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ax·i·al
ˈaksēəl/
adjective
1.of, forming, or relating to an axis.
AXIAL SKELETON
The Skeleton
• Consists of:
• Bones, cartilage, joints, and ligaments
• Joints—also called articulations
• Is composed of 206 named bones grouped into two
divisions
• Axial skeleton (80 bones)
• Skull, vertebral column, and thoracic cage
• Appendicular skeleton (126 bones)
• Upper and lower limbs
Figure 7.1a The human skeleton.
Cranium
Cranium
Clavicle
Clavicle
Scapula
Scapula
Skull
Facial bones
Thoracic cage
(ribs and
sternum)
Bones of
pectoral
girdle
Upper
limb
Sternum
Vertebral
column
Rib
Rib
Humerus
Humerus
Vertebra
Vertebra
Radius
Ulna
Radius
Ulna
Bones
of
pelvic
girdle
Sacrum
Carpals
Carpals
Phalanges
Phalanges
Metacarpals
Metacarpals
Femur
Femur
Patella
Lower
limb
Tibia
Tibia
Fibula
Fibula
Tarsals
Metatarsals
Anterior view
Phalanges
Posterior view
The Skull
• Is the body’s most complex bony structure
• Is formed by cranial and facial bones
• Bones of the cranium
• Enclose and protect the brain
• Provide attachment sites for some muscles of the head and neck
The Skull
• Facial bones
•
•
•
•
•
Form framework of the face
Form cavities for sense organs of sight, taste, and smell
Provide openings for passage of air and food
Hold the teeth in place
Anchor muscles of the face
CRANIUM AND FACE
Bones of cranium
Coronal
suture
Squamous
suture
Lambdoid
suture
Facial
bones
Brain sits within
the cranial fossae
Anterior cranial
fossa
Middle cranial
fossa
Posterior cranial
fossa
Superior view of the cranial fossae
Fossa – shallow basinlike
depression in a bone,
often serving as an
articular surface.
The brain, sitting
within the cranial
fossae, occupies
cranial cavity
Temporal lobe
of cerebrum
Frontal lobe
of cerebrum
Cerebellum
Cranial
fossae
Posterior
Middle
Anterior
Lateral view of cranial fossae
showing the contained brain regions
Overview of Skull Geography
• The skull contains smaller CAVITIES:
• Middle and inner ear cavities—in lateral aspect of cranial base
• Nasal cavity—lies in and posterior to the nose
• Orbits—house the eyeballs
• Air-filled sinuses— mucosal-lined air cavities that lead to nasal
cavity.
• The skull contains approximately 85 named OPENINGS:
• These are called: foramina, canals, and fissures
• They provide openings for the:
• Spinal cord
• Blood vessels serving the brain
• 12 pairs of cranial nerves
The Cranium Contains 8 bones:
• Paired bones
include
• Temporal bones
• Parietal bones
• Unpaired bones
include
•
•
•
•
Frontal bone
Occipital bone
Sphenoid bone
Ethmoid bone
Coronal suture
Frontal bone
Parietal bone
Sphenoid bone
(greater wing)
Squamous suture
Ethmoid bone
Lambdoid suture
Lacrimal bone
Lacrimal fossa
Occipital bone
Nasal bone
Temporal bone
Zygomatic bone
Maxilla
Zygomatic process
Occipitomastoid suture
External acoustic meatus
Mastoid process
Alveolar processes
Styloid process
Mandible
Condylar process
Mental foramen
Mandibular notch
Mandibular ramus
Mandibular
angle
External anatomy of the right side of the skull
Coronoid process
The cranium
contains 4
sutures:
Coronal suture
Squamous suture
Sagittal suture
Coronal suture
Frontal bone
Parietal bone
Sphenoid bone
(greater wing)
Squamous suture
Ethmoid bone
Lambdoid suture
Lacrimal bone
Lacrimal fossa
Occipital bone
Nasal bone
Temporal bone
Zygomatic bone
Maxilla
Zygomatic process
Occipitomastoid suture
Lambdoid suture
External acoustic meatus
Mastoid process
Alveolar processes
Styloid process
Mandible
Condylar process
Mental foramen
Mandibular notch
Mandibular ramus
Mandibular
angle
External anatomy of the right side of the skull
Coronoid process
Figure 7.4a Lateral aspect of the skull.
Coronal suture
Frontal bone
Parietal bone
Sphenoid bone
(greater wing)
Squamous suture
Ethmoid bone
Lambdoid suture
Lacrimal bone
Lacrimal fossa
Occipital bone
Nasal bone
Temporal bone
Zygomatic bone
Maxilla
Zygomatic process
Occipitomastoid suture
External acoustic meatus
Mastoid process
Alveolar processes
Styloid process
Mandible
Condylar process
Mental foramen
Mandibular notch
Mandibular ramus
Mandibular
angle
External anatomy of the right side of the skull
Coronoid process
Frontal Bone
• Forms the forehead and
roofs of orbits
• Supraorbital margin—
superior margin of orbits
• Supraorbital foramen—
passage for supraorbital
nerve and artery
Frontal bone
Parietal bone
Glabella
Squamous part
of frontal bone
Frontonasal suture
Supraorbital foramen
(notch)
Nasal bone
Sphenoid bone
(greater wing)
Supraorbital margin
Temporal bone
Optic canal
Ethmoid bone
Inferior orbital fissure
Superior orbital fissure
Lacrimal bone
Zygomatic bone
Middle nasal concha
Perpendicular plate
• Glabella—smooth part of
frontal bone between
superciliary arches (ridges
on the frontal bone above
the eye sockets)
• Frontal sinuses within
frontal bone
Infraorbital foramen
Ethmoid
bone
Inferior nasal concha
Maxilla
Vomer
Mandible
Mental
foramen
Mental
protuberance
Anterior view of skull
Occipital Bone
-- condyle – a round prominence at the end of a bone
• Features and structures
• Foramen magnum
Parietal bone
• Occipital condyles
Sagittal suture
• Hypoglossal foramen
Sutural bone
• Opening for
hypoglossal nerve, one
of 12 cranial nerves
Lambdoid
suture
Occipital bone
• External occipital
protuberance
Superior nuchal line
External occipital
protuberance
• Superior nuchal* lines
Inferior nuchal line
Nuchal - of or relating to the back
External occipital
crest
(nape) of neck. Nuchal lines
are
Occipital
ridges on the back of the occipital
bone
condyle
• Inferior nuchal lines
Occipitomastoid
suture
*nuchal is pronounced “newkal”
Incisive fossa
Maxilla
(palatine process)
Intermaxillary suture
Median palatine suture
Hard
palate Palatine bone
(horizontal plate)
Zygomatic bone
Infraorbital foramen
Maxilla
FORAMEN MAGNUM
Sphenoid bone
(greater wing)
Vomer
Pterygoid process
Temporal bone
(zygomatic process)
Foramen ovale
Foramen spinosum
Foramen lacerum
Mandibular fossa
Styloid process
Mastoid process
Temporal bone
(petrous part)
Basilar part of
the occipital bone
Occipital bone
Carotid canal
External acoustic meatus
Stylomastoid
foramen
Jugular foramen
Occipital condyle
Inferior nuchal line
Superior nuchal line
External occipital crest
External occipital
protuberance
Inferior view of the skull (mandible removed)
Foramen magnum
The temporal bone:
External
acoustic
meatus
Squamous
part
Zygomatic
process
Petrous
part
Mastoid process
Styloid
process
Mandibular
fossa
Tympanic
part
Petrous - the hard dense portion of the temporal bone,
containing the internal auditory organs; petrosal.
Temporal Bone
Frontal bone
Coronal suture
Sphenoid bone
(greater wing)
Parietal bone
Ethmoid bone
Squamous suture
Lacrimal bone
Temporal bone
Nasal bone
Zygomatic process
Lambdoid suture
Lacrimal fossa
Occipital bone
Zygomatic bone
Occipitomastoid
suture
External acoustic
meatus
Mastoid process
Coronoid process
Maxilla
Alveolar
processes
Styloid process
Mandible
Condylar process
Mental foramen
Mandibular notch
Mandibular angle
Mandibular ramus
The mastoid process
Site for neck muscle attachment
Contains air sinuses
The Sphenoid Bone
called the “keystone of the cranium” because it articulates with all the cranial bones.
• Spans the width of the cranial floor
• Resembles a bat with its wings spread
• Consists of a body and three pairs of processes
• Contains five important openings (SEE NEXT)
The Sphenoid Bone
• Important
landmarks
Optic
canal
Lesser wing
• Body
• Sella turcica
• Sphenoidal
sinuses
• Greater wings
• Lesser wings
• Pterygoid
processes
Foramen
rotundum
Greater
wing
Foramen ovale
Sella
turcica
Body of sphenoid
Foramen
spinosum
Superior view
Body of sphenoid
Lesser
wing
Superior
orbital
fissure
Greater
wing
Pterygoid
process
Posterior view
The Ethmoid Bone – irregular-shaped bone anterior to the sphenoid bone
• Lies between nasal and sphenoid bones
• Forms most of the medial bony region between the nasal cavity and orbits
The Ethmoid Bone
• Cribriform plate
• Where olfactory fibers pass from
nasal cavity to brain through
cribriform foramina
• Crista galli
• Attachment for dura mater
• Perpendicular plate
• Forms superior part of nasal
septum
Anterior view
Facial Bones
• Unpaired bones
• Mandible and
vomer
• Paired bones
•
•
•
•
•
•
Maxillae
Zygomatic bones
Nasal bones
Lacrimal bones
Palatine bones
Inferior nasal
conchae
Frontal bone
Parietal bone
Glabella
Squamous part
of frontal bone
Frontonasal suture
Supraorbital foramen
(notch)
Nasal bone
Sphenoid bone
(greater wing)
Supraorbital margin
Temporal bone
Optic canal
Ethmoid bone
Inferior orbital fissure
Superior orbital fissure
Lacrimal bone
Zygomatic bone
Middle nasal concha
Perpendicular plate
Infraorbital foramen
Ethmoid
bone
Inferior nasal concha
Maxilla
Vomer
Mandible
Mental
foramen
Mental
protuberance
Anterior view of skull
Mandible: Lower jaw bone, the largest and strongest facial bone
• the only movable bone
of the skull
• Composed of two main
parts
• Horizontal body
• Two upright rami
[rami –
an arm or branch of a bone]
• Major landmarks
are shown in the figure:
Temporomandibular
joint
Mandibular fossa
of temporal bone
Mandibular notch
Condylar
process
Coronoid process – site
of muscle attachment
mandibular foramen
(permits passage of
Coronoid the nerve involved
process in tooth sensation,
cranial nerve V
Mandibular foramen
Alveolar process
Ramus
of
mandible
Mental foramen
Mandibular
angle
Body of mandible
Mandible, right lateral view
Alveolar process: the thickened
Ridge of bone that contains the tooth sockets
Mental
foramen
transmits
nerve to
lower jaw
Maxillary Bones
• Articulate with all other facial
bones except the mandible
• Forms part of the inferior
orbital fissure
• Are the “keystone” bones of
the face
Maxilla, right lateral view
Articulates with
frontal bone
Frontal process
Orbital
surface
Zygomatic
process
(cut)
Infraorbital
foramen
Anterior nasal
spine
Alveolar
process
Other Bones of the Face (Identify these during lab)
• Zygomatic bones
• Vomer
• Forms the inferior part of
the nasal septum
• Form lateral wall of orbits
• Nasal bones
• Form bridge of nose
• Inferior nasal conchae
• Lacrimal bones
• Located in the medial orbital walls
• Palatine bones
• Complete the posterior part of the hard palate
• Thin, curved bones that
project medially form the
lateral walls of the nasal
cavity
Paranasal Sinuses
• Air-filled sinuses are
located within:
•
•
•
•
Frontal
sinus
Ethmoidal
air cells
(sinus)
Frontal bone
Ethmoid bone
Sphenoid bone
Maxillary bones
Sphenoidal
sinus
Maxillary
sinus
• Lined with mucous
membrane
• Lighten the skull
Anterior aspect
The Hyoid Bone
• Lies inferior to the mandible
• The only bone with no direct
articulation with any other bone
• Acts as a movable base for the
tongue
Greater horn
Lesser horn
Body
The Vertebral
Column
• Surrounds and protects the spinal
cord
• Serves as attachment sites for
muscles of the neck and back
C1
2
3
4
Cervical curvature (concave)
7 vertebrae, C1  C7
5
6
7
T1
2
3
4
Spinous
process
Transverse
processes
5
6
7
Thoracic curvature
(convex)
12 vertebrae,
T1  T12
Regions
8
• The vertebral column has five major
regions
•
•
•
•
7 cervical vertebrae of the neck region
12 thoracic vertebrae
5 lumbar vertebrae
Sacrum—five fused bones
9
Intervertebral
discs
10
11
Intervertebral
foramen
12
L1
2
3
Lumbar curvature
(concave)
5 vertebrae, L1  L5
4
5
Sacral curvature
(convex)
5 fused vertebrae
sacrum
• Inferior to lumbar vertebrae
• Coccyx—inferior to sacrum
Coccyx
4 fused vertebrae
Anterior view
Right lateral view
Normal Curvatures
• Curvatures of the spineincrease resilience of
spine
• Cervical and lumbar
curvatures (secondary
curvature)
• Concave posteriorly
• Thoracic and sacral
curvatures (primary
curvature)
• Convex posteriority
Major supporting ligaments:
• Anterior longitudinal ligament
• Attaches to bony vertebrae and
intervertebral discs
• Intervertebral diskscushions found in between
vertebrae
• Prevents hyperextension
• Posterior longitudinal ligament
• Narrow and relatively weak
• Attaches to intervertebral discs
Ligaments of the Spine
Posterior longitudinal
ligament
Anterior longitudinal
ligament
Body of a vertebra
Intervertebral disc
Anterior view of part of the spinal column
Structure of a typical vertebra.
Common structures to all vertebrae:
Posterior
Lamina
• Body
• Vertebral arch
• Vertebral foramen
• Spinous process
• Transverse process
• Superior and inferior articular
processes
• Intervertebral foramina
Spinous
process
Transverse
process
Superior
articular
process
and
facet
Vertebral
arch
Vertebral
foramen
Pedicle
Body
Pedicle – a small, stalk-like structure
Anterior
Facet = surface
LOCATION OF Atlas and Axis
Dens of axis
Transverse ligament
of atlas
C1 (atlas)
C2 (axis)
C3
Inferior articular process
Bifid spinous process
Transverse processes
C7 (vertebra prominens)
Cervical vertebrae
The Atlas
• C1 is the atlas
• C1 lacks a body and
spinous process
• Allows flexion and
extension of neck
Posterior
C1
Posterior tubercle
Posterior arch
Transverse
foramen
Lateral
masses
• Nodding the head “yes”
Superior articular
facet
Anterior arch
Anterior tubercle
Superior view of atlas (C1)
Figure 7.22c The first and second cervical vertebrae.
The Axis
• Has a body and spinous
process
• Dens (odontoid process)
projects superiorly
• Is formed from fusion of the
body of the atlas with the
axis
• Acts as a pivot for rotation
of the atlas and skull
• Participates in rotating the
head from side to side
C2
Posterior
Spinous process
Inferior
articular
process
Lamina
Pedicle
Superior
articular
facet
Transverse
process
Dens
Body
Superior view of axis (C2)
Thoracic Vertebrae
CHARACTERISTICS
• Spinous processes are long
and point inferiorly
• Vertebral foramen are
circular
• Transverse processes
articulate with tubercles of
ribs
• Superior articular facets
point posteriorly
• Inferior articular processes
point anteriorly
• Allows rotation and prevents
flexion and extension
Lateral
Superior
Lumbar Vertebrae (L1–L5)
• Bodies are thick and robust
• Transverse processes are thin
and tapered
• Spinous processes are thick and
blunt and point posteriorly
• Vertebral foramina are
triangular
• Superior and inferior articular
facets point medially
• Allows flexion and extension—
rotation prevented
Sacrum (S1–S5)
• Formed from 5 fused
vertebrae
• Superior surface
articulates with L5
• Inferiorly articulates
with coccyx
Sacral promontory
Ala
Body of
first
sacral
vertebra
Body
Facet of superior
articular process
Auricular
surface
Median
sacral
crest
Transverse ridges
(sites of vertebral
fusion)
Anterior
sacral
foramina
Apex
• Sacral promontory
• Where the first sacral
vertebrae bulges
into pelvic cavity
Sacral
canal
Coccyx
Anterior view
Lateral
sacral
crest
Posterior
sacral
foramina
Coccyx
Posterior view
The coccyx is the tail bone
The coccyx is Formed from 3–5 fused vertebrae
Sacral
hiatus
The Thoracic Cage (Rib
Cage)
Jugular notch
Clavicular notch
• Components
• Thoracic vertebrae—
posteriorly
• Ribs—laterally
• Sternum and costal cartilage—
anteriorly
• Protects thoracic organs
• Supports shoulder girdle and
upper limbs
• Provides attachment sites for
many muscles of the back
Manubrium
Sternal angle
Body
Xiphisternal
joint
True
ribs
(17)
Xiphoid
process
False
ribs
(812)
Intercostal
spaces
Costal
cartilage
Floating
ribs (11, 12)
L1
Vertebra
Skeleton of the thoracic cage, anterior view
Costal
margin
Sternum
Superior view of the articulation between a rib and a
thoracic vertebra
Articular facet
on tubercle of rib
Spinous process
Shaft
Ligaments
Transverse
costal facet
(for tubercle
of rib)
Neck of rib
Head of rib
Superior costal facet
(for head of rib)
Body of
thoracic
vertebra
Sternum
• Formed from three sections
• Manubrium—superior
section
• Clavicular notches
articulate with medial
end of clavicles
• Body—bulk of sternum
• Sides are notched at
articulations for costal
cartilage of ribs 2–7
• Xiphoid process—inferior
end of sternum
• Ossifies around age 40
Other characteristics:
• Jugular notch
• Central indentation
at superior border
of the manubrium
• Sternal angle
• A horizontal ridge
where the
manubrium joins
the body
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