Skeletal System

1. Skeletal System Overview: • “skeleton” Greek for “dried up body” • Designed for protection and motion • The skeleton is a tower of bones arranged in a way we can stand upright and balance

2. The skeleton is divided into two divisions: • Axial skeleton • Bones that form the longitudinal axis of the body • Head, thorax • Appendicular skeleton • Bones of the limbs and girdles • Hips, arms, hands, legs and feet • Also includes: • Joints, cartilages and ligaments

3. Functions of the Bones • Support • form internal framework that supports and anchors all soft organs. • Legs provide for support for our axial skeleton • Rib cage supports the thoracic wall

4. Protection • Provide protection for all soft organs • Skull::brain; rib cage::lungs, heart; vertebrae::spinal cord

5. Movement: • Skeletal muscles attached to bones via tendons allow for movement of the skeletal system.

6. Storage: • Bones provide a means of storing fats, minerals (Calcium and phosphorus) • “deposits” and “withdrawals” of calcium to and from bones take place all the time

7. Blood cell Formation: • a.k.ahematopoiesis, occurs within the marrow of certain cavities of certain bones.

8. Classification of Bones • 206 bones in adults • Two basic types of osseus or bone tissue: • Compact bone is dense and looks smooth and homogenous • Spongy bone is composed of small needlelike pieces of bone and lots of open space. • Bones come in a variety of shapes and sizes • The unique shape of each bone fulfills a particular need.

9. Bone Classification: Shape • Bones are classified according to shape into four groups: • Long • Short • Flat • Irregular

10. Long Bones • Typically longer than they are wide • Composed of a shaft with a head at each end • Mostly compact bone • All bones of the limbs other than wrist and ankles

11. Short Bones • Generally cube-shaped • Contain mostly spongy bone • Wrist and ankles contain short bones • Sesamoid bones, form with tendons (kneecap)

12. Flat Bones • Thin, flattened and usually curved • Two thin outer layers of compact bone with a layer of spongy bone between them • Ribs, sternum and most bones of the skull

13. Irregular Bones • Bones that do not fit one of the preceding categories • Vertebrae and hips are examples

14. Structure of a Long Bone • Diaphysis or shaft • Makes up most of the bones length • Compact bone • Covered and protected by a fibrous connective tissue membrane called periosteum • The periosteum is secured to the bone by many connective tissue fibersSharpey’s fibers.

15. Epiphyses are the ends of the long bone • Compact bone enclosing an area filled with spongy bone • Covered with articular cartilage • Articular cartilage (hyaline cartilage) it provides a smooth, slippery surface to reduce friction in joints • In adult bones, a thin line of bony tissue throughout the epiphysis that is different in appearance. This is called the epiphyseal line, which is a remnant of the epiphyseal plate– a flat late of hyaline cartilage, cause the lengthwise growth of long bones. • E. P. – completely replaced by bone at the end of puberty

16. In adults the cavity of the shaft is a primary storage for adipose tissue • a.k.a. yellow marrow, or medullary cavity • In infants this area forms blood cells and red marrow is found in the cavity • In adults, red marrow is confined to the cavities of spongy bone of flat bones and the epiphyses of some long bones

17. Bone Markings • Bones are noticeably rough and scarred with bumps, holes and ridges. • The markings reveal where the attachment of muscles, tendons and ligaments attach and where blood vessels and nerves passed. • Two categories: • Projections or Process – grow out from the bone surface (all markings that begin with “t”) • Depressions or Cavities – indentations in the bone (all markings that begin with “f” except facet)