1. : An Overview

2. Subdivisions of the Skeleton The skeleton is subdivided into two divisions: 1.The axial skeleton - which consists of the bones that form the longitudinal axis of the body & 1.The appendicular skeleton, the bones of the limbs and girdles.

3. The Skeletal System In addition to the bones, the skeletal system includes joints, cartilages, and ligaments (fibrous cords that bind the bones together at joints). The joints give the body flexibility and allow movement to occur.

4. The Skeletal System At one time or another, all of us have heard the expressions “bone tired”, “dry as a bone”, or “bag of bones”. This is an inaccurate representation of some of our most phenomenal organs. Our brain, not our bones, convey feelings of fatigue. Bones are far from dry. As our bones are more evident in some of us than others, without our bones we would fall to the ground and creep along like slugs.

5. The 5 Functions of the Bones: 1.Support - Bones form the internal framework that supports and anchors all soft organs. 2.Protection - Bones protect soft body organs. 3.Movement - Skeletal muscles, attached to bones by tendons, use the bones as levers to move the body and its parts. 4.Storage - Fat is stored in the internal cavities of bones. Bone itself serves as a storehouse for minerals, the most important being calcium and phosphorus, although there are others. 5.Blood Cell Formation - (or hematopoiesis) occurs within the marrow cavities of certain bones.

6. Classification of Bones The adult skeleton is composed of 206 bones. There are two basic types of osseous, or bone, tissue: Compact bone is dense and looks smooth and homogeneous. Spongy bone is composed of small needlelike pieces of bone and lots of open space.

7. Classification of Bone Bones are classified according to shape into four groups: Long Bones - are typically longer than they are wide. As a rule, they have a shaft with heads at both ends. Long bones are mostly compact bone. All the bones of the limbs, except the wrist and ankle bones, are long bones. Short Bones - are generally cubed shaped and contain mostly spongy bone. The bones of the wrist and ankle are short bones. Flat Bones - are thin, flattened, and usually curved. They have two thin layers of compact bone sandwiching a layer of spongy bone. Most bones of the skull, ribs, and sternum are flat bones. Irregular Bones - do not fit into any of the other categories. The vertebrae, which make up the spinal column, are irregular bones.

8. Classification of Bone

9. Gross Anatomy of a Long Bone Slide 5.6 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Diaphysis  Shaft  Composed of compact bone  Epiphysis  Ends of the bone  Composed mostly of spongy bone Figure 5.2a

10. Structures of a Long Bone Slide 5.7 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Periosteum  Outside covering of the diaphysis  Fibrous connective tissue membrane  Sharpey’s fibers  Secure periosteum to underlying bone  Arteries  Supply bone cells with nutrients Figure 5.2c

11. Structures of a Long Bone Slide 5.8a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Articular cartilage  Covers the external surface of the epiphyses  Made of hyaline cartilage  Decreases friction at joint surfaces Figure 5.2a

12. Structures of a Long Bone Slide 5.8b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Medullary cavity  Cavity of the shaft  Contains yellow marrow (mostly fat) in adults  Contains red marrow (for blood cell formation) in infants Figure 5.2a

13. Bone Markings Slide 5.9 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Surface features of bones  Sites of attachments for muscles, tendons, and ligaments  Passages for nerves and blood vessels  Categories of bone markings  Projections and processes – grow out from the bone surface  Depressions or cavities – indentations

14. Microscopic Anatomy of Bone Slide 5.10a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Osteon (Haversian System)  A unit of bone  Central (Haversian) canal  Opening in the center of an osteon  Carries blood vessels and nerves  Perforating (Volkman’s) canal  Canal perpendicular to the central canal  Carries blood vessels and nerves

15. Microscopic Anatomy of Bone Slide 5.10b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 5.3

16. Microscopic Anatomy of Bone Slide 5.11a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Lacunae  Cavities containing bone cells (osteocytes)  Arranged in concentric rings  Lamellae  Rings around the central canal  Sites of lacunae Figure 5.3

17. Microscopic Anatomy of Bone Slide 5.11b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Canaliculi  Tiny canals  Radiate from the central canal to lacunae  Form a transport system Figure 5.3

18. Changes in the Human Skeleton Slide 5.12 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  In embryos, the skeleton is primarily hyaline cartilage  During development, much of this cartilage is replaced by bone  Cartilage remains in isolated areas  Bridge of the nose  Parts of ribs  Joints

19. Bone Growth Slide 5.13a Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Epiphyseal plates allow for growth of long bone during childhood  New cartilage is continuously formed  Older cartilage becomes ossified  Cartilage is broken down  Bone replaces cartilage

20. Bone Growth Slide 5.13b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings  Bones are remodeled and lengthened until growth stops  Bones change shape somewhat  Bones grow in width

21. Long Bone Formation and Growth Slide 5.14b Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 5.4b