Skeletal System

Introduction

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• The first correct illustrations of all bones was done by Leonardo da Vinci.

• Primarily made of connective tissue.

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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

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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

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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

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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

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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 BonesAre 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