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Chapter 7 The Skeleton Shilla Chakrabarty, Ph.D.
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The Axial Skeleton Consists of 80 bones Three major regions Skull
Thoracic cage (ribs and sternum) (a) Anterior view Facial bones Cranium Sacrum Vertebral column Clavicle Scapula Sternum Rib Humerus Vertebra Radius Ulna Carpals Phalanges Metacarpals Femur Patella Tibia Fibula Tarsals Metatarsals Consists of 80 bones Three major regions Skull Vertebral column Thoracic cage
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The Skull Two sets of bones Cranial 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 Facial bones Framework of face Cavities for special sense organs for sight, taste, and smell Openings for air and food passage Sites of attachment for teeth and muscles of facial expression
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Bones of cranium (cranial vault)
Coronal suture Squamous suture Lambdoid suture Facial bones (a) Cranial and facial divisions of the skull Figure 7.2a
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(b) Superior view of the cranial fossae
Anterior cranial fossa Middle cranial fossa Posterior cranial fossa (b) Superior view of the cranial fossae Figure 7.2b
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Cranial And Facial Bones Of The Skull
Parietal bone Squamous part of frontal bone Nasal bone Sphenoid bone (greater wing) Temporal bone Ethmoid bone Lacrimal bone Zygomatic bone Maxilla Mandible Infraorbital foramen Mental foramen (a) Anterior view Mandibular symphysis Frontal bone Glabella Frontonasal suture Supraorbital foramen (notch) Supraorbital margin Superior orbital fissure Inferior orbital Middle nasal concha Inferior nasal concha Vomer Optic canal Perpendicular plate Ethmoid bone
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Cranial Bones Frontal bone Parietal bones (2) Occipital bone
Temporal bones (2) Sphenoid bone Ethmoid bone
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Frontal Bone Anterior portion of cranium
Most of anterior cranial fossa Superior wall of orbits Contains air-filled frontal sinus
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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: Coronal suture—between parietal bones and frontal bone Sagittal suture—between right and left parietal bones Lambdoid suture—between parietal bones and occipital bone Squamous (squamosal) sutures—between parietal and temporal bones on each side of skull
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Occipital Bone Most of skull’s posterior wall and posterior cranial fossa Articulates with 1st vertebra Sites of attachment for the ligamentum nuchae and many neck and back muscles Figure 7.4b Lambdoid suture Occipital bone Superior nuchal line External occipital protuberance Sutural bone Occipitomastoid (b) Posterior view Occipital condyle crest Inferior nuchal line Mastoid process Parietal Sagittal suture
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Temporal Bones Squamous External acoustic meatus Mastoid region
Figure 7.8 Mastoid region External acoustic meatus process Styloid process Tympanic region Mandibular fossa Zygomatic process Squamous Inferolateral aspects of skull and parts of cranial floor Four major regions Squamous Tympanic Mastoid Petrous
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(a) External anatomy of the right side of the skull
Coronal suture Frontal bone Sphenoid bone (greater wing) Parietal bone Ethmoid bone Temporal bone Lacrimal bone Lambdoid suture Lacrimal fossa Squamous suture Nasal bone Occipital bone Zygomatic bone Zygomatic process Maxilla Occipitomastoid suture External acoustic meatus Mastoid process Alveolar margins Styloid process Mandibular condyle Mandible Mandibular notch Mental foramen Mandibular ramus Mandibular angle Coronoid process (a) External anatomy of the right side of the skull Figure 7.5a
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Anterior cranial fossa Optic canal Lesser wing Sphenoid
Cribriform plate Frontal bone Ethmoid bone Crista galli Olfactory foramina Anterior cranial fossa Optic canal Lesser wing Sphenoid Foramen rotundum Greater wing Foramen ovale Hypophyseal fossa of sella turcica Foramen spinosum Foramen lacerum Middle cranial fossa Internal acoustic meatus Temporal bone (petrous part) 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
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Sphenoid Bone Complex, bat-shaped bone
Body of sphenoid Greater wing Superior orbital fissure Lesser Pterygoid process Hypophyseal fossa of sella turcica Foramen rotundum ovale spinosum orbital fissure (a) Superior view Optic canal Lesser wing Complex, bat-shaped bone Keystone bone: Articulates with all other cranial bones Three pairs of processes Greater wings Lesser wings Pterygoid processes (b) Posterior view
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Ethmoid Bone Deepest skull bone
Superior part of nasal septum, roof of nasal cavities Contributes to medial wall of orbits Orbital plate Ethmoidal air cells Perpendicular Middle nasal concha Cribriform Olfactory foramina Crista galli Left lateral mass
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Cranial And Facial Bones Of The Skull
Frontal bone Glabella Parietal bone Frontonasal suture Supraorbital foramen (notch) Squamous part of frontal bone Supraorbital margin Nasal bone Superior orbital fissure Sphenoid bone (greater wing) Optic canal Temporal bone Inferior orbital fissure Ethmoid bone Lacrimal bone Middle nasal concha Zygomatic bone Ethmoid bone Infraorbital foramen Perpendicular plate Maxilla Inferior nasal concha Mandible Vomer Mental foramen (a) Anterior view Mandibular symphysis Figure 7.4a
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Sutural Bones Tiny irregularly shaped bones that appear within sutures
Figure 7.4b Lambdoid suture Occipital bone Superior nuchal line External occipital protuberance Sutural bone Occipitomastoid (b) Posterior view Occipital condyle crest Inferior nuchal line Mastoid process Parietal Sagittal suture
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Facial Bones Mandible Maxillary bones (maxillae) (2)
Zygomatic bones (2) Nasal bones (2) Lacrimal bones (2) Palatine bones (2) Vomer Inferior nasal conchae (2)
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Intermaxillary suture Hard palate Palatine bone (horizontal plate)
(palatine process) Incisive fossa Intermaxillary suture Hard palate Palatine bone (horizontal plate) Median palatine suture Infraorbital foramen Maxilla Zygomatic bone Sphenoid bone (greater wing) Temporal bone (zygomatic process) Foramen ovale Vomer Foramen spinosum Foramen lacerum Mandibular fossa Carotid canal External acoustic meatus Styloid process Stylomastoid foramen Mastoid process Temporal bone (petrous part) Jugular foramen Occipital condyle Pharyngeal tubercle of basilar region of the occipital bone Inferior nuchal line Parietal bone Superior nuchal line External occipital crest External occipital protuberance Foramen magnum (a) Inferior view of the skull (mandible removed) Figure 7.6a
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Mandible Lower jaw Largest, strongest bone of face
Temporomandibular joint: only freely movable joint in skull Coronoid process Mandibular foramen Mental foramen Mandibular angle Ramus of mandible condyle Mandibular notch Mandibular fossa of temporal bone Body of mandible Alveolar margin (a) Mandible, right lateral view Temporomandibular joint
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Maxillary Bones Medially fused to form upper jaw and central portion of facial skeleton Keystone bones: Articulate with all other facial bones except mandible Frontal process Articulates with frontal bone Anterior nasal spine Infraorbital foramen Alveolar margin (b) Maxilla, right lateral view Orbital surface Zygomatic process (cut)
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Zygomatic Bones Cheekbones Inferolateral margins of orbits
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Nasal Bones and Lacrimal Bones
Nasal bones: Form bridge of nose Lacrimal bones In medial walls of orbits Lacrimal fossa houses lacrimal sac Parietal bone Squamous part of frontal bone Nasal bone Sphenoid bone (greater wing) Temporal bone Ethmoid bone Lacrimal bone Zygomatic bone Maxilla Mandible Infraorbital foramen Mental foramen (a) Anterior view Mandibular symphysis Frontal bone Glabella Frontonasal suture Supraorbital foramen (notch) Supraorbital margin Superior orbital fissure Inferior orbital Middle nasal concha Inferior nasal concha Vomer Optic canal Perpendicular plate Ethmoid bone
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Palatine Bones and Vomer
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 Palatine
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Cranial And Facial Bones Of The Skull
Parietal bone Squamous part of frontal bone Nasal bone Sphenoid bone (greater wing) Temporal bone Ethmoid bone Lacrimal bone Zygomatic bone Maxilla Mandible Infraorbital foramen Mental foramen (a) Anterior view Mandibular symphysis Frontal bone Glabella Frontonasal suture Supraorbital foramen (notch) Supraorbital margin Superior orbital fissure Inferior orbital Middle nasal concha Inferior nasal concha Vomer Optic canal Perpendicular plate Ethmoid bone
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External anatomy of the right side of the skull
Coronal suture Frontal bone Sphenoid bone (greater wing) Ethmoid bone Lacrimal bone Lacrimal fossa Nasal bone Zygomatic bone Maxilla Alveolar margins Mandible Mental foramen Parietal bone Lambdoid suture Squamous Occipital Occipitomastoid External acoustic meatus Mastoid process Styloid process Mandibular condyle Mandibular notch Mandibular ramus Mandibular angle Coronoid process process Temporal bone
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Inferior view of the skull (mandible removed)
Incisive fossa Median palatine suture Intermaxillary suture Infraorbital foramen Maxilla Sphenoid bone (greater wing) Foramen ovale Foramen lacerum Carotid canal External acoustic meatus Stylomastoid foramen Jugular foramen Foramen magnum Occipital condyle Inferior nuchal line Superior nuchal line Foramen spinosum (palatine process) Hard palate Zygomatic bone Temporal bone (zygomatic process) Mandibular fossa Vomer Styloid process External occipital crest External occipital protuberance Mastoid process (petrous part) Pharyngeal tubercle of basilar region of the occipital bone Parietal bone Palatine bone (horizontal plate)
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Inferior Nasal Conchae
Form part of lateral walls of nasal cavity (a) Bones forming the left lateral wall of the nasal cavity (nasal septum removed) Maxillary bone (palatine process) Palatine bone (perpendicular plate) (horizontal plate) Pterygoid process Sphenoid sinus bone Anterior nasal spine Frontal sinus Superior nasal concha Middle Ethmoid Inferior nasal concha Nasal bone Superior, middle, and inferior meatus
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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 Vomer Anterior septal cartilage
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Crista galli Ethmoid bone Cribriform plate Frontal sinus Sella turcica
Nasal bone Perpendicular plate of ethmoid bone Sphenoid sinus Septal cartilage Palatine bone Vomer Alveolar margin of maxilla Hard palate Palatine process of maxilla (b) Nasal cavity with septum in place showing the contributions of the ethmoid bone, the vomer, and septal cartilage Figure 7.14b
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Orbits Encase eyes and lacrimal glands
Sites of attachment for eye muscles Formed by parts of seven bones (next slide) Roof of orbit Medial wall Supraorbital notch Optic canal Floor of orbit Nasal bone Lateral wall of orbit Zygomatic bone Inferior orbital fissure Infraorbital groove Infraorbital foramen Superior orbital fissure (b) Contribution of each of the seven bones forming the right orbit • Lesser wing of sphenoid bone • Orbital plate of frontal bone • Zygomatic process of frontal bone • Greater wing of sphenoid bone • Orbital surface of zygomatic bone • Sphenoid body • Orbital plate of ethmoid bone • Frontal process of maxilla • Lacrimal bone • Orbital process of palatine bone • Orbital surface of maxillary bone • Zygomatic bone
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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 Frontal sinus Ethmoidal air cells (sinus) Maxillary Sphenoid (a) Anterior aspect (b) Medial aspect
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Hyoid Bone Greater horn Lesser horn Body Not a bone of the skull
Does not articulate directly with another bone Site of attachment for muscles of swallowing and speech Figure 7.12 Greater horn Lesser horn Body
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