L15
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L15

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What is the role of osteoprogenitor cells in bone tissue?

  • They differentiate into osteoblasts and help in bone formation. (correct)
  • They secrete osteoid that binds calcium to form hydroxyapatite.
  • They reside inside lacunae and maintain bone matrix.
  • They are specialized cells that break down bone tissue.

    • Which type of cell is responsible for the actual deposition of bone matrix?

  • Osteocytes
  • Osteoclasts
  • Osteoblasts (correct)
  • Chondrocytes

    • Where are osteocytes located within the bone structure?

  • On the surface of bones
  • In the periosteum
  • Inside lacunae within the bone matrix (correct)
  • In the bone marrow

    • What is the primary function of osteoid secreted by osteoblasts?

    <p>To bind calcium phosphate and hydroxide for mineralization</p> Signup and view all the answers

    Which components are found in the matrix of bone tissue?

    <p>Collagen fibers and hydroxyapatite</p> Signup and view all the answers

    How do osteocytes communicate with each other?

    <p>Via tiny channels called canaliculi</p> Signup and view all the answers

    What is the main source of osteoblasts in bone tissue?

    <p>Osteoprogenitor cells</p> Signup and view all the answers

    What general function do specialized bone cells serve?

    <p>They maintain and regulate bone tissue.</p> Signup and view all the answers

    What is the primary function of osteoclasts in the formation of the medullary cavity?

    <p>They carve away the center of the calcified region.</p> Signup and view all the answers

    Which zone of the epiphyseal plate is closest to the diaphysis?

    <p>Zone of ossification</p> Signup and view all the answers

    What effect do sex hormones have during puberty on bone growth?

    <p>They increase the rate of calcification.</p> Signup and view all the answers

    What initiates growth in thickness (appositional growth) of bone?

    <p>Creation of osteoblasts from periosteal osteoprogenitor cells.</p> Signup and view all the answers

    What happens to the epiphyseal plate as osteoblasts increase their activity?

    <p>It becomes the epiphyseal line.</p> Signup and view all the answers

    How does bone remodeling contribute to bone health?

    <p>It allows the bone structure to adjust under different types of stress.</p> Signup and view all the answers

    What is a consequence of regular weight training on bone structure?

    <p>Bones may become thicker and stronger.</p> Signup and view all the answers

    Which of the following best describes the role of the endosteum in bone structure?

    <p>It helps in the creation of concentric lamellae.</p> Signup and view all the answers

    What is the primary function of osteoclasts in bone tissue?

    <p>To carve away bone through a process called bone resorption</p> Signup and view all the answers

    Which of the following best describes the structure of osteoclasts?

    <p>Massive, multinucleated cells with a ruffled border</p> Signup and view all the answers

    What is the purpose of the sealing zone in osteoclast function?

    <p>To tightly bind the osteoclast to the bone surface</p> Signup and view all the answers

    Which organic material makes up about one-third of the bone matrix?

    <p>Collagen I</p> Signup and view all the answers

    What primarily forms the inorganic component of the bone matrix?

    <p>Calcium hydroxyapatite and mineral salts</p> Signup and view all the answers

    Which protein binds calcium ions to collagen in the bone matrix?

    <p>Osteonectin</p> Signup and view all the answers

    What is the primary function of calcitonin in blood calcium regulation?

    <p>Inhibits osteoclastic bone resorption</p> Signup and view all the answers

    What role does the periosteum play in bone structure?

    <p>It covers and protects the outer surface of bones</p> Signup and view all the answers

    What does the ruffled border of osteoclasts release to aid in bone resorption?

    <p>Low pH fluids and proteases</p> Signup and view all the answers

    Which hormone directly stimulates the resorption of calcium from bone?

    <p>Parathyroid hormone</p> Signup and view all the answers

    What is the first stage in the typical repair of bone fractures?

    <p>Reactive (inflammatory) phase</p> Signup and view all the answers

    What happens during the reparative phase of bone repair?

    <p>Fibrous cartilage callus forms</p> Signup and view all the answers

    During which phase do osteoblasts replace spongy bone with compact bone?

    <p>Bone remodeling phase</p> Signup and view all the answers

    Which condition describes a bone that heals in an abnormal position?

    <p>Malunion</p> Signup and view all the answers

    What is a major consequence of nonunion in bone healing?

    <p>Bone fails to heal properly</p> Signup and view all the answers

    What does calcitriol do in terms of calcium levels in the body?

    <p>Promotes absorption of calcium from the gastrointestinal tract</p> Signup and view all the answers

    What type of cells do osteoclasts originate from?

    <p>Monocytes</p> Signup and view all the answers

    Which lamella surrounds an osteon?

    <p>Concentric lamella</p> Signup and view all the answers

    During which phase of bone repair is a fracture hematoma formed?

    <p>Reactive phase</p> Signup and view all the answers

    What material is primarily found in spongy bone?

    <p>Trabecular tissue</p> Signup and view all the answers

    What is the primary function of osteoblasts?

    <p>Form new bone tissue</p> Signup and view all the answers

    What type of growth occurs at the epiphyseal plate?

    <p>Lengthwise growth</p> Signup and view all the answers

    What is the role of chondroblasts during bone repair?

    <p>Produce a fibrocartilage callus</p> Signup and view all the answers

    Which hormone is known to help maintain blood calcium levels?

    <p>Parathyroid hormone</p> Signup and view all the answers

    Study Notes

    Bone Histology

    • Bone tissue is composed of specialized cells, bone matrix, and a specific organization.
    • Cells are classified as:
      • Osteoprogenitor cells: Unspecialized stem cells that give rise to osteoblasts, located in the periosteum and endosteum, derived from mesenchymal tissue.
      • Osteoblasts: Immature bone cells that build bone in a process called bone deposition, found on the surface of bones, typically appearing as cuboidal-shaped cells in groups, osteoblasts secrete osteoid.
      • Osteocytes: Mature osteoblasts surrounded by bone matrix, located within lacunae, essential for detecting mechanical stress and maintaining bone matrix, appear as small cells surrounded by compact bone, communicate with other osteocytes via canaliculi.
      • Osteoclasts: Large, multi-nucleated bone cells that carve away bone in a process known as bone resorption, derived from monocytes (a type of leukocyte), found on the surface of bones, appear as massive, multinucleated cells with resorption lacunae, sealing zone, and ruffled border.
    • Bone matrix is composed of organic and inorganic materials.
      • Organic materials: (about 1/3 of bone) provide flexibility and a framework for the inorganic mineral salts, mainly secreted by osteoblasts as osteoid, collagen (I) is the most abundant organic substance in bone.
      • Inorganic materials: (about 2/3 of bone) give bones their strength and rigidity, make up calcium hydroxyapatite which is the most abundant inorganic substance.
    • Periosteum: Dense irregular connective tissue covering bone, comprises an outer fibrous layer (collagen (I), blood vessels, and nerves) and an inner cellular layer (osteoprogenitor cells)
    • Endosteum: Connective tissue lining the medullary (marrow) cavity and the canals that pass through compact bone, composed of osteoprogenitor cells.

    Bone Tissue Types

    • Compact bone: Dense, solid bone that makes up the outer layer of most bones, it is resistant to compression and bending stress.
    • Spongy (cancellous) bone: Lighter, porous bone that contains a network of trabeculae which forms the inner layer of most bones, it also helps to reduce weight, allow for bone marrow production, and provides strength.
    • Lamellae: Concentric rings of bone matrix that make up osteons.
      • Concentric lamellae: Rings in osteons surrounding the central canal.
      • Interstitial lamellae: Incomplete lamellae between osteons.
      • Circumferential lamellae: Rings located at the periphery of compact bone.
    • Osteons: Cylindrical structures in compact bone that contain a central canal, lamellae, lacunae, and canaliculi.

    Bone Formation

    • Intramembranous ossification: Formation of bone directly from mesenchymal tissue, forming flat bones like the skull, clavicle, and jaw.
    • Endochondral ossification: Begins with a hyaline cartilage model that is replaced by bone, forming most of the long bones in the body.

    Bone Growth

    • Lengthwise growth: Occurs at the epiphyseal plate, a region of hyaline cartilage between the epiphysis and diaphysis of a long bone, divided into five zones.
    • Growth in thickness (appositional): Occurs by adding new bone tissue to the outer surface of existing bone, controlled by periosteal osteoprogenitor cells, creates new osteons.

    Bone Remodeling

    • Continuous process of bone replacement, adaptation of bone structure to different stresses.
    • Osteoclasts resorb old bone tissue, Osteoblasts deposit new bone tissue.

    Calcium Homeostasis

    • Regulation of blood calcium levels through the action of hormones:
      • Calcitonin (CT): Decreases blood calcium by inhibiting osteoclastic bone resorption and accelerating calcium deposition into bones.
      • Parathyroid hormone (PTH): Increases blood calcium by indirectly stimulating osteoclastic bone resorption and stimulating the formation of calcitriol.
      • Calcitriol: Increases blood calcium levels by promoting calcium absorption in the gastrointestinal tract.

    Bone Repair

    • Reactive (inflammatory) phase: Early inflammatory stage involving blood clot formation and cell death, debris is removed by macrophages and osteoclasts.
    • Reparative phase: Formation of a fibrous cartilage callus following the reactive phase.
      • Fibrocartilage callus: Connects the broken bone, formed by fibroblasts and chondroblasts.
      • Bony callus: Replaces the fibrocartilage callus with spongy bone trabeculae formed by osteoblasts.
    • Bone remodeling phase: Reshaping of the bony callus by osteoclasts, replacement of spongy bone with compact bone.
    • Complications:
      • Malunion: Bone heals in an abnormal position.
      • Nonunion: Bone fails to heal, possibly due to inadequate blood supply, interference from other tissues, or excessive mobility.

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    Description

    Test your knowledge of bone histology with this quiz that explores the specialized cells involved in bone tissue. Understand the roles of osteoprogenitor cells, osteoblasts, osteocytes, and osteoclasts, as well as their functions and locations within the bone matrix. Challenge yourself on the key concepts of bone composition and organization.

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