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Questions and Answers
What is one of the primary functions of bones in the human body?
Which of the following is NOT a category of bone shape?
What type of bone develops in tendons under stress?
Which structure is known as the shaft of a long bone?
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What is the primary function of osteocytes in bone tissue?
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Which of the following best describes the matrix composition of bone tissue?
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Which cells are responsible for breaking down bone tissue?
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What is the function of articular cartilage in long bones?
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What provides the hardness of bone?
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Which of the following structures house osteocytes in compact bone?
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What is the main distinction between compact bone and spongy bone?
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Osteogenesis refers to which process in the human body?
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Which type of ossification primarily forms flat bones such as those of the skull?
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What is found in the spaces of spongy bone that supports blood cell production?
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Which feature describes the arrangement of osteons in compact bone?
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What term describes the removal of older osteons during bone remodeling?
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What is the primary function of the zone of resting cartilage in the epiphyseal plate?
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At what age do the epiphyseal plates typically close, marking the end of growth in length for bones?
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Which zone of the epiphyseal plate is characterized by rapid cell division and appears as stacked coins?
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What process is responsible for the increase in thickness or diameter of bones?
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What happens to cartilage cells in the zone of calcified cartilage?
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What is the role of osteoclasts in the epiphyseal plate?
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What occurs after the periosteal cells differentiate into osteoblasts during bone growth in thickness?
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Which of the following statements about bone fractures is true?
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What is the logical sequence of events in the intramembranous ossification process?
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Which of the following bones is primarily formed by endochondral ossification?
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What initiates the calcification during endochondral ossification?
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What role do osteoclasts play in the development of a medullary cavity during ossification?
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How does the growth in length of a bone primarily occur?
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Which structure remains as cartilage at the ends of long bones after endochondral ossification?
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What is the primary function of the periosteal bud in the ossification process?
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What type of growth allows a cartilage model to increase in width during endochondral ossification?
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Study Notes
Functions of Bone
- Protects and supports soft tissues
- Provides attachment sites for muscles, enabling movement
- Stores minerals calcium and phosphate, crucial for mineral homeostasis
- Produces blood cells in red bone marrow (hemopoiesis)
- Stores energy in yellow bone marrow
Classification of Bone Shape
- Long Bones: Longer than wide, cylindrical shape (e.g., femur, phalanges)
- Short Bones: Nearly equal in width and length, cube-shaped (e.g., carpals, tarsals)
- Flat Bones: Thin and flat (e.g., skull bones, sternum, ribs, shoulder blades)
- Irregular Bones: Complex shape, don't fit other categories (e.g., vertebrae, hip bones)
- Sesamoid Bones: Develop within tendons under friction and stress (e.g., patella)
- Sutural Bones: Classified by location, tiny bones in sutures between cranial bones
Anatomy of a Long Bone
- Diaphysis: Shaft of the bone
- Epiphysis: Ends of the long bone
- Metaphyses: Areas between epiphysis and diaphysis, containing the epiphyseal plate in growing bones
- Articular Cartilage: Covers joint surfaces, reduces friction and acts as a shock absorber
- Medullary Cavity: Marrow cavity within the diaphysis
- Endosteum: Lining of the marrow cavity
- Periosteum: Tough membrane covering bone (excluding cartilage)
Histology of Bone Tissue
- Connective tissue with widely spaced cells
- Matrix composed of 25% water, 25% collagen fibers, and 50% mineral salts
- Minerals: Primarily hydroxyapatite (85%), calcium carbonate (10%), and others like calcium fluoride, magnesium fluoride
- Four types of bone cells:
- Osteogenic Cells: Divide and differentiate into osteoblasts
- Osteoblasts: Bone-building cells
- Osteocytes: Mature bone cells, maintain bone tissue
- Osteoclasts: Derived from monocytes, break down bone tissue
Matrix of Bone
- Inorganic Mineral Salts: Provide bone's hardness (hydroxyapatite and calcium carbonate)
- Organic Collagen Fibers: Provide bone's flexibility, resist stretching and tearing
- Bone is not solid, contains spaces for vessels and red bone marrow
- Spongy Bone: Many spaces
- Compact Bone: Fewer spaces
Compact Bone
- Arranged in units called osteons
- Osteons contain:
- Blood vessels, lymphatic vessels
- Nerves, osteocytes
- Calcified matrix
- Aligned along lines of stress, which can change over time
- Concentric rings (lamellae): Calcified matrix surrounding a central blood vessel
- Lacunae: Spaces containing osteocytes
- Canaliculi: Tiny canals filled with extracellular fluid, connecting osteocytes
Spongy Bone
- Lacks osteons
- Consists of trabeculae surrounding red marrow-filled spaces
- Forms most of the structure in short, flat, and irregular bones, and epiphyses of long bones
- Lightweight, supports and protects red bone marrow
Trabeculae of Spongy Bone
- Latticework of thin bone plates aligned along lines of stress
- Spaces between trabeculae filled with red marrow
Bone Formation (Osteogenesis or Ossification)
- Begins with mesenchymal cells forming template for ossification
- Two types:
- Intramembranous Ossification: Bone formation directly from fibrous connective tissue membranes
- Endochondral Ossification: Bone formation from hyaline cartilage models
Intramembranous Ossification
- Forms flat bones of skull, mandible, and clavicles
- Ossification Center: Mesenchymal cells convert to osteoblasts and lay down osteoid matrix
- Matrix calcifies as osteoblasts become osteocytes, forming bridges of trabeculae
- Peripheral mesenchyme forms periosteum
Endochondral Ossification
- Replaces cartilage with bone, forms most bones
- Development of Cartilage Model: Mesenchymal cells form cartilage model
-
Growth of Cartilage Model:
- Interstitial Growth: Chondrocyte cell division and matrix formation, lengthens cartilage
- Appositional Growth: New matrix formation on periphery by chondroblasts, widens cartilage
- Calcification: Cells in midregion burst, trigger calcification and chondrocyte death
Endochondral Ossification (Continued)
-
Development of Primary Ossification Center:
- Periosteal Bone Collar: Perichondrium lays down bone collar
- Nutrient Artery: Penetrates cartilage model center
- Periosteal Bud: Brings osteoblasts and osteoclasts, forming spongy bone trabeculae
- Medullary Cavity: Formed by osteoclasts
Endochondral Ossification (Continued)
- Development of Secondary Ossification Center: Blood vessels enter epiphyses near birth, forming spongy bone without a medullary cavity
- Formation of Articular Cartilage: Cartilage on bone ends remains as articular cartilage
Growth in Length
- Epiphyseal plate (growth plate) is crucial for bone growth in length
-
Zones of Epiphyseal Plate:
- Zone of Resting Cartilage: Anchors plate to bone
- Zone of Proliferating Cartilage: Rapid cell division
- Zone of Hypertrophic Cartilage: Enlarged cells remain in columns
- Zone of Calcified Cartilage: Thin zone, cells dead, matrix calcified, osteoclasts remove matrix, osteoblasts and capillaries form bone
Growth in Thickness (Appositional Growth)
- Bone grows in thickness by appositional growth at bone surface
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Process:
- Periosteal cells differentiate into osteoblasts, forming matrix
- Ridges fuse, periosteum becomes endosteum
- New concentric lamellae form
- Osteoblasts under periosteum form circumferential lamellae
Fractures
- Broken bones
- Typically heal on their own, but repositioning is necessary for proper healing.
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Description
This quiz covers the essential functions of bone, classifications of bone shapes, and the specific anatomy of long bones. Understand the protective, supportive, and mineral-storage roles of bones, along with details about different bone types and structures.
