Histology: Bone

Questions and Answers

What happens to osteoblasts that secrete osteoid?

They transform directly into osteoclasts.

They continue to proliferate indefinitely.

They undergo apoptosis. (correct)

They become osteocytes only.

What is the initial step in bone mineralization involving osteoblasts?

Secretion of osteoprotegerin.

Apoptosis of inactive progenitor cells.

Deposition of osteoid. (correct)

Formation of osteocalcin.

What are the cells called that are located within lacunae surrounded by bony matrix?

Osteoclasts.

Lining cells.

Osteocytes. (correct)

Osteoblasts.

What is the composition of the mineral crystals that are formed during bone mineralization?

[Ca10(PO4)6(OH)2] crystals. Signup and view all the answers

What substance secreted by osteoblasts plays a critical role in binding calcium ions?

Osteocalcin. Signup and view all the answers

Which process is NOT mentioned as part of bone appositional growth?

Direct conversion of osteocytes to osteoblasts. Signup and view all the answers

What is a unique characteristic of primary bone tumors?

They account for 1% of all cancer deaths. Signup and view all the answers

During the process of matrix mineralization, which of the following occurs?

Calcium salts are deposited into the osteoid matrix. Signup and view all the answers

What is the primary function of the sealing zone formed by the membrane domain of an active osteoclast?

To allow for localized matrix digestion Signup and view all the answers

Which type of collagen predominantly makes up the outer fibrous layer of the periosteum?

Type I collagen Signup and view all the answers

What role do osteoprogenitor cells play in the bone structure?

They give rise to new osteoblasts for bone growth and repair. Signup and view all the answers

What promotes the local signaling for the activation of osteoclasts?

Local factors from other bone cells Signup and view all the answers

What happens to hydroxyapatite as a result of the acidification process in the osteoclast’s microenvironment?

It dissolves to facilitate matrix digestion. Signup and view all the answers

Which of the following is TRUE about the endosteum?

It covers the small trabeculae of bony matrix in marrow cavities. Signup and view all the answers

What is a significant characteristic of perforating (Sharpey) fibers?

They strengthen the connection between the periosteum and bone matrix. Signup and view all the answers

In osteopetrosis, which of the following is primarily disrupted?

The activity and metabolism of osteoclasts Signup and view all the answers

What is the primary mechanism for raising blood calcium levels?

Mobilization of ions from hydroxyapatite Signup and view all the answers

Which type of bone replaces the immature woven bone of the callus during remodeling?

Lamellar bone Signup and view all the answers

During appositional growth, new bone tissue is added to which surface of the bone?

Periosteal surface Signup and view all the answers

What is the result of bone remodeling during the healing process?

Restoration of the original bone structure Signup and view all the answers

What type of growth refers to the formation of the bone collar during endochondral ossification?

Appositional growth Signup and view all the answers

How is calcium mobilization primarily regulated?

Paracrine interactions among bone cells Signup and view all the answers

Which of the following describes a characteristic of cancellous bone?

It contains large marrow-filled spaces. Signup and view all the answers

In what phase of life does the process of radial bone growth primarily occur?

Infancy Signup and view all the answers

What distinguishes woven bone from lamellar bone?

Woven bone is characterized by random disposition of collagen fibers. Signup and view all the answers

What is the significance of tetracycline in bone studies?

It specifically labels newly deposited osteoid during mineralization. Signup and view all the answers

In healthy adults, what percentage of bone is typically turned over annually?

5%-10% Signup and view all the answers

What characteristic is associated with woven bone during embryonic development?

It is the first bone tissue to appear. Signup and view all the answers

Which feature is true regarding woven bone?

It has a lower mineral content and is more penetrable by x-rays. Signup and view all the answers

What happens to woven bone after it forms in adults?

It is replaced by lamellar bone. Signup and view all the answers

The cycle of osteoid secretion in osteoblasts results in what structure in bones?

Bony plates. Signup and view all the answers

What happens to woven bone during fracture repair?

It forms quickly but is later replaced by stronger bone. Signup and view all the answers

What is the primary function of the nucleus pulposus in an intervertebral disc?

It acts as a shock absorber. Signup and view all the answers

What occurs most frequently in the posterior region of the intervertebral disc?

Slipped or herniated disc. Signup and view all the answers

Which of the following characteristics best describes the annulus fibrosus?

It has concentric fibrocartilage laminae with orthogonally arranged collagen bundles. Signup and view all the answers

What happens to the nucleus pulposus as an individual ages?

It gradually decreases in size and replaces with fibrocartilage. Signup and view all the answers

What type of joint allows for free bone movement, as described in the content?

Diarthroses Signup and view all the answers

What consequence can result from a herniated disc compressing adjacent nerve fibers?

Severe pain and neurologic disturbances. Signup and view all the answers

Which cellular component is primarily responsible for the viscosity of the nucleus pulposus?

Hyaluronic acid and vacuolated cells Signup and view all the answers

What structural feature contributes to the toughness of the intervertebral disc?

Multiple lamellae of fibrocartilage Signup and view all the answers

Study Notes

Bone Development and Cell Types

Osteoblasts, responsible for bone formation, secrete osteoid and can differentiate into osteocytes or undergo apoptosis.
Active osteoblasts appear rounded, while osteocytes are flattened and located in lacunae within the bone matrix.
Bone appositional growth involves the secretion of osteoid between the osteoblast layer and existing bone surface, initiating the calcification process.
Calcium salts are deposited into the newly formed matrix, embedding collagen fibers and proteoglycans.
Osteocalcin, a vitamin K-dependent protein, is secreted by osteoblasts to bind calcium ions, aiding in mineralization.

Osteoclast Function

Osteoclasts form a specialized microenvironment for bone resorption through a sealing zone and a ruffled border.
These cells pump protons into the area to acidify and dissolve hydroxyapatite, utilizing metalloproteinases for matrix protein digestion.
Osteoclast activity is regulated by osteoblasts through signaling factors including M-CSF and RANKL, which promote osteoclast formation and activity.

Bone Structure

The periosteum covers the outer surface of bones while the endosteum lines the internal surfaces; both are composed of connective tissue.
The outer periosteum contains dense connective tissue, type I collagen, fibroblasts, and blood vessels, while the inner layer includes osteoblasts, bone lining cells, and osteoprogenitor cells.
Small trabeculae of bony matrix exist in the endosteum, projecting into marrow cavities.

Woven and Lamellar Bone

Woven bone is nonlamellar, characterized by irregularly arranged collagen fibers, appearing first in embryonic development and fracture repair; typically replaced by lamellar bone in adults.
Woven bone has lower mineral content and is more easily penetrated by X-rays than mature lamellar bone, which has a higher strength.
Tetracycline can be used to measure bone growth by binding to newly deposited osteoid during mineralization.

Bone Remodeling

Blood calcium levels are maintained by mobilizing calcium ions from hydroxyapatite within cancellous bone, regulated by paracrine signals from bone cells.
Bone changes in diameter through appositional growth, forming new tissue beneath the periosteum while resorbing bone at the endosteal surface.

Intervertebral Discs

Intervertebral discs consist of an outer annulus fibrosus made of concentric fibrocartilage laminae and an inner nucleus pulposus providing shock absorption.
Nucleus pulposus contains a viscous matrix and vacuolated cells, decreasing in size with age and partially replaced by fibrocartilage.
Herniated discs occur due to degeneration of the annulus fibrosus, often compressing nearby nerves and causing pain.

Synovial Joints

Diarthroses (synovial joints) allow significant mobility, connecting long bones with flexibility; examples include elbow and knee joints.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the intricate processes of bone development, focusing on the roles of osteoblasts and osteoclasts. This quiz discusses bone formation, appositional growth, and the functions of different cell types involved in bone health. Test your knowledge about the significance of proteins like osteocalcin and the regulatory mechanisms of bone resorption.