6 The Skeletal System: The Framework
Multimedia Asset Directory Slide 30 Hip Displacement Animation Slide 45 Bone Healing Animation Slide 54 Knee Displacement Animation Slide 58 Classification of Joints Animation Slide 64 Movement of the Joints Animation Slide 65 Ankle Dorsiflexion/Extension Animation Slide 66 Ankle Inflexion/Eversion Animation Slide 67 Elbow Pronation/Supination Animation Slide 68 Elbow Flexion/Extension Animation Slide 69 Hand Opposition Animation Slide 70 Humerus Adduction/Abduction Animation Slide 71 Humerus Circumduction Animation Slide 72 Humerus Rotation Animation
Multimedia Asset Directory Slide 73 Wrist Circumduction Animation Slide 74 Wrist Flexion/Extension Animation Slide 97 Osteoporosis Video Slide 98 Arthritis Video Slide 112 Fractures Animation Slide 113 Radiologic Technology Video
Introduction • The skeletal system provides support and allows us to move. • The bones (also known as osseous tissue) that make up the skeleton also protect the soft body parts, produce blood cells, and act as a storage unit for minerals and fat. • There are 206 bones in the adult skeleton, along with cartilage, ligaments, and joints.
Learning Objectives • Describe the functions of the skeletal system. • Identify and describe the anatomy and physiology of bone. • Locate and describe the various bones within the body. • Differentiate between bone, cartilage, ligaments, and tendons. • Locate and describe the various joints and types of movement of the body.
appendicular skeleton (app en DIK yoo lahr) arthritis (ahr THRYE tis) articulation (ahr TICK you LAY shun) axial skeleton (AK see al) callus (KAL us) diaphysis (dye AFF ih sis) epiphyseal plate (EP ih FEEZ ee al) epiphysis (eh PIFF ih sis) haversian (haah VER shun) Pronunciation Guide Click on the megaphone icon before each item to hear the pronunciation.
hemopoiesis (HEE moh poy EE sus) ischium (IS kee um) medullary cavity (MED uh lair ee) osseous tissue (OSS see us) ossification (OSS ih fih KAY shun) osteoarthritis (OSS tee oh ahr THRYE tis) osteocyte (OSS tee oh site) osteons (OSS tee ons) periosteum (pair ee OSS tee um) Pronunciation Guide Click on the megaphone icon before each item to hear the pronunciation.
synovial fluid (sin OH vee al) trabeculae (tra BECK you lay) vertebrae (VER teh bray) Pronunciation Guide Click on the megaphone icon before each item to hear the pronunciation.
Bones • The primary components of the skeleton are bones. • Although bones are composed of non-living minerals such as calcium and phosphorous, they are very much alive, constantly building and repairing themselves. • The word ‘skeleton’ comes from the Greek meaning “dried up body.”
General Bone Classifications • Bones are classified according to their shape. • Long bones • these bones are longer than they are wide and can be found in the arms and legs. • Short bones • these bones are fairly equal in width and length and are found mostly in the wrists and ankles.
General Bone Classifications • Bones are classified according to their shape. • Flat bones • these bones are thinner and can be either flat or curved. They can be plate-like in nature and would include the skull, ribs, and sternum (breast bone). • Irregular bones • these bones are like parts of a jigsaw puzzle, odd in shape, and include the hip bone and vertebrae.
Basic Bone Anatomy • Periosteum is a tough and fibrous connective tissue. • The periosteum contains blood vessels which transport blood and nutrients to nurture bone cells. • It also contains lymph vessels and nerves. • The periosteum acts as an anchor point for ligaments and tendons.
Basic Bone Anatomy • Epiphysis is the expanded end of the long bone. • Diaphysis is the region running between the two epiphyses. • The diaphysis is hollow. This hollow area is called the medullary cavity, and acts as a storage area for the yellow marrow. • Yellow marrow has a high fat content and can convert to red marrow, which makes red blood cells, in an emergency.
Bone Tissue • Bone can be composed of two types of tissue • Compact • Spongy
Compact Bone • Compact bone is a dense, hard tissue normally found in the shafts of long bones and the outer layer of other bones. • The tightly-packed material that composes this type of bone tissue makes for a dense and strong structure. • The material forms microscopic, cylindrical-shaped units called osteons, or haversian systems.
Compact Bone • Each of these units has mature bone cells (osteocytes) forming concentric circles around a central (haversian) canal, containing blood vessels. • The area around the osteocyte is filled with protein fibers, calcium, and other minerals. • The osteons run parallel to each other with perforating canals (blood vessel passages) literally connecting with them to ensure sufficient oxygen and nutrients for the bone cells.
Spongy Bone • Spongy, or cancellous, bone is arranged in bars and plates called trabeculae. • There are irregular holes between the trabeculae making the bone lighter in weight and providing space for red bone marrow, which produces red blood cells. • The holes give the bone a spongy appearance.
Surface Structure of Bones • Bone is not perfectly smooth. • There are a variety of projections, bumps, and depressions. • Projections act as points of attachment for muscles, ligaments, or tendons. • Grooves and depressions act as pathways for nerves and blood vessels. • Projecting structures and depressions can work together as joining or articulation points to form joints such as the ball and socket joint in your hip.
From the Streets:Intraosseous (IO) Needle Placement • Large bones are highly vascular, allowing large volumes of fluid to be transferred to the central circulation. • Specially designed IO needles pierce the cortex of the bone • IO route viable route for critically ill or injured patients.
From the Streets:Intraosseous (IO) Needle Placement • Current trauma practices call for limited fluid administration in trauma, so the expanding role of IO therapy appears to be in cardiac arrest when an IV cannot be placed.
Figure 6-4 Intraosseous needle properly placed in marrow cavity and medullary sinusoids.
Figure 6-5 Special intraosseous needle for emergency intraosseous access.
Figure 6-6 Bone injection gun (BIG) IO device. (a) adult; (b) pediatric.
Figure 6-6 Bone injection gun (BIG) IO device. (a) adult; (b) pediatric.
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Bone Growth and Repair • Ossification is the term used to describe the formation of bone in the body. • Bones grow longitudinally in order to develop height and they grow horizontally (wider and thicker) so they can more efficiently support our body weight and any other weight we support.
Types of Cells Involved in Formation and Growth • Osteoprogenitor cells • Osteoblasts • Osteocytes • Osteoclasts
Osteoprogenitor Cells • Osteoprogenitor cells are non-specialized cells found in the periosteum, endosteum, and central canal of compact bones. • Non-specialized cells can turn into other types of cells as needed.
Osteoblasts • Osteoblasts are the cells that actually form bones. • They arise from the non-specialized osteoprogenitor cells and are the cells that secrete the matrix of calcium with other minerals that give bone its typical characteristics.
Osteocytes • Osteocytes are considered mature bone cells and started as osteoblasts. • Osteoblasts surround themselves with a matrix to then become the mature osteocytes.
Osteoclasts • It is believed that osteoclasts originate from a type of white blood cell called a monocyte that is found in red bone marrow. • The osteoclasts’ job is to tear down bone material and help move calcium and phosphate into the blood.
Bone Development and Growth • Bone development begins when you are an embryo. • Intramembranous ossification • Occurs when bone develops between two sheets composed of fibrous connective tissue. • Cells from connective tissue turn into osteoblasts and form a matrix while other osteoblasts create compact bone over the surface of the spongy bone. • Once the matrix surrounds the osteoblasts they become osteocytes. • This is how the bones of the skull develop.
Bone Development and Growth • Endochondral ossification • The majority of bones form through endochondral ossification. • Shaped cartilage is replaced by bone. • Periosteum surrounds the diaphysis of the cartilage model as the cartilage begins to break down.
Bone Development and Growth • Endochondral ossification • Osteoblasts come into the diaphysis and create spongy bone in an area that is then referred to as the primary ossification center. • Other osteoblasts begin to form compact bone under the periosteum. The osteoclasts break down the spongy bone of the diaphysis to create the medullary cavity.
Epiphyseal Plate • After you are born, the epiphysis on your long bones continues to grow. • A thin band of cartilage forms an epiphyseal plate (growth plate) between the primary and secondary ossification centers. • This plate exists as long as bones need to lengthen. Controlled by hormones, the plate will eventually ossify and stop the growth process.
Bone Repair • When a bone is fractured, it must be repaired. • Bone repair is accomplished by the same process as bone growth, endochondral ossification. • Bone tissue is very good at repairing itself, but for a bone fracture to heal, the ends of broken bone must be touching. If they are not, then a medical procedure called reduction (setting) must be performed. Then the bone must be immobilized so the ends will stay touching.
Bone Repair • Stage 1 is hematoma formation and inflammation. • Stage 2 is soft (fibrocartilage) callus formation. Cartilage fills in the space between the bones. • Stage 3 is hard (bony) callus formation. Bone replaces the cartilage via endochondral ossification. • In stage 4, the bone is remodeled via the activity of osteoblasts and osteoclasts until the fracture is nearly undetectable.
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Cartilage • Cartilage is a special form of dense connective tissue that can withstand a fair amount of flexing, tension, and pressure. • The flexible parts of your nose and ears are cartilage. • Cartilage also makes a flexible connection between bones, as between the ribs and sternum, allowing chest flexion during deep breathing.
Cartilage • Cartilage acts as a cushion between bones. Articular cartilage is located on the ends of bones and acts as a shock absorber, preventing the ends from grinding together when you move. • In this location, a small sac, called a bursa, secretes a lubricant called synovial fluid. • Joints can still wear out and become inflamed despite all this protection, resulting in arthritis or osteoarthritis.
Joints and Ligaments • When two or more bones join together it forms a joint or articulation. • Articulating joints are held together, yet are still movable. This is accomplished by special connective tissue called ligaments. • Ligaments are very tough, whitish bands that connect from bone to bone and can withstand heavy stress. • Tendons are cord-like structures that attach muscle to bone.
Types of Joints • Classified by function • Joints can be immobile, can move a little, or can move freely. For example, skull sutures are immobile, the pubic symphysis between your pelvic bones moves a little, and your elbow moves freely.