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Questions and Answers
Which cell type in the skeletal system is involved in the resorption and remodeling of bone tissue?
What constitutes approximately 35% of the dry weight of bone?
Which characteristic is true for osteoprogenitor cells?
Which statement correctly describes the inorganic component of the bone matrix?
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What is the primary role of osteoblasts in the skeletal system?
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Where are osteocytes typically found within the bone structure?
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Which of the following best describes bone tissue's role in metabolism?
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What is the primary reason for the presence of hydroxyapatite crystals in bone tissue?
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Which type of bone retains its original shape when its organic components are extracted, but becomes extremely brittle?
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What cellular component found in the inner layer of the periosteum has the potential to differentiate into osteoblasts?
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What is the primary function of Sharpey's fibers in the periosteum?
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Which of the following structures is found within a typical Harvesian system?
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What is the primary histological feature distinguishing cancellous (spongy) bone from compact bone?
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What type of marrow is filled within the irregular cavities of cancellous bone?
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Which structural feature of bone consists of parallel lamellae containing osteocytes within lacunae?
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What composition primarily makes up the outer layer of the periosteum?
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What is the correct sequence of stages in intramembranous osteogenesis?
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Which artery is primarily responsible for the blood supply to the growing ends of long bones?
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How does the direction of the nutrient foramen relate to the growing ends of long bones?
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What is a common complication in the healing of fractures?
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What misconception might arise regarding the role of osteoblasts in bone formation?
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What defines the growing end of a long bone during development?
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Which condition is primarily characterized by the softening of bones in children?
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Which statement about the epiphyses of long bones is true?
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Study Notes
Bone Tissue
- Main component of the adult skeleton
- Supports fleshy structures and protects internal organs
- Site of haematopoiesis (bone marrow production)
- Highly vascularized and metabolically active
- Reservoir of calcium, phosphate, and other minerals
Bone Cells
- Osteoprogenitor cells: Located in the periosteum, haversian canals, and endosteum; derived from embryonic mesenchyme; capable of dividing and differentiating into osteoblasts
- Osteoblasts: Formed from osteoprogenitor cells; synthesize the organic component of the bone matrix; possess receptors for parathyroid hormone; found where new bone is forming
- Osteocytes: Mature bone cells; transformed from osteoblasts; reside in cavities (lacunae) within the bone matrix; found in mature bone tissue
- Osteoclasts: Bone-destroying cells; multinucleated giant cells derived from fused marrow precursors; act as macrophages of bone; involved in bone resorption and remodeling; originate from the fusion of bone marrow-derived mononucleated cells
Bone Matrix
- Contains both organic and inorganic components
- Extracellular matrix comprises 25% water, 25% fibers, and 50% crystallized minerals
- Organic component: Constitutes 35% of the dry weight of bone; primarily composed of type I collagen fibers; type I collagen makes up 80-90% of the organic components
- Inorganic component: Constitutes 65% of the dry weight; mainly composed of calcium and phosphorus, along with bicarbonate, citrate, magnesium, sodium, and potassium; calcium and phosphorus exist primarily as hydroxyapatite crystals
Bone Strength
- One of the hardest and strongest substances in the body
- Decalcified bone (mineral removed) maintains shape but becomes flexible and bendable
- Bone without the organic component retains shape but is extremely brittle and easily fractured
Periosteum and Endosteum
- Periosteum: Composed of an outer layer of collagen fibers and fibroblasts; Sharpey's fibers (bundles of periosteal collagen) penetrate the bone matrix; inner cellular layer contains osteoprogenitor cells
- Endosteum: Covers the internal surfaces of bone; composed of bone-forming cells and connective tissue
Types of Bone Tissue
- Compact bone: Dense and solid without cavities
- Cancellous bone (spongy bone): Contains numerous interconnecting cavities
- Both have the same basic histological structure
Harvesian Canal Systems (Osteon)
- Components:
- Central harvesian canal
- Bone lamellae
- Lacunae
- Osteocytes
- Canaliculi
- Volkman's canal (connects two harvesian canals)
Cancellous Bone
- Trabeculae: Slender strands of bone tissue forming a framework
- Marrow cavities: Filled with hematopoietic tissue (red marrow)
- Red marrow consists of developing blood cells, platelets, and adipose cells
- Trabeculae composed of parallel lamellae containing lacunae with osteocytes
Differences between Compact and Spongy Bone
Osteogenesis (Ossification)
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Intramembranous Osteogenesis:
- Presence of mesenchymal cells at the site of bone formation
- Area becomes highly vascularized
- Mesenchymal cells lay down collagen fibers
- Mesenchymal cells transform into osteoblasts
- Osteoblasts secrete matrix to embed fibers
- Fibres and matrix swell, forming osteoid
- Calcium deposited in osteoid under the influence of osteoblasts
- Osteoid becomes calcified, forming bone lamella
- Additional osteoid layers are laid down, forming more lamellae
Endochondral Osteogenesis
Blood Supply of Bones
- Nutrient artery
- Periosteal artery
- Epiphyseal artery
- Metaphyseal artery
Growing End of Long Bones
- Epiphyses (ends) fuse at different times in most long bones
- The end that fuses later is called the growing end
- Secondary centers appear first at the growing end
- The growing end is located opposite the direction of the nutrient foramen
Growing End: Direction of Nutrient Foramen
- "To the elbow I go and to the knee I flee"
- In milking cow position, the direction is always downwards
Clinical Anatomy
- Healing of fractures
- Osteomalacia/Rickets
- Osteoporosis
- Osteopetrosis
- Bone Tumors/Ganglion
Complications of Healing
- Non-union
- Mal-union
- Delayed union
- Osteomyelitis (infection)
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Description
Explore the essential components of bone tissue, including its functions and the types of bone cells. Understand how osteoprogenitor cells, osteoblasts, osteocytes, and osteoclasts contribute to the formation and maintenance of bone. This quiz provides insights into the complex structure and functions of the skeletal system.
