Skeletal System Introduction

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 2 The first correct illustrations of all bones was done by Leonardo da Vinci. Primarily made of connective tissue.

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 3 The Functions of the Skeletal System Support of the body organs and tissues Protection of vital organs and soft tissues Assists in movement by providing levers for muscles to pull on Manufacture blood cells (Hematopoiesis) Store mineral salts as the inorganic matrix of bone and fat in yellow bone marrow.

The Skeletal System Parts of the skeletal system – Bones (skeleton) – Joints – Cartilages – Ligaments Divided into two divisions – Axial skeleton – Appendicular skeleton

The Axial and Appendicular Skeleton Axial: Forms the longitudinal part of the body Divided into three parts – Skull – Vertebral column – Bony thorax Appendicular: Appendages (Everything else)

Axial and Appendicular Skeleton

Bones of the Human Body The adult skeleton has 206 bones Two basic types of bone tissue – Compact bone Homogeneous – Spongy bone Small needle-like pieces of bone Many open spaces Figure 5.2b

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 8 Spongy Bone Aka ‘cancellous’ or ‘trabecular’ bone Trabeculae - meshwork of bone Spongy appearance created by trabeculae Bone marrow fills spaces between trabeculae Weaker than compact bone but lighter

Types of Bone Cells Osteocytes – Mature bone cells Osteoblasts – Bone-forming cells Osteoclasts – Bone-destroying cells – Break down bone matrix for remodeling and release of calcium Bone remodeling is a process by both osteoblasts and osteoclasts

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 10 The Classification of Bones Long Short Flat Irregular Sesamoid – intermittent occurrence, imbedded in tendons, nonarticular

Classification of Bones on the Basis of Shape Figure 5.1

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 12 Bone Markings (See textbook table 7.2 on p. 137) Processes - projections from the surface – spine, condyle, tubercle, trochlea, trochanter, crest, line, head, neck Fossae - depressions – suture, foramen, meatus, sinus, sulcus Functions - muscle attachment, articulation, passageways

©2006 by Thomson Delmar Learning, a part of the Thomson Corporation. ALL RIGHTS RESERVED. 13 Bone Marrow Red marrow – hematopoiesis – ribs, sternum, vertebrae, pelvis Yellow marrow – fat storage – shafts of long bones

Classification of Bones on the Basis of Shape Figure 5.1

Classification of Bones Are you sure you need to write this down? Long bones – Typically longer than wide – Have a shaft with heads at both ends – Contain mostly compact bone Examples: Femur, humerus

More self-evident classifications of bones. Flat bones – Thin and flattened – Usually curved – Thin layers of compact bone around a layer of spongy bone Examples: Skull, ribs, sternum Short bones – Generally cube-shape – Contain mostly spongy bone Examples: Carpals, tarsals