1 The Skeletal System continues…

2 Skeletal System Parts of the skeletal system: 1.Bones 2.Joints 3.Ligaments 4.Cartilage Separated into 2 main divisions: 1.Axial 2.Appendicular

3 Review of the Functions of the Skeletal System 1.Support of the body 2.Protection of soft organs – Skull and vertebrae for brain and spinal cord – Rib cage for thoracic cavity organs 3.Movement due to attached skeletal muscles 4.Storage of minerals (Ca + and P) & fats 5.Blood cell formation (hematopoiesis)

4 Bones of the Human Body The adult skeleton has 206 bones 2 basic types of bone tissue: 1.Compact Bone – dense, looks smooth and homogenous; provides strength and stability. 2. Spongy Bone – lattice-like pieces of bone with open spaces; provides shock absorption and flexibility Figure 5.2b Spongy bone Compact bone

5 Classification of Bone Shapes Figure 5.1 Bones are classified as: –Long –Short –Flat –Irregular

6 Classification of Bone Shapes

7 1. Long bones – longer than they are wide – Usually shaft w/head at ends – Limb bones except wrist and ankle – Mostly compound bone – Example: Humerus 2. Short bones – cube shaped – Mostly spongy bone – Wrist and ankle – Sesamoid bones are a type of short bone which form within tendons (ex. patella)

8 Classification of Bone Shapes 3. Flat bones – Thin, flat and usually curved – 2 thin layers of flat compound bone sandwiching spongy bone – Ex. Skull, ribs and sternum 4. Irregular bones – miscellaneous – Vertebrae, hip bones

9 Anatomy of a Long Bone Diaphysis – shaft of bone – Compact bone – Covered by connective tissue called periosteum Epiphysis – ends of bone – Compact bone surrounding spongy bone center Figure 5.2a Distal epiphysis Diaphysis Proximal epiphysis Articular cartilage Spongy bone Epiphyseal line Periosteum Compact bone Medullary cavity (lined by endosteum) (a

Where do Long Bones get their strength? The diaphysis region of a long bone functions to transfer loads more evenly from weight-bearing joint surfaces throughout both the diaphysis and the epiphysis.

11 Epiphyseal plate – Flat plate of hyaline cartilage seen in young, growing bone Epiphyseal line – Remnant of the epiphyseal plate – Seen in adult bones Anatomy of a Long Bone Distal epiphysis Diaphysis Proximal epiphysis Articular cartilage Spongy bone Epiphyseal line Periosteum Compact bone Medullary cavity (lined by endosteum) (a)

12 Changes in the Human Skeleton In embryos/fetus, the skeleton is primarily hyaline cartilage During development, much of this cartilage is replaced by bone - ossification Cartilage remains in isolated areas: – Bridge of the nose – Parts of ribs – Joints

13 Long Bone Formation and Growth Figure 5.4a

14 Types of Bone Cells Osteocytes – Mature bone cells Osteoblasts – Bone-forming cells Osteoclasts — Giant bone-destroying cells – Break down bone matrix for remodeling and release of calcium Bones are remodeled in response to Ca + levels in the blood and the pull of gravity and muscles on the bones; such as occurs with activity or exercise. Rickets – disease where bones fail to calcify, legs bow out -Caused by a lack of vitamin D -Bones can also atrophy in bed ridden people

Synovial Fluid the principal role of synovial fluid is to reduce friction between the cartilage of two bones meeting at joints, especially during movement.

What is a Sprain? A sprain is an injury to a ligament (the tissue that connects 2+ bones at a joint). In a sprain, one or more ligaments is either over stretched/ extended or torn.