Bone Histology and Function

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Questions and Answers

What is the primary function of osteoblasts in bone formation?

To provide structural support to the body

To protect internal organs

To produce the organic components of bone matrix (correct)

To break down bone matrix

What is the name of the protein that binds Ca2+ in the bone matrix?

Glycoproteins

Osteonectin

Osteocalcin (correct)

Type I collagen

What is the name of the layer of collagen-rich material formed between the osteoblast layer and the preexisting bone surface?

Proteoglycans

Bone matrix

Osteoid (correct)

Hydroxyapatite crystals

What is the function of osteoclasts in bone formation?

To break down bone matrix Signup and view all the answers

What is the main component of bone matrix?

Calcified extracellular material Signup and view all the answers

What is the function of osteocytes in bone?

To maintain bone health Signup and view all the answers

What is the process of bone growth that involves the deposition of calcium salts into the newly formed matrix?

Bone appositional growth Signup and view all the answers

What is the origin of osteoblasts?

Mesenchymal stem cells Signup and view all the answers

What is the primary function of osteocytes in bone?

To maintain the integrity of lacunae and canaliculi Signup and view all the answers

What is the characteristic of osteocyte cytoplasm?

Eosinophilic or lightly basophilic Signup and view all the answers

How do osteocytes communicate with one another?

Through gap junctions Signup and view all the answers

What is the function of perforating fibers in the periosteum?

To bind the periosteum to the bone Signup and view all the answers

What is the function of osteoclasts in bone?

To remove bone matrix Signup and view all the answers

What is the primary function of osteoclasts in bone removal?

Demineralization of bone matrix Signup and view all the answers

Which of the following hormones stimulates bone removal?

Parathyroid hormone Signup and view all the answers

Which type of bone tissue is characterized by random disposition of type I collagen fibers?

Woven bone Signup and view all the answers

What is the characteristic of osteoclast nuclei?

Multiple nuclei Signup and view all the answers

What is the role of diffusion in bone?

To transport nutrients from bone to blood vessels Signup and view all the answers

What is the main difference between woven bone and lamellar bone in terms of mineral content?

Woven bone has a lower mineral content Signup and view all the answers

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

65% Signup and view all the answers

What is the function of osteoprogenitor cells in bone growth and repair?

To produce new osteoblasts Signup and view all the answers

What is the name of the pits occupied by osteoclasts during bone resorption?

Lacunae of Howship Signup and view all the answers

Which type of collagen is found in bone?

Type I collagen Signup and view all the answers

What is the primary location of osteoclasts in bone?

At surfaces where bone removal is taking place Signup and view all the answers

What is the main characteristic of the endosteum?

A sparse, delicate matrix of collagen fibers Signup and view all the answers

What is the term used to describe the mixture of organic ground substance and collagen fibers before mineralization?

Osteoid Signup and view all the answers

What is the typical thickness of a lamella in lamellar bone?

3-7 μm Signup and view all the answers

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

Hydroxyl ions Signup and view all the answers

What is the primary function of osteoblasts in bone?

Synthesizing collagen fibers Signup and view all the answers

What is the function of periosteal blood vessels?

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

In which type of bone tissue are osteocytes more abundant?

Woven bone Signup and view all the answers

What covers the external and internal surfaces of all bones?

Periosteum and endosteum Signup and view all the answers

What is the typical diameter of an osteon?

100-250 μm Signup and view all the answers

What is the function of the canaliculi in an osteon?

To facilitate communication between osteocytes Signup and view all the answers

What is the outer boundary of each osteon composed of?

A layer called the cement line that includes many noncollagen proteins Signup and view all the answers

What is the purpose of the transverse perforating canals (or Volkmann canals)?

To facilitate communication between osteons Signup and view all the answers

What is the term for the irregularly shaped groups of parallel lamellae that are scattered among the intact osteons?

Interstial lamellae Signup and view all the answers

What is the term for the layer of lamellae immediately beneath the periosteum in compact bone?

External circumferential lamellae Signup and view all the answers

What is the main function of the osteons in compact bone?

To strengthen the bone by enclosing vascularized osteons Signup and view all the answers

What is the term for the process by which osteons are partially destroyed during growth and remodeling of bone?

Osteoclastic resorption Signup and view all the answers

Study Notes

Objectives of Bone Histology

Understand the important features of bone
Learn about the composition of bone
Identify the types of bone and their covering
Recognize the cells of bone and their functions

Bone Function

Supports the body
Protects internal organs
Acts as the body's Ca2+ reservoir

Osteoblasts

Originates from mesenchymal stem cells
Produces the organic components of bone matrix, including:
- Type I collagen fibers
- Proteoglycans
- Glycoproteins such as osteonectin
Deposition of inorganic components of bone depends on osteoblast activity
Active osteoblasts are located exclusively at the surfaces of bone matrix, bound by integrins, forming a single layer of cuboidal cells joined by adherent and gap junctions

Osteocytes

Are the cells of mature bone
Lie in the lacunae of bone, representing osteoblasts that have become 'imprisoned' in the matrix during bone formation
Have eosinophilic or lightly basophilic cytoplasm, correlated with negligible secretory activity and the presence of only a small amount of endoplasmic reticulum in the cytoplasm
Present in greatest numbers in young bone, decreasing with age
Functions:
- Maintain the integrity of lacunae and canaliculi, keeping open channels for diffusion of nutrition through bone
- Play a role in removal or deposition of matrix and calcium when required

Osteoclasts

Are bone-removing cells
Found in relation to surfaces where bone removal is taking place
Occupy pits called resorption bays or lacunae of Howship
Are very large cells (20 to 100 μm or more in diameter) with numerous nuclei and mitochondria
Have a ruffled membrane at sites of bone resorption
Removal of bone by osteoclasts involves demineralization and removal of matrix
Bone removal can be stimulated by factors secreted by osteoblasts, macrophages, lymphocytes, and parathyroid hormone

Bone Matrix

Composed of:
- Inorganic salts (about 65% of dry weight)
- Organic ground substance and collagen fibers (about 35%)
Organic matrix consists of:
- Glycosaminoglycans
- Proteoglycans
- Water
- Special glycoproteins osteonectin and osteocalcin
Collagen fibers (Type I) are synthesized by osteoblasts and embedded in the ground substance

Periosteum and Endosteum

Periosteum:
- An outer fibrous layer of dense connective tissue
- Contains bundled type I collagen, fibroblasts, and blood vessels
- Penetrates the bone matrix and binds to the bone
Endosteum:
- A thin layer covering small trabeculae of bony matrix
- Contains osteoprogenitor cells, osteoblasts, and bone lining cells
- Within a sparse, delicate matrix of collagen fibers

Types of Bone

Woven bone:
- Nonlamellar, with random disposition of type I collagen fibers
- First bone tissue to appear in embryonic development and fracture repair
- Usually temporary, replaced by lamellar bone in adults, except in a few places
Lamellar bone:
- Characterized by multiple layers or lamellae of calcified matrix
- Typical of compact or cancellous bone in adults
- Organized as parallel sheets or concentrically around a central canal
- Contains osteocytes in lacunae, interconnected by canaliculi with dendritic processes

Compact Bone

Compact bone:
- Also includes parallel lamellae organized as multiple external circumferential lamellae
- Inner circumferential lamellae around the marrow cavity
- Lamellae of outer and innermost areas of compact bone enclose and strengthen the middle region containing vascularized osteons

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Description

This quiz covers the structure, composition, and functions of bones, including types of bone, bone cells, and their roles in the body.