Skeletal System Axial Skeleton

1. Skeletal SystemAxial Skeleton Anatomy Chapter 7

2. Axial skeleton • axis- center • consists of the center bones of the body • 80 bones • 3 major regions: • skull • vertebral column • thoracic cage

4. Skull • most complex structure • mostly flat bones • has about 85 named openings • 22 bones, usu interlocked along suture lines • 8 cranium bones • 14 facial bones

5. Cranium • helmet • encloses and protects the brain, provides areas for muscle attachment for head movements and chewing • held together by sutures- immovable joints

6. 8 bones

7. frontal- forehead • parietal- largest part (2) • occipital- external occipital protuberance foramen magnum occipital condyles • temporal (2)- Latin- temporum- time passing external auditory meatus mastoid process styloid process- (stake-like) zygomatic process

8. Frontal Occipital

9. Temporal

10. 5. sphenoid- (spheno-wedge) helps form base of cranium, sides of skull, floors and sides of orbits; keystone sellaturcica- Turk’s saddle 6. ethmoid bone- forms most of bony area of nasal cavity & eye orbits cribiform plates cristagalli- cock’s comb

11. Sphenoid

12. Facial bones • 14 bones- 13 immovable; 1 movable • Fxn: form basic shape of face, provide attachment for muscles, contain cavities for special sense organs, provide openings for air & food, & secure teeth

13. 1. Maxillae • keystone bone of the face • form upper jaw, roof of mouth, floors of orbits and nasal cavity

14. Cleft palate

15. 2. Zygomatic bones • form cheekbones

16. 3. Mandible • horseshoe shaped body

17. Sinuses • fxn: • warm and humidify air • lighten skull • enhance resonance of voice • sinus infections

18. Fontanels • aka soft spot • allows for movement through birth canal • close up by 2 years of age

19. Vertebral Column • ~ 28” long in adults • 26 irregular bones adults • infants 33 bones • separated by intervertebral discs

20. Cervical Vertebrae C1 – atlas nod yes; up and down m’ment C2- axis shake no; side to side m’ment 7 vertebrae

21. Thoracic Vertebrae • Larger than cervical • Articulate with ribs • 12 vertebrae

22. Lumbar Vertebrae • biggest vertebrae • bears most of body’s weight • small of back • 5 vertebrae

23. Sacrum and Coccyx • sacrum- 5 fused vertebrae • form base of column • coccyx- lowest part of column • 4 fused bones

24. Thoracic Cage • includes ribs, thoracic vetebrae, sternum, costal cartilages • fxn: support pectoral girdle, protect viscera, aid in breathing

25. Ribs • 12 pairs (usually) • join to a thoracic vertebra • 1st 7 ribs are TRUE RIBS- join sternum directly by their costal cartilages • next 5 pairs are FALSE RIBS- cartilage doesn’t reach sternum diriectly • next 2 (3) pairs are FLOATING RIBS- no cartilaginous attachment to sternum

27. usu break at greatest curvature • middle ribs commonly fractured

28. Sternum • aka breastbone • ~ 6” long • xyphoid process doesn’t completely ossify until about 40 years old

29. Hyoid Bone • Only bone in body that doesn’t articulate w/ other bones • Enables us to talk

31. Ossification • process of bone developing • bones form by replacing existing connective tissue in either of 2 ways: 1. intramembranous ossification- formation of bone directly on or within fibrous membranes

32. simplest, most direct type of bone development • osteoblasts form bone tissue • skull & clavicles formed this way

33. 2. endochondral ossification • replacement of hyaline cartilage shapes by bone tissue • endo= within chondro= cartilage

34. growth takes place at the epiphyseal plates on the long bones

35. most bones of body form this way • more complex method • by age 25 all bones are ossified • clavicle- last bone to stop growing • bone REMODELING occurs continuously thru-out life