Chapter 7: The Skeleton
Part A
The Axial Skeleton Consists of 80 bones Three major regions
Skull Vertebral column Thoracic cage
Figure 7.1a
Skull
Thoracic cage(ribs andsternum)
(a) Anterior view
Facial bonesCranium
Sacrum
Vertebralcolumn
ClavicleScapulaSternumRibHumerusVertebraRadiusUlnaCarpals
PhalangesMetacarpalsFemurPatella
TibiaFibula
TarsalsMetatarsalsPhalanges
The Axial Skeleton
The Skull Two sets of bones
1. Cranial bones Enclose the brain in the cranial cavity Gives attachment sites for head and neck muscles
2. Facial bones Framework of face Contains cavities for the special sense organs of
sight, taste, and smell Provides openings for the passage of air and food Secures the teeth Anchors the facial muscles of expression, which we
use to show emotion
Figure 7.2a
Bones of cranium (cranial vault)
Lambdoidsuture
Facialbones
Squamoussuture
(a) Cranial and facial divisions of the skull
Coronalsuture
Cranial Bones Occipital bone Parietal bones (2) Frontal bone Temporal bones (2) Ethmoid bone Sphenoid bone
Remember: Old P-People From T-Texas Eat Spiders
Figure 7.4a
Parietal bone
Nasal boneSphenoid bone(greater wing)Temporal boneEthmoid boneLacrimal boneZygomatic bone
MaxillaMandible
(a) Anterior view Mandibular symphysis
Frontal bone
Vomer
Ethmoidbone
Parietal Bones and Major Associated Sutures Superior and lateral aspects of cranial
vault Four 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
Coronal suture Frontal bone
Sphenoid bone(greater wing)
Ethmoid bone
Lacrimal bone
Nasal bone
Zygomaticbone
Maxilla
Mandible
Parietal bone
Lambdoidsuture
SquamoussutureOccipitalbone
Occipitomastoidsuture
(a) External anatomy of the right side of the skull
Zygomaticprocess
Temporal bone
Figure 7.5a
Occipital Bone Most of skull’s posterior wall and posterior
cranial fossa Contains the foramen magnum “large hole”
through which the brain connects with the spinal cord
Articulates at the occipital condyles with 1st vertebra
Sites of attachment for the many neck and back muscles
Figure 7.4b
Lambdoidsuture
Occipital bone
Suturalbone
Occipitomastoidsuture
(b) Posterior view
Parietalbone
Sagittal suture
Figure 7.6a
Median palatine sutureIntermaxillary suture
Maxilla
Sphenoid bone(greater wing)
Foramen magnum
Maxilla
Zygomatic bone
Temporal bone(zygomatic process)
Vomer
(a) Inferior view of the skull (mandible removed)
Temporal bone
Parietal bone
Palatine bone
Temporal Bones Inferolateral aspects of skull and parts of
cranial floor Contains the zygomatic process, external
acoustic meatus, the styloid process, and the mastoid process
Articulates with the mandibleat the TMJ
Sphenoid Bone
Complex, butterfly-shaped bone Keystone bone
Articulates with all other cranial bones Three pairs of processes Contains the sella turcica and the
hypophyseal fossa that surround the pituitary gland
Ethmoid Bone
Deepest skull bone Superior part of nasal septum, roof of nasal
cavities Contributes to medial wall of orbits Contains the superior and middle nasal conchae Contains the crista galli (rooster’s comb)
The attachment site for the outermost covering of the brain
Figure 7.10
Sutural Bones Tiny irregularly shaped bones that appear
within sutures
http://www.sciencekids.co.nz/videos/humanbody/skullbones.html
Figure 7.4b
Lambdoidsuture
Occipital bone
Suturalbone
Occipitomastoidsuture
(b) Posterior view
Parietalbone
Sagittal suture
Facial Bones (14 Total)Unpaired Bones:
Mandible Vomer
Paired Bones:
Maxillary bones (2) Zygomatic bones (2) Nasal bones (2) Lacrimal bones (2) Palatine bones (2) Inferior nasal Conchae
(2)
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Mandible Lower jaw Largest, strongest bone of face Articulates at the temporomandibular joint
(TMJ): only freely movable joint in skull
Figure 7.11a
Mandibularangle
Ramusofmandible
Body of mandible(a) Mandible, right lateral view
Temporomandibularjoint
Maxillary Bones Medially fused to form upper jaw and central
portion of facial skeleton Keystone bone of the facial bones: all facial
bones except the mandible articulate with it
Zygomatic Bones
Cheekbones Inferolateral margins of
orbits Articulates with 3
separate zygomatic processes
Frontal zygomatic process Maxillary zygomatic
process Temporal zygomatic
process
Nasal Bones and Lacrimal Bones Nasal bones
Form bridge of nose Attach to the cartilage that forms most of the
skeleton of the nose
Lacrimal bones In medial walls of orbits Forms part of the canal that drains tears into the
nasal cavity
Lacrimation = crying/tear production
Figure 7.4a
Parietal bone
Nasal boneSphenoid bone(greater wing)Temporal boneEthmoid boneLacrimal boneZygomatic bone
MaxillaMandible
(a) Anterior view Mandibular symphysis
Frontal bone
Vomer
Ethmoidbone
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
Figure 7.6a
Median palatine sutureIntermaxillary suture
Maxilla
Sphenoid bone(greater wing)
Foramen magnum
Maxilla
Zygomatic bone
Temporal bone(zygomatic process)
Vomer
(a) Inferior view of the skull (mandible removed)
Temporal bone
Parietal bone
Palatine bone
Orbits Encase eyes and lacrimal glands Sites of attachment for eye muscles Formed by parts of seven bones
Frontal bones Zygomatic Sphenoid bones Palatine Ethmoid Lacrimal Maxilla
Friendly Zebras Speed Past Elderly Lions Mating
Roof of orbit
Medial wall
Floor of orbit
Nasal bone
Lateral wall of orbit
Zygomatic bone
(b) Contribution of each of the seven bones forming the right orbit
• Lesser wing ofsphenoid bone
• Orbital plate offrontal bone
• Zygomatic processof frontal bone
• Greater wing ofsphenoid bone
• Orbital surface ofzygomatic bone
• Sphenoid body
• Orbital plateof ethmoid bone
• Lacrimal bone
• Orbital surface ofmaxillary bone
• Zygomatic bone
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
Figure 7.14a
Maxillary bone(palatine process)
Palatine bone(perpendicular plate)
Palatine bone(horizontal plate)
(a) Bones forming the left lateral wall of the nasal cavity (nasal septum removed)
Sphenoidbone
Frontal sinus
Ethmoidbone
Nasal bone
Paranasal Sinuses Mucosa-lined, air-filled spaces Lighten the skull Enhance resonance of voice Found in frontal, sphenoid, ethmoid, and
maxillary bones
Figure 7.15
Frontalsinus
Ethmoidalair cells(sinus)
Maxillarysinus
Sphenoidsinus
Frontalsinus
Ethmoidalair cells
Maxillarysinus
Sphenoidsinus
(a) Anterior aspect (b) Medial aspect
Hyoid Bone
Not a bone of the skull Does not articulate directly with another bone Site of attachment for muscles of swallowing
and speech
Developmental Aspects of the Skull
At birth, the newborn’s skull not fully developed and sutures have not yet fused
• Allows for head compression during birth• Allows for brain growth in the infant
Unossified regions are covered with fibrous membranes called fontanelles “little fountains”
Anterior fontanelle is present until 1-1/2 –2 years of age
Homeostatic Imbalance of the SkullThe Cleft Lip and Palate
Caused by right and left halves of the palate failing to fuse medially
Leads to difficulties feeding/nursingRisk for aspiration (inhalation) pneumonia
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