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ax·i·al ˈaksēəl/ adjective 1.of, forming, or relating to an axis. AXIAL SKELETON The Skeleton • Consists of: • Bones, cartilage, joints, and ligaments • Joints—also called articulations • Is composed of 206 named bones grouped into two divisions • Axial skeleton (80 bones) • Skull, vertebral column, and thoracic cage • Appendicular skeleton (126 bones) • Upper and lower limbs Figure 7.1a The human skeleton. Cranium Cranium Clavicle Clavicle Scapula Scapula Skull Facial bones Thoracic cage (ribs and sternum) Bones of pectoral girdle Upper limb Sternum Vertebral column Rib Rib Humerus Humerus Vertebra Vertebra Radius Ulna Radius Ulna Bones of pelvic girdle Sacrum Carpals Carpals Phalanges Phalanges Metacarpals Metacarpals Femur Femur Patella Lower limb Tibia Tibia Fibula Fibula Tarsals Metatarsals Anterior view Phalanges Posterior view The Skull • Is the body’s most complex bony structure • Is formed by cranial and facial bones • Bones of the cranium • Enclose and protect the brain • Provide attachment sites for some muscles of the head and neck The Skull • Facial bones • • • • • Form framework of the face Form cavities for sense organs of sight, taste, and smell Provide openings for passage of air and food Hold the teeth in place Anchor muscles of the face CRANIUM AND FACE Bones of cranium Coronal suture Squamous suture Lambdoid suture Facial bones Brain sits within the cranial fossae Anterior cranial fossa Middle cranial fossa Posterior cranial fossa Superior view of the cranial fossae Fossa – shallow basinlike depression in a bone, often serving as an articular surface. The brain, sitting within the cranial fossae, occupies cranial cavity Temporal lobe of cerebrum Frontal lobe of cerebrum Cerebellum Cranial fossae Posterior Middle Anterior Lateral view of cranial fossae showing the contained brain regions Overview of Skull Geography • The skull contains smaller CAVITIES: • Middle and inner ear cavities—in lateral aspect of cranial base • Nasal cavity—lies in and posterior to the nose • Orbits—house the eyeballs • Air-filled sinuses— mucosal-lined air cavities that lead to nasal cavity. • The skull contains approximately 85 named OPENINGS: • These are called: foramina, canals, and fissures • They provide openings for the: • Spinal cord • Blood vessels serving the brain • 12 pairs of cranial nerves The Cranium Contains 8 bones: • Paired bones include • Temporal bones • Parietal bones • Unpaired bones include • • • • Frontal bone Occipital bone Sphenoid bone Ethmoid bone Coronal suture Frontal bone Parietal bone Sphenoid bone (greater wing) Squamous suture Ethmoid bone Lambdoid suture Lacrimal bone Lacrimal fossa Occipital bone Nasal bone Temporal bone Zygomatic bone Maxilla Zygomatic process Occipitomastoid suture External acoustic meatus Mastoid process Alveolar processes Styloid process Mandible Condylar process Mental foramen Mandibular notch Mandibular ramus Mandibular angle External anatomy of the right side of the skull Coronoid process The cranium contains 4 sutures: Coronal suture Squamous suture Sagittal suture Coronal suture Frontal bone Parietal bone Sphenoid bone (greater wing) Squamous suture Ethmoid bone Lambdoid suture Lacrimal bone Lacrimal fossa Occipital bone Nasal bone Temporal bone Zygomatic bone Maxilla Zygomatic process Occipitomastoid suture Lambdoid suture External acoustic meatus Mastoid process Alveolar processes Styloid process Mandible Condylar process Mental foramen Mandibular notch Mandibular ramus Mandibular angle External anatomy of the right side of the skull Coronoid process Figure 7.4a Lateral aspect of the skull. Coronal suture Frontal bone Parietal bone Sphenoid bone (greater wing) Squamous suture Ethmoid bone Lambdoid suture Lacrimal bone Lacrimal fossa Occipital bone Nasal bone Temporal bone Zygomatic bone Maxilla Zygomatic process Occipitomastoid suture External acoustic meatus Mastoid process Alveolar processes Styloid process Mandible Condylar process Mental foramen Mandibular notch Mandibular ramus Mandibular angle External anatomy of the right side of the skull Coronoid process Frontal Bone • Forms the forehead and roofs of orbits • Supraorbital margin— superior margin of orbits • Supraorbital foramen— passage for supraorbital nerve and artery Frontal bone Parietal bone Glabella Squamous part of frontal bone Frontonasal suture Supraorbital foramen (notch) Nasal bone Sphenoid bone (greater wing) Supraorbital margin Temporal bone Optic canal Ethmoid bone Inferior orbital fissure Superior orbital fissure Lacrimal bone Zygomatic bone Middle nasal concha Perpendicular plate • Glabella—smooth part of frontal bone between superciliary arches (ridges on the frontal bone above the eye sockets) • Frontal sinuses within frontal bone Infraorbital foramen Ethmoid bone Inferior nasal concha Maxilla Vomer Mandible Mental foramen Mental protuberance Anterior view of skull Occipital Bone -- condyle – a round prominence at the end of a bone • Features and structures • Foramen magnum Parietal bone • Occipital condyles Sagittal suture • Hypoglossal foramen Sutural bone • Opening for hypoglossal nerve, one of 12 cranial nerves Lambdoid suture Occipital bone • External occipital protuberance Superior nuchal line External occipital protuberance • Superior nuchal* lines Inferior nuchal line Nuchal - of or relating to the back External occipital crest (nape) of neck. Nuchal lines are Occipital ridges on the back of the occipital bone condyle • Inferior nuchal lines Occipitomastoid suture *nuchal is pronounced “newkal” Incisive fossa Maxilla (palatine process) Intermaxillary suture Median palatine suture Hard palate Palatine bone (horizontal plate) Zygomatic bone Infraorbital foramen Maxilla FORAMEN MAGNUM Sphenoid bone (greater wing) Vomer Pterygoid process Temporal bone (zygomatic process) Foramen ovale Foramen spinosum Foramen lacerum Mandibular fossa Styloid process Mastoid process Temporal bone (petrous part) Basilar part of the occipital bone Occipital bone Carotid canal External acoustic meatus Stylomastoid foramen Jugular foramen Occipital condyle Inferior nuchal line Superior nuchal line External occipital crest External occipital protuberance Inferior view of the skull (mandible removed) Foramen magnum The temporal bone: External acoustic meatus Squamous part Zygomatic process Petrous part Mastoid process Styloid process Mandibular fossa Tympanic part Petrous - the hard dense portion of the temporal bone, containing the internal auditory organs; petrosal. Temporal Bone Frontal bone Coronal suture Sphenoid bone (greater wing) Parietal bone Ethmoid bone Squamous suture Lacrimal bone Temporal bone Nasal bone Zygomatic process Lambdoid suture Lacrimal fossa Occipital bone Zygomatic bone Occipitomastoid suture External acoustic meatus Mastoid process Coronoid process Maxilla Alveolar processes Styloid process Mandible Condylar process Mental foramen Mandibular notch Mandibular angle Mandibular ramus The mastoid process Site for neck muscle attachment Contains air sinuses The Sphenoid Bone called the “keystone of the cranium” because it articulates with all the cranial bones. • Spans the width of the cranial floor • Resembles a bat with its wings spread • Consists of a body and three pairs of processes • Contains five important openings (SEE NEXT) The Sphenoid Bone • Important landmarks Optic canal Lesser wing • Body • Sella turcica • Sphenoidal sinuses • Greater wings • Lesser wings • Pterygoid processes Foramen rotundum Greater wing Foramen ovale Sella turcica Body of sphenoid Foramen spinosum Superior view Body of sphenoid Lesser wing Superior orbital fissure Greater wing Pterygoid process Posterior view The Ethmoid Bone – irregular-shaped bone anterior to the sphenoid bone • Lies between nasal and sphenoid bones • Forms most of the medial bony region between the nasal cavity and orbits The Ethmoid Bone • Cribriform plate • Where olfactory fibers pass from nasal cavity to brain through cribriform foramina • Crista galli • Attachment for dura mater • Perpendicular plate • Forms superior part of nasal septum Anterior view Facial Bones • Unpaired bones • Mandible and vomer • Paired bones • • • • • • Maxillae Zygomatic bones Nasal bones Lacrimal bones Palatine bones Inferior nasal conchae Frontal bone Parietal bone Glabella Squamous part of frontal bone Frontonasal suture Supraorbital foramen (notch) Nasal bone Sphenoid bone (greater wing) Supraorbital margin Temporal bone Optic canal Ethmoid bone Inferior orbital fissure Superior orbital fissure Lacrimal bone Zygomatic bone Middle nasal concha Perpendicular plate Infraorbital foramen Ethmoid bone Inferior nasal concha Maxilla Vomer Mandible Mental foramen Mental protuberance Anterior view of skull Mandible: Lower jaw bone, the largest and strongest facial bone • the only movable bone of the skull • Composed of two main parts • Horizontal body • Two upright rami [rami – an arm or branch of a bone] • Major landmarks are shown in the figure: Temporomandibular joint Mandibular fossa of temporal bone Mandibular notch Condylar process Coronoid process – site of muscle attachment mandibular foramen (permits passage of Coronoid the nerve involved process in tooth sensation, cranial nerve V Mandibular foramen Alveolar process Ramus of mandible Mental foramen Mandibular angle Body of mandible Mandible, right lateral view Alveolar process: the thickened Ridge of bone that contains the tooth sockets Mental foramen transmits nerve to lower jaw Maxillary Bones • Articulate with all other facial bones except the mandible • Forms part of the inferior orbital fissure • Are the “keystone” bones of the face Maxilla, right lateral view Articulates with frontal bone Frontal process Orbital surface Zygomatic process (cut) Infraorbital foramen Anterior nasal spine Alveolar process Other Bones of the Face (Identify these during lab) • Zygomatic bones • Vomer • Forms the inferior part of the nasal septum • Form lateral wall of orbits • Nasal bones • Form bridge of nose • Inferior nasal conchae • Lacrimal bones • Located in the medial orbital walls • Palatine bones • Complete the posterior part of the hard palate • Thin, curved bones that project medially form the lateral walls of the nasal cavity Paranasal Sinuses • Air-filled sinuses are located within: • • • • Frontal sinus Ethmoidal air cells (sinus) Frontal bone Ethmoid bone Sphenoid bone Maxillary bones Sphenoidal sinus Maxillary sinus • Lined with mucous membrane • Lighten the skull Anterior aspect 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 The Vertebral Column • Surrounds and protects the spinal cord • Serves as attachment sites for muscles of the neck and back C1 2 3 4 Cervical curvature (concave) 7 vertebrae, C1 C7 5 6 7 T1 2 3 4 Spinous process Transverse processes 5 6 7 Thoracic curvature (convex) 12 vertebrae, T1 T12 Regions 8 • The vertebral column has five major regions • • • • 7 cervical vertebrae of the neck region 12 thoracic vertebrae 5 lumbar vertebrae Sacrum—five fused bones 9 Intervertebral discs 10 11 Intervertebral foramen 12 L1 2 3 Lumbar curvature (concave) 5 vertebrae, L1 L5 4 5 Sacral curvature (convex) 5 fused vertebrae sacrum • Inferior to lumbar vertebrae • Coccyx—inferior to sacrum Coccyx 4 fused vertebrae Anterior view Right lateral view Normal Curvatures • Curvatures of the spineincrease resilience of spine • Cervical and lumbar curvatures (secondary curvature) • Concave posteriorly • Thoracic and sacral curvatures (primary curvature) • Convex posteriority Major supporting ligaments: • Anterior longitudinal ligament • Attaches to bony vertebrae and intervertebral discs • Intervertebral diskscushions found in between vertebrae • Prevents hyperextension • Posterior longitudinal ligament • Narrow and relatively weak • Attaches to intervertebral discs Ligaments of the Spine Posterior longitudinal ligament Anterior longitudinal ligament Body of a vertebra Intervertebral disc Anterior view of part of the spinal column Structure of a typical vertebra. Common structures to all vertebrae: Posterior Lamina • Body • Vertebral arch • Vertebral foramen • Spinous process • Transverse process • Superior and inferior articular processes • Intervertebral foramina Spinous process Transverse process Superior articular process and facet Vertebral arch Vertebral foramen Pedicle Body Pedicle – a small, stalk-like structure Anterior Facet = surface LOCATION OF Atlas and Axis Dens of axis Transverse ligament of atlas C1 (atlas) C2 (axis) C3 Inferior articular process Bifid spinous process Transverse processes C7 (vertebra prominens) Cervical vertebrae The Atlas • C1 is the atlas • C1 lacks a body and spinous process • Allows flexion and extension of neck Posterior C1 Posterior tubercle Posterior arch Transverse foramen Lateral masses • Nodding the head “yes” Superior articular facet Anterior arch Anterior tubercle Superior view of atlas (C1) Figure 7.22c The first and second cervical vertebrae. The Axis • Has a body and spinous process • Dens (odontoid process) projects superiorly • Is formed from fusion of the body of the atlas with the axis • Acts as a pivot for rotation of the atlas and skull • Participates in rotating the head from side to side C2 Posterior Spinous process Inferior articular process Lamina Pedicle Superior articular facet Transverse process Dens Body Superior view of axis (C2) Thoracic Vertebrae CHARACTERISTICS • Spinous processes are long and point inferiorly • Vertebral foramen are circular • Transverse processes articulate with tubercles of ribs • Superior articular facets point posteriorly • Inferior articular processes point anteriorly • Allows rotation and prevents flexion and extension Lateral Superior Lumbar Vertebrae (L1–L5) • Bodies are thick and robust • Transverse processes are thin and tapered • Spinous processes are thick and blunt and point posteriorly • Vertebral foramina are triangular • Superior and inferior articular facets point medially • Allows flexion and extension— rotation prevented Sacrum (S1–S5) • Formed from 5 fused vertebrae • Superior surface articulates with L5 • Inferiorly articulates with coccyx Sacral promontory Ala Body of first sacral vertebra Body Facet of superior articular process Auricular surface Median sacral crest Transverse ridges (sites of vertebral fusion) Anterior sacral foramina Apex • Sacral promontory • Where the first sacral vertebrae bulges into pelvic cavity Sacral canal Coccyx Anterior view Lateral sacral crest Posterior sacral foramina Coccyx Posterior view The coccyx is the tail bone The coccyx is Formed from 3–5 fused vertebrae Sacral hiatus The Thoracic Cage (Rib Cage) Jugular notch Clavicular notch • Components • Thoracic vertebrae— posteriorly • Ribs—laterally • Sternum and costal cartilage— anteriorly • Protects thoracic organs • Supports shoulder girdle and upper limbs • Provides attachment sites for many muscles of the back Manubrium Sternal angle Body Xiphisternal joint True ribs (17) Xiphoid process False ribs (812) Intercostal spaces Costal cartilage Floating ribs (11, 12) L1 Vertebra Skeleton of the thoracic cage, anterior view Costal margin Sternum Superior view of the articulation between a rib and a thoracic vertebra Articular facet on tubercle of rib Spinous process Shaft Ligaments Transverse costal facet (for tubercle of rib) Neck of rib Head of rib Superior costal facet (for head of rib) Body of thoracic vertebra Sternum • Formed from three sections • Manubrium—superior section • Clavicular notches articulate with medial end of clavicles • Body—bulk of sternum • Sides are notched at articulations for costal cartilage of ribs 2–7 • Xiphoid process—inferior end of sternum • Ossifies around age 40 Other characteristics: • Jugular notch • Central indentation at superior border of the manubrium • Sternal angle • A horizontal ridge where the manubrium joins the body