The Skeletal System

1. Chapter 7 The Skeletal System

2. Introduction • Skeleton: supporting structure • Bones and associated cartilage, tendons and ligaments • Works with muscles for movement

3. Introduction (cont’d.) • Mineral salts form the inorganic matrix of bone • Leonardo da Vinci: constructed first correct illustrations of all bones

4. The Functions of the Skeletal System

5. The Functions of the Skeletal System (cont’d.) • Supports surrounding tissues • Protects vital organs and soft tissues • Provides levers for muscles to pull on • Manufactures blood cells • Stores mineral salts

6. The Functions of the Skeletal System (cont’d.) • Cartilage • Connective tissue • Environment in which bone develops in fetus • Found at ends of bones and in joints • Ligaments • Attach bones to bones

7. The Functions of the Skeletal System (cont’d.) • Tendons • Attach muscles to bones

8. The Growth and Formation of Bone

9. Introduction • A three-month fetal skeleton is completely formed (cartilage) • Ossification and growth begin • Longitudinal growth continues until: • 15 years of age for girls • 16 years of age for boys • Bone maturation until 21 years of age

10. Deposition of Bone • Osteoblasts: embryonic bone cells • Osteocytes: mature osteoblasts • Strain on bone (exercise) increases bone strength • Osteoclasts: bone reabsorption and remodeling

11. Types of Ossification • Intramembranous • Dense connective membranes replaced by calcium salts • Cranial bones • Endochondral • Bone develops inside cartilage environment • All other bones of the body

12. Maintaining Bone • Endocrine system control • Calcium storage • Blood calcium levels • Excretion of excess calcium • Parathormone: calcium release • Calcitonin: calcium storage

13. The Histology of Bone

14. Introduction • Two types of bone: compact and cancellous (spongy) • Osteocytes same but arrangement of blood supply different • Cancellous has bone marrow

15. The Haversian System of Compact Bone • Clopton Havers: histology of compact bone • Haversian canals: run parallel to surface • Surrounded by concentric rings of bone • Lacunae: cavity containing osteocyte • Lacunae connected by canaliculi

16. Cancellous Bone • Trabeculae: meshwork of bone • Spongy appearance created by trabeculae • Bone marrow fills spaces between trabeculae

17. Bone Marrow • Red marrow • Hematopoiesis • Ribs, sternum, vertebrae, pelvis • Yellow marrow • Fat storage • Shafts of long bones

18. The Classification of Bones Based on Shape

19. Introduction

20. Long Bones • Length exceeds width • Consist of • Diaphysis: shaft • Metaphysis: flared portion • Epiphysis: extremity

21. Long Bones (cont’d.) • Structure of a long bone

22. Short Bones • Not merely shorter versions of long bones • Lack a long axis • Somewhat irregular shape

23. Flat Bones • Thin bones found wherever need for extensive muscle attachment • Usually curved

24. Irregular Bones • Very irregular shape • Example: vertebrae • Spongy bone enclosed by thin layers of compact bone

25. Sesamoid Bones • Small rounded bones • Enclosed in tendon and fascial tissue • Located adjacent to joints

26. Bone Markings

27. Introduction • Processes: projections • Fossae: depressions • Functions: muscle attachment, articulation, passageways

28. Processes • Processes: projections from the surface • Spine, condyle, tubercle, trochlea, trochanter, crest, line, head, neck

29. Fossae • Fossae: depressions • Suture, foramen, meatus, sinus, sulcus

30. Divisions of the Skeleton

31. Divisions of the Skeleton (cont’d.) • Typically has 206 named bones • Axial part • Skull, hyoid, vertebrae, ribs, sternum • Appendicular part • Upper extremities or arms • Lower extremities or legs

32. Divisions of the Skeleton (cont’d.) • Adult human skeleton: anterior view

33. Divisions of the Skeleton (cont’d.) • Adult human skeleton: posterior view

34. The Axial Skeleton

35. The Cranial Bones • Frontal bone (1) • Parietal bones (2) • Occipital bone (1) • Temporal bone (2) • Sphenoid bone (1) • Ethmoid bone (1) • Auditory ossicles (6)

36. The Facial Bones • Nasal bones (2) • Palatine bones (2) • Maxillary bones (2) • Zygomatic bones (2) • Lacrimal bones (2) • Nasal conchae (2)

37. The Facial Bones (cont’d.) • Vomer bone (1) • Mandible (1)

38. The Facial Bones (cont’d.) • Bones of the face and skull, lateral view

39. Orbits: cavities enclose and protect the eyes The Orbits

40. Nose framework surrounds the two nasal cavities The Nasal Cavities

41. The Foramina of the Skull • Passageways for blood vessels and nerves • Foramen magnum: spinal cord passage

42. The Hyoid Bone • No articulation with other bones • Suspended by ligaments from styloid process • Supports the tongue

43. How to Study the Bones of the Skull • Refer to color illustrations in textbook • Use a model of a human skull • Search for sutures as a guide

44. The Torso or Trunk • Vertebrae • Seven cervical • Twelve thoracic • Five lumbar • Sacrum • Coccyx

45. The Thorax • Thorax or rib cage made up of: • Sternum • Costal cartilages • Ribs • Bodies of thoracic vertebrae • Encloses and protects heart and lungs

46. The Thorax (cont’d.)

47. The Sternum • Breastbone • Has three parts • Manubrium • Gladiolus • Xiphoid process • Attachment for diaphragm and rectus abdominis

48. The Ribs • Also called costae • Attach posteriorly to thoracic vertebrae • 12 pairs • True ribs, false ribs, floating ribs

49. The Appendicular Skeleton

50. The Bones of the Upper Extremities • Shoulder girdle: clavicle and scapula • Arm • Upper arm: humerus • Forearm: ulna and radius • Wrist: carpals • Hand: metacarpals (5/hand) • Fingers: phalanges (14/hand)