Histology of Bone Tissue

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Questions and Answers

What is the primary reason for the eosinophilic or lightly basophilic cytoplasm in osteocytes?

Negligible secretory activity (correct)
High secretory activity
Presence of numerous nuclei
Abundance of endoplasmic reticulum

What is the function of osteocytes in maintaining bone integrity?

Producing acid phosphatase
Maintaining lacunae and canaliculi for diffusion (correct)
Removing bone matrix
Depositing calcium in bone

What is the purpose of the ruffled membrane in osteoclasts?

Absorbing calcium from bone
Regulating bone deposition
Secreting osteoid tissue
Increasing surface area for bone resorption (correct)

What is the significance of gap junctions in osteocytes?

Enabling communication with nearby cells (A) Signup and view all the answers

What is the characteristic feature of osteocytes during bone formation?

Extension of long dendritic processes (C) Signup and view all the answers

What is the role of osteoclasts in bone development?

Removing bone matrix (D) Signup and view all the answers

What is the function of lysosomes in osteoclasts?

Breaking down bone matrix (A) Signup and view all the answers

What is the primary function of osteoblasts in bone formation?

To produce the organic components of bone matrix (A) Signup and view all the answers

What is unique about the cytoplasm of osteoclasts?

Presence of numerous mitochondria and lysosomes (D) Signup and view all the answers

What is the term for the process by which bone grows through the deposition of new bone material?

Bone appositional growth (C) Signup and view all the answers

What is the name of the protein produced by osteoblasts that binds calcium ions?

Osteocalcin (D) Signup and view all the answers

What type of fibers are produced by osteoblasts?

Type I collagen fibers (B) Signup and view all the answers

What is the term for the layer of cuboidal cells that form a single layer on the surface of bone matrix?

Osteoblast layer (C) Signup and view all the answers

What is the purpose of integrins in osteoblasts?

To bind to existing bone matrix (A) Signup and view all the answers

What is the term for the unique collagen-rich material secreted by osteoblasts?

Osteoid (A) Signup and view all the answers

What is the fate of some osteoblasts after completing their synthetic activity?

They become osteocytes entrapped in matrix-bound lacunae (B) Signup and view all the answers

What is the percentage of inorganic salts in the dry weight of bone?

65% (A) Signup and view all the answers

What type of collagen is found in bone collagen fibres?

Type I collagen (A) Signup and view all the answers

What is the term applied to the mixture of organic ground substance and collagen fibres before it is mineralized?

Osteoid (A) Signup and view all the answers

Which of the following is NOT a component of the ground substance of bone?

Keratin (D) Signup and view all the answers

What is the main function of osteonectin and osteocalcin in bone development?

To bind readily to calcium ions and play a role in mineralization (A) Signup and view all the answers

What is the outer fibrous layer of dense connective tissue that covers the external surface of bones?

Periosteum (B) Signup and view all the answers

Which of the following ions is NOT typically found in significant amounts in bone?

Sulphate (A) Signup and view all the answers

What stimulates bone removal by osteoclasts?

Osteoblasts, macrophages, lymphocytes, and parathyroid hormone (B) Signup and view all the answers

What is the primary function of perforating fibers in the bone?

To bind the periosteum to the bone (C) Signup and view all the answers

Which type of bone is characterized by a higher proportion of osteocytes and lower mineral content?

Woven bone (A) Signup and view all the answers

What is the primary location of osteoprogenitor cells in the bone?

In the periosteum's inner layer (C) Signup and view all the answers

What is the main difference between woven bone and lamellar bone?

Woven bone forms more quickly but has less strength (C) Signup and view all the answers

Which of the following is NOT a characteristic of lamellar bone?

Higher proportion of osteocytes (B) Signup and view all the answers

What is the approximate diameter of an osteon?

100-250 μm (B) Signup and view all the answers

What is the function of osteoprogenitor cells in the bone?

To produce new osteoblasts (A) Signup and view all the answers

What is the function of the canaliculi in an osteon?

To permit the exchange of nutrients and waste between osteocytes (B) Signup and view all the answers

Where are osteoblasts typically found in the bone?

In the periosteum's inner layer (A) Signup and view all the answers

What is the outer boundary of each osteon composed of?

A layer of noncollagen proteins, mineral, and collagen (B) Signup and view all the answers

What is the purpose of periosteal blood vessels in the bone?

To carry metabolites to and from bone cells (C) Signup and view all the answers

How do the osteons communicate with the marrow cavity and the periosteum?

Through the central canal (A) Signup and view all the answers

What are the irregularly shaped groups of parallel lamellae called?

Interstitial lamellae (B) Signup and view all the answers

What is the function of the transverse perforating canals?

To communicate between central osteonic canals (B) Signup and view all the answers

What is the organization of lamellae in compact bone?

Parallel lamellae organized as multiple external circumferential lamellae and fewer inner circumferential lamellae (B) Signup and view all the answers

What is the purpose of the lamellae in compact bone?

To enclose and strengthen the middle region containing vascularized osteons (D) Signup and view all the answers

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Study Notes

Bone Composition and Cells

Bone is a specialized connective tissue rich in a vascular supply and composed of calcified extracellular material called the bone matrix.
The three major cell types in bones are osteocytes, osteoblasts, and osteoclasts.
Osteoblasts originate from mesenchymal stem cells and produce organic components of the bone matrix such as collagen fibers, proteoglycans, and glycoproteins like osteonectin.
Osteocytes are mature bone cells that maintain the lacunae and canaliculi within the bone through diffusion and communication with nearby cells.
Osteoclasts are bone-resorbing cells that remove bone matrix and are stimulated by factors like osteoblasts, macrophages, and parathyroid hormone.

Bone Matrix

Inorganic salts make up about 65% of the dry weight of bone, while organic components like collagen fibers and ground substance make up the remaining 35%.
The organic matrix of bone includes glycosaminoglycans, proteoglycans, water, and specialized glycoproteins like osteonectin and osteocalcin.
Collagen fibers in bone are synthesized by osteoblasts and help in the mineralization of bone.
Key inorganic ions present in bone are calcium and phosphorus, along with magnesium, carbonate, chloride, and other ions.

Periosteum & Endosteum

The external and internal surfaces of bones are covered by the periosteum and endosteum, respectively.
The periosteum is a fibrous outer layer containing collagen, fibroblasts, and blood vessels, while the endosteum covers trabeculae of bony matrix internally.
Both periosteum and endosteum contain osteoprogenitor cells, osteoblasts, and bone lining cells, critical for bone growth and repair.

Types of Bone

Woven bone is nonlamellar, with a random arrangement of collagen fibers and higher proportion of osteocytes, usually replaced by lamellar bone in adults.
Lamellar bone, found in most adults, is organized into multiple layers or lamellae of calcified matrix, with collagen fibers arranged parallel to one another.
Compact bone, like in the diaphysis of long bones, is organized into external circumferential lamellae beneath the periosteum and inner circumferential lamellae around the marrow cavity.

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