1. Part B Bone Structure

2. Bones Bones are organs!Bones are organs! –Contains various types of tissues Osseous tissue (dominates) Nervous tissue Cartilage Fibrous connective tissue (lining cavities) Muscle and epithelial tissues in blood vessels

3. Bones We will look at bone structure on three levels Gross Microscopic Chemical

4. Gross Anatomy Bone Markings, Bone Textures, Bone Structures

5. Bone Markings Surface features of bones –Sites for attachments for muscles, tendons and ligaments –Joint surfaces –Passages for nerves and blood vessels

6. Bone Markings Categories of bone markings –Projections Bulges that grow outward from the bone surface –Depressions and openings Indentations, holes, and cavities

7. Projections That Are Sites of Muscle and Ligament Attachment Tuberosity – rounded projection Crest – narrow, prominent ridge of bone Trochanter – large, blunt, irregular surface Line – narrow ridge of bone Tubercle – small rounded projection Epicondyle – raised area above a condyle Spine – sharp, slender projection Process – any bony prominence

8. Projections That help to Form Joints Head – bony expansion carried on a narrow neck Facet – smooth, nearly flat articular surface Condyle – rounded articular projection Ramus – armlike bar of bone

9. Depressions and Openings Allowing Blood Vessels & Nerves to Pass Meatus – canal-like passageway Sinus – cavity within a bone Fossa – shallow, basinlike depression Groove – furrow Fissure – narrow, slitlike opening Foramen – round or oval opening through a bone

10. Bone Textures Compact bone – dense outer layer –Looks solid to the eye Spongy bone – honeycomb or spongy appearance –Has small needle-like or flat pieces called trabeculae filled with red or yellow bone marrow

11. Structure of Long Bone General structure of Long Bones –Diaphysis –Epiphyses –Membranes

12. Structure of Long Bone Diaphysis –Shaft constructed of a thick collar of compact bone that surrounds the medullary cavity

13. Structure of Long Bone Medullary Cavity –Cavity of the shaft –Contains yellow marrow (mostly fat) in adults –Contains red marrow (for blood cell formation) in infants

14. Structure of Long Bone Epiphyses –Expanded ends of long bones –Exterior is compact bone, interior is spongy bone –Joint surface is covered with articular cartilage –Epiphyseal line separates the diaphysis from the epiphyses

15. Structure of Long Bone Articular cartilage –Covers the external surface of the epiphyses –Made of hyaline cartilage –Decreases friction at joint surfaces

16. Structure of Long Bone Epiphyseal Line –Remnant of epiphyseal plate Disc of hyaline cartilage that grows during childhood to lengthen the bone

17. Structure of Long Bone Membranes of long bones –Periosteum –Endosteum

18. Structure of Long Bone Periosteum –Outside covering of the bone Except joint surfaces –Glistening white, double- layered membrane

19. Structure of Long Bone Periosteum –Outer Fibrous layer is dense connective tissue –Inner osteogenic layer (next to bone surface) is mostly osteoblasts (bone germinators) and osteoclasts (bone breakers)

20. Structure of Long Bone Periosteum –Richly supplied with nerve fibers, lymphatic vessels, blood vessels which enter the diaphysis by a nutrient foramen (opening)

21. Structure of Long Bone Sharpey’s fibers –Secures periosteum to underlying bone –Made of collagen fibers –Extends into bone matrix

22. Structure of Long Bone Arteries –Supplies bone cells with nutrients

23. Structure of Long Bone Endosteum –Delicate connective tissue –Contains osteoblasts & osteoclasts

24. Structure of Long Bone Endosteum –Covers internal surfaces of bone Medullary cavity Trabeculae (spongy) Canals through compact bone

25. Structure of Long Bone Figure 6.3

26. Structure of Short, Irregular, and Flat Bones

27. Thin plates of periosteum-covered compact bone on the outside with endosteum-covered diploë on the inside Spongy bone in flat bone is called diploë

28. Structure of Short, Irregular, and Flat Bones Have no diaphysis or epiphyses Contain bone marrow between the trabeculae

29. Hematopoietic Tissue

30. In infants –Found in the medullary cavity and all areas of spongy bone

31. Location of Hematopoietic Tissue (Red Marrow) In adults –Found in the diploë of flat bones, and the head of the femur and humerus –Remember, the diploë is the spongy bone of flat bones

32. Yellow marrow is found in the medullary cavities Yellow marrow can revert back to red marrow if a person becomes very anemic and needs enhanced red blood cell production

33. Microscopic Anatomy

34. Microscopic Structure of Compact Bone Haversian system, or osteon –the structural unit of compact bone

35. Microscopic Structure of Compact Bone Each osteon is a group of hollow tubes of bone matrix, called lamella, each one placed outside the next

36. Microscopic Structure of Compact Bone Each osteon is oriented parallel to the long axis of the bone

37. Microscopic Structure of Compact Bone Osteons are like tiny weight- bearing pillars

38. Microscopic Structure of Compact Bone Lamella –The weight- bearing, column—like matrix tubes composed mainly of collagen

39. Microscopic Structure of Compact Bone Haversian, or central canal –channel in the center of the osteon –containing blood vessels and nerves

40. Microscopic Structure of Compact Bone Volkmann’s canals –channels lying at right angles to the central canal, connecting blood and nerve supply of the periosteum to that of the central canal

41. Microscopic Structure of Bone: Compact Bone Osteocytes –Mature bone cells –Spider-shaped Lacunae –small cavities in bone that contain osteocytes

42. Microscopic Structure of Bone: Compact Bone Canaliculi –Tiny, hair-like canals –connect lacunae to each other and the central canal –Forms a transport system

43. Microscopic Structure of Compact Bone Figure 6.6a, b

44. Organic components and inorganic components

45. Chemical Composition of Bone: Organic Osteoblasts – bone-forming cells Osteocytes – mature bone cells Osteoclasts – large cells that resorb or break down bone matrix Osteoid – unmineralized bone matrix composed of proteoglycans, glycoproteins, and collagen

46. Chemical Composition of Bone: Inorganic Hydroxyapatites, or mineral salts –Sixty-five percent of bone by mass –Mainly calcium phosphates –Responsible for bone hardness and its resistance to compression

47. Chemical Composition of Bone: Inorganic Hydroxyapatites, or mineral salts –Bone is half as strong as steel in resisting compression and fully as strong as steel in resisting tension –Bones last long after death, sometimes many centuries

48. Paris catacombs

49. Quiz Next Time!