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Questions and Answers
Which of the following is NOT a function of bone?
Which of the following is NOT a function of bone?
Which type of bone is described as having a solid structure?
Which type of bone is described as having a solid structure?
What process describes the formation of bones such as the skull and clavicles in utero?
What process describes the formation of bones such as the skull and clavicles in utero?
What cell type is responsible for the destruction of bone?
What cell type is responsible for the destruction of bone?
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Which component of bone primarily resists tension?
Which component of bone primarily resists tension?
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What is the main process through which most bones form?
What is the main process through which most bones form?
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What is the function of osteoblasts in bone remodeling?
What is the function of osteoblasts in bone remodeling?
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Which layer is NOT part of the epiphyseal plate?
Which layer is NOT part of the epiphyseal plate?
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What hormone primarily regulates calcium homeostasis in the body?
What hormone primarily regulates calcium homeostasis in the body?
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What happens to blood calcium levels during the breakdown of bone?
What happens to blood calcium levels during the breakdown of bone?
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Which statement about the growth plate is accurate?
Which statement about the growth plate is accurate?
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How frequently is spongy bone replaced in the body?
How frequently is spongy bone replaced in the body?
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What condition occurs when bone resorption outpaces bone deposition?
What condition occurs when bone resorption outpaces bone deposition?
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Which factor does NOT affect bone remodeling?
Which factor does NOT affect bone remodeling?
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What occurs when blood calcium levels become too high?
What occurs when blood calcium levels become too high?
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Study Notes
Bone Functions
- Provides structural support for the body, acting as a framework.
- Protects vital organs, such as the brain, heart, and lungs.
- Facilitates movement by interacting with muscles.
- Serves as a storage site for minerals, primarily calcium and phosphorus.
- Involved in hematopoiesis, the production of blood cells.
Bone Tissue
- Classified as connective tissue.
- Composed of cells, fibers, and matrix.
- Cells include:
- Osteogenic cells: bone stem cells
- Osteoblasts: bone-forming cells
- Osteocytes: mature bone cells
- Osteoclasts: bone-destroying cells
- Fibers are primarily collagen, providing tensile strength.
- Matrix is composed of calcium phosphate salts, imparting compressive strength.
Chemical Composition of Bone
- Contains approximately 1/3 organic compounds.
- Organic compounds include cells and collagen, contributing to bone's tensile strength.
- Contains approximately 2/3 inorganic compounds, primarily calcium phosphate in the form of hydroxyapatites.
- Inorganic compounds contribute to bone's compressive strength.
- Calcification: the process of hardening the bone matrix by depositing calcium phosphate.
Types of Bone Tissue
- Compact bone: Solid, dense bone tissue found in the outer layer of bones.
- Spongy bone (Cancellous bone): Porous bone tissue with interconnected spaces, found in the interior of bones.
Microscopic Structure of Compact Bone
- Composed of lamellae (concentric layers) arranged in osteons (Haversian systems).
- Contains osteocytes (mature bone cells) housed within lacunae (small cavities) within the lamellae.
- Features canaliculi (tiny canals) that connect lacunae and allow for nutrient and waste exchange.
Red Bone Marrow
- Located within the spongy bone.
- Responsible for blood cell formation (hematopoiesis).
Parts of a Long Bone
- Diaphysis: the shaft or central region of a long bone.
- Epiphysis: The ends of a long bone.
- Metaphysis: The region between the diaphysis and epiphysis.
- Periosteum: A fibrous membrane covering the outer surface of bone, containing blood vessels and nerves.
Bone Development (Ossification)
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Intramembranous ossification: Bone develops directly from mesenchymal tissue.
- Occurs in skull bones and clavicles.
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Endochondral ossification: Bone develops from a cartilage model.
- Occurs in most bones of the skeleton, excluding skull bones and clavicles.
Bone Growth in Length
- Occurs at the epiphyseal plate (growth plate).
- Growth plate consists of four zones:
- Resting cartilage cells
- Zone of proliferation
- Zone of hypertrophy
- Zone of calcification
- Bone growth in length ceases when the epiphyseal plate closes.
Bone Remodeling
- Continuous process of bone deposition (bone formation) and bone resorption (bone breakdown).
- Osteoblasts are responsible for bone deposition.
- Osteoclasts are responsible for bone resorption.
- Remodeling is influenced by various factors, including vitamins, hormones, and mechanical stress.
Factors Affecting Bone Remodeling
- Vitamins: Vitamins A, C, and D play crucial roles in bone health.
- Hormones: Growth hormone, thyroid hormone, and sex hormones influence bone growth and remodeling.
- Mechanical stress: Exercise and physical activity stimulate bone deposition and increase bone density.
- Calcium levels: Bone remodeling helps regulate blood calcium levels.
Regulation of Blood Calcium Levels
- Bone plays a crucial role in maintaining blood calcium homeostasis.
- Hypercalcemia: High blood calcium levels.
- Hypocalcemia: Low blood calcium levels.
Mechanisms of Calcium Homeostasis
- Parathyroid hormone (PTH): Increases blood calcium levels by stimulating osteoclast activity, increasing calcium absorption in the kidneys, and promoting vitamin D synthesis.
- Calcitonin: Lowers blood calcium levels by inhibiting osteoclast activity and stimulating bone deposition by osteoblasts.
Osteoporosis
- A condition characterized by decreased bone density and increased bone fragility.
- Occurs when bone resorption exceeds bone deposition.
- Increased risk of fractures.
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