Podcast
Questions and Answers
What role do osteoclasts play in the growth of the epiphyseal plate?
What role do osteoclasts play in the growth of the epiphyseal plate?
How does growth hormone (GH) influence bone growth?
How does growth hormone (GH) influence bone growth?
What happens to the epiphyseal plate at the end of adolescence?
What happens to the epiphyseal plate at the end of adolescence?
What structural change do osteoblasts contribute to during growth in thickness of bones?
What structural change do osteoblasts contribute to during growth in thickness of bones?
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What is the function of osteoclasts secretions during bone remodeling?
What is the function of osteoclasts secretions during bone remodeling?
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What process occurs when osteoblasts migrate into a cavity formed in bone?
What process occurs when osteoblasts migrate into a cavity formed in bone?
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What role does RANK ligand play in bone remodeling?
What role does RANK ligand play in bone remodeling?
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What is the consequence of a balance between RANK ligand and osteoprotegerin (OPG) in bone health?
What is the consequence of a balance between RANK ligand and osteoprotegerin (OPG) in bone health?
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What is the functional unit of compact bone called?
What is the functional unit of compact bone called?
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What is the purpose of the canaliculi in bone tissue?
What is the purpose of the canaliculi in bone tissue?
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How is Ca2+ rapidly moved to plasma from bone?
How is Ca2+ rapidly moved to plasma from bone?
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What happens to calcium and phosphate when bone is dissolved?
What happens to calcium and phosphate when bone is dissolved?
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What is found in the central canal of an osteon?
What is found in the central canal of an osteon?
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What are the main components of connective tissue?
What are the main components of connective tissue?
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Which type of bone cell is primarily responsible for the formation of new bone?
Which type of bone cell is primarily responsible for the formation of new bone?
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What is the primary function of the skeletal system?
What is the primary function of the skeletal system?
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Which statement about the extracellular matrix (ECM) is correct?
Which statement about the extracellular matrix (ECM) is correct?
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What role do osteocytes play within bone tissue?
What role do osteocytes play within bone tissue?
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Which of the following is a function of bones in the body?
Which of the following is a function of bones in the body?
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What is the main role of osteoclasts in bone tissue?
What is the main role of osteoclasts in bone tissue?
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What substance primarily surrounds connective tissue cells?
What substance primarily surrounds connective tissue cells?
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Which component of bone contributes to its hardness?
Which component of bone contributes to its hardness?
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The Haversian system is primarily associated with which aspect of bone?
The Haversian system is primarily associated with which aspect of bone?
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What is the primary function of osteoblasts?
What is the primary function of osteoblasts?
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Which component primarily makes up the dry weight of bone?
Which component primarily makes up the dry weight of bone?
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What distinguishes woven bone from lamellar bone?
What distinguishes woven bone from lamellar bone?
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During which growth periods do mammals experience rapid growth?
During which growth periods do mammals experience rapid growth?
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What is the primary role of osteocytes in bone?
What is the primary role of osteocytes in bone?
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What type of bone is primarily involved in fracture repair?
What type of bone is primarily involved in fracture repair?
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Which of the following statements accurately describes bone matrix composition?
Which of the following statements accurately describes bone matrix composition?
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What role do proteoglycans play in the bone matrix?
What role do proteoglycans play in the bone matrix?
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Which structure is found at the ends of growing bones and facilitates growth in length?
Which structure is found at the ends of growing bones and facilitates growth in length?
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What describes the periosteum?
What describes the periosteum?
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Study Notes
Bone Structure and Function
- Bone is a type of connective tissue, along with ligaments and tendons
- Bone is composed of specialized cells within an extracellular matrix composed of specific molecules
- Bone, ligaments, and tendons connect and support body parts
- Bone provides structural support for the body
- Bone protects soft tissues and internal organs from injury
- Bone facilitates movement by providing rigid rods and levers for muscles to act on, allowing interaction with the environment
- Bone plays a crucial role in calcium homeostasis, acting as a reservoir to regulate calcium levels
- Bone marrow is found within the central cavity of bone, responsible for blood cell production
- Bone is continuously remodeling and turning over
- Bone has two main types: compact (lamellar) and spongy (trabecular)
Bone Tissue—Cells and Matrix
- Bone is made of cells (osteocytes, osteoblasts and osteoclasts)
- Osteoblasts create bone, line bone surfaces, and produce osteoid
- Osteocytes are osteoblasts trapped in the bone matrix, maintaining the structure and assisting in bone nutrition
- Osteoclasts break down bone via phagocytosis, important in bone remodeling
- Osteoid, the organic component of bone matrix, comprises ~90% collagen type I and glycoproteins and is responsible for the tensile strength of bone
- Minerals predominantly hydroxyapatite (Ca10(PO4)6(OH)2), comprising ~60-70% dry weight of bone, provide compression strength and make the bone radio-opaque
Bone Tissue - Haversian System
- Compact bone is composed of units known as osteons (Haversian systems)
- Osteons are composed of concentric layers of osteocytes (lamellae) arranged around a central canal (containing blood vessels)
- Osteoblasts are on the outer and inner surfaces of the central canal
- Osteoclasts are located on surfaces where bone resorption occurs
- Osteons run parallel to the long axis of the bone
- The osteocytic-osteoblastic bone membrane (OOBM) is a network of fluid-filled canals (canaliculi) connecting osteocytes for exchange of substances
Bone Growth
- Most mammals have two periods of rapid growth: postnatal and pubertal
- Postnatal growth spurt occurs in early life, increasing body protein, mainly skeletal muscle
- Pubertal growth spurt increases growth hormone release and stimulates hypertrophy and hyperplasia of cells, leading to bone thickening and lengthening
- Chondrocytes (cartilage cells) proliferate in the outer edge of epiphyseal plates next to epiphysis resulting in temporary widening of the epiphyseal plate which is gradually replaced by bone as growth in length proceeds
- Osteoclasts remove dead chondrocytes and calcified matrix, followed by infiltration of osteoblasts from diaphysis, producing new bone and capillary blood supply
- Bone growth in thickness is achieved by osteoblasts adding new bone to the outer surface, concurrent with osteoclasts removing bone on the inside of bone (reducing the bone marrow cavity)
- Bone growth in length stops when the epiphyseal plate becomes completely ossified
Bone Remodeling
- Bone is constantly undergoing turnover due to concurrent bone deposition and resorption (remodeling)
- Remodeling maintains mechanical effectiveness and plasma Ca2+ levels
- Osteoclasts attach to osteoid (ECM) forming a ruffled membrane, increasing contact area with bone
- Osteoclasts secrete organic acids (e.g., HCl) to dissolve hydroxyapatite and enzymes to break down ECM
- Osteoblasts migrate into the cavity and fill it with osteoid, which mineralizes to form new bone
- Formation/resorption rates in the adult remain approximately equal, maintaining constant bone mass
- Remodeling facilitates changes in bone shape, material, and repair of damaged bone, and release of mineral ions
Regulation of Bone Growth
- Growth hormone (GH) stimulates insulin-like growth factor (IGF-I) production and paracrine action, stimulating chondrocyte and osteoblast activity
- Androgens (e.g., testosterone) promote protein synthesis, influencing bone growth but halt growth at the end of adolescence, closing the epiphyseal plate
Regulation of Plasma Ca2+ Levels
- Bone contains a labile pool of calcium in the bone fluid. Rapid exchange between the bone fluid and plasma maintains calcium homeostasis
- Osteocytic-osteoblastic membrane (OOBM) pumps calcium from the bone fluid into the plasma during fast exchange, stimulated by parathyroid hormone (PTH)
- Slow exchange involves PTH-induced bone dissolution, releasing calcium from the mineralized bone into the plasma
- The balance between RANKL and OPG signaling pathways regulates osteoclast activity and overall bone density
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Description
Test your knowledge on the structure and function of bones. This quiz covers bone types, their cellular composition, and their roles in the human body. Understand how bones contribute to support, protection, and blood cell production.
