The Axial Skeleton

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The Axial Skeleton
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Axial Skeleton

• the skull is actually several bones that come
  together as an embryo develops
• the cranial bones protect the brain, ears and
  eyes
• some cranial bones provide attachment points for
  muscle ? movement of head, jaw, and neck

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Axial Skeleton

• the cranial bones are divided into the calvaria
  and the cranial base
• calvaria frontal, occipital, parietal,
  temporal
• cranial base ethmoid, sphenoid
• the rest of the skull is made of 14 facial bones

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Axial Skeleton

• several of the bones of the skull contain sinuses
  cavities lined with ciliated epithelial cells
  that secrete mucous

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Axial Skeleton

• the left and right frontal sinuses are posterior
  to the frontal bone
• not present at birth
• begin development from age 2 to 5
• fully develop in the late teens
• function lighten skull, warm air

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Axial Skeleton

• the frontal bone
• forms the forehead and eyebrow ridges
• flat vertical forehead
• lower concave orbits (

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Axial Skeleton

• comparative anatomy note
• males have a thicker orbital ridge than females
• the eyebrows of a male sit lower on the orbital
  ridge

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Axial Skeleton

• the temporal bone
• complex shape
• distinct features
• noteworthy features of the temporal bones
• mastoid process
• styloid process
• tympanic region
• zygomatic process

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Axial Skeleton

• mastoid process
• attachment of neck muscles
• complex of cavities mastoid sinuses
• mastoid sinuses connected to inner ear
• vulnerable to bacterial infection that affects
  ears and throat
• adjust inne ear to pressure changes

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Axial Skeleton

• styloid process
• varies in length from individual to individual
• important attachment point for muscles and
  tendons of the neck and throat

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Axial Skeleton

• tympanic region
• houses the internal components of the ears
  includes the 3 small bones of the
• malleus (
• incus (
• stapes (
• these bones develop from the facial bones in an
  embryo

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Axial Skeleton

• zygomatic process
• forms the zygomatic arch with the zygomatic bone
  (facial)
• forms the cheek
• attachment for muscles used in chewing

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Axial Skeleton

• The parietal bone
• forms the top, side, and posterior portion of the
  cranium
• protects the posterior portion of the brain

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Axial Skeleton

• The occipital bone
• forms the posterior base of the cranial vault
• series of bones fused together in an embryo
• an opening is left foramen magnum or occipital
  foramen

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Axial Skeleton

• The occipital bone
• the spinal cord enters through the occipital
  foramen
• occipital condyles provide attachment of the head
  to the vertebral column, allow head movement

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Axial Skeleton

• The sphenoid bone
• in contact with almost all other skull bones
• helps form facial features
• contains sphenoidal sinuses
• connected to, and help form nasal cavities
• major blood vessels and nerves of the eyes and
  face pass through the sphenoid
• forma a structure, sella turica, which protects
  the pituitary gland

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Axial Skeleton

• The ethmoid bone
• passageway for the nerves that detect smell
• contains the ethmoid labyrinth
• cleans and moistens air that enters the nose

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Axial Skeleton

• Most of a persons facial features are determined
  by the
• mandible
• maxillary bones
• zygomatic bones

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Axial Skeleton

• zygomatic bones
• zygomatic arch
• maxillary bones
• upper jaw
• larger facial bones
• form area around nose (lateral surfaces)
• area under eyes (medial border of orbits)

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Axial Skeleton

• maxillary bones
• passageway for major blood vessels and nerves
  inferior orbital foramen
• teeth develop on the lower surface

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Axial Skeleton

• palatine bones
• between the maxillary and sphenoid bones
• help form the
• 1) the walls of the nasal cavity
• 2) the roof of the mouth
• 3) the bottom of the orbits
• this bone pair grows in height as facial features
  mature birth ? adolescence

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Axial Skeleton

• mandible
• largest facial bone
• body of the mandible contains teeth
• condyle of the mandible articulates with the
  temporal bones
• contains passageways for blood vessels and nerves
  to the the chin and lower lip mental foramen

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Axial Skeleton

• mandible
• only skull bone not fused to other bones of the
  skull (ear bones, hyoid)
• hyoid bone
• horshoe-shaped bone
• suspended below mandible by muscles
• anchors muscles of the neck
• attaches to muscles of the tongue

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Axial Skeleton

• teeth
• bones that grow out of an alveolus in the
  mandible or maxilla
• has a crown projects above the gum
• has a root embedded in the alveolus
• a hard enamel covers the crown

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Axial Skeleton

• The remainder of the facial bones are tiny bones
• nasal, lacrimal, vomer

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Axial Skeleton
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Axial Skeleton

• The vertebral column and ribs

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Axial Skeleton

• vertebral column

region association/articulation
cervical 7 neck
thoracic 12 rib cage
lumbar 5 lower back
sacral 5 hip bones
coccygeal 3 - 5 tail end
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Axial Skeleton

• most vertebrae have a
• vertebral body
• vertebral arch
• vertebral foramen

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Axial Skeleton

• vertebral body
• supports weight of body

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Axial Skeleton

• vertebral arch
• dorsal to the body
• has several features
• pedicles (2)
• articular processes (4)
• transverse processes (2) lateral
• spinous process
• processes provide muscle attachment movement of
  appendages, head, neck, vertebral column

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Axial Skeleton

• vertebral foramen
• passageway for spinal cord

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Axial Skeleton

• cervical
• smaller body
• small transverse processes
• short, bifurcated spinous process
• unique feature
• 2 transverse foramina for major blood vessels to
  the skull
• cervical 1 2 atlas and axis

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Axial Skeleton

• atlas
• supports the skull
• lacks a body
• large articular surfaces attach to the occipital
  bone
• axis
• large protrusion dens (odontoid process) ?
  rotation and free movement of the atlas and skull

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Axial Skeleton

• thoracic
• larger body
• long, narrow spinous process
• unique features
• each transverse process (2) has a facet for
  articulation with a rib
• another facet is located on the dorsal portion
  of the body
• ? articulation that allows the ribs to flex
  during breathing

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Axial Skeleton

• lumbar
• largest
• thickest
• support most of the bodys weight
• anchor the back muscles balance while moving,
  sitting, or standing
• short stubby spinous process ? bend backward

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Axial Skeleton

• sacral
• form the sacrum
• have large, lateral articular surfaces fuse
  with hip bone
• in females
• sacrum is
• shorter
• wider
• less curved

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Axial Skeleton

• In most individuals the vertebral arch is not
  present on the last 2 vertebra sacral canal
• The spinal cavity is exposed in the sacral canal
• The spinal cord ends in the lumbar region
• Result
• opportunity to collect spinal fluid with minimal
  risk of nerve damage

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Axial Skeleton

• coccygeal
• coccyx (tailbone)
• no foramen
• muscle attachment of upper leg muscles

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Axial Skeleton

• The rib cage consists of
• costal cartilage
• ribs
• sternum
• serves as a protective structure
• assists in breathing

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Axial Skeleton

• normally 12 ribs, but . . .
• some individuals develop small cervicacl and
  lumbar ribs
• Why?
• Scientists have discovered that each vertebra
  has the genetical potential to become a rib

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Axial Skeleton

• 7 upper ribs true ribs
• attach directly to the sternum by costal
  cartilage
• ribs 8, 9, 10 false ribs
• attached by costal cartilage to the rib above
• last 2 ribs floating ribs
• not attached ventrally

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Axial Skeleton

• The sternum serves as
• an articulation with the clavicles
• an articulatioin with ribs 1 7
• an attachment for the chest and shoulder muscles
• an attachment for the stomach muscles

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Axial Skeleton