1. Macroscopic structure of bone
Diagram of the outside of a long bone:

2. Figure 6.01 Parts of a Long Bone
©2004 John Wiley & Sons, Inc. All rights reserved.

3. Diaphysis – (die-AF-i-sis) main middle portion of the bone
Epiphyses – (e-PIF-i-seez) distal and proximal ends of the bone

4. Metaphyses – (me-TAF-i-seez) region in a mature bone where the diaphysis meets the epiphysis
Epiphyseal (e-pi-FIZ-ee-al) plate – a layer of cartilage in growing bone where the diaphysis can grow in length
Epiphyseal line – a bony structure that replaces the epiphyseal plate when the bone is no longer growing

5. Articular cartilage – thin layer of cartilage over the epiphysis where the bone connects with another bone.
Cushions and protects the ends of the bone.
Has limited ability to repair damage to it.

6. Periosteum (per-ee-OS-tee–um) dense irregular connective tissue that surrounds the parts of the bone that do not have articular cartilage.
Contains cells that enable the bone to grow wider and thicker, but not longer.

7. Chew… Draw a long bone cut lengthwise.
Label the diaphysis, epiphysis, metaphysis, epiphyseal plate/line, articular cartilage and periosteum.

8. Protects the bone
Assists in fracture repair
Helps nourish bone tissue
Attachment point for ligaments and tendons

9. Inside of a long bone:

10. Figure 6.01 Parts of a Long Bone
©2004 John Wiley & Sons, Inc. All rights reserved.

11. Medullary (MED-you-larry)cavity – space inside the diaphysis that contains yellow bone marrow in adults.
Endosteum (end-OS-tee-um) – membrane lining the inside of the medullary cavity.
Contains a single layer of bone-forming cells.

12. Compact bone – dense bone for protection and support
Spongy bone – looks like a network of bone with marrow in between

13. Microscopic structure of bone
Bone is a connective tissue
Matrix:
50% crystallized mineral salts to provide hardness
25% collagen fibers to provide some flexibility
25% water

14. Cells – 3 kinds
Osteoblasts – bone building cells which produce the matrix
Osteocytes – mature bone cells
Develop from osteoblasts
Maintain metabolism of bone – take in nutrients and release wastes into blood

15. 3 kinds of bone cells continued
Osteoclasts – huge cells created by the fusion of 50+ monocytes (white blood cells)
Produce lysosomal enzymes and acids to break down bone matrix (called resorption)

16. Compact bone tissue
Contains few spaces between the cells and matrix
Arranged in units called Haversian systems or osteons.

17. Figure 6.02a Histology of Bone
©2004 John Wiley & Sons, Inc. All rights reserved.

18. Parts of a Haversian system
Haversian canal – a central canal in the osteon
Contains blood vessels, lymphatic vessels and nerves
Connects to perforating (Volkmann’s) canals which lead into the bone from the periosteum.

19. More parts of a Haversian system
Concentric lamellae – rings of hard, calcified matrix around the Haversian canal
Lacunae – small spaces between the lamellae which contain osteocytes

20. More parts of a Haversian system
Canaliculi – small channels filled with extracellular fluid which connect the lacunae with each other and the central canal
Canals provide a route for diffusion of oxygen, nutrients and wastes since diffusion through lamellae is very slow

21. Figure 6.02a Histology of Bone
©2004 John Wiley & Sons, Inc. All rights reserved.

22. Spongy bone tissue features
Does not contain osteons
Has trabeculae which is a network of thin columns of bone
Contains spaces between the trabeculae filled with red bone marrow

23. More spongy bone features
Osteocytes in lacunae lie within the lamellae.
Canaliculi radiate out from the lacunae

24. Figure 6.02b-c Histology of Bone
©2004 John Wiley & Sons, Inc. All rights reserved.

25. Differences between spongy and compact bone
Spongy bone makes up the epiphyses of long bones and makes up most of the flat, short and irregular bones
Compact bone is found in the diaphysis of long bones

26. Figure 6.01 Parts of a Long Bone
©2004 John Wiley & Sons, Inc. All rights reserved.

27. More differences between spongy and compact bone
Spongy bone is lighter than compact bone
Spongy bone is the only site of hemopoiesis in adults

28. Pictures used by permission from Introduction to the Human Body, 6th edition by Tortora and Grabowski. Published by Wiley Publishing.