones of the skull are joined by interlocking

joints called sutures. Only the mandible, or lower jawbone, is

attached to the rest of the skull by a freely moveable joint.

Copyright © 2009 Pearson Education, Inc., publishing as Pearson Benjamin Cummings

The Skull

Figure 7–2 Cranial and Facial Subdivisions of the Skull.

Terminology Aids

Sinuses

Cavities that decrease the weight of the skull

Lined with mucous membranes

Protect the entrances of the respiratory system

Sutures

The immovable joints of the skull

The four major sutures

Lambdoid suture

Coronal suture

Sagittal suture

Squamous suture

For a suture, compare the uniting of two skull

bones with fibrous connective tissue to the

sewing together of two pieces of fabric with a

zigzag stitch. The word suture comes from

sutura, Latin for seam.

imagine the ethmoid as a capital letter “T.” (Make a “T” with

your hands, as you would if signaling a time-out.)

The knuckles of the hand that form the cross bar of the “T”

are analogous to the crista galli, which can only be viewed

from inside the cranial cavity.

Crista galli = rooster’s comb

The term ethmoid derives from “sieve-like”

and numerous ethmoid sinuses of the

ethmoid bone. Cribriform may remind

students of a corncrib.

Functions of the

ethmoid

Forms floor of the

cranium

Roof of the nasal cavity

Part of the nasal

septum and medial

orbital wall

Contains ethmoidal air

cells (network of

sinuses)

Three Parts of the

Ethmoid

The cribriform plate

Roof of the nasal

cavity

Contains the crista

galli

The two lateral

masses

Ethmoidal labyrinth

(ethmoidal air cells)

The perpendicular

plate

Part of the nasal

septum

Foramina of the

Ethmoid

Olfactory

foramina

In the cribriform

plate

For olfactory

nerves

If the perpendicular plate of the ethmoid bone

is displaced from its medial position narrowing

the nasal cavity (deviated septum), the result

can be chronic sinus problems

Associate the Latin adjective magnum with

the word magnify to indicate that this foramen

is BIG.

The parietal bones get their name because

they form the wall of the cranium, just as a

parietal membrane covers the wall of a body

cavity.

The squamous portion of a bone refers to the

flattened region, just as squamous epithelium

refers to flattened cells.

Sphenoid means “wedge-shaped.” The

sphenoid bone is “wedged” between the

cranial and facial bones. Trace the outline of

the “bat with wings” that the sphenoid

resembles.

The pituitary gland “rides” protected in its

sella turcica, literally, “Turkish saddle.”

Marks of Temporal Bones

Mandibular fossa: articulates with the mandible

Zygomatic process

Articulates with temporal process of zygomatic bone

Forms zygomatic

arch (cheekbone)

Marks of Temporal Bones

Mastoid process: For muscle attachment Contains mastoid

air cells connected to middle ear

the word mastoid (mastos), referring to a breast-like shape

(recall mastectomy, removal of the breast).

Marks of the Temporal Bones

Styloid (stylo = stake) process

attach tendons and ligaments of the hyoid, tongue, and pharynx

Auditory ossicles

Three tiny bones in tympanic cavity (middle ear)

Transfer sound from tympanic membrane (eardrum) to inner ear

Coronoid comes from the word corona, a

crown. Imagine this process as the point in a

king’s crown. The word coronation is related.

The word mental pertains to the chin. Recall

Rodin’s The Thinker.

Functions of the hyoid

bone

Supports the larynx

Attaches muscles

of the larynx,

pharynx, and

tongue

Articulations of the

hyoid bone

Connects lesser

horns to styloid

processes of

temporal bones

The hyoid bone “hides” behind the mandible.

Not really counted as a skull bone, located in

throat.

The hyoid bone is the only bone in the body

that doesn’t articulate with another bone. The

space between the muscular base of the

tongue and the soft tissue above the thyroid

cartilage (hyoid bone).

The vomer is probably the least famous skull

bone. It means plowshare (from its shape).

the zygomatic process is on the zygomatic

bone. Note the color coded diagram, that

demonstrates that this feature also belongs to

the temporal bone.

The maxilla holds the upper teeth, but it also

composes much of the face, including the

floor of the orbit and the roof of the mouth.

Andre the Giant (Andre Rene Roussimoff), world-renowned

professional wrestler and actor, suffered from pituitary

gigantism and acromegaly. Acromegaly develops in those for

whom hypersecretion of growth hormone continues past

epiphyseal closure. After closure, elongation of endochondral

bones is over, but appositional growth of these bones and

intramembranous bones continues. This leads to deformity of

the face, skull, and mandible; a coarsening of facial features;

and thickening of fingers and toes.

The Infant Skull

The Infant Skull Grows rapidly, Is large compared to the body

It Has many ossification centers

Fusion is not complete at birth

Fontanel (fountain or spring)

Are areas of fibrous connective tissue (soft spots—pulse

can be felt, especially anterior)

Cover unfused sutures in the infant skull

Allows the skull to flex during birth