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Chapter 7:
The Axial Skeleton
part 1
The Axial Skeleton - longitudinal axis
• Supports and protects organs
in body cavities
• Attaches to muscles of:
– head, neck, and trunk
– respiration
– appendicular skeleton
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
The Skull
• The skull protects:
– the brain
– entrances to
respiratory and
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
Cranial Bones
1. The Frontal Bone
– Forms the anterior cranium and upper eyesockets
– Contains frontal sinuses
Figure 7–6
The Frontal Bone-con’t
• Marks
– Frontal
squama/glabella
(forehead)
– Supraorbital margin
(protects eye)
– Lacrimal fossa (for tear
ducts)
2-3. The Parietal Bones
– forms part of the superior and
lateral surfaces of the cranium
4-5. The Temporal Bones
– Part of lateral walls
of cranium and
zygomatic arches
– Surround and
protect inner ear
– Attach muscles of
jaws and head
Figure 7–7
• Marks
– Mandibular fossaarticulates with the
mandible
– Zygomatic process:
• inferior to the
squamous portion
• articulates with
temporal process of
zygomatic bone
• forms zygomatic arch
(cheekbone)
– 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
– Auditory ossicles:
• 3 tiny bones in tympanic
cavity (middle ear)
• transfer sound from
tympanic membrane to
inner ear
• Foramina
– Carotid canal:
• for internal carotid artery
– Foramen lacerum:
• for carotid and small arteries
• hyaline cartilage
• auditory tube
Cranial Bones - 8
6. The Occipital Bone
• Forms posterior/inferior surfaces of
cranium
• Largest cranial bone
• Marks
– Occipital condyles -articulate with neck
– Inferior and superior nuchal lines -to attach ligaments
– External occipital protuberance(Inion)for trapezius attachment
– External occipital crest -to attach ligaments
• Foramina
– Foramen magnum-connects cranial and spinal cavities
7. The Sphenoid
– Part of the floor of the cranium
– Unites cranial and facial bones
– Strengthens sides of the skull
– Contains sphenoidal sinuses
Figure 7–8
• 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 sella
turcica
• holds the pituitary gland
– Sphenoidal sinuses:
• either side of the body
• inferior to the sella turcica
7. The Ethmoid
–
–
–
–
Forms anteromedial floor of the cranium
Roof of the nasal cavity
Part of the nasal septum and medial orbital wall
Contains ethmoidal (sinuses)
Figure 7–9
• Foramina
– Optic canals:
• for optic nerves
– Superior orbital fissure:
• For blood vessels and nerves
of the orbit
– Foramen rotundum:
• for blood vessels and nerves
of the face
– Foramen ovale:
• for blood vessels and nerves
of the face
– Foramen spinosum:
• for blood vessels and nerves
of the jaws
Ethmoid
Cribiform plate
– roof of the nasal cavity
– -contains crista galli
Perpendicular plate is part of the nasal septum
Olfactory
foramina in
the cribriform
plate for
olfactory
nerves
The 4 Major Sutures
1.
2.
3.
4.
Lambdoid sutureseparates occipital from
parietal bones
Coronal suture-attaches
frontal bone to parietal
bones
Sagittal suture-between
the parietal bones
lambdoid suture to
coronal suture
Squamous suture-form
boundaries between
temporal bones and
parietal bones
(immovable joints of the skull)
The Infant Skull
• 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
Figure 7–15
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
The Facial Bones
• Superficial facial bones
for muscle
attachment
– Maxillary
–
–
–
–
Lacrimal
Nasal
Zygomatic
Mandible
• Deep facial bones
separate the oral and
nasal cavities & form the
nasal septum
– Palatine bones
– Inferior nasal conchae
– Vomer
Facial Bones - 14
• Maxillary (2) • 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)
-failure to fuse results in cleft palate
Figure 7–10a
• Marks
– Anterior nasal spineattaches cartilaginous
anterior nasal septum
– Alveolar processes-borders
the mouth, supports upper
teeth
-Maxillary sinuses-to lighten
bone
-Infraorbital foramen:
for sensory nerve to brain (via
foramen rotundum of sphenoid)
The Palatine Bones (2)
• Functions
– Form the posterior portion
of the hard palate
– Contribute to the floors of
the orbits
Figure 7–10b,c
Nasal Bones- 2
-Support the bridge of the nose
– Connect to cartilages of the distal part of the nose
(external nares)
Vomer (1)
– Forms the inferior portion of the bony nasal
septum
Inferior Nasal Conchae (2)
-create air turbulence in the nasal cavity,
increase the epithelial surface area, warm and
humidify inhaled air
Zygomatic Bones (2)
– Contribute to the rim and lateral wall of the orbit
– Form part of the zygomatic arch
•Marks
Temporal process
Lacrimal Bones (2) (smallest facial bones)
– Form part of the medial wall of the orbit
Lacrimal sulcus:
• location of the lacrimal sac
• milk eye squirt - YouTube
The Mandible (1)
– Forms the lower jaw
• Articulations
– Mandibular fossae of the
temporal bones
•
– Body of the mandible - horizontal
portion
– Alveolar processes - support the lower
teeth
– Ramus - ascending from the mandibular
angle on either side
Figure 7–12a,b
• Foramina
– Mental foramen-for sensory nerves of lips
and chin
– Mandibular foramen-for blood vessels and
nerves of lower teeth
The Hyoid Bone (assoc w/facial bones)
• Functions
– Supports the larynx
– Attaches muscles of the
larynx, pharynx, and tongue
• Articulations
– Connects lesser horns to
styloid processes of
temporal bones