
Formed by two sets of bones.
◦ Cranium: encloses and protects the fragile brain
tissue
◦ Facial bones: hold the eyes in an anterior position
and allow the facial muscles to show our feelings


Sutures are interlocking, immovable joints.
All but the mandible (jawbone) are joined
together by sutures.


Cranial “cavity” – houses brain
Smaller cavities
◦
◦
◦
◦

Housing middle and inner ear
Nasal cavity
Orbits
Sinuses
Openings (foramina, canals, fissures) for:
◦ Spinal cord
◦ Blood vessels
◦ Twelve cranial nerves: I-XII




Composed of eight large, flat bones
Except for two paired bones ( the parietal and
temporal), they are all single bones
1. Frontal bone – forms the forehead, the
bony projections under the eyebrows, and the
superior part of each eye’s orbit
2 &3. Parietal bones – paired bones that form
the superior and lateral walls of the cranium,
meeting at the midline of the skull

4 & 5. Temporal bones – lie inferior to parietal
bones and have several important bone markings
◦ External acoustic meatus – canal that leads to the
eardrum
◦ Styloid process- attachment point for neck muscles
◦ Zygomatic process- thin bridge of bone that joins with
the cheekbone (zygomatic bone)
◦ Mastoid process – behind ear, contains mastoid sinuses
and point of attachment for neck muscles
◦ Jugular foramen, Internal acoustic meatus, and carotid
canal – passageways for blood vessels and nerves

6. Occipital bone – most posterior bone of
the cranium, forms the floor and back wall of
the skull
◦ In the base of there is a large hole, foramen
magnum, that surrounds the lower part of the brain
and allows the spinal cord to connect with the brain

7. Sphenoid bone – butterfly- shaped bone
that spans the width of the skull and forms
part of the floor of the cranial cavity.
◦ Contains Turk’s saddle, which holds the pituitary
gland in place
◦ Contains foramen ovale so the cranial nerves can
pass through

8. Ethmoid bone- irregular and lies anterior
to the sphenoid, forms the roof of the nasal
cavity and part of the medial walls of the
orbits.
Facial bones (anterior aspect of skull)
◦
◦
◦
◦
◦
Form framework of face
Form cavities for sense organs of sight, taste and
smell
Provides openings for passage of air and food
Hold the teeth
Anchor the muscles of the face


Fourteen bones
Following are all paired:
◦ Maxillae, zygomatics, palatines, nasals, lacrimals,
and inferior nasal conchae

Unpaired:
◦ Vomer and mandible

Hyoid: not really a skull bone, supported in
the neck only by ligaments



Only bone which does
not articulate with any
other bone
Moveable base for the
tongue
Points of attachment
for neck muscles that
raise and lower the
larynx during
swallowing





Maxillae : upper jaw
Palatine: posterior part of hard palate
Zygomatic: Cheekbones, form part of lateral
orbital walls
Lacrimal: medial walls of orbits, groove
serves as tear passage
Nasal bones: nose bridge
(part of slide 18)
nasal bone



Of bone and cartilage
Roof is ethmoid
Floor formed by
palatine processes of
the 2 maxillae and
horizontal plates of
palatine bones
◦ These nasal-floor
structures form roof of
the mouth, called the
hard palate
ethmoid
inf nasal concha
maxilla___________
vomer



Vomer bone: forms nasal septum
Inferior conchae: lateral walls of the nasal
cavity
Mandible: lower jaw
Remember that the
Axial skeleton
includes:
Skull
Vertebral column
Thoracic cage
Axial skeleton is shown in green


Fetus and infant: 33 separate
bones, or vertebrae
Adult: 24 vertebrae
◦ Inferior 9 have fused forming
 The sacrum (5) and
 The coccyx (4)





Cervical – 7
Thoracic - 12
Lumbar - 5
Sacrum (5 fused)
Coccyx (4 fused)



Cervical and lumbar are
concave posteriorly*
(lordosis)
Thoracic and sacral are
convex posteriorly* (kyphosis)
Abnormal
◦ Too much of either
◦ Scoliosis (more than 10 degrees
of lateral curvature)
*when viewed from the side
C1 (atlas)
C2 (axis)
Cervical Vertebrae






Smallest
Lightest
Most flexible
Triangular
vertebral foramen
Transverse
processes have
foramina
(transverse
foramen)
Spinous process
bifid (forked)
except for C7
Thoracic Vertebrae T1-T12




Heart shaped
body
Additional
small costal
facets
(costal=ribs)
Round or oval
vertebral
foramen
Form posterior
part of rib cage
Lumbar Vertebrae L1-L5



Massive
blocklike bodies
Short, thick
hatchet-shaped
spinous
processes
Limited mobility
Shapes posterior wall of pelvis
Composite bone of 5 fused vertebrae
Sacral foramina allow passage of vessels & nerves
Coccyx
(the tailbone)
Remember that the
Axial skeleton
includes:
Skull
Vertebral column
Thoracic cage
Axial skeleton is shown in green

Manubrium

True ribs 1-7

Body

False ribs 8-12

Xiphoid process

Floating ribs 11,12



Skulls of newborns contain fontanels
(membranous areas), which allow brain
growth.
The infant’s facial bones are very small
compared to the size of the cranium
Fetal skull ossifies after 22-24 months





Unossified remnants
of membranes
Present at birth
Anterior fontanel
largest
Called “soft spots”
Ossify by 1 ½ - 2
years
Continue to ossify into
adulthood; the sutures can
become fused in old age