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Questions and Answers
Bone is a special type of connective tissue.
Bone is a special type of connective tissue.
True (A)
What are the three types of bone cells?
What are the three types of bone cells?
What is the main inorganic component of bone matrix?
What is the main inorganic component of bone matrix?
The organic component of bone matrix is responsible for its flexibility.
The organic component of bone matrix is responsible for its flexibility.
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Match the following bone cell types with their main functions:
Match the following bone cell types with their main functions:
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What is the name of the membrane that covers the external surface of bone?
What is the name of the membrane that covers the external surface of bone?
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What is the name of the membrane that lines the internal cavities of bone?
What is the name of the membrane that lines the internal cavities of bone?
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The epiphyseal plate is responsible for bone growth in width.
The epiphyseal plate is responsible for bone growth in width.
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Which of the following is NOT a site where cancellous bone is found?
Which of the following is NOT a site where cancellous bone is found?
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What is the structural unit of compact bone?
What is the structural unit of compact bone?
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What are the four types of lamellae found in compact bone?
What are the four types of lamellae found in compact bone?
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Volkmann's canals run parallel to the long axis of a bone.
Volkmann's canals run parallel to the long axis of a bone.
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What is the primary function of trabeculae in cancellous bone?
What is the primary function of trabeculae in cancellous bone?
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Intramembranous ossification is the process by which most long bones are formed.
Intramembranous ossification is the process by which most long bones are formed.
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What is the name of the areas in the skull of a newborn that are not yet ossified?
What is the name of the areas in the skull of a newborn that are not yet ossified?
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Endochondral ossification involves the replacement of hyaline cartilage with bone tissue.
Endochondral ossification involves the replacement of hyaline cartilage with bone tissue.
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Which type of cells are responsible for synthesizing new osteoid during bone remodelling?
Which type of cells are responsible for synthesizing new osteoid during bone remodelling?
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What are the two main functions of bone remodelling?
What are the two main functions of bone remodelling?
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Bone remodelling is regulated solely by hormonal factors.
Bone remodelling is regulated solely by hormonal factors.
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Which of the following is NOT a function of bones?
Which of the following is NOT a function of bones?
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The ends of bones in a synovial joint are covered with hyaline cartilage.
The ends of bones in a synovial joint are covered with hyaline cartilage.
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What type of fluid fills the joint cavity of a synovial joint?
What type of fluid fills the joint cavity of a synovial joint?
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What is the name of the membrane that lines the joint capsule of a synovial joint?
What is the name of the membrane that lines the joint capsule of a synovial joint?
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Type A cells in the synovium are phagocytic.
Type A cells in the synovium are phagocytic.
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What is the main characteristic of osteogenesis imperfecta?
What is the main characteristic of osteogenesis imperfecta?
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Osteomalacia is a disease characterized by bone fragility and multiple fractures.
Osteomalacia is a disease characterized by bone fragility and multiple fractures.
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Osteoporosis primarily affects young children.
Osteoporosis primarily affects young children.
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Paget's disease is caused by increased osteoblast activity.
Paget's disease is caused by increased osteoblast activity.
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The function of bones includes protection of vital organs
The function of bones includes protection of vital organs
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Bones do not play a role in blood cell formation.
Bones do not play a role in blood cell formation.
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Flashcards
Bone Structure
Bone Structure
Bone is a specialized connective tissue, the hardest, weight-bearing tissue in the body. It comprises periosteum (outer layer), endosteum (inner layer), bone cells (osteoblasts, osteocytes, osteoclasts), and bone matrix (organic and inorganic components).
Bone Matrix Composition
Bone Matrix Composition
Bone matrix is a composite material: organic (osteoid) part consisting mostly of collagen type I, and inorganic part consisting mainly of calcium phosphate crystals, like hydroxyapatite, for strength & hardness.
Osteoblasts
Osteoblasts
Bone-forming cells that synthesize and secrete the organic components (osteoid) of the bone matrix, essential for bone growth and repair.
Osteocytes
Osteocytes
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Osteoclasts
Osteoclasts
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Compact Bone
Compact Bone
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Cancellous Bone
Cancellous Bone
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Bone Remodeling
Bone Remodeling
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Study Notes
Bone Structure and Function
- Bone is a specialized connective tissue, the hardest, vascular, and weight-bearing type of connective tissue.
- Bones are characterized by a solid, stony hard matrix.
- Bone is composed of:
- Periosteum: covers the outer surface of bone.
- Endosteum: covers the inner surface of bone.
- Bone cells: osteoblasts, osteocytes, and osteoclasts.
- Bone matrix: composed of calcified organic material.
- Organic: collagen type-I and proteoglycans (osteoid)
- Inorganic: mineral salts, primarily calicum phosphate.
- The matrix and its components are vital to bone's strength.
- If mineral is removed, bone is too bendable.
- If collagen is removed, bone is too brittle.
- Bone cells include:
- Osteoblasts: responsible for bone formation (synthesizing organic components of the matrix).
- Osteocytes: maintain bone tissue, found within cavities (lacunae).
- Osteoclasts: break down bone (bone resorption, remodeling).
- Osteocytes connect via gap junctions to transfer nutrients and they act as sensors for mechanical stresses. Lack of exercise can decrease bone density.
- Osteoclasts are large, multinucleated cells originating from monocytes (blood cells). They lie in cavities called resorption bays or Howship's lacunae in the endosteum.
- EM or electron microscope studies show osteoclasts have:
- Ruffled border: site of active bone resorption.
- Clear zone: area of adhesion to bone matrix.
- Vesicular zone: contains lysosomal enzymes (exocytosis) and endocytotic vesicles (taking up bone fragments).
- Basal zone: contains organelles and nuclei.
- Osteoclasts function in bone resorption. They transport H+ to form acids for decalcification of bone and secret enzymes to degrade collagen and GAG in the matrix.
- Periosteum has two layers:
- Outer fibrous layer: collagen type-I, fibroblasts, and blood vessels.
- Inner layer: osteoblasts and osteoprogenitor cells.
- Endosteum is a thin layer containing osteoblasts and osteoclasts, lining internal spaces, including spaces in cancellous bone.
- Function of periosteum and endosteum includes nutrient delivery to the bone, and growth and repair of the bone.
Bone Types and Structure
- Bone types based on gross observation:
- Compact (cortical/lamellar) bone: dense without cavities.
- Cancellous (spongy/trabecular) bone: has many interconnecting cavities.
- Sites of compact bone:
- Shaft of long bones.
- Outer/inner tables of flat bones (e.g., skull).
- Outer covering of vertebrae and ribs.
- Sites of cancellous bone are:
- Epiphyses of long bones.
- All flat bones.
- All irregular bones.
- Shafts of the ribs.
- Cancellous bone structure consists of trabeculae (branching/anastomosing). These trabeculae have bone marrow cavities. Covered with endosteum.
Long Bone Structure
- Diaphysis: the shaft.
- Epiphysis: end of the bone.
- Cancellous bone is at the end; compact bone in the shaft.
- Epiphyseal plate or growth plate: hyaline cartilage present until growth stops.
- Epiphyseal line: when bone growth in length stops.
- Medullary cavity: the hollow inside of the bone shaft. Contains bone marrow.
Microscopic Structure of Compact Bone
- Compact bone is composed of osteons or Haversian systems.
- These osteons contain concentric lamellae.
- Central canal (Haversian canal) contains blood vessels and nerves.
- Perforating canals (Volkmann's canals) run perpendicular to the central canal. Contain blood vessels.
- Osteocytes are located in lacunae in the concentric lamellae.
- Canaliculi connect lacunae to the central canal to allow nutrients and wastes to be exchanged.
- The organization of lamellae includes:
- External circumferential lamellae: immediately under the periosteum.
- Inner circumferential lamellae: around the marrow cavity.
- Interstitial lamellae: between osteons.
Bone Formation
- Histogenesis of bone: Intramembranous bone formation and endochondral bone formation.
- Intramembranous ossification: process by which most flat bones form (e.g., skull, mandible, maxilla). Involves formation of ossification centers in embryonic mesenchymal membrane tissue. Examples: Fontanels.
- Endochondral ossification: Segment of hyaline cartilage forms model of bone; occurs in most long bones. A primary ossification center forms in the first trimester. Secondary centers form later. Cartilage remains in articular surfaces and epiphyseal plates.
Bone Growth
- Bone growth increases in length and width.
- Growth in length is due to cell division in the epiphyseal plate. Includes zones of resting, proliferation, hypertrophy & maturation, calcification, and ossification.
- Growth in width occurs through appositional growth, adding new bone tissue to the outer surface of the bone.
Bone Remodeling
- Bone is continuously remodelled throughout life by coordinated osteoblast and osteoclast activity.
- In healthy adults about 10% of bone is replaced annually.
- Bone remodeling is triggered by hormonal and physical factors.
Bone Disorders
- Osteogenesis imperfecta: Defect in collagen type I, leading to bone fragility, fractures, and deformities.
- Osteomalacia: Defective mineralization due to insufficient calcium or phosphate, leading to soft bones. In children, this is called rickets.
- Osteoporosis: Progressive bone loss leading to increased vulnerability to fractures.
- Paget's disease: Increased osteoclast activity leading to bone resorption and irregular new bone formation, making bone prone to fractures.
Function of Bones
- Support: Provides a framework for the body.
- Protection: Protects vital organs such as the brain and heart.
- Movement: Skeletal muscles use bones as levers for movement.
- Mineral storage: Bones store important minerals like calcium.
- Blood cell formation: Red bone marrow in bones produces blood cells.
Joints
- Joints connect bones.
- Types of joints:
- Synarthrosis: Limited mobility.
- Diarthrosis (synovial): Free movement (e.g., elbow, knee).
- Synovial joint characteristics:
- Hyaline cartilage covers bone ends (no perichondrium).
- Synovial fluid fills the joint cavity.
- Fibrous capsule encloses the joint.
- Synovial membrane lines the capsule.
- Synovial fluid contains: hyaluronic acid and lubricin.
- lubricant in the joint.
- Supplies oxygen and nutrients to the chondrocytes of articular cartilage.
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