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Objectives AXIAL SKELETON SKULL CRANIAL BONES (8 total flat bones w/ 2 paired) 1. On a skull or diagram, identify and name the bones of the skull 2. Identify the structure and function of the bones of the skull 3. Describe how a fetal skull differs from the adult skull 4. Explain the function of the fontanels. 1. Frontal Bone • forms forehead & upper portion of eyesocket (orbital) 2. Parietal Bones • paired bones; form superior & lateral walls of cranium 3. Temporal Bones • paired bones; inferior to parietal bones A. External auditory meatus – canal leading to eardrum & middle ear B. Styloid process – sharp projection below meatus; attachment of neck & tongue muscles 1 C. Zygomatic process – bridge of bone that joins with cheekbone D. Mastoid process – rough projection inferior & posterior to meatus (feel behind ears); attachment of neck muscles E. Jugular foramen – found at junction of occipital & temporal bones; opening for jugular vein F. Carotid canal – superior to jugular foramen; passage for carotid artery 4. Occipital Bone • most posterior bone; forms base of skull A. Foramen magnum – large opening for passage of spinal cord B. Occipital condyles – lateral to foramen magnum; projections that rest on 1st cervical vertebrae 5. Sphenoid Bone • butterfly shaped; spans entire width of skull SPHENOID 2 A. Sella turcica – “Turk’s saddle”; depression that holds the pituitary gland B. Foramen ovale – large oval opening at posterior end of sella turcica; passage of cranial nerves that control chewing Sella turcica Foramen ovale 6. Ethmoid Bone • irregular bone anterior to sphenoid • Forms roof of nasal cavity & part of medial walls of orbitals A. Cristi galli – “cock’s comb”; projection on superior surface to which outermost brain attaches B. Cribiform plates – holey areas on each side of cristi galli; passage of olfactory nerves Bone of the Orbit 1. Frontal bone 2. Ethmoid bone 3. Sphenoid bone 4. Zygomatic bone 5. Lacrimal bone 6. Maxillary bone 3 SUTURES OF SKULL (immovable joints of skull bones) 1. Coronal – between frontal & parietal bones 2. Sagittal – between paired parietal bones 3. Lamboidal – between parietal & occipital bones 4. Squamosal – between parietal & temporal bones 1 – Coronal 5 – Squamosal 9 – lamboidal 15 - sagittal FETAL SKULL • Contains cartilage filled spaces called fontanels that allow for brain growth & compression during birth • Face is smaller in comparison to cranium • Adult’s cranium 1/8 of total body length • Infant’s cranium ¼ of total body length • Frontal bones split • Temporal bone is a ring of bone • Conical projections present – growth areas FONTANELS 1. Frontal (anterior) – between parietal & frontal bones; diamond shaped; largest; closes within 18 – 24 months 2. Occipital (posterior) – between parietal & occipital bones; closes within 2 months 3. Sphenoidal (anterolateral) – paired; at the junction of the frontal, parietal, temporal & sphenoid bones ; closes within 3 months 4. Mastoid (posterolateral); at the junction of parietal, occipital & temporal bones 4 FACIAL BONES (14 bones w/ 2 being paired) 1. Maxillae – 2 bones that fuse to form the upper jaw • All facial bones except mandible join to maxillae A. Alveolar margin (process) – holds teeth B. Palantine process – anterior hard palate 2. Palatine Bones – posterior to palatine processes of maxillae • If not fused cleft palate results 3. Zygomatic Bones – cheekbones 4. Lacrimal Bones – smallest facial bone; forms most of the medial walls of the orbits 5 1. Frontal bone 2. Ethmoid bone 3. sphenoid bone 4. Zygomatic bone 5. Nasal Bones – form the bridge of the nose 6. Vomer Bone – “plow shaped”; single bone in the median of nasal cavity 7. Conchae – “scroll shaped”; form lateral walls of nasal cavity 5. Lacrimal bone 6. Maxillary bone 8. Mandible – lower jaw; only free moving joint of skull Nasal bones A. Body – horizontal; chin conchae vomer B. Rami – perpendicular uprights C. Angle – where body meets rami D. Coronoid process – spine like process; anterior E. Condylar process – knob like process; posterior; forms temporal mandibular joint F. Mandibular notch – depression between processes G. Mandibular foramen – opening on inner surface of rami H. Mental foramen – opening on body HYOID BONE • U shaped • Only bone that doesn’t directly articulate with any other bone in body • Located above the larynx ; suspended from styloid process • 3 parts: – Greater cornua – superior – Lesser cornua – inferior – Body – anterior 6 OSSICLES Greater cornua Lesser cornua • • • • Bones of inner ear Incus – anvil Malleus – hammer Stapes - stirrup 7