The Skull & Axial Skeleton

1. The Skull & Axial Skeleton Skull Vertebral Column Bony Thorax (Sternum & Ribs)

2. The Skull Cranium, facial bones, & hyoid bone

3. The Skull • Flat bones = sandwich of two thin layers of compact bone around a layer of spongy bone

4. Cranium (8 bones) • Frontal bone • Forehead • Superior eye orbits • Parietal bones (2) • Lateral & superior walls

5. Cranium (8 bones) • Temporal bones (2) • Inferior to parietal bones, behind ears • External auditory meatus = canal to inner ear • Styloid process = needle-like attachment point for muscles • Zygomatic arch connects to cheekbone • Mastoid process = attachment for neck muscles • Jugular foramen = hole for jugular vein • Carotid canal = hole for carotid artery

6. Cranium (8 bones) • Occipital bone • Posterior & rear floor of skull • Foramen magnum = large hole for spinal cord to go through • Occipital condyles rest on first vertebra

7. Cranium (8 bones) • Sphenoid bone • Butterfly-shaped, floor of cranial cavity • Connects cranium to facial bones • Ethmoid bone • Anterior to sphenoid • Roof of nasal cavity

8. Cranium (8 bones) Superior view (top of cranium removed)

10. Facial bones (14 bones) • Maxillae (2) • Upper jaw • Connect to all facial bones (except mandible) • Palatine processes form anterior hard palate • Zygomatic bones (2) • Cheekbones • Lacrimal bones (2) • Fingernail-sized, medial walls of eye orbits • Has a groove for tears

11. Facial bones (14 bones) • Palatine bones (2) • Posterior hard palate • Nasal bones (2) • Form bridge of nose • Vomer bone • Median line of nasal cavity • Inferior conchae (2) • Thin, curved bones • Project from lateral walls of nasal cavity

12. Facial bones (14 bones) • Mandible • Lower jaw • Only freely movable joints in the skull

13. Hyoid bone • Hyoid bone • Only bone in the body that does not articulate directly with another bone • Connected by ligaments to styloid processes of temporal bones • Mid-neck, 2 cm above larynx • Movable base for tongue, attachment for neck muscles that control larynx *Technically NOT a part of the skull

14. Sutures: immovable joints that connect skull bones • Coronal suture • Where frontal bone connects to parietal bones • Sagittal suture • Where parietal bones connect to each other • Squamous sutures (2) • Where parietal bones connect to temporal bones • Lambdoid suture • Where occipital bone connects to parietal bones

15. Sutures: immovable joints that connect skull bones • Coronal suture • Where frontal bone connects to parietal bones • Sagittal suture • Where parietal bones connect to each other • Squamous sutures (2) • Where parietal bones connect to temporal bones • Lambdoid suture • Where occipital bone connects to parietal bones

16. The fetal skull • Many bones are unfused and not completely ossified • Fontanels = unossified membranous areas  flexibility • Compression during birth • Allows brain to grow in early infancy • Ossify typically by 2 years old

17. The fetal skull Fetal skull development: from 20 to 40 weeks of gestation

18. Sinuses • Air cavities lined with mucous membranes, found in certain cranial bones • Lighten skull bones, amplify vocal sounds • Connected to mucous membranes in nose & throat, so infections there can spread to sinuses

19. Sinuses • Air cavities lined with mucous membranes, found in certain cranial bones • Lighten skull bones, amplify vocal sounds • Connected to mucous membranes in nose & throat, so infections there can spread to sinuses

20. Sinuses • Frontal sinuses • Frontal bone • Ethmoid sinuses • Ethmoid bones • Sphenoid sinuses • Sphenoid bone • Maxillary sinuses • Maxillae