Skeletal Tissue & The Axial Skeleton
Human Anatomy
Sonya Schuh-Huerta, Ph.D.
Skeletal Tissue, Ch 6
The Skeletal System
• Composed of bones, cartilages, & joints
that form the internal framework of body
-We’ll explore the microscopic & gross structure
of the skeletal tissues & system
Cartilage
• Location & basic structure
– Found throughout adult body
• Ear & epiglottis
• Articular cartilages & costal cartilage
• Larynx, trachea, & nose
• Intervertebral discs, pubic symphysis, & articular discs
Cartilage
Epiglottis
Cartilage in
external ear
Cartilages in
nose
Articular cartilage
of a joint
Thyroid
cartilage
Cricoid
cartilage
Larynx
Trachea
Lung
Costal cartilage
Cartilage
in intervertebral
disc
Pubic
symphysis
Meniscus (padlike
cartilage in
knee joint)
Articular cartilage
of a joint
Respiratory
tube cartilages
in neck and thorax
Cartilages
Hyaline cartilages
Elastic cartilages
Fibrocartilages
Cartilage
• Is surrounded by perichondrium
• Consists primarily of water
• Resilient tissue  it springs back to
original shape
Types of Cartilage – Review!
• Hyaline cartilage (glassy)
– Most abundant cartilage
– Provides support through flexibility
• Elastic cartilage  contains many elastic
fibers
– Able to tolerate repeated bending
• Fibrocartilage  resists strong
compression & strong tension
– An intermediate between hyaline & elastic
Cartilages in the Adult Body (remember these?…)
Chondrocyte
in a lacuna
Matrix
Chondrocyte
in a lacuna
Elastic fibers
Lacuna
Gelatinous
ground
substance
Perichondrium
(a) Hyaline cartilage (180)
(b) Elastic cartilage (470)
Chondrocyte
in a lacuna
Collagen fibers
(c) Fibrocartilage (285)
Growth of Cartilage
• Appositional growth
– Chondroblasts in surrounding perichondrium
produce new cartilage
• Interstitial growth
– Chondrocytes within cartilage divide &
secrete new matrix
• Cartilage stops growing when the skeleton
stops growing
Tissues in Bone
• Bones contain several types of tissues
– Dominated by bone CT
– Contain nervous tissue & blood
– Contain cartilage in articular cartilages
– Contain ET lining blood vessels
Function of Bones
• Support – provides hard framework
• Movement – skeletal muscles use
bones as levers
• Protection of underlying organs
• Mineral storage – reservoir for important minerals
 Ca2+
• Blood-cell formation – bone contains red marrow
• Energy metabolism – osteoblasts secrete
osteocalcin; & yellow marrow stores fat
Bone Tissue
• Bone tissue
– Organic components  cells, fibers, & ground
substance
– Inorganic components  mineral salts that
invade bony matrix (calcium phosphate)
Extracellular Matrix
• Unique composition of matrix
– Gives bone exceptional properties
– 35%  organic components
• Contributes to flexibility & tensile strength
– 65%  inorganic components
• Provides exceptional
hardness, &
resists compression!
Cells in Bone
• 3 types of cells in bone produce or
maintain bone:
– Osteogenic cells  stem cells that
differentiate into osteoblasts
– Osteoblasts  actively produce & secrete
bone matrix
• Bone matrix = osteoid
– Osteocytes  housed within lacunae, keep
bone matrix healthy
Cells in Bone
• Osteoclasts – 4th type of cell
– Responsible for resorption of bone
– Secrete hydrochloric acid (HCl) & lysosomal
enzymes to break down bone
– The “Grim Reaper”
of bone
http://faculty.une.edu/com/abell/histo/histolab3.htm
Classification of Bones
• Long bones  longer than wide; a shaft
plus ends
• Short bones  roughly cube-shaped
• Flat bones  thin and flattened, usually
curved
• Irregular bones  various shapes, do not
fit into other categories
Classification of Bones
Gross Anatomy of Bones
• Compact bone  dense outer layer of
bone
• Spongy bone  internal network of bone
Structure of a Typical Long Bone
•
•
•
•
Diaphysis = “shaft” of a bone
Epiphysis = ends of a bone
Blood vessels  well vascularized
Medullary cavity = hollow cavity filled
with yellow marrow
• Membranes
– Periosteum, perforating fibers, &
endosteum
Structure of a Long Bone
Articular cartilage
Compact bone
Proximal
epiphysis
Spongy bone
Endosteum
Epiphyseal
line
Endosteum
Periosteum
Compact bone
Medullary
cavity (lined
by endosteum)
Diaphysis
Yellow
bone marrow
Compact bone
Periosteum
Perforating
(Sharpey’s)
fibers
Nutrient
arteries
Distal
epiphysis
Microscopic Structure of
Compact Bone
• Compact Bone
– Contains passage ways for blood vessels,
lymph vessels, & nerves
– Osteons  long cylindrical structures
• Function in support
• Structurally – resembles rings of a tree in c.s.
Microscopic Structure of Compact Bone
Compact bone
Central
(Haversian) canal
Spongy bone
Perforating
(Volkmann’s)
canal
Endosteum lining
bony canals and
covering trabeculae
Osteon
(Haversian system)
Circumferential
lamellae
Perforating (Sharpey’s) fibers
Lamellae
Nerve
Vein
Artery
Canaliculi
Osteocyte
in a lacuna
Lamellae
Central canal
Lacunae
Periosteal blood vessel
Periosteum
Lamellae
Central
canal
Lacunae
Interstitial
lamellae
Lacuna (with
osteocyte)
Microscopic Structure of Compact Bone
• Osteons contain:
– Lamellae
– Central canal
– Perforating canals
– Canaliculi
Interstitial
lamellae
Lamellae
Central
canal
Lacunae
Lacuna (with
osteocyte)
Microscopic Structure of Compact Bone
Artery with
capillaries
Structures
in the
central
canal
Vein
Nerve fiber
Lamellae
Collagen
fibers
run in
different
directions
Twisting
force
Microscopic Structure of
Spongy Bone
• Spongy Bone
– Is less complex than compact bone
– Trabeculae contain layers of lamellae &
osteocytes
• Are too small to contain osteons (no “tree rings”)
Microscopic Structure of Spongy Bone
Marrow
space
Trabecula
Osteocytes
Endosteum
Osteoblasts
Structure of Short, Irregular, & Flat Bones
– Contain bone
marrow but no
marrow cavity
– Diploë
= Internal spongy
bone of flat
bones
Spongy bone
(diploë)
Compact bone
Trabeculae
Gross Anatomy of Bones
Load here
(body weight)
• Bone design & stress
– Anatomy of a bone
reflects stresses
– Compression &
tension greatest at
external surfaces
Head of
femur
Compression
here
Tension
here
Point
of no stress
Bone Markings
• Superficial surfaces of bones reflect
stresses on them
• 3 broad categories of bone markings:
– Projections for muscle attachment
– Surfaces that form joints
– Depressions & openings
Bone Markings
Bone Development
• Ossification (osteogenesis) = bone-tissue
formation
– Membrane bones  formed directly from
mesenchyme (during embryonic period)
• Intramembranous ossification
– Other bones  develop initially from hyaline
cartilage
• Endochondral ossification
Intramembranous Ossification
Mesenchymal
cell
Collagen
fiber
Ossification
center
Osteoid
Osteoblast
1 Ossification centers appear in the fibrous
connective tissue membrane.
• Selected centrally located mesenchymal cells cluster
and differentiate into osteoblasts, forming an
ossification center.
Osteoblast
Osteoid
Osteocyte
Newly calcified
bone matrix
2 Bone matrix (osteoid) is secreted within the
fibrous membrane and calcifies.
• Osteoblasts begin to secrete osteoid, which is
calcified within a few days.
• Trapped osteoblasts become osteocytes.
Intramembranous Ossification
Mesenchyme
condensing
to form the
periosteum
Trabeculae of
woven bone
Fibrous
periosteum
Osteoblast
Plate of
compact bone
Diploë (spongy
Blood vessel
bone) cavities
contain red
marrow
4
Lamellar bone replaces woven bone, just
3 Woven bone and periosteum form.
• Accumulating osteoid is laid down between embryonic deep to the periosteum. Red marrow appears.
• Trabeculae just deep to the periosteum thicken and
blood vessels in a random manner. The result is a
are later replaced with mature lamellar bone, forming
network (instead of lamellae) of trabeculae called
compact bone plates.
woven bone.
• Vascularized mesenchyme condenses on the external • Spongy bone (diploë), consisting of distinct
trabeculae, persists internally, and its vascular tissue
face of the woven bone and becomes the periosteum.
becomes red marrow.
Endochondral Ossification
• All bones except some bones of the skull &
clavicles
• Bones are 1st modeled in hyaline cartilage
• Begins forming late in the 2nd month of
embryonic development
• Continues forming until early adulthood
Primary ossification centers in the skeleton
of a 12-week fetus
Parietal
bone
Occipital
bone
Mandible
Clavicle
Scapula
Frontal
bone of
skull
Radius
Ulna
Humerus
Ribs
Vertebra
Ilium
Tibia
Femur
Stages in Endochondral Ossification
Month 3
Week 9
Childhood to
adolescence
Birth
Articular
cartilage
Secondary
ossification Spongy
bone
center
Epiphyseal
blood vessel
Area of
deteriorating
cartilage matrix
Hyaline
cartilage
Epiphyseal
plate
cartilage
Medullary
cavity
Spongy
bone
formation
Bone
collar
Primary
ossification
center
1 Bone collar forms
around hyaline
cartilage model.
Blood
vessel of
periosteal
bud
2 Cartilage in the
center of the
diaphysis calcifies
and then develops
cavities.
3 The periosteal
bud invades the
internal cavities,
and spongy bone
begins to form.
4 The diaphysis
elongates and a
medullary cavity forms
as ossification continues.
Secondary ossification
centers appear in the
epiphyses in preparation
for stage 5.
5 The epiphyses
ossify. When completed,
hyaline cartilage
remains only in the
epiphyseal plates and
articular cartilages.
Anatomy of Epiphyseal Growth Areas
• In epiphyseal plates of growing bones:
– Cartilage is organized for quick, efficient
growth
– Cartilage cells form tall stacks
• Chondroblasts at the top of stacks divide quickly
– Pushes the epiphysis away from the diaphysis
– As chondrocytes die, osteoblasts replace them
& secrete bone matrix  lengthens bone
Anatomy of Epiphyseal Growth Areas
• Older chondrocytes signal surrounding matrix to
calcify
• Older chondrocytes then die & disintegrate
– Leaves long trabeculae (spicules) of calcified
cartilage on diaphysis side
– Trabeculae are partly eroded by osteoclasts
– Osteoblasts then cover trabeculae with bone tissue
– Trabeculae finally eaten away from their tips by
osteoclasts
Organization of Cartilage within
Epiphyseal Plate of Growing Long Bone
Resting zone
1 Proliferation zone
Cartilage cells undergo mitosis.
2 Hypertrophic zone
Older cartilage cells enlarge.
Calcified cartilage
spicule
Osseous tissue
3 Calcification zone
Matrix becomes calcified;
cartilage cells die; matrix
begins deteriorating.
4 Ossification zone
New bone formation is occurring.
Postnatal Growth of Endochondral
Bones
• During childhood & adolescence:
– Bones lengthen entirely by growth of the
epiphyseal plates
– Cartilage is replaced with bone CT as quickly
as it grows
– Epiphyseal plate maintains constant thickness
– Whole bone lengthens
Hormonal Regulation of Bone
Growth
• Growth hormone  produced by the pituitary
gland
– Stimulates epiphyseal plates (lengthens bones)
• Thyroid hormone  ensures that the skeleton
retains proper proportions
• Sex hormones (estrogen & testosterone)
– Promote bone growth
– But also later induces closure of epiphyseal
plates (~stop growing shortly after puberty!)
Postnatal Growth of Endochondral
Bones
• As adolescence draws to an end:
– Chondroblasts divide less often
– Epiphyseal plates become thinner
• Cartilage stops growing
• Replaced by bone tissue  no more addition
– Long bones stop lengthening when diaphysis
& epiphysis fuse
Postnatal Growth of Endochondral
Bones
• Growing bones widen as they lengthen
– Osteoblasts  add bone tissue to the
external surface of the diaphysis
– Osteoclasts  remove bone from the
internal surface of the diaphysis
• Appositional growth  growth of a bone
by addition of bone tissue to its surface
Bone Remodeling
• Bone is dynamic living tissue
– 500 mg of calcium may enter or leave the
adult skeleton each day!!!
– Some bone of the skeleton is replaced every
3–4 years
– Compact bone is replaced every 10 years
Bone Remodeling
• Bone deposit & removal
– Occurs at periosteal & endosteal surfaces
• Bone remodeling
– Bone deposition  accomplished by
osteoblasts
– Bone reabsorption  accomplished by
osteoclasts
Osteoclast: A Bone-Degrading Cell
• A giant cell with many nuclei
• Crawls along bone surfaces
• Breaks down bone tissue (reabsorption)
– Secretes
concentrated HCl
– Lysosomal
enzymes are
released
– Derived from
blood stem cells
Bone matrix
Osteocyte within
a lacuna
Ruffled border
of osteoclast
Nuclei
Injuries to Bone:
Common Types of Fractures
Common Types of Fractures
Common Types of Fractures
Stages of Healing a Fracture
Hematoma
A hematoma forms.
Bony
callus of
spongy
bone
New
blood
vessels
Internal
callus
(fibrous
tissue and
cartilage)
1
External
callus
Healed
fracture
Spongy
bone
trabecula
2
Fibrocartilaginous
callus forms.
3
Bony callus forms.
4
Bone remodeling
occurs.
Disorders of Bones
• Osteoporosis
– Characterized by low bone mass
• Bone reabsorption outpaces
bone deposition
• Occurs most often in women
after menopause (no/low estrogen!)
• Also aging men (with low T)
Osteoporosis
Disorders of Bones
• Osteomalacia
– Occurs in adults  bones are inadequately
mineralized (not enough Ca2+ & phosphorus)
• Rickets
–
–
–
–
–
–
Occurs in children  analogous to osteomalacia
Vit D/Ca2+/P deficiency  not enough Ca2+ absorbed
Bones are brittle, weak, deteriorate
Common in industrial Europe (little sunlight)
Now in most countries milk, etc. fortified w/ Vit D
But Rickets on the rise in U.S. & many countries
Disorders of Bones
• Paget’s disease
– Characterized by excessive rate of bone deposition
 enlarged & deformed bones, can lead to pain,
arthritis, deformities, fractures, & other complications
– Prevalence  1-8% ( > 40 yrs old)
• Osteosarcoma
– Most common form of bone cancer
– Occurs mainly at the ends of long bones
– ~68% survival rates
The Skeleton Throughout Life
• Cartilage grows quickly in youth
• Skeleton has fewer chondrocytes in the elderly
• Bones are a timetable
– Mesoderm
• Gives rise to embryonic mesenchyme cells
– Mesenchyme
• Produces membranes & cartilage
– Membranes & cartilage ossify (harden)
– New bone is added during childhood & youth
The Skeleton Throughout Life
• Skeleton grows until age ~18–21 years
• In children & adolescents: bone formation exceeds rate
of resorption
• In young adults: bone formation &
resorption are in balance
• In old age: resorption predominates
• Bone mass declines with age
 Healthy diet, moderate sunlight, &
exercise can help keep your bones in
better shape as you age!
The Axial Skeleton, Ch 7
(also to be used as Lab Guide)
The Skeleton
• Consists of:
– Bones, cartilage, joints, & ligaments
• Composed of 206 bones grouped into 2
divisions:
– Axial skeleton (80 bones)
– Appendicular skeleton (126 bones)
Axial Skeleton
Skull
• Formed from 80
named bones
• Consists of skull,
vertebral column, &
bony thorax
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
Axial Skeleton
Cranium
Clavicle
Scapula
Rib
Humerus
Vertebra
Radius
Ulna
Bones of
pelvic girdle
Bones of
pectoral
girdle
Upper
limb
Carpals
Phalanges
Metacarpals
Femur
Lower
limb
Tibia
Fibula
(b) Posterior view
The Skull – Cranial & Facial
Bones
• Facial bones serve to:
– Form framework of face
– Form cavities for the sense organs of sight,
taste, & smell
– Provide openings for passage of air & food
– Hold the teeth in place
– Anchor muscles of face
Facial Bones
• Unpaired bones
– Mandible & vomer
• Paired bones
– Maxillae
– Zygomatic bones
– Nasal bones
– Lacrimal bones
– Palatine bones
– Inferior nasal conchae
Facial Bones
Frontal bone
Parietal bone
Glabella
Squamous part
of frontal bone
Frontonasal suture
Supraorbital foramen
(notch)
Nasal bone
Sphenoid bone
(greater wing)
Supraorbital margin
Superior orbital fissure
Temporal bone
Ethmoid bone
Lacrimal bone
Optic canal
Inferior orbital fissure
Zygomatic bone
Middle nasal concha
Ethmoid
Perpendicular plate bone
Inferior nasal concha
Infraorbital foramen
Maxilla
Vomer
Mandible
Mental
foramen
Mental
protuberance
Mandible
• The lower jawbone is the largest &
strongest facial bone
• Composed of 2 main parts
– Horizontal body
– 2 upright rami
Mandible
Temporomandibular
joint
Mandibular notch
Mandibular fossa
of temporal bone
Coronoid
process
Mandibular
condyle
Mandibular foramen
Alveolar
margin
Ramus
of
mandible
Mental
foramen
Mandibular
angle
Body of mandible
Maxillary Bones (Maxillae)
• Articulate with all other facial bones except
the mandible
• Contain maxillary sinuses  largest
paranasal sinuses
• Forms part of the inferior orbital fissure
• Are the “keystone” bones of the face
Maxillary Bones
Articulates with
frontal bone
Frontal process
Orbital surface
Zygomatic
process
(cut)
Infraorbital
foramen
Anterior nasal
spine
Alveolar
margin
(b) Maxilla, right lateral view
Inferior View of the Skull
Maxilla
(palatine process)
Hard
palate
Palatine bone
(horizontal plate)
Zygomatic bone
Vomer
Temporal bone
(zygomatic process)
Mandibular fossa
Styloid process
Mastoid process
Temporal bone
(petrous part)
Basilar part of
the occipital bone
Occipital bone
External occipital crest
External occipital
protuberance
Incisive fossa
Intermaxillary suture
Median palatine suture
Infraorbital foramen
Maxilla
Sphenoid bone
(greater wing)
Pterygoid process
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
Other Bones of the Face
• Zygomatic bones
– Form lateral wall of orbits (& cheekbones!)
• Nasal bones
– Form bridge of nose
• Lacrimal bones
– Located in the medial orbital walls
• Palatine bones
– Posterior part of the hard palate (roof of mouth)
• Vomer
– Forms the inferior part of the nasal septum
• Inferior nasal conchae
– Thin, curved bones that project medially from the
lateral walls of the nasal cavity
The Cranium
Bones of cranium (cranial vault)
Coronal
suture
Squamous
suture
Lambdoid
suture
Facial
bones
(a) Cranial & facial divisions of the skull
The Cranium
• Is the body’s most complex bony structure
• Formed by cranial & facial bones
• The cranium
– Encloses & protects the brain
– Provides attachment for head & neck muscles
Overview of Skull Geography
• Facial bones form anterior aspect
• Cranium is divided into cranial vault & base
• Internally, prominent bony ridges divide skull into
distinct fossae
Anterior cranial
fossa
Temporal lobe
of cerebrum
Frontal lobe
of cerebrum
Cerebellum
Middle cranial
fossa
Posterior cranial
fossa
(b) Superior view of the cranial fossae
Cranial Posterior
fossae Middle
Anterior
(c) Lateral view of cranial fossae showing the
contained brain regions
Overview of Skull Geography
• The skull contains smaller cavities
– Middle & inner ear cavities  in lateral
aspect of cranial base
– Nasal cavity  lies in & posterior to the nose
– Orbits  house the eyeballs
– Air-filled sinuses  occur in several bones
around nasal cavity
Overview of Skull Geography
• The skull contains about 85 openings:
– Foramina, canals, & fissures
– Provide openings for important structures
• Spinal cord
• Blood vessels serving the brain
• 12 pairs of cranial nerves
– You do not need to learn all of these openings,
only a few….
– External & internal acoustic meatus
– Foramen magnum
– Obturator foramen
Cranial Bones
• Formed from 8 large bones
– Paired bones include:
• Temporal bones
• Parietal bones
– Unpaired bones include:
•
•
•
•
Frontal bone
Occipital bone
Sphenoid bone
Ethmoid bone
Parietal Bones & Sutures
• Parietal bones form superior & lateral
parts of skull
• 4 sutures of the cranium
– Coronal suture  runs in the coronal plane
• Located where parietal bones meet the frontal
bone
– Squamous suture  occurs where each
parietal bone meets a temporal bone inferiorly
Parietal Bones & Sutures
• 4 sutures of the cranium (cont…)
– Sagittal suture  occurs where right & left
parietal bones meet superiorly
– Lambdoid suture  occurs where the
parietal bones meet the occipital bone
posteriorly
Sutural Bones
• Small bones that occur within sutures
• Irregular in shape, size, & location
• Not all people have sutural bones
The Skull – Posterior View
Sagittal suture
Parietal bone
Sutural bone
Lambdoid
suture
Occipital bone
Superior nuchal line
External occipital
protuberance
Inferior nuchal line
External occipital crest
Occipital
condyle
Occipitomastoid
suture
Frontal Bone
• Forms the forehead & roofs of orbits
• Supraorbital margin = superior margin of
orbits (=brow)
• Glabella = smooth part of frontal bone
between superciliary arches
– Frontal sinuses within frontal bone
• Contributes to anterior cranial fossa
Occipital Bone
• Forms the posterior portion of the cranium
& cranial base
• Articulates with the temporal bones &
parietal bones
• Forms the posterior cranial fossa
• Foramen magnum located at its base
Occipital Bone
• Features & structures:
– Occipital condyles
– Hypoglossal foramen
– External occipital protuberance
– Superior nuchal lines
– Inferior nuchal lines
Inferior Aspect of the Skull
Maxilla
(palatine process)
Hard
palate
Palatine bone
(horizontal plate)
Zygomatic bone
Vomer
Temporal bone
(zygomatic process)
Mandibular fossa
Styloid process
Mastoid process
Temporal bone
(petrous part)
Incisive fossa
Intermaxillary suture
Median palatine suture
Infraorbital foramen
Maxilla
Sphenoid bone
(greater wing)
Pterygoid process
Foramen ovale
Foramen spinosum
Foramen lacerum
Carotid canal
Ext. acoustic meatus
Stylomastoid
foramen
Jugular foramen
Occipital condyle
Basilar part of
the occipital bone
Inferior nuchal line
Occipital bone
External occipital crest
Superior nuchal line
External occipital
protuberance
Foramen magnum
Temporal Bones
• Lie inferior to parietal bones
• Form the inferolateral portion of the skull
• Term “temporal” comes from Latin word for
time
• Specific regions of temporal bone:
– Squamous, tympanic, petrous, & mastoid regions
Lateral Aspect of the Skull
Frontal bone
Sphenoid bone
(greater wing)
Coronal suture
Parietal bone
Ethmoid bone
Lacrimal bone
Squamous suture
Nasal bone
Temporal bone
Lacrimal fossa
Zygomatic
bone
Zygomatic process
Coronoid
process
Maxilla
Lambdoid suture
Occipital bone
External occipital
protuberance
Alveolar
margins
Occipitomastoid
suture
Mandible
Mental foramen
External acoustic
meatus
Mastoid process
Mandibular
notch
Mandibular
condyle
Styloid
process
Mandibular ramus
Mandibular angle
The Temporal Bone
External acoustic
meatus
Squamous
region
Mastoid
region
Zygomatic
process
Mastoid process
Mandibular
fossa
Styloid process
Tympanic
region
The Temporal Bone
• The mastoid process
– Site for neck muscle attachment
– Contains air sinuses
• Petrous region
– Projects medially, contributes to cranial base
– Houses cavities of middle & internal ear
• Contributes to the middle & posterior
cranial fossae
The Temporal Bone
• Foramina of the temporal bone
– Jugular foramen
– Carotid canal
– Foramen lacerum
– Extermal & Internal accoustic meatus
Inferior Aspect of the Skull
Hard palate
Zygomatic bone
Zygomatic process
of temporal bone
Foramen ovale
Foramen spinosum
Mandibular
fossa
Foramen lacerum
Carotid canal
Mastoid
process
Styloid process
Jugular foramen
Occipital condyle
Foramen magnum
Superior nuchal
line
The Sphenoid Bone
•
•
•
•
•
Spans the width of the cranial floor
Resembles a butterfly or bat!
Consists of a body & 3 pairs of processes
Contains 5 important openings
Is the “keystone” of the cranium
The Sphenoid Bone
Optic
canal
Greater
wing
Lesser wing
Foramen rotundum
Foramen ovale
Sella
turcica
Foramen spinosum
Body of sphenoid
(a) Superior view
Figure 7.10a
The Sphenoid Bone
Body of sphenoid
Lesser
wing
Superior
orbital
fissure
Greater
wing
Pterygoid
process
(b) Posterior view
Figure 7.10b
The Ethmoid Bone
• Lies between nasal & sphenoid bones
• Forms most of the medial bony region
between the nasal cavity & orbits
The Ethmoid Bone
• Cribriform plate  superior surface of the
ethmoid bone
– Contains olfactory foramina (= holes for
olfactory neurons)
• Crista galli  attachment site for falx cerebri
(=strong sheet of dura matter between right & left
cerebral hemispheres)
• Perpendicular plate  forms superior part of
nasal septum
• Lateral masses  contain air cells (nasal sinuses)
• Superior & middle nasal conchae
– Extend medially from lateral masses
The Ethmoid Bone
Crista galli
Olfactory
foramina
Orbital
plate
Cribriform
plate
Left
lateral
mass
Ethmoidal
air cells
Perpendicular
plate
Middle
nasal concha
Special Parts of the Skull
•
•
•
•
Orbits
Nasal cavity
Paranasal sinuses
Hyoid bone
Nasal Cavity
Frontal sinus
Superior, middle, &
inferior meatus
Superior
nasal concha
Ethmoid
Middle
bone
nasal concha
Inferior nasal concha
Nasal bone
Anterior nasal spine
Sphenoid
bone
Maxillary bone
(palatine process)
Sphenoid
sinus
Pterygoid
process
Palatine bone
(perpendicular
plate)
Palatine bone
(horizontal plate)
(a) Bones forming the left lateral wall of the nasal cavity
(nasal septum removed)
Nasal Septum
Ethmoid
bone
Sella turcica
Sphenoid sinus
Crista galli
Cribriform
plate
Frontal sinus
Nasal bone
Perpendicular
plate of
ethmoid bone
Septal
cartilage
Vomer
Palatine bone
Hard
palate
Palatine process
of maxilla
Alveolar margin
of maxilla
(b) Nasal cavity with septum in place showing the contributions of the
ethmoid bone, the vomer, & septal cartilage
Paranasal Sinuses
• Air-filled sinuses are located within
– Frontal bone
– Ethmoid bone
– Sphenoid bone
– Maxillary bones
• Lined with mucous membrane
• Lighten the skull
Paranasal Sinuses
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
Orbits
Supraorbital notch
Roof of orbit
Lesser wing of
sphenoid bone
Orbital plate of
frontal bone
Lateral wall of orbit
Zygomatic process
of frontal bone
Greater wing of
sphenoid bone
Orbital surface of
zygomatic bone
Superior
orbital fissure
Inferior orbital fissure
Infraorbital groove
Zygomatic bone
Optic canal
Medial wall
Sphenoid body
Orbital plate
of ethmoid bone
Frontal process
of maxilla
Lacrimal bone
Nasal bone
Floor of orbit
Orbital process of
palatine bone
Orbital surface of
maxillary bone
Infraorbital foramen
(b) Contribution of each of the 7 bones forming the right orbit
Zygomatic bone
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
Questions…?
What’s Next?
Lab Today: Axial & Append Skeleton
Mon Lecture: Appendicular Skeleton
& Joints
Mon Lab: Finish Bones;
Selected Joints