Bones and Skeletal Tissues: Structure, Types, and Functions

Bones and Skeletal Tissues

Introduction

The skeletal system is composed of bones and associated tissues, including various types of cartilage. These structures provide support, protection, movement, and serve as sites for blood cell formation and mineral storage.

Structure and Composition of Cartilage

General Features of Cartilage

• Cartilage is a type of connective tissue that is highly resilient and molded, consisting primarily of water. This high water content allows cartilage to withstand compression and return to its original shape.

• Cartilage is avascular (lacks blood vessels) and aneural (lacks nerves).

• The perichondrium is a dense layer of connective tissue that surrounds most cartilage, providing mechanical support and containing blood vessels for nutrient delivery.

• Cartilage is composed of chondrocytes (cartilage cells) that reside in small spaces called lacunae within a jelly-like extracellular matrix.

Types of Cartilage

Hyaline Cartilage

• Most abundant type of cartilage.

• Provides support, flexibility, and resilience.

• Contains only fine collagen fibers.

• Locations: Articular cartilage (joints), costal cartilage (ribs), respiratory cartilage (larynx, trachea), and nasal cartilage (nose tip).

Elastic Cartilage

• Similar to hyaline cartilage but contains more elastic fibers, allowing for greater flexibility.

• Locations: External ear and epiglottis.

Fibrocartilage

• Contains thick collagen fibers, providing great tensile strength.

• Locations: Menisci of the knee and intervertebral discs.

Microscopic Structure of Cartilage

Histological Features

• Chondrocytes are visible within lacunae, surrounded by the extracellular matrix.

• The perichondrium is seen as a dense outer layer, providing nutrients and support.

• Cartilage matrix appears smooth and glassy under the microscope (as shown in the provided 400X image).

Functions of Cartilage

• Provides flexible support in various parts of the body.

• Reduces friction and absorbs shock in joints.

• Maintains the shape of certain structures (e.g., ear, nose).

• Serves as a template for bone formation during fetal development and growth.

Summary Table: Types of Cartilage

Type	Main Fibers	Key Locations	Main Function
Hyaline	Collagen (fine)	Joints, ribs, larynx, nose	Support, flexibility, resilience
Elastic	Collagen & elastic fibers	External ear, epiglottis	Flexible support
Fibrocartilage	Thick collagen	Menisci, intervertebral discs	Tensile strength, shock absorption

Key Terms

• Chondrocyte: A mature cartilage cell found in lacunae.

• Extracellular matrix: The non-cellular component of cartilage, providing structural support.

• Perichondrium: Dense connective tissue layer surrounding cartilage (except at joints).

• Lacuna: Small cavity within the matrix that houses a chondrocyte.

Example Application

• Articular cartilage in synovial joints (such as the knee) reduces friction and absorbs shock during movement, preventing bone damage.

Additional info: The notes above are based on standard content for introductory Anatomy & Physiology courses, with inferred details to ensure completeness and clarity.