1. Suzanne D'Anna1 The Skeletal System

2. Suzanne D'Anna2 Axial Skeletal System n 80 bones n forms longitudinal axis of the body - skull - cranial and facial bones - auditory ear ossicles - hyoid bone - vetebral column - vertebrae, sacrum, and coccyx - thoracic cavity - ribs and sternum

3. Suzanne D'Anna3 Appendicular Skeletal System n 126 bones - bones of the limbs - pectoral and pelvic girdle

4. Suzanne D'Anna4 Functions of the Skeletal System n support n protection n movement n storage of minerals n blood cell production (hemopoiesis)

5. Suzanne D'Anna5 Structure of Bone (long bone) n diaphysis n epiphysis n metaphysis n articular cartilage n periosteum n medullary canal n endosteum n epiphyseal line

6. Suzanne D'Anna6 Diaphysis n shaft n long portion of a bone n contains medullary cavity Epiphysis n ends of long bones n articulate with another joint

7. Suzanne D'Anna7 Metaphysis n in mature bone - where diaphysis joins epiphysis n in growing bone - includes epiphyseal plate (where cartilage is replaced by bone) Epiphyseal Line n bony structure n replaces epiphyseal cartilage n when it appears, bone stops growing

8. Suzanne D'Anna8 Articular Cartilage n thin layer of hyaline cartilage covering epiphysis where bone forms a joint with another bone n reduces friction n absorbs shock

9. Suzanne D'Anna9 Periosteum peri = around / osteo = bone n connective tissue membrane around surface of bone n Two layers : - fibrous - outer (consists of fibroblasts and collagen fibers) - osteogenic - inner (contains osteoprogenitor cells) n essential for bone growth n attachment site for ligaments and tendons

10. Suzanne D'Anna10 Medullary Canal n space within diaphysis n contains yellow marrow in adults - stores fat Endosteum n lines the medullary canal n contains osteoprogenitor cells

11. Suzanne D'Anna11 Bone Tissue Histology

12. Suzanne D'Anna12 Osteoprogenitor Cells osteo = bone / pro = precursor n derived from mesenchyme n can undergo mitosis n develop into osteoblasts n found in inner portion of periosteum, endosteum, Volkmann’s (perforating) and Haversian (central) canals

13. Suzanne D'Anna13 Osteoprogenitor

14. Suzanne D'Anna14 Osteoblasts osteo = bone / blasts = germ or bud n derived from osteoprogenitor cells n cells that form bone n found on bone surfaces n secrete collagen, organic compounds (matrix)

15. Suzanne D'Anna15 Osteoblasts

16. Suzanne D'Anna16 Osteocytes osteo = bone / cyte = cell n mature bone cells n derived from osteoblasts n osteoblasts found on bone surfaces; become surrounded with matrix and become osteocytes n main cells of bone tissues (matrix) n found in lacunae

17. Suzanne D'Anna17 Osteocytes

18. Suzanne D'Anna18 Osteoclasts osteo = bone / clasts = to break n function in bone resorption n important in development, growth, maintenance, and repair of bone n found on bone surfaces

19. Suzanne D'Anna19 Osteoclasts

20. Suzanne D'Anna20 Compact Bone

21. Suzanne D'Anna21 Calcification or Remineralization n deposition of mineral salts, (hydroxyapatite), in framework formed by collagen fibers in they tissues harden n hardness of bone depends on crystallized inorganic mineral salts n organic collagen reinforces and makes bone less brittle n calcification occurs in presence of collagen

22. Suzanne D'Anna22 Calcification or Remineralization (cont.) n mineral salts accumulate in microscopic spaces between collagen fibers n mineral salts crystallize and harden n after spaces are filled, mineral salts deposit around collagen fibers n salts crystallize and harden

23. Suzanne D'Anna23 Calcification or Remineralization (cont.) n bone is not completely solid; it has many small spaces between hardened portions n spaces allow for blood vessels n spaces reduce the weight of the bone

24. Suzanne D'Anna24 Microscopic Anatomy of Compact Bone n Volkmann’s canals (perforating) n Haversian canals (central) n concentric lamellae n lacunae n canaliculi n osteocytes

25. Suzanne D'Anna25 Volkmann’s (perforating) Canals n spaces through which blood vessels, lymphatic vessels and nerves from periosteum penetrate (pathway to outside) n transverse canals

26. Suzanne D'Anna26 Haversian (central) Canals n run longitudinally through bone n connect blood vessels of Volkmann's canals with vessels and nerves of medullary cavity

27. Suzanne D'Anna27 Concentric Lamellae n rings of hard, calcified matrix around Haversian canal Lacunae (lacuna = little lake) n small spaces between lamellae n contain osteocytes

28. Suzanne D'Anna28 Osteons of Compact Bone central canal lacunae containing one osteocyte lamellae

29. Suzanne D'Anna29 Canaliculi n tiny canals radiating in all directions from lacunae n filled with extracellular fluid n inside are processes of osteocytes n connect with one another and eventually with central canals (mini circulatory system within the bone)

30. Suzanne D'Anna30 Haversian System (osteon) n each central canal n surrounding lamellae n lacunae n osteocytes n canaliculi Many osteons cemented together form adult compact bone

31. Suzanne D'Anna31 Compact Bone n contains few spaces n forms external layer of all bones n wall of diaphysis is composed mainly of compact bone n provides protection and support n resists stress

32. Suzanne D'Anna32 Spongy Bone n makes up most of short, flat, and irregularly shaped bones n epiphysis of long bones n does not contain true osteons (basic unit of compact bone) - Haversian system n contains osteocytes n intercellular material

33. Suzanne D'Anna33 Spongy Bone (cont.) n not arranged around osteonic canals n consists of numerous branching bony plates (trabeculae) n spaces between trabeculae filled with red marrow; produces blood cells n within trabeculae are osteocytes that lie in lacunae (small spaces between lamellae)

34. Suzanne D'Anna34 Spongy Bone (cont.) n radiating from lacunae are canaliculi n blood vessel from periosteum penetrate through spongy bone n spongy bone (hipbones, ribs, sternum, vertebrae, skull and some long bones) is only site in bone of red marrow and blood cell production (hematopoiesis)

35. Suzanne D'Anna35 Bone n constantly broken down and rebuilt n living tissue