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Bone Histology and Physiology
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Bone Histology and Physiology
Bone Histology and Physiology
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1
Question
What is bone in the context of general histology and embryology?
Answer
Bone is the main constituent of the adult skeleton and is a specialized connective tissue composed of the bone matrix.
2
Question
What are the mechanical and metabolic functions of bone?
Answer
Bone provides solid support for the body, protects vital organs, serves as enclosure for bone marrow, and facilitates bodily movements.
3
Question
What is the bone matrix?
Answer
The bone matrix is the calcified extracellular material that makes up the structure of bone.
4
Question
What are osteocytes?
Answer
Osteocytes are bone cells that are differentiated from osteoblasts, located within lacunae, and have long dendritic processes extending into canaliculi.
5
Question
What are lacunae?
Answer
Lacunae are cavities in the bone where osteocytes are enclosed.
6
Question
What are lamellae?
Answer
Lamellae are the matrix layers in the bone.
7
Question
What are canaliculi?
Answer
Canaliculi are thin, cylindrical spaces in bone that serve as communication canals for the exchange of metabolites between osteocytes and blood capillaries.
8
Question
What are osteoblasts?
Answer
Osteoblasts are cells that originate from mesenchymal stem cells (osteoprogenitor cells) and are responsible for producing the organic components of the bone matrix.
9
Question
What are the characteristics of active osteoblasts?
Answer
Active osteoblasts are located exclusively at the surfaces of the bone matrix, are bound by integrins, and form a simple cuboidal layer with adherent and gap junctions.
10
Question
What are inactive osteoblasts?
Answer
Inactive osteoblasts are osteoblasts that have transitioned to osteocytes, bone lining cells, or undergone apoptosis.
11
Question
What is osteoid?
Answer
Osteoid is a layer of unique collagen-rich material produced by osteoblasts during matrix synthesis.
12
Question
What is osteocalcin?
Answer
Osteocalcin is a non-collagen protein secreted by osteoblasts that is vitamin K-dependent and binds calcium ions.
13
Question
What are matrix vesicles?
Answer
Matrix vesicles are rich in alkaline phosphatase and other enzymes, which raise the local concentration of phosphate ions and serve as foci for the formation of hydroxyapatite crystals.
14
Question
What is hydroxyapatite?
Answer
Hydroxyapatite is a mineral crystalline structure represented by the formula Ca10(PO4)6(OH)2, formed during the calcification of bone.
15
Question
What are the key functions of osteocytes?
Answer
Osteocytes maintain the calcified matrix, secrete factors that regulate bone remodeling, detect stress-induced microdamage, and communicate with other bone cells through gap junctions.
16
Question
What are osteoclasts?
Answer
Osteoclasts are large, motile cells with multiple nuclei that are essential for matrix resorption during bone growth and remodeling.
17
Question
What is the origin of osteoclasts?
Answer
Osteoclasts originate from the fusion of bone marrow-derived monocytes.
18
Question
What role does parathyroid hormone play in bone remodeling?
Answer
Parathyroid hormone activates osteoblasts to produce macrophage-colony stimulating factor (M-CSF), RANKL, and other factor regulators.
19
Question
What is osteopetrosis?
Answer
Osteopetrosis, also known as marble bones, is a genetic disease characterized by dense, heavy bones, lack of ruffled borders, defective bone resorption, overgrowth and thickening of bones, and obliteration of marrow cavities.
20
Question
What are the inorganic materials found in the bone matrix?
Answer
The inorganic materials in the bone matrix include calcium hydroxyapatite, bicarbonates, citrate, magnesium, potassium, sodium ions, and non-crystalline calcium phosphate.
21
Question
What are the organic materials found in the bone matrix?
Answer
The organic materials in the bone matrix include type 1 collagen (90%), proteoglycans, osteonectin (multiadhesive glycoproteins), osteocalcin (calcium-binding), and phosphatases.
22
Question
What is the periosteum?
Answer
The periosteum is the organized outer fibrous layer of dense connective tissue covering the bone, containing bundled type I collagen, fibroblasts, and blood vessels.
23
Question
What are Sharpey fibers?
Answer
Sharpey fibers, also known as perforating fibers, are bundles of periosteal collagen that penetrate the bone matrix and bind the periosteum to the bone.
24
Question
What are osteoprogenitor cells?
Answer
Osteoprogenitor cells are stem cells that proliferate extensively and produce many new osteoblasts, playing a prominent role in bone growth and repair.
25
Question
What is osteoporosis?
Answer
Osteoporosis is a condition that occurs when bone resorption exceeds bone formation, often seen in immobilized patients and postmenopausal women, leading to calcium loss and reduced bone mineral density (BMD).
26
Question
What are the two types of bone?
Answer
The two types of bone are dense bone, making up 80% of total bone mass, and cancellous bone, making up 20% of total bone mass.
27
Question
What are long bones?
Answer
Long bones have epiphyses (the bulbous ends composed of cancellous bone covered by compact bone) and a diaphysis (the cylindrical part composed of dense compact bone with a thin region of cancellous bone around the central marrow cavity).
28
Question
What is the Haversian system?
Answer
The Haversian system, also known as the osteon, refers to the complex of concentric lamellae surrounding a central canal that contains small blood vessels, nerves, and endosteum.
29
Question
What are Volkmann canals?
Answer
Volkmann canals, also known as perforating canals, are canals that communicate with one another through transverse connections, allowing blood vessels and nerves to pass between Haversian systems.
30
Question
What is bone remodeling?
Answer
Bone remodeling occurs throughout life, involving the resorption of old osteons and the production of new ones by osteoclasts and osteoblasts.