Bone Tissue

Introduction

Bone tissue is a specialized connective tissue that forms the rigid part of the skeleton in vertebrates. It provides structural support, protects vital organs, and serves as a reservoir for minerals. This study guide covers the structure, function, and cellular composition of bone tissue, as well as related disorders.

Functions of the Skeletal System

Overview of Skeletal Functions

The skeletal system performs several essential functions necessary for human physiology and movement.

• Support: Provides a framework for the body and supports soft tissues.

• Protection: Shields internal organs (e.g., skull protects the brain, rib cage protects the heart and lungs).

• Movement: Facilitates movement by serving as points of attachment for muscles.

• Mineral Storage: Stores and releases minerals, especially calcium and phosphorus, as needed.

• Blood Cell Production: Houses red bone marrow, which produces blood cells (hematopoiesis).

• Energy Storage: Stores lipids in yellow bone marrow.

Bone Shape Classification

Types of Bones by Shape

Bones are classified according to their shapes, which relate to their functions and locations in the body.

Bone Structure

Long Bone Anatomy

Long bones have a distinct structure that supports their function in movement and weight-bearing.

• Diaphysis: The shaft of the bone, composed mainly of compact bone.

• Epiphysis: The ends of the bone, containing spongy bone and red marrow.

• Metaphysis: The region between diaphysis and epiphysis; includes the growth plate in children.

• Medullary Cavity: Central cavity containing yellow marrow (fat storage).

• Periosteum: Dense connective tissue covering the bone's outer surface.

• Endosteum: Thin membrane lining the medullary cavity.

Flat Bone Structure

Flat bones consist of two layers of compact bone enclosing a layer of spongy bone (diploë).

• Compact Bone: Dense outer layers providing strength.

• Spongy Bone (Diploë): Inner layer containing marrow and trabeculae.

Bone Cells

Types of Bone Cells

Bone tissue contains several specialized cell types, each with distinct functions.

• Osteocytes: Located in lacunae, maintain bone matrix and communicate via canaliculi.

• Osteoblasts: Responsible for bone formation and mineralization.

• Osteoclasts: Large, multinucleated cells involved in bone resorption.

Bone Matrix

Composition of Bone Matrix

The bone matrix is a composite material that provides strength and flexibility.

• Mineralized Crystals:

  • Calcium phosphate (main mineral component)

  • Hydroxyapatite (Ca10(PO4)6(OH)2)

  • Other minerals and ions

• Collagen Fibers: Provide tensile strength and flexibility.

Bone Disorders

Osteogenesis Imperfecta

Osteogenesis imperfecta is a genetic disorder characterized by defective collagen production, leading to brittle bones.

• Symptoms: Frequent fractures, bone deformities, short stature.

• Pathology: Abnormal bone matrix due to faulty collagen.

• Types: Several types exist, varying in severity.

Summary Table: Bone Cell Types and Functions

Additional info:

• Bone histology includes microscopic analysis of bone cells and matrix organization.

• Compact bone is organized into osteons (Haversian systems), while spongy bone consists of trabeculae.