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The Skeletal System- Osseous Tissue & Skeletal Structure Chapter 5.

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Presentation on theme: "The Skeletal System- Osseous Tissue & Skeletal Structure Chapter 5."— Presentation transcript:

1 The Skeletal System- Osseous Tissue & Skeletal Structure Chapter 5

2 The skeletal system includes:  Bones  Cartilage  Joints  Ligaments  Other connective tissues

3 Functions of the Skeletal System  Support against gravity  Protection of soft internal organs  Movement (Leverage)  Storage Minerals (calcium, phosphorous) – within the matrix of bone tissue Energy reserve (adipose) – within the yellow marrow of long bones  Blood cell production – within red marrow of spongy bone tissue

4 The Structure of a Typical Bone All bones have a combination of spongy (cancellous) & compact (dense) bone tissue

5 The Histological Features of Spongy Bone  Lamellae (layers) of matrix laid down in trabeculae - branching network of bony tissue  Osteocytes located within lacunae  Canaliculi branch out from lacunae  Many marrow cavities which contain red marrow & small blood vessels

6 The Histological Features of Compact Bone Osteon/Haversian system - basic functional unit of compact bone Concentric lamellae (layers) of matrix surrounding central (Haversian) canal Osteocytes located within lacunae Canaliculi branch out radially from lacunae Central canals (containing BVs) run vertically down the length of the bone Perforating (Volkmann’s) canals (containing BVs) run horizontally across the width

7 Bone Cells In addition to Osteocytes, the mature bone cells found within the matrix of bone tissue, there are three other cells that are associated with bones  Osteoprogenitor cells  Osteoblasts  Osteoclasts

8 Bone Cells Osteoprogenitor cells  Derived from mesenchymal cells  Can undergo mitosis  Mature into osteoblasts

9 Bone Cells Osteoblasts  Responsible for osteogenesis – create bone tissue  Mature into osteocytes

10 Bone Cells Osteoclasts  Derived from embryological WBCs  Secrete enzymes for osteolysis – resorb/break down bone tissue  Necessary for calcium homeostasis

11 Long bones Short bones Flat bones Irregular bones Sesamoid bones Sutural bones Anatomical Classification of Bones Bones are classified by their basic shape

12 Structure of a Typical Long Bone diaphysis (compact bone)

13 The Structure of a Long Bone diaphysis epiphysis (spongy bone) epiphysis

14 The Structure of a Long Bone diaphysis epiphysis articular cartilage

15 The Structure of a Long Bone epiphysis metaphysis – location of epiphyseal plate – in children epiphyseal line – in adults diaphysis metaphysis articular cartilage

16 The Structure of a Long Bone medullary cavity filled with yellow marrow in adults lined with endosteum

17 The Structure of a Long Bone periosteum  Outer fibrous layer of dense irregular CT for attachment of tendons& ligaments; provides route for blood vessels & nerves; separates bone tissue from surrounding tissues  Double layered membrane surrounding bone except at articular cartilage  Inner cellular layer contains osteoprogenitor cells, osteoblasts, osteoclasts; therefore functions in bone growth & repair

18 Bone Formation and Growth Ossification - Process of converting other tissues to bone; begins around week 6-8 of embryological development as mesenchymal CT begins to differentiate Two types of ossification processes occur during embryological formation: Intramembranous Endochondral

19 Intramembranous Ossification  Forms flat bones of skull, mandible, clavicle  Replacement of mesenchymal membrane with osseous tissue  Mesenchymal cells differentiate to osteoprogenitor cells, which then become osteoblasts  Osteoblasts create spongy bone tissue, which then remodels into compact bone where necessary  Other mesenchymal cells around the developing bone form the periosteum Mesenchymal tissue forms Osteoblasts begin to secrete osteoid forming spongy bone tissue Blood vessels infiltrate tissue. Calcium salts deposit in osteoid. Periosteum develops

20 Endochondral Ossification  Most bones formed this way  Mesenchyme creates hyaline Cartilage model, which gets replaced by bone  Replacement begins in middle (diaphysis) & follows in ends (epiphyses)

21 Chondrocytes at the center of the growing cartilage model enlarge and then die as the matrix calcifies. Cartilage model Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Endochondral Ossification Cartilage model grows in length (interstitial growth) & in width (appositional growth)

22 Figure 5.7 Enlarging chondrocytes within calcifying matrix Chondrocytes at the center of the growing cartilage model enlarge and then die as the matrix calcifies. Newly derived osteoblasts cover the shaft of the cartilage in a thin layer of bone. Cartilage model Bone formation Epiphysis Diaphysis Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings The perichondrium, which surrounded the cartilage model, now must be referred to as the periosteum.

23 Figure 5.7 Enlarging chondrocytes within calcifying matrix Chondrocytes at the center of the growing cartilage model enlarge and then die as the matrix calcifies. Newly derived osteoblasts cover the shaft of the cartilage in a thin layer of bone. Blood vessels penetrate the dying cartilage. Newly developed osteoblasts form a primary ossification center. Cartilage model Bone formation Epiphysis Diaphysis Marrow cavity Primary ossification center Blood vessel Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

24 Figure 5.7 Enlarging chondrocytes within calcifying matrix Chondrocytes at the center of the growing cartilage model enlarge and then die as the matrix calcifies. Newly derived osteoblasts cover the shaft of the cartilage in a thin layer of bone. Blood vessels penetrate the cartilage. New osteoblasts form a primary ossification center. Bone tissue continues to replace cartilage of the diaphysis, and & continues toward each epiphysis. Cartilage model Bone formation Epiphysis Diaphysis Marrow cavity Primary ossification center Blood vessel Marrow cavity Blood vessel Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings The medullary cavity begins to hollow out

25 Blood vessels invade the epiphyses and osteoblasts form secondary centers of ossification. Cartilage remains only at the ends (articular cartilage) & at metaphysis (epiphyseal plate) Enlarging chondrocytes within calcifying matrix Chondrocytes at the center of the growing cartilage model enlarge and then die as the matrix calcifies. Newly derived osteoblasts cover the shaft of the cartilage in a thin layer of bone. Blood vessels penetrate the cartilage. New osteoblasts form a primary ossification center. The bone of the shaft thickens, and the cartilage near each epiphysis is replaced by shafts of bone. Cartilage model Bone formation Epiphysis Diaphysis Marrow cavity Primary ossification center Blood vessel Marrow cavity Blood vessel Secondary ossification center Epiphyseal cartilage Articular cartilage

26 An Overview of the Skeleton Skeletal Divisions Axial skeleton (80 bones)  Skull  Thoracic cage and sternum  Vertebral column Appendicular skeleton (126 bones)  Upper, lower limbs  Pectoral girdle  Pelvic girdle There are 206 bones in the adult human body

27 Bone Markings (Surface Features) Markings for articulations:  head  condyle  facet General elevations & projections:  process  ramus Table 5-1

28 Bone Markings (Surface Features) Processes for attachment:  trochanter (femur only)  tuberosity  tubercle  epicondyle  crest  line  spinous process (vertebrae only)  transverse process (vertebrae only) Spinous process Transverse process

29 Bone Markings (Surface Features) Spinous process Transverse process Depressions:  fossa  sulcus Openings:  foramen (canal)  meatus  fissure  sinus

30 Bone Markings (Surface Features)


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