Chapter 6 Bones and Skeletal System Classification of

Chapter 6 Bones and Skeletal System

Classification of Bones • Axial skeleton – bones of the skull, vertebral column, and rib cage • Appendicular skeleton – bones of the upper and lower limbs, shoulder, and hip

Function of Bones • Support – form the framework that supports the body and cradles soft organs • Protection – provide a protective case for the brain, spinal cord, and vital organs • Movement – provide levers for muscles • Mineral storage – reservoir for minerals, especially calcium and phosphorus • Blood cell formation – hematopoiesis occurs within the marrow cavities of bones

Classification of Bones: By Shape • Long bones – longer than they are wide (e. g. , humerus) • Short bones • Cube-shaped bones of the wrist and ankle • Bones that form within tendons (e. g. , patella) • Flat bones – thin, flattened, and a bit curved (e. g. , sternum, and most skull bones) * Irregular bones – bones with complicated shapes (e. g. , vertebrae and hip bones)

General Facts a. The skull is made of 22 bones: 8 cranial, 13 facial, mandible b. There are 206 individual bones in an adult. Some are hinged and others are fused to one another c. The upper jaw (maxillae) is fused to the cranium. The lower jaw (mandible) is moveable. d. The infant skull is incompletely developed and features fontanels or soft spots to aid passage thru the birth canal

General Facts continued. . . e. The vertebrate is made of: f. i. 7 cervical vertebrae g. ii. 12 thoracic vertebrae h. iii. 5 massive lumbar vertebrae i. iv. Sacrum, which is a triangular bone made of 5 fused bones at the end of the vertebral column. j. v. Coccyx, which is made up of 4 fused bones at the end of the sacrum (tailbone). It is immovable in humans, but flexible in cats, dogs, and monkeys

General Facts continued. . . f. There are 12 pairs of ribs which attach to the sternum thru the thoracic vertebrae. g. -the first 7 pairs of ribs are true (or vertebrosternal) ribs that join the sternum directly by their costal cartilages. h. -the remaining 5 ribs are false ribs: the first 3 pairs are vertebrochondral ribs and the last 2 pairs are floating ribs. g. Bones grow from the growth in the epiphyseal disks plates

Parts of the Long Bone • Periosteum – double-layered protective membrane – Outer fibrous layer is dense regular connective tissue – Inner osteogenic layer is composed of osteoblasts and osteoclasts – Richly supplied with nerve fibers, blood, and lymphatic vessels, which enter the bone via nutrient foramina – Secured to underlying bone by Sharpey’s fibers • Endosteum – delicate membrane covering internal surfaces of bone

Parts of the Long Bone (cont. ) • Marrow: i. Yellow: Located in the center of the diaphysis in the medullary canal. Made mostly of fat cells, contains many blood vessels, some leukocytes (WBC). Functions as a fat storage center. ii. Red: Located at the ends of the long bones. Where some erythrocytes (RBC) and WBCs are made.

Gross Anatomy of Bones: Bone Textures • Compact bone – dense outer layer. Makes up the walls of the diaphysis. • Spongy bone – honeycomb of trabeculae filled with yellow bone marrow. Fills the epiphyses to reduce the weight of the skeleton.

Bone Markings Structure of Long Bone • Long bones consist of a diaphysis and an epiphysis – Diaphysis • Tubular shaft that forms the axis of long bones • Composed of compact bone that surrounds the medullary cavity • Yellow bone marrow (fat) is contained in the medullary cavity

Structure of Long Bone (cont. ) • Epiphyses – Expanded ends of long bones – Exterior is compact bone, and the interior is spongy bone – Joint surface is covered with articular (hyaline) cartilage – Epiphyseal line separates the diaphysis from the epiphyses

Microscopic Structure of Bone: Compact Bone • Osteocytes – mature bone cells • Lacunae – small cavities in bone that contain osteocytes • Canaliculi – hairlike canals that connect lacunae to each other and the central canal

Microscopic Structure of Bone: Compact Bone • Haversian system, or osteon – the structural unit of compact bone • Lamella – weight-bearing, column-like matrix tubes composed mainly of collagen • Haversian, or central canal – central channel containing blood vessels and nerves • Volkmann’s canals – channels lying at right angles to the central canal, connecting blood and nerve supply of the periosteum to that of the Haversian canal

Formation of the Bony Skeleton • Begins at week 8 of embryo development • Bones form by replacing connective tissue in the fetus. This process is called ossification

Bone Development (cont. ) There are 2 types of bones: i. Intramembraneous bones 1. Osteopblasts deposti bondy tissue around themselves and they become oseteocytes. 2. The membrane layer on the outside of the developing bone become the periosteum.

Bone Development (cont. ) There are 2 types of bones: ii. Endochondral bones 1. Classification of most bones in the body. 2. Starts as hyaline cartilage and are replaced by bones. 3. Cartilage is invaded by blood vessels and oseoblasts that first form the spongy bone.

10 Types of Fractures 1. Compression Fracture: bone crushed; common in the vertebral column 2. Comminuted fracture: most commonly seen in the brittle bones of the elderly 3. Compound fracture: fracture in which the bone ends penetrate the skin 4. Closed reduction: non-surgical realignment of broken bone ends and splinting of the bone. 5. Depressed fracture: common fracture of the skull in which the bones become concave

10 Types of Fractures (cont. ) 6. Simple fracture: bone is cleanly broken and does not penetrate the skin; commonly called a closed fracture 7. Impacted fracture: fracture in which the broken ends are pushed into each other 8. Open fracture: fracture that required surgical realignment of the broken bone ends 9. Greenstick fracture: common in children; bone splinters but doesn’t break completely; sometimes referred to as a “hairline” fracture 10. Spiral fracture: bone breaks due to twisting forces: common in sports injuries

Closed reduction Open reduction compound

Impacted

Bone Videos • X-rays • http: //video. about. com/orthopedics/How. Does-an-X-Ray-Work--. htm • Hip Replacements • http: //video. about. com/orthopedics/Hip. Replacement. htm • Knee Replacement • http: //video. about. com/orthopedics/Knee. Replacement. htm