The skeletal system: the axial skeleton

1. The skeletal system:the axial skeleton

2. Essential Question • What is the main contribution the axial skeleton makes to homeostasis?

3. Divisions of the Skeleton • AXIAL SKELETON • Skull • Cranium • Face • Hyoid • Auditory Ossicles • Vertebral Column • Thorax • APPENDICULAR SKELETON: • Pectoral Girdle • Upper Limbs • Pelvic Girdle • Lower Limbs

4. Types of Bone • bones fall into 1 of 5 main types based on shape: • Long • Short • Flat • Irregular • Sesamoid

5. Long Bones • longer than they are wide • may be slightly curved (to absorb stress of weight at more points along the bone i.e. Straight bones would fracture more easily) • Consist of: • shaft & variable #s of ends • compact bone in diaphysis and spongy bone in epiphysis

6. Long Bones

7. Short Bones • somewhat cube-shaped • nearly equal in length as width • Consist of: • Spongy Bone except @ surface

8. Short Bones

9. Flat Bones • Composed of: • 2 nearly parallel plates of compact bone enclosing spongy bone inside • Function: • give considerable protection • place for muscle attachment

10. Flat Bones

11. Irregular Bones • complex shapes (do not fit in other categories) • vary in amt spongy bone

12. Sesamoid Bones • develop w/in certain tendons where there is considerable friction, tension, & physical stress • Function: protect tendon from excessive wear & tear • vary in # person to person but everyone has 2 patella which develop in quadriceps femoris tendon

13. Sesamoid Bone

14. Sutural Bones • classified by location (w/in a suture: a seam between 2 cranial bones) • not everyone has them

15. Bone Surface Markings • 2 major types: • depressions & openings • form joints or allow passage of vessels & nerves • processes • projections or outgrowths that either help form joints or serve as attachment points for ligaments & tendons

17. SKULL

18. Skull • 22 bones in 2 categories: • Cranium • 8 bones that form cranial cavity • 1 frontal bone • 2 parietal bones • 2 temporal bones • 1 occipital bone • 1 sphenoid bone • 1 ethmoid bone

19. Skull 2. Facial Bones 14 bones that form the face • 2 nasal bones • 2 maxillae • 1 mandible • 2 zygomatic • 2 lacrimal • 2 palantine • 2 inferior nasal conchae • 1 vomer

20. Skull: Cavities • Cranial Cavity • Nasal Cavity • Orbits • Paranasal Sinuses • Middle & Inner Ear Cavities

21. Movable Joints of the Skull • Mandible • Auditory Ossicles

22. Functions of Cranial Bones • protecting brain • stabilizing position of brain, vessels, & nerves through attachments to the meninges • outer surfaces provide large areas of attachment for muscles that move parts of the head & some for facial expression

23. Cranial Bones: Frontal Bone • forms: • forehead • upper part of eye socket • most of anterior part of cranial floor • in newborns: rt & lt which fuse shortly after birth

24. Frontal Bone

25. Parietal Bones • form greater portion of sides & roof of cranial cavity

26. Temporal Bones • form inferior, lateral aspects of the cranium & part of the cranial floor • its zygomaticproceess forms the lateral half of the zygomatic arch • mandibularfossa: where condylar process of mandible forms TMJ (temporal mandibular joint)

27. Temporal Bones

28. Temporal Bones • external auditory meatus: ear canal • mastoid: posterior & inferior to external auditory meatus, contains “air cells” (mastoiditis: inflammation in air cells)

29. Temporal Bone: Petrous Portion • base of skull between sphenoid & occipital bones • houses middle & inner ear • Carotid foramen & Jugular foramen

30. Temporal Bones • internal auditory meatus: passage of Cranial nerves VII (facial n.) and VIII (vestibulocochlear n.) • styloid process: point of attachment for muscles & ligaments of the tongue & neck

31. Temporal Bone: Internal Surface

32. Occipital Bone • forms back of head & most of base of skull • foramen magnum: large hole spinal cord passes thru, • occipital condyles: articulate with 1st cervical vertebra (atlas)

33. Occipital Bone

34. Sphenoid Bone • middle base of skull • *articulates with all other cranial bones • shape resembles a bat

35. Sphenoid Bone • sellaturcica: (Turkish saddle) the “seat” of the saddle is the hypophysealfossa: where the pituitary gland sits • optic foramen: between body & lesser wings, cranial nerve II (optic n.) and opthlamic artery pass thru

36. Sphenoid Bone

37. Ethmoid Bone • “like a sieve” • midline of anterior part of cranial floor, anterior to sphenoid, posterior to nasal bones • cribiforme plate: forms roof of nasal cavity, the holes of the sieve where olfactory nerves pass from roof of nasal cavity to brain • cristagalla: triangular process which serves as pt of attachment for meninges of brain

38. Ethmoid Bone

39. Ethmoid Bone • perpendicular plate: forms superior portion of nasal cavity • superior & middle nasal conchae: (or turbinate) increase vascular & mucous membrane surface area in nasal cavities: aids in sense of smell, warms, filters & moistens air being inhaled. Filters because the turbinates cause air to swirl as a result inhaled particles strike & become trapped in mucus

40. Ethmoid Bone

41. “Sometimes when you study anatomy, you start seeing others differently.”

42. Facial Bones • shape of face changes dramatically during 1st 2 yrs of life: • brain & cranial bones expand • 1st set of teeth erupt • paranasal sinuses enlarge • growth of face stops ~16 years old

43. Facial Bones • 14 facial bones: • 2 nasal bones • 2 maxillae • 2 zygomatic bones • 1 mandible • 2 lacrimal bones • 2 palatine bones • 2 inferior nasal conchae • 1 vomer

44. Nasal Bones • form part of the bridge of the nose (rest is cartilage)

45. Maxillae • = upper jaws • *articulate with every bone in face except the mandible • form part of floor of orbits, parts of nasal cavity, & most of the hard palate (bony roof of mouth) • each one has large maxillary sinus • alveolar process is small arch that contains the alveolar sockets for upper set of teeth

46. Maxillae

47. Cleft Palate & Cleft Lip • 10-12 wks gestation the palatine processes of maxillae typically join • not doing so  cleft palate +/- cleft lip • speech & swallowing can be affected • many ear infections • reparative surgery recommended 1st few wks of life / surgery needs to be completed by 12 – 18 mos b/4 speech: speech therapy & orthodontic care frequently necessary

49. Zygomatic Bones • “cheekbones”: the temporal process of the zygomatic bone articulates with the zygomatic process of the temporal bone • also part of floor of orbit

50. Lacrimal Bones • thin, about the size of pinky fingernail (smallest bones of face) • part of medial wall of each orbit • each contain lacrimalfossa that houses lacrimal sac: gathers tears  nasal cavity