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The Axial Skeleton Forms the longitudinal axis of the body
Divided into three parts Skull Vertebral column Bony thorax
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Figure 5.8a Cranium Skull Facial bones Clavicle Thoracic cage Scapula
(ribs and sternum) Scapula Sternum Rib Humerus Vertebra Vertebral column Radius Ulna Sacrum Carpals Phalanges Metacarpals Femur Patella Tibia Fibula Tarsals Metatarsals Phalanges (a) Anterior view Figure 5.8a
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Figure 5.8b Cranium Bones of pectoral girdle Clavicle Scapula Upper
limb Rib Humerus Vertebra Radius Bones of pelvic girdle Ulna Carpals Phalanges Metacarpals Femur Lower limb Tibia Fibula (b) Posterior view Figure 5.8b
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The Skull Two sets of bones Bones are joined by sutures
Cranium Facial bones Bones are joined by sutures Only the mandible is attached by a freely movable joint
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Coronal suture Frontal bone Parietal bone Sphenoid bone Temporal bone Ethmoid bone Lambdoid suture Lacrimal bone Squamous suture Nasal bone Occipital bone Zygomatic bone Zygomatic process Maxilla External acoustic meatus Mastoid process Alveolar processes Styloid process Mandible (body) Mental foramen Mandibular ramus Figure 5.9
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Frontal bone Cribriform plate Ethmoid bone Crista galli Sphenoid bone Optic canal Sella turcica Foramen ovale Temporal bone Jugular foramen Internal acoustic meatus Parietal bone Occipital bone Foramen magnum Figure 5.10
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Maxilla (palatine process) Hard palate Palatine bone Maxilla
Zygomatic bone Sphenoid bone (greater wing) Temporal bone (zygomatic process) Foramen ovale Vomer Mandibular fossa Carotid canal Styloid process Mastoid process Jugular foramen Occipital condyle Temporal bone Parietal bone Foramen magnum Occipital bone Figure 5.11
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Coronal suture Frontal bone Parietal bone Nasal bone Superior orbital fissure Sphenoid bone Optic canal Ethmoid bone Temporal bone Lacrimal bone Zygomatic bone Middle nasal concha of ethmoid bone Maxilla Inferior nasal concha Vomer Mandible Alveolar processes Figure 5.12
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The Hyoid Bone The only bone that does not articulate with another bone Serves as a moveable base for the tongue Aids in swallowing and speech
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Greater horn Lesser horn Body Figure 5.14
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The Fetal Skull The fetal skull is large compared to the infant’s total body length Fetal skull is 1/4 body length compared to adult skull which is 1/8 body length Fontanels—fibrous membranes connecting the cranial bones Allow skull compression during birth Allow the brain to grow during later pregnancy and infancy Convert to bone within 24 months after birth
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Anterior fontanel Frontal bone Parietal bone Posterior fontanel
Occipital bone (a) Figure 5.15a
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Anterior fontanel Sphenoidal fontanel Parietal bone Frontal bone
Posterior fontanel Occipital bone Mastoid fontanel Temporal bone (b) Figure 5.15b
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The Vertebral Column Each vertebrae is given a name according to its location There are 24 single vertebral bones separated by intervertebral discs Seven cervical vertebrae are in the neck Twelve thoracic vertebrae are in the chest region Five lumbar vertebrae are associated with the lower back
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The Vertebral Column Nine vertebrae fuse to form two composite bones
Sacrum Coccyx
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Anterior Posterior 1st cervical vertebra (atlas) Cervical curvature (concave) 7 vertebrae, C1 – C7 2nd cervical vertebra (axis) 1st thoracic vertebra Transverse process Spinous process Thoracic curvature (convex) 12 vertebrae, T1 – T12 Intervertebral disc Intervertebral foramen 1st lumbar vertebra Lumbar curvature (concave) 5 vertebrae, L1 – L5 Sacral curvature (convex) 5 fused vertebrae Coccyx 4 fused vertebrae Figure 5.16
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The Vertebral Column Primary curvatures are the spinal curvatures of the thoracic and sacral regions Present from birth Form a C-shaped curvature as in newborns Secondary curvatures are the spinal curvatures of the cervical and lumbar regions Develop after birth Form an S-shaped curvature as in adults
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Figure 5.17
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Figure 5.18
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A Typical Vertebrae Body Vertebral arch Vertebral foramen
Pedicle Lamina Vertebral foramen Transverse processes Spinous process Superior and inferior articular processes
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Posterior Vertebral Lamina arch Transverse Spinous process process
Superior articular process and facet Pedicle Vertebral foramen Body Anterior Figure 5.19
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(a) ATLAS AND AXIS Transverse process Posterior arch Anterior arch Superior view of atlas (C1) Spinous process Transverse process Facet on superior articular process Dens Body Superior view of axis (C2) Figure 5.20a
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(b) TYPICAL CERVICAL VERTEBRAE
Facet on superior articular process Spinous process Vertebral foramen Transverse process Superior view Superior articular process Body Spinous process Transverse process Facet on inferior articular process Right lateral view Figure 5.20b
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(c) THORACIC VERTEBRAE
Spinous process Transverse process Vertebral foramen Facet for rib Facet on superior articular process Body Superior view Facet on superior articular process Body Facet on transverse process Costal facet for rib Spinous process Right lateral view Figure 5.20c
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(d) LUMBAR VERTEBRAE Spinous process Vertebral foramen Transverse process Facet on superior articular process Body Superior view Superior articular process Body Spinous process Facet on inferior articular process Right lateral view Figure 5.20d
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Sacrum and Coccyx Sacrum Coccyx Formed by the fusion of five vertebrae
Formed from the fusion of three to five vertebrae “Tailbone,” or remnant of a tail that other vertebrates have
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Superior articular process Auricular surface Sacral canal Ala Body Median sacral crest Sacrum Posterior sacral foramina Sacral hiatus Coccyx Figure 5.21
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The Bony Thorax Forms a cage to protect major organs
Consists of three parts Sternum Ribs True ribs (pairs 1–7) False ribs (pairs 8–12) Floating ribs (pairs 11–12) Thoracic vertebrae
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T1 vertebra Jugular notch Clavicular notch Manubrium Sternal angle
Body Sternum Xiphisternal joint True ribs (1 –7) Xiphoid process False ribs (8 –12) Intercostal spaces L1 Vertebra Costal cartilage Floating ribs (11, 12) (a) Figure 5.22a
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T2 Jugular notch T3 T4 Sternal angle Heart Xiphisternal T9 joint (b)
Figure 5.22b
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