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The Skeletal System

The Skeletal System. Axial Skeleton Appendicular Skeleton

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  • The Skeletal System

  • Axial SkeletonAppendicular Skeleton

  • Axial Skeleton

  • Axial Skeleton

  • Axial Skeleton

  • Axial Skeleton

  • Axial Skeleton Hyoid Bone

  • Axial Skeleton

  • Axial Skeleton

  • Appendicular Skeleton

  • Appendicular Skeleton

  • Appendicular Skeleton

  • Appendicular Skeleton

  • Bone TissueOsteoblasts bone forming cellsOsteocytes The BONE CELLSOsteoclasts bone reabsorbing cells

  • Two Types of Bone TissueCompact Bone and Spongy Bone

  • Classification of BonesLong Bones Short Bones Flat BonesIrregular BonesProximalEpiphysisDiaphysisDistalEpiphysis

  • Features of Bone

    Projections that form jointsFeatures of Bone

    Projections that form joints

    Projections that are sites of muscle & ligament attachment

    Features of Bone

    Projections that form joints

    Projections that are sites of muscle & ligament attachment

    Openings that allow blood vessels and nerves to pass

    Features of Bone

    Projections that form joints

    Projections that are sites of muscle & ligament attachment

    Openings that allow blood vessels and nerves to pass


  • Structure of Bone

  • Bone Development & GrowthTwo Categories of Bone Development

    Intramembranous (Direct) forms spongy bone and eventually may form compact bone from embryonic fibrous membrane

    Endochondral - bone forms from cartilage; forms skull & flatbones

    Before week 8 of fetal life, the human skeleton is all fibrous membrane & hyaline cartilage

  • Bone Development & Growth

  • Epiphyseal Plate Growth Plate

  • Joints or Articulation

  • Joints Three Types

    Fixed Joint

    Cartilaginous Joint

    Synovial Joint

  • Synovial Joints

  • Broken Bone Repairs

  • Michael Paulus' Cartoon Skeletons

    **The adult human skeleton usually consists of 206 named bones.

    Femur (say: fee-mur) Largest bone in the body. More commonly known as the thigh bone. The femur is the longest, strongest, and heaviest bone in the body. The femur supports much of our body weight. The smallest are the ear ossicles. All 3 would find on a dime.

    The human skeleton consists of more than 200 bones of varying size, shape, and composition. In addition to their supporting function, bones, by virtue of their articulations with each other and their attachments to muscles, are responsible for the mobility of the head, trunk, and limbs. They also protect the skull, vertebral column, sensory organs, brain, and spinal cord. In their interior they accommodate the bone marrow. As a reservoir of phosphate and calcium, bone tissue plays an important role in mineral metabolism. Bone undergoes constant restructuring (remodelling) and is thereby adapted to changes in static forces. Coordination of the processes involved in the breakdown, formation, and remodelling of bone, including the deposition and removal of bone substance and the formation of new bone during the healing of fractures, is undertaken mostly by cellular messenger substances, hormones produced by the parathyroid gland, enzymes, and vitamin D. The kidneys, liver, and gastrointestinal tract influence bone tissue via their effects on protein and mineral metabolism. One factor that has an important influence on bone in both men and women is estrogen. Bones possess high compressive and tensile strength. Cortical (compact) bone consists of a layer of varying thickness that is bounded externally by periosteum and internally by a unicellular endosteal layer. Spongy (trabecular, cancellous) bone is the spongiform, porous bone that lies internal to the cortical bone and itself accommodates the bone marrow. *These bones can be grouped in two divisions: axial skeleton and appendicular skeleton. The 80 bones of the axial skeleton form the vertical axis of the body. They include the bones of the head, vertebral column, ribs and breastbone or sternum.

    The appendicular skeleton consists of 126 bones and includes what is called the free appendages and their attachements to the axial skeleton. The free appendages are the upper and lower extremities, or limbs, and their attachments which are called girdles. These 4 parts are the pectoral girdle, upper extremities, the pelvic girdle and the lower extremities. and their attachments to the axial skeleton. *Parietal (2) Temporal (2) bone where middle and inner ear embededFrontal (1) Occipital (1) Ethmoid (1) - inside orbital (eye) and nose eth moidSphenoid (1) spfee noid

    Sutures places where these bones are fused together by fibers, a little elasticisty; at birth not fused soft membranous areas between plates called fontanelle by age 2 these are ossified (hard, bone)*Maxilla (2) max cilaZygomatic (2) zy go maticMandible (1) Nasal (2) Vomer (1) inside nose, middle behind cartilageLacrimal (2) inside, btw eye & nose, next to ethnoid

    *Malleus (2) mal lee usIncus (2) Stapes (2) stay peas

    The inner and middle ear are embedded in the temporal bone*Our gift of the gab is all due to a small horseshoe-shaped bone suspended in the muscles of our neck, like a piece of fruit trapped in Jell-O. The hyoid bone, which is the only bone in the body not connected to any other, is the foundation of speech and is found only in humans and Neanderthals. Other animals have versions of the hyoid, but only the human variety is in the right position to work in unison with the larynx and tongue and make us the chatterboxes of the animal world.

    This image shows the human hyoid bone, which helps to support the tongue and serves as an attachment point for several muscles that help to elevate the larynx during swallowing and speech. The hyoid bone is unique in that it is the only bone of the body that does not articulate with any other bone. Instead, it is suspended above the larynx where it is anchored by ligaments to the styloid processes of the temporal bones of the skull.

    Hi oid*This bone is not on the list for your to memorize*Cervical vertebrae (7) Thoracic vertebrae (12) Lumbar vertebrae (5) Sacrum (1) 5 fused vertebrae say crumCoccyx (1) - 4 fused vertebrae cock sis

    *Sternum (1) Ribs (24)

    The ribs are connected to it by the costal cartilage. Without the sternum, there would be a hole in the bone structure in the middle of your chest, right above your heart and lungs. The sternum protects this vital area and completes the circle of the rib cage.

    1). True Ribs: (1-7)Superior 7 pairs of ribs attach to the sternum with costal cartilage.2). False Ribs (8-10)3 pairs of ribs lack the sternal attachment, but connect to the costal cartilage of the rib 7.3). Floating Ribs (11-12)no anterior attachment

    *Clavicle (2) collar boneScapula (2) shoulder blade scap u la

    *Humerus (2) Radius (2) Ulna (2) ul naCarpals (16) Metacarpals (10) Phalanges (28) fa lange

    *Pelvic girdle

    Coxal, innominate, or hip bones (2)

    ring of bone forming the skeleton of the pelvis, supporting the vertebral column*Femur (2) - thigh boneTibia (2) Fibula (2) Patella (2) - kneecap - front of kneeTarsals (14) connection between leg & foot tarsusMetatarsals (10) Phalanges (28) *Osteoblasts are bone-forming cells. They are connective tissue cells found at the surface of bone. They can be stimulated to proliferate and differentiate as osteocytes.Osteocytes are bone cells. Osteocytes manufacture type I collagen and other substances that make up the bone extracellular matrix. Osteocytes will be found enclosed in bone.Osteoclasts are bone-resorbing cells ("-clast" means to break; osteoclasts break down bone). They are large, multinucleate cells that form through the fusion of precursor cells. Unlike osteoblasts, which are related to fibroblasts and other connective tissue cells, osteoclasts are derived from stem cells in the bone marrow that also give rise to monocytes.

    Osteoclasts resorb bone tissueNew bone substance is produced by osteoblasts, which tend to refill resorption lacunae as they arise. The new bone material, or osteoid, formed in this way is rendered hard by deposition of calcium phosphate crystals. Once the original bone-forming cell has been incorporated into this bone matrix, it stops dividing and (now known as an osteocyte) comes to occupy a small cavity (bone lacuna) in the matrix. From this lacuna radiate slender channels containing extensions of the osteocyte. These communicate with the osteocytes of neighbouring lacunae. Osteoclasts, by contrast, break down bone matrix. These large cells, which have become multinucleate by a process of cell fusion, are derived from hemopoietic stem cells of the bone marrow. They erode bone substance by forming resorption lacunae. In the middle of such a lacuna grows a blood capillary that supplies nutrients to the bone cells. Once the lacuna acquires a certain depth, osteoblasts respond by filling it with osteoid. While some tunnels are closed with bone material, osteoclasts construct others, in the process cutting older concentric rings of osteocytes. The more osteoclasts are activated, the more bone material is resorbed. Each osteoclast leaves behind a resorption lacuna with an average size of 30 (width) x 70 (length) x 30 (depth) microns. As the number and depth of resorption lacunae increases and as the diameter of the remaining trabeculae (lamellae) decreases, the trabecular bone becomes increasingly brittle. Only 5 to 20 percent of the bone surface undergoes remodelling at any given time, the rest remaining in the quiescent phase. The local remodelling process, which begins with activation of osteoclasts and ends with osteoblastic new bone formation, takes three to four months. In a healthy person between five and ten percent of bone substance is replaced annually. *Compact bone consists of closely packed osteons or haversian systems. The osteon consists of a central canal called the osteonic (haversian) canal, which is surrounded by concentric rings (lamellae) of matrix. Between the rings of matrix, the bone cells (osteocytes) are located in spaces called lacunae. Small channels (canaliculi) radiate from the lacunae to the osteonic (haversian) canal to provide passageways through the hard matrix. In compact bone, the haversian systems are packed tightly together to form what appears to be a solid mass. The osteonic canals contain blood vessels that are parallel to the long axis of the bone. These blood vessels interconnect, by way of perforating canals, with vessels on the surface of the bone.

    Spongy (cancellous) bone is lighter and less dense than compact bone. Spongy bone consists of plates (trabeculae) and bars of bone adjacent to small, irregular cavities that contain red bone marrow. The canaliculi connect to the adjacent cavities, instead of a central haversian canal, to receive their blood supply. It may appear that the trabeculae are arranged in a haphazard manner, but they are organized to provide maximum strength similar to braces that are used to support a building. The trabeculae of spongy bone follow the lines of stress and can realign if the direction of stress changes.*Periosteum: thin membrane that covers a bone

    What is bone marrow?The bone marrow is a soft, spongy tissue found inside the bones. The bone marrow in the hips, breast bone, spine, ribs, and skull contain stem cells that produce the body's blood cells. The bone marrow is responsible for the development and storage of about 95 percent of the body's blood cells. The three main types of blood cells produced in the bone marrow include:red blood cells (erythrocytes) - carry oxygen to the tissues in the body. white blood cells (leukocytes) - help fight infections and to aid in the immune system. platelets - help with blood clotting. Each of these cells carries a life-maintaining function. The bone marrow is a vital part of the human body.The soft tissue filling the cavities of bones. Bone marrow exists in two types, yellow and red. Yellow marrow is found in the large cavities of large bones and consists mostly of fat cells and a few primitive blood cells. Red marrow is a hematopoietic tissue and is the site of production of erythrocytes and granular leukocytes. Bone marrow is made up of a framework of connective tissue containing branching fibers with the frame being filled with marrow cells.

    red blood cells (erythrocytes) - carry oxygen to the tissues in the body. white blood cells (leukocytes) - help fight infections and to aid in the immune system. platelets - help with blood clotting. Each of these cells carries a life-maintaining function. The bone marrow is a vital part of the human body.

    **The bones of the body come in a variety of sizes and shapes. The four principal types of bones are long, short, flat and irregular.

    Long bones - Bones that are longer than they are wide are called long bones. They consist of a long shaft with two bulky ends or extremities. They are primarily compact bone but may have a large amount of spongy bone at the ends or extremities. Long bones include bones of the thigh, leg, arm, and forearm.

    Short Bones - Short bones are roughly cube shaped with vertical and horizontal dimensions approximately equal. They consist primarily of spongy bone, which is covered by a thin layer of compact bone. Short bones include the bones of the wrist and ankle.

    Flat Bones - Flat bones are thin, flattened, and usually curved. Most of the bones of the cranium are flat bones. They protect organs

    Irregular Bones - Bones that are not in any of the above three categories are classified as irregular bones. They are primarily spongy bone that is covered with a thin layer of compact bone. The vertebrae and some of the bones in the skull are irregular bones. Ex is vertebrae

    All bones have surface markings and characteristics that make a specific bone unique. There are holes, depressions, smooth facets, lines, projections and other markings. These usually represent passageways for vessels and nerves, points of articulation with other bones or points of attachment for tendons and ligaments.**Computer color-enhanced X ray depicting the hand development of a two, six, and nineteen year old male.

    DEVELOPMENT OF BONE - 2 CATEGORIES: 1. Intramembranous (Direct) - forms spongy bone and eventually may form compact boneBone forms directly from mesenchyme *2. Endochondral - bone forms replacing cartilage "model (long bones)

    1. Formation of Primary Center of Ossificationa) hyaline cartilage model is formed b) Osteoblasts invade cartilage and start to fill with trecular

    2. Expansion of Primary Center of Ossificationa) as bone increases in size by appositional growth (laying down of layers), primary center of ossification expands toward ends of bone b) epiphyses at each end continue interstitial production of cartilage, but epiphyseal regions don't expand because cartilage is replaced on diaphyseal side by bone at same rate as it is produced c) epiphyseal plate extends horizontally across bone and is the region where cartilage replacement during expansion occurs. AT adulthood this plate gets calcified and forms the Epiphyseal line, a visual line but no growth.The growth plate, also known as the epiphyseal plate or physis, is the area of growing tissue near the ends of the long bones in children and adolescents. Each long bone has at least two growth plates: one at each end. The growth plate determines the future length and shape of the mature bone. When growth is completesometime during adolescencethe growth plates close and are replaced by solid bone.

    Because the growth plates are the weakest areas of the growing skeletoneven weaker than the nearby ligaments and tendons that connect bones to other bones and musclesthey are vulnerable to injury. Injuries to the growth plate are called fractures.**A joint, or articulation, is where two or more bones meet and also often where movement occurs.

    There are over 100 different types of joints but they are generally linked together by the amount of movement which they allow. The moveable joints in the body permit different kinds of movement. The type, direction and amount of movement is governed by the limitations (structure) of the joint.

    Muscles move our joints. If we have weak muscles the joints don't move so well. It is important we keep using our muscles even if we have arthritis. Ligaments hold the bones together at the joints and look like thick white bands of tissue Tendons attach the muscles to the bones so that the bones can be moved Cartilage coats the end of the bones to stop the bones rubbing together.

    *There are three main different types of joint. Immovable or Fibrous joints These are very stable and allow no observable movement. Bones are often joined by strong fibres called sutures; eg, the sutures of the cranium.

    Slightly movable joints or Cartilaginous A cartilaginous joint allows some slight movement. The ends of bones, which are covered in articular or hyaline cartilage, are separated by pads of white fibrocartilage and slight movement is made possible only because the pads of cartilage compress. In addition, the pads of cartilage act as shock absorbers. The intervertebral discs are examples of this type of joint. Freely movable joints or Synovial joints A synovial joint is a freely moving joint, and is the most common type of joint in the body, and the most important in terms of physical activity, since they allow a wide range of movement. These types of joint are divided up according to the movement that they make possible. Surrounding the joint is a membrane called the Synovial Membrane which is where Synovial fluid is formed. This fluid acts as a lubricator and is formed within the joint AND allows friction free movement. A good example of this is the knee joint.

    *Synovial joints permit the greatest degree of flexibility and have the ends of bones covered with a connective tissue filled with synovial fluid; example: hip.

    The outer surface of the synovial joints contains ligaments that strengthen joints and hold bones in position. The inner surface (the synovial membrane) has cells producing synovial fluid that lubricates the joint and prevents the two cartilage caps on the bones from rubbing together. Some joints also have tendons (connective tissue linking muscles to bones). Bursae are small sacs filled with synovial fluid that reduce friction in the joint. The knee joint contains 13 bursaeYOUR JOB

    find out how this is done. Textbook chp 6

    ***Michael Paulus' Cartoon Skeletons