7
The Skeleton: Part A
The Axial Skeleton
• Consists of 80 bones
• Three major regions
– Skull
– Vertebral column
– Thoracic cage
Skull
Thoracic cage
(ribs and
sternum)
Vertebral
column
Sacrum
Cranium
Facial bones
Clavicle
Scapula
Sternum
Rib
Humerus
Vertebra
Radius
Ulna
Carpals
Phalanges
Metacarpals
Femur
Patella
Tibia
Fibula
(a) Anterior view
Tarsals
Metatarsals
Phalanges
Figure 7.1a
•
•
•
•
•
•
•
The
Skull
Contains 22 cranial
and
facial bones
Forms the framework of the face
Contain cavities for special sense organs
Provide openings for air and food passage
Secures the teeth
Anchor muscles of facial expression
Most skull bones are flat bones joined by
interlocking joints called sutures (exception:
mandible: movable joint)
The Skull
• Anterior aspect: facial bones
• Remainder: cranium
• Skull cavities:
– Cranial cavity- houses the brain
– Ear cavities
– Nasal cavity
– Orbits- house the eyeballs
• 85 named openings providing passageways for
the spinal cord, major blood vessels, and the
cranial nerves.
•
The
Skull
Two sets of bones
1. Cranial bones
•
•
Eight strong, superiorly curved bones
Enclose the brain in the cranial cavity
–
–
•
Cranial vault (calvaria)
Cranial base: anterior, middle, and posterior cranial fossae
Provide sites of attachment for head and neck muscles
2. Facial bones
•
•
•
•
The Skull
Framework of face
Cavities for special sense organs for sight, taste, and
smell
Openings for air and food passage
Sties of attachment for teeth and muscles of facial
expression
Bones of cranium (cranial vault)
Coronal
suture
Squamous
suture
Lambdoid
suture
Facial
bones
(a) Cranial and facial divisions of the skull
Figure 7.2a
Anterior cranial
fossa
Middle cranial
fossa
Posterior cranial
fossa
(b) Superior view of the cranial fossae
Figure 7.2b
Cranial Bones
•
•
•
•
•
•
Frontal bone
Parietal bones (2)
Occipital bone
Temporal bones (2)
Sphenoid bone
Ethmoid bone
Frontal Bone
• Articulates posteriorly with the parietal bones
via the coronal suture
• Anterior portion of cranium (cranial fossa)
• Most of anterior cranial fossa
• Superior wall of orbits (supraorbital margins)
• Contains air-filled frontal sinus
Frontal bone
Glabella
Frontonasal suture
Supraorbital foramen
(notch)
Supraorbital margin
Superior orbital
fissure
Optic canal
Inferior orbital
fissure
Middle nasal
concha
Ethmoid
Perpendicular bone
plate
Inferior nasal concha
Vomer
Parietal bone
Squamous part
of frontal bone
Nasal bone
Sphenoid bone
(greater wing)
Temporal bone
Ethmoid bone
Lacrimal bone
Zygomatic bone
Infraorbital foramen
Maxilla
Mandible
Mental
foramen
(a) Anterior view
Mandibular symphysis
Figure 7.4a
Parietal Bones and Major
Associated Sutures
•
•
2 large, rectangular bones on superior and lateral
aspects of cranial vault (majority of cranial vault)
Four largest sutures mark the articulations of parietal
bones with frontal, occipital, and temporal bones:
1. Coronal suture—between parietal bones and frontal bone
2. Sagittal suture—between right and left parietal bones
3. Lambdoid suture—between parietal bones and occipital
bone
4. Squamous (squamosal) sutures—between parietal and
temporal bones on each side of skull
Frontal bone
Sphenoid bone
(greater wing)
Coronal suture
Parietal bone
Ethmoid bone
Temporal bone
Lacrimal bone
Lacrimal fossa
Lambdoid
suture
Squamous
suture
Occipital
bone
Zygomatic
process
Occipitomastoid
suture
External acoustic
meatus
Mastoid process
Styloid process
Nasal bone
Zygomatic
bone
Maxilla
Alveolar
margins
Mandible
Mental foramen
Mandibular condyle
Mandibular notch
Mandibular ramus
Mandibular angle
Coronoid process
(a) External anatomy of the right side of the skull
Figure 7.5a
Occipital
Bone
• Most of skull’s
posterior wall
and posterior
cranial fossa (base of skull)
• Articulates with 1st vertebra, parietal,
temporal, & sphenoid bones
• Sites of attachment for the ligamentum
nuchae and many neck and back muscles
• Foramen magnum- large opening connects
brain to the spinal cord (in the base of the
occipital bone)
Sagittal suture
Parietal
bone
Sutural
bone
Lambdoid
suture
Occipital bone
Superior nuchal line
External
occipital
protuberance
Occipitomastoid
suture
(b) Posterior view
External
occipital
crest
Occipital
condyle
Mastoid
process
Inferior
nuchal
line
Figure 7.4b
Maxilla
(palatine process)
Hard
Palatine bone
palate
(horizontal plate)
Zygomatic bone
Temporal bone
(zygomatic process)
Vomer
Mandibular
fossa
Styloid process
Mastoid process
Temporal bone
(petrous part)
Pharyngeal tubercle
of basilar region of
the occipital bone
Parietal bone
External occipital crest
External occipital
protuberance
(a) Inferior view of the skull (mandible removed)
Incisive fossa
Intermaxillary suture
Median palatine suture
Infraorbital foramen
Maxilla
Sphenoid bone
(greater wing)
Foramen ovale
Foramen spinosum
Foramen lacerum
Carotid canal
External acoustic meatus
Stylomastoid
foramen
Jugular foramen
Occipital condyle
Inferior nuchal line
Superior nuchal line
Foramen magnum
Figure 7.6a
Temporal Bones
• Articulate with the parietal bones
• Inferolateral aspects of skull and parts of cranial floor
• Mandibular fossa: forms part of the temporomandibular
joint
• external auditory meatus & petrous: house the ear
• Four major regions
–
–
–
–
Squamous
Tympanic
Mastoid
Petrous
External
acoustic
meatus
Mastoid
region
Squamous
region
Zygomatic process
Mastoid
process
Mandibular fossa
Tympanic region
Styloid process
Figure 7.8
Maxilla
(palatine process)
Hard
Palatine bone
palate
(horizontal plate)
Zygomatic bone
Temporal bone
(zygomatic process)
Vomer
Mandibular
fossa
Styloid process
Mastoid process
Temporal bone
(petrous part)
Pharyngeal tubercle
of basilar region of
the occipital bone
Parietal bone
External occipital crest
External occipital
protuberance
(a) Inferior view of the skull (mandible removed)
Incisive fossa
Intermaxillary suture
Median palatine suture
Infraorbital foramen
Maxilla
Sphenoid bone
(greater wing)
Foramen ovale
Foramen spinosum
Foramen lacerum
Carotid canal
External acoustic meatus
Stylomastoid
foramen
Jugular foramen
Occipital condyle
Inferior nuchal line
Superior nuchal line
Foramen magnum
Figure 7.6a
Ethmoid
bone
Cribriform plate
Crista galli
Frontal bone
Olfactory foramina
Anterior cranial fossa
Optic canal
Sphenoid Lesser wing
Greater wing
Hypophyseal fossa
of sella turcica
Middle cranial
fossa
Temporal bone
(petrous part)
Foramen rotundum
Foramen ovale
Foramen spinosum
Foramen lacerum
Internal acoustic
meatus
Jugular foramen
Hypoglossal canal
Posterior
cranial fossa
Foramen magnum
View
Parietal bone
Occipital bone
(a) Superior view of the skull, calvaria removed
Figure 7.7a
Sphenoid
Bone
Spans the width of the middle cranial fossa
•
• Complex, bat-shaped bone
• Keystone bone
– Articulates with all other cranial bones
• Three pairs of processes
– Greater wings
– Lesser wings
– Pterygoid processes
Optic canal
Greater
wing
Hypophyseal
fossa of
sella turcica
Body of sphenoid
Lesser wing
Superior
orbital fissure
Foramen
rotundum
Foramen
ovale
Foramen
spinosum
(a) Superior view
Figure 7.9a
Body of sphenoid
Greater
wing
Lesser
wing
Superior
orbital
fissure
Pterygoid
process
(b) Posterior view
Figure 7.9b
Ethmoid Bone
• Lies between the sphenoid and nasal bones
• forms most of the bony area between the
nasal cavity and the orbits.
• Deepest skull bone
• Superior part of nasal septum, roof of nasal
cavities
• Contributes to medial wall of orbits
Olfactory
foramina
Orbital
plate
Crista galli
Cribriform
plate
Left lateral mass
Ethmoidal
air cells
Perpendicular
plate
Middle nasal concha
Figure 7.10
Frontal bone
Glabella
Frontonasal suture
Supraorbital foramen
(notch)
Supraorbital margin
Superior orbital
fissure
Optic canal
Inferior orbital
fissure
Middle nasal
concha
Ethmoid
Perpendicular bone
plate
Inferior nasal concha
Vomer
Parietal bone
Squamous part
of frontal bone
Nasal bone
Sphenoid bone
(greater wing)
Temporal bone
Ethmoid bone
Lacrimal bone
Zygomatic bone
Infraorbital foramen
Maxilla
Mandible
Mental
foramen
(a) Anterior view
Mandibular symphysis
Figure 7.4a
Ethmoid
bone
Cribriform plate
Crista galli
Frontal bone
Olfactory foramina
Anterior cranial fossa
Optic canal
Sphenoid Lesser wing
Greater wing
Hypophyseal fossa
of sella turcica
Middle cranial
fossa
Temporal bone
(petrous part)
Foramen rotundum
Foramen ovale
Foramen spinosum
Foramen lacerum
Internal acoustic
meatus
Jugular foramen
Hypoglossal canal
Posterior
cranial fossa
Foramen magnum
View
Parietal bone
Occipital bone
(a) Superior view of the skull, calvaria removed
Figure 7.7a
Sutural Bones
• Groups of tiny irregularly shaped bones that
appear within sutures
• A.k.a. Wormian bones
• vary in number
• not present on all skulls
Sagittal suture
Parietal
bone
Sutural
bone
Lambdoid
suture
Occipital bone
Superior nuchal line
External
occipital
protuberance
Occipitomastoid
suture
(b) Posterior view
External
occipital
crest
Occipital
condyle
Mastoid
process
Inferior
nuchal
line
Figure 7.4b
Facial Bones
• Mandible
• Maxillary bones (maxillae)
(2)
• Zygomatic bones (2)
• Nasal bones (2)
•
•
•
•
Lacrimal bones (2)
Palatine bones (2)
Vomer
Inferior nasal conchae (2)
Mandible
• Lower jaw
• Largest, strongest bone of face
• Articulates with the mandibular fossae of the
temporal bones via the mandibular condyles
to form the temporomandibular joint
• Temporomandibular joint: only freely movable
joint in skull
Temporomandibular
joint
Mandibular notch
Mandibular
condyle
Mandibular fossa
of temporal bone
Coronoid
process
Mandibular foramen
Ramus
of
mandible
Alveolar
margin
Mental
foramen
Mandibular
angle
Body of mandible
(a) Mandible, right lateral view
Figure 7.11a
Maxillary Bones
• Medially fused to form upper jaw and central
portion of facial skeleton
• Keystone bones
– Articulate with all other facial bones except
mandible
Articulates with
frontal bone
Frontal process
Orbital
surface
Zygomatic
process
(cut)
Infraorbital
foramen
Anterior nasal
spine
Alveolar
margin
(b) Maxilla, right lateral view
Figure 7.11b
Frontal bone
Glabella
Frontonasal suture
Supraorbital foramen
(notch)
Supraorbital margin
Superior orbital
fissure
Optic canal
Inferior orbital
fissure
Middle nasal
concha
Ethmoid
Perpendicular bone
plate
Inferior nasal concha
Vomer
Parietal bone
Squamous part
of frontal bone
Nasal bone
Sphenoid bone
(greater wing)
Temporal bone
Ethmoid bone
Lacrimal bone
Zygomatic bone
Infraorbital foramen
Maxilla
Mandible
Mental
foramen
(a) Anterior view
Mandibular symphysis
Figure 7.4a
Maxilla
(palatine process)
Hard
Palatine bone
palate
(horizontal plate)
Zygomatic bone
Temporal bone
(zygomatic process)
Vomer
Mandibular
fossa
Styloid process
Mastoid process
Temporal bone
(petrous part)
Pharyngeal tubercle
of basilar region of
the occipital bone
Parietal bone
External occipital crest
External occipital
protuberance
(a) Inferior view of the skull (mandible removed)
Incisive fossa
Intermaxillary suture
Median palatine suture
Infraorbital foramen
Maxilla
Sphenoid bone
(greater wing)
Foramen ovale
Foramen spinosum
Foramen lacerum
Carotid canal
External acoustic meatus
Stylomastoid
foramen
Jugular foramen
Occipital condyle
Inferior nuchal line
Superior nuchal line
Foramen magnum
Figure 7.6a
Zygomatic Bones
• Cheekbones
• Inferolateral margins of orbits
• Articulate with temporal, frontal, and
maxillary bones
Frontal bone
Glabella
Frontonasal suture
Supraorbital foramen
(notch)
Supraorbital margin
Superior orbital
fissure
Optic canal
Inferior orbital
fissure
Middle nasal
concha
Ethmoid
Perpendicular bone
plate
Inferior nasal concha
Vomer
Parietal bone
Squamous part
of frontal bone
Nasal bone
Sphenoid bone
(greater wing)
Temporal bone
Ethmoid bone
Lacrimal bone
Zygomatic bone
Infraorbital foramen
Maxilla
Mandible
Mental
foramen
(a) Anterior view
Mandibular symphysis
Figure 7.4a
Nasalbones
Bones
• Nasal
and Lacrimal Bones
– Form bridge of nose
– Articulate with the frontal, maxillary, and ethmoid
bones, along with the cartilages that form most of
the skeleton of the external nose
• Lacrimal bones
– In medial walls of orbits
– Lacrimal fossa houses lacrimal sac
– Articulate with the frontal, ethmoid, and maxillary
bones
Frontal bone
Sphenoid bone
(greater wing)
Ethmoid bone
Coronal suture
Parietal bone
Temporal bone
Lacrimal bone
Lacrimal fossa
Lambdoid
suture
Squamous
suture
Occipital
bone
Zygomatic
process
Occipitomastoid
suture
External acoustic
meatus
Mastoid process
Styloid process
Nasal bone
Zygomatic
bone
Maxilla
Alveolar
margins
Mandible
Mental foramen
Mandibular condyle
Mandibular notch
Mandibular ramus
Mandibular angle
Coronoid process
(a) External anatomy of the right side of the skull
Figure 7.5a
Palatine Bones and Vomer
• Palatine bones
– Posterior one-third of
hard palate
– Posterolateral walls of
the nasal cavity
– Small part of the orbits
• Vomer
– Plow shaped
– Lower part of nasal
septum
– Lies in the nasal cavity
Maxilla
(palatine process)
Hard
Palatine bone
palate
(horizontal plate)
Zygomatic bone
Temporal bone
(zygomatic process)
Vomer
Mandibular
fossa
Styloid process
Mastoid process
Temporal bone
(petrous part)
Pharyngeal tubercle
of basilar region of
the occipital bone
Parietal bone
External occipital crest
External occipital
protuberance
(a) Inferior view of the skull (mandible removed)
Incisive fossa
Intermaxillary suture
Median palatine suture
Infraorbital foramen
Maxilla
Sphenoid bone
(greater wing)
Foramen ovale
Foramen spinosum
Foramen lacerum
Carotid canal
External acoustic meatus
Stylomastoid
foramen
Jugular foramen
Occipital condyle
Inferior nuchal line
Superior nuchal line
Foramen magnum
Figure 7.6a
Inferior Nasal Conchae
• Form part of lateral walls of nasal cavity
• Thin, curved bones in the nasal cavity
• project medially from the lateral walls of the
nasal cavity
Frontal sinus
Superior, middle, and
inferior meatus
Superior
nasal concha Ethmoid
Middle
bone
nasal concha
Inferior nasal
concha
Nasal bone
Sphenoid
Sphenoid sinus
Pterygoid
bone
process
Palatine bone
(perpendicular plate)
Anterior nasal spine
Maxillary bone
(palatine process)
Palatine bone
(horizontal plate)
(a) Bones forming the left lateral wall of the nasal cavity
(nasal septum removed)
Figure 7.14a
Orbits
• Bony cavity that encases eyes and lacrimal
glands (tear-producing)
• Sites of attachment for eye muscles
• Formed by parts of seven bones (next slide)
• consist of the frontal, sphenoid, zygomatic,
maxilla, palatine, lacrimal, and ethmoid bones
Roof of orbit
Supraorbital notch
Superior
orbital fissure
Optic canal
• Lesser wing of
sphenoid bone
• Orbital plate of
frontal bone
Medial wall
• Sphenoid body
Lateral wall of orbit
• Orbital plate
of ethmoid bone
• Zygomatic process
of frontal bone
• Frontal process
of maxilla
• Greater wing of
sphenoid bone
• Lacrimal bone
• Orbital surface of
zygomatic bone
Nasal bone
Floor of orbit
Inferior orbital fissure
• Orbital process of
palatine bone
Infraorbital groove
Zygomatic bone
• Orbital surface of
maxillary bone
Infraorbital foramen
• Zygomatic bone
(b) Contribution of each of the seven bones forming the right orbit
Figure 7.13a
Nasal Cavity
• Roof, lateral walls, and floor formed by parts of four
bones
–
–
–
–
Ethmoid
Palatine bones
Maxillary bones
Inferior nasal conchae
• Nasal septum of bone and hyaline cartilage
–
–
–
–
Ethmoid
Vomer
Anterior septal cartilage
Divides nasal cavity into right and left halves
Frontal sinus
Superior, middle, and
inferior meatus
Superior
nasal concha Ethmoid
Middle
bone
nasal concha
Inferior nasal
concha
Nasal bone
Sphenoid
Sphenoid sinus
Pterygoid
bone
process
Palatine bone
(perpendicular plate)
Anterior nasal spine
Maxillary bone
(palatine process)
Palatine bone
(horizontal plate)
(a) Bones forming the left lateral wall of the nasal cavity
(nasal septum removed)
Figure 7.14a
Ethmoid
bone
Crista galli
Cribriform
plate
Sella turcica
Sphenoid
sinus
Frontal
sinus
Nasal bone
Perpendicular
plate of
ethmoid bone
Septal cartilage
Palatine
bone
Hard Palatine process
palate of maxilla
Vomer
Alveolar margin
of maxilla
(b) Nasal cavity with septum in place showing the contributions
of the ethmoid bone, the vomer, and septal cartilage
Figure 7.14b
Paranasal Sinuses
•
•
•
•
Mucosa-lined, air-filled spaces
Lighten the skull
Enhance resonance of voice
Found in frontal, sphenoid, ethmoid, and
maxillary bones
Frontal
sinus
Ethmoidal
air cells
(sinus)
Sphenoid
sinus
Maxillary
sinus
(a) Anterior aspect
Frontal
sinus
Ethmoidal
air cells
Sphenoid
sinus
Maxillary
sinus
(b) Medial aspect
Figure 7.15
Hyoid Bone
• Not a bone of the skull
• Does not articulate directly with another bone
• Site of attachment for muscles of swallowing
and speech
• lies inferior to the mandible in the anterior
neck
Greater horn
Lesser horn
Body
Figure 7.12
Vertebral Column
•
•
•
•
Transmits weight of trunk to lower limbs
Surrounds and protects spinal cord
extending from the skull to the pelvis
provides attachment for ribs and muscles of the neck and
back
• Flexible curved structure containing 26 irregular bones
(vertebrae)
–
–
–
–
–
Cervical vertebrae (7)—vertebrae of the neck
Thoracic vertebrae (12)—vertebrae of the thoracic cage
Lumbar vertebrae (5)—vertebra of the lower back
Sacrum—bone inferior to the lumbar vertebrae
Coccyx—terminus of vertebral column
Vertebral Column: Curvatures
• Increase the resilience and flexibility of the spine
– Two posteriorly concave curvatures
• Cervical and lumbar
– Two posteriorly convex curvatures
• Thoracic and sacral
• Abnormal spine curvatures
– Scoliosis (abnormal lateral curve)
– Kyphosis (hunchback)
– Lordosis (swayback)
C1
Cervical curvature
(concave)
7 vertebrae, C1–C7
Spinous
process
Transverse
processes
Thoracic
curvature
(convex)
12 vertebrae,
T1–T12
Intervertebral
discs
Intervertebral
foramen
Lumbar curvature
(concave)
5 vertebrae, L1–L5
Sacral curvature
(convex)
5 fused vertebrae
sacrum
Anterior view
Coccyx
4 fused vertebrae
Right lateral view
Figure 7.16
Ligaments
• Anterior and posterior longitudinal ligaments
– From neck to sacrum
– major supporting ligaments of the spine
– run as continuous bands down the front and back surfaces
of the spine
– support the spine and prevent hyperflexion and
hyperextension
• Ligamentum flavum
– Connects adjacent vertebrae
• Short ligaments
– Connect each vertebra to those above and below
•
•
•
Intervertebral
Discs
act as shock
absorbers
allow the spine to flex, extend, and bend
laterally
Cushionlike pad composed of two parts
1. Nucleus pulposus
•
Inner gelatinous nucleus that gives the disc its
elasticity and compressibility
2. Anulus fibrosus
•
Outer collar composed of collagen and fibrocartilage
Supraspinous ligament
Transverse process
Sectioned
spinous process
Ligamentum flavum
Interspinous
ligament
Intervertebral
disc
Anterior
longitudinal
ligament
Intervertebral foramen
Posterior longitudinal
ligament
Anulus fibrosus
Nucleus pulposus
Inferior articular process
Sectioned body
of vertebra
Median section of three vertebrae, illustrating the composition
of the discs and the ligaments
Figure 7.17a
Vertebral spinous process
(posterior aspect of vertebra)
Spinal cord
Spinal nerve root
Transverse
process
Herniated portion
of disc
Anulus fibrosus
of disc
Nucleus
pulposus
of disc
(c) Superior view of a herniated intervertebral disc
Figure 7.17c
General Structure of Vertebrae
• Body or centrum
– Anterior weight-bearing region
• Vertebral arch (posterior)
– Composed of 2 pedicles and 2 laminae that, along with
centrum, enclose vertebral foramen
• Vertebral foramina
– Together make up vertebral canal for spinal cord
• Intervertebral foramina
– Lateral openings between adjacent vertebrae for spinal
nerves
– notches on the superior and inferior borders of pedicles
General Structure of Vertebrae
• Seven processes per vertebra:
– Spinous process—projects posteriorly (median)
– Transverse processes (2)—project laterally
– Superior articular processes (2)—protrude
superiorly inferiorly
– Inferior articular processes (2)—protrude
inferiorly
PLAY
Animation: Rotatable Spine (horizontal)
PLAY
Animation: Rotatable Spine (vertical)
Lamina
Transverse
process
Posterior
Spinous
process
Superior
articular
process
and
facet
Pedicle
Anterior
Vertebral
arch
Vertebral
foramen
Body
(centrum)
Figure 7.18
Cervical Vertebrae
• C1 to C7: smallest, lightest vertebrae
• C3 to C7 share the following features
– Oval body
– Short spinous processes are bifid (except C7)
– Large, triangular vertebral foramen
– Transverse foramen in each transverse process
Table 7.2
Dens of axis
Transverse ligament
of atlas
C1 (atlas)
C2 (axis)
C3
Inferior articular
process
Bifid spinous
process
Transverse processes
C7 (vertebra
prominens)
(a) Cervical vertebrae
Figure 7.20a
Cervical Vertebrae
• C1 (atlas) and C2 (axis) have unique features
• Atlas (C1)
– No body or spinous process
– Consists of anterior and posterior arches, and two lateral
masses
– Articular facets on the superior surfaces of lateral masses
articulate with the occipital condyles of the skull superiorly
– articular facets on the inferior surface that articulate with
the second cervical vertebra, the axis, inferiorly.
C1
Posterior
Lateral
masses
Posterior
Posterior
tubercle
Posterior arch
Anterior
Anterior arch
tubercle
(a) Superior view of atlas (C1)
Transverse
foramen
Superior
articular
facet
Posterior arch
Transverse
process
Lateral
masses
Posterior
tubercle
Inferior
articular
facet
Transverse
Anterior
foramen
arch
Facet for dens
Anterior tubercle
(b) Inferior view of atlas (C1)
Figure 7.19a-b
Cervical Vertebrae
• Axis (C2)
– has a body, spine, and other typical vertebral
processes
– Knoblike Dens (odontoid process) projects
superiorly from the body into the anterior arch of
the atlas
– Dens is a pivot for the rotation of the atlas
Posterior
C2
Inferior
articular
process
Spinous process
Lamina
Pedicle
Transverse
process
Superior
articular
facet
Dens
Body
(c) Superior view of axis (C2)
Figure 7.19c
Thoracic Vertebrae
• T1 to T12
• All articulate with ribs at facets and demifacets
• gradually transition between cervical structure at the top,
and lumbar structure toward the bottom
• have a roughly heart-shaped body, which bear two facets
on each side for rib articulation
• circular vertebral foramen and superior and inferior
articular processes
• Long spinous process
• Location of articular facets allows rotation of this area of
spine
Table 7.2
Transverse
process
Superior articular
process
Transverse
costal facet (for
tubercle of rib)
Intervertebral
disc
Body
Spinous
process
Inferior costal
facet (for head
of rib)
Inferior articular
process
(b) Thoracic vertebrae
Figure 7.20b
Lumbar Vertebrae
• L1 to L5
• large vertebrae that have kidney-shaped
bodies
• Short, thick pedicles and laminae
• triangular vertebral foramen
• Short, flat hatchet-shaped spinous processes
• Orientation of articular facets locks lumbar
vertebrae together so as to prevent rotation
Table 7.2
Superior
articular
process
Transverse
process
Body
Intervertebral
disc
Inferior
articular
process
Spinous
process
(c) Lumbar vertebrae
Figure 7.20c
Sacrum and Coccyx
• Sacrum
• Coccyx
–
–
–
–
–
–
–
–
5 fused vertebrae (S1–S5)
Forms posterior wall of pelvis
Articulates with L5 superiorly
Articulates with the coccyx
inferiorly and the hip bones
laterally via the sacroiliac
joint
– Vertebral canal continues
through the sacrum, often
ending at a large external
opening, the sacral hiatus
Tailbone
Small bone
3–5 fused vertebrae
Articulates superiorly with
sacrum
Sacral promontory
Ala
Body of
first
sacral
vertebra
Transverse
ridges (sites
of vertebral
fusion)
Apex
Anterior
sacral
foramina
Coccyx
(a) Anterior view
Figure 7.21a
Ala
Sacral
canal
Body
Facet of
superior
articular
process
Auricular
surface
Median
sacral
crest
Lateral
sacral
crest
Posterior
sacral
foramina
Coccyx
Sacral
hiatus
(b) Posterior view
Figure 7.21b
• Composed of
Thoracic Cage
– Thoracic vertebrae dorsally
– Sternum anteriorly
– Ribs (laterally) and their costal cartilages (anteriorly)
• Functions
– Protects vital organs of thoracic cavity
– Supports shoulder girdle and upper limbs
– Provides attachment sites for many muscles, including
intercostal muscles used during breathing
Sternum (Breastbone)
• Anterior midline of the thorax
• flat bone resulting from the fusion of three bones: the
manubrium, body, and xiphoid process
• Three fused bones
– Manubrium
• Articulates with clavicles and ribs 1 and 2
– Body
• Articulates with costal cartilages of ribs 2 through 7
– Xiphoid process
• Inferior end
• Articulates only with the body
• Site of muscle attachment
• Not ossified until ~ age 40
Ribs and Their Attachments
• Form sides of the thoracic cage
• 12 pairs
• All attach posteriorly to thoracic vertebrae and
curve inferiorly toward the anterior body
surface
• Pairs 1 through 7
– True (vertebrosternal) ribs
– Attach directly to the sternum by individual costal
cartilages
Ribs and Their Attachments
• Pairs 8 through12
– False ribs
– Pairs 8–10 also called vertebrochondral ribs
• Attach indirectly to sternum by joining costal cartilage
of rib above
– Pairs 11–12 also called vertebral (floating) ribs
• No attachment to sternum
Jugular notch
Clavicular notch
Manubrium
Sternal angle
Body
Xiphisternal
joint
Xiphoid
process
True
ribs
(1–7)
False
ribs
(8–12)
Sternum
Intercostal spaces
Costal cartilage
Costal margin
L1
Vertebra
Floating ribs (11, 12)
(a) Skeleton of the thoracic cage, anterior view
Figure 7.22a
Structure of a Typical Rib
• Main parts:
– Head
• Articulates posteriorly with facets (demifacets) on
bodies of two adjacent vertebrae
– Neck
– Tubercle
• Articulates posteriorly with transverse costal facet of
same-numbered thoracic vertebra
– Shaft
Transverse costal facet
(for tubercle of rib)
Angle
of rib
Superior costal facet
(for head of rib)
Body of vertebra
Head of rib
Intervertebral disc
Neck of rib
Tubercle of rib
Shaft Sternum
Crosssection
of rib
Costal groove Costal cartilage
(a) Vertebral and sternal articulations of a
typical true rib
Figure 7.23a
Articular facet
on tubercle of rib
Spinous process
Shaft
Ligaments
Neck of rib
Head of rib
Transverse
costal facet
(for tubercle
of rib)
Body of
thoracic
vertebra
Superior costal facet
(for head of rib)
(b) Superior view of the articulation between a
rib and a thoracic vertebra
Figure 7.23b