Connective Tissue - Bone Study Guide

Questions and Answers

What is the main difference between cortical bone and cancellous bone?

Cancellous bone contains no blood vessels.

Cortical bone is denser and forms the tough outer layer. (correct)

Cancellous bone is primarily found in the outer layer of bones.

Cortical bone is softer than cancellous bone.

Which type of cells are responsible for breaking down the extracellular matrix in bone?

Osteocytes

Osteoclasts (correct)

Bone lining cells

Osteoblasts

What is the primary function of osteoblasts?

To resorb bone tissues and release minerals.

To secrete extracellular matrix and support bone formation. (correct)

To line the surfaces of bones.

To maintain the extracellular matrix.

What distinguishes immature bone from mature bone?

Immature bone, also called woven bone, is weaker than mature bone. Signup and view all the answers

Which of the following components is non-mineralized in the bone structure?

Osteoid Signup and view all the answers

What role do osteocytes serve in bone health?

They help maintain the extracellular matrix. Signup and view all the answers

Which statement about bone lining cells is correct?

They line the surfaces of bones. Signup and view all the answers

What is the main mineralized component of bone?

Hydroxyapatite Signup and view all the answers

What structure of bone is known for its concentric rings?

Osteon structure Signup and view all the answers

Which of the following is a factor that influences the duration of fracture repair?

Fracture location Signup and view all the answers

What is the role of osteoprogenitor cells in the healing process?

They can differentiate into osteoblasts and osteoclasts. Signup and view all the answers

Which process begins after approximately 1 week during fracture healing?

Soft callus formation Signup and view all the answers

What type of tissue forms during the inflammatory stage of fracture repair?

Granulation tissue Signup and view all the answers

What phase of fracture healing involves the resorption of excessive callus?

Remodeling phase Signup and view all the answers

What are Volkmann's canals primarily responsible for?

Connecting osteons together Signup and view all the answers

What occurs during the endochondral ossification phase of fracture healing?

Formation of bone from cartilage Signup and view all the answers

Study Notes

General Structure of Bone

Cortical bone (compact bone) serves as the tough outer layer and constitutes the majority of the bone in the body.
Covered by a periosteum that contains blood vessels for nourishment.
Cancellous bone (trabecular/spongy bone) features a spongy, mesh-like structure and is in contact with bone marrow.

Cellular and Non-Cellular Components of Bone

Cellular Component:
- Osteoblasts are immature bone cells that secrete extracellular matrix, contributing to the bone's material properties, which can differentiate into osteocytes, bone lining cells, or undergo apoptosis.
- Osteocytes are mature bone cells, responsible for maintaining the extracellular matrix and responding to mechanical and hormonal stimuli.
- Osteoclasts break down extracellular matrix, releasing minerals into the bloodstream and creating space for osteoblasts.
- Bone lining cells provide a protective layer on bone surfaces.
Non-Cellular Component:
- Non-mineralized component includes osteoid, primarily composed of collagen.
- Mineralized component consists of hydroxyapatite, which provides strength and structure to bone.

Classifications of Bone Based on Maturity Level

Immature bone, or woven bone, known as primary bone, is found during fracture repair and fetal growth. It has an irregular collagen structure and is weaker due to less mineral content.
Mature bone, also known as lamellar or secondary bone, is formed during the remodeling process and is stronger than woven bone. It features an osteon structure with concentric rings, osteocytes housed in lacunae, Haversian canals containing blood vessels, and Volkmann’s canals connecting osteons.
Both cortical and cancellous bones can present in immature forms.

Process of Fracture Repair

Fracture repair involves regeneration and remodeling, with no scar formation and a return to optimal function possible.
Healing duration varies based on factors such as fracture site, type, treatment, soft tissue involvement, and individual considerations including age and nutritional status.
Phases of Healing:
- Initial Response: Internal bleeding delivers cells to the injury site, secreting growth factors and subsequent clotting. Key cell types involved include fibroblasts, platelets, osteoprogenitor cells (bone precursor cells), mesenchymal cells (can differentiate into various cell types), and inflammatory cells.
- Hematoma Formation: Lasts approximately one week, providing a foundation for healing.
- Inflammation Phase: Granulation tissue forms alongside fibrosis and neovascularization (new blood vessel formation).
- Soft Callus Formation: Begins around two weeks. Osteoclasts clear necrotic bone, while periosteum and endosteum regenerate into hyaline cartilage (soft callus) and bony spicules (hard callus) to immobilize the fracture.
- Hard Callus Development: Starts more than a week after soft callus formation, involving fibrocartilage and endochondral ossification, turning cartilage into bone.
- Remodeling Phase: Can take months to years, replacing woven bone with lamellar bone, resorbing excess callus, and reshaping bone in response to mechanical stresses according to Wolff’s Law.

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Description

This study guide provides an overview of bone structure, including both cortical and cancellous bone types. It outlines the unique characteristics of each type, such as the tough outer layer of cortical bone and the spongy nature of cancellous bone. Perfect for students looking to understand the basic anatomy of bones.