Bones and Skeletal Tissues: Structure, Function, and Development

Bones and Skeletal Tissues

Introduction

The study of bones and skeletal tissues is fundamental to understanding the human body's support, movement, and protection systems. Knowledge of bone anatomy and the process of bone remodeling is essential for diagnosing and treating bone diseases such as osteoporosis.

6.1 Skeletal Cartilages

Overview of Skeletal Cartilage

• The human skeleton initially consists entirely of cartilage, which is gradually replaced by bone during development, except in areas where flexibility is required (e.g., joints, ear, nose).

• Cartilage is a resilient, molded connective tissue that provides support and flexibility.

Basic Structure, Types, and Location

• Skeletal Cartilage is composed primarily of water, making it resilient and able to withstand compression.

• It contains no blood vessels or nerves.

• Perichondrium is a layer of dense connective tissue that surrounds cartilage, acting as a girdle to resist outward expansion and containing blood vessels for nutrient delivery.

• Chondrocytes are the primary cells of cartilage, encased in small cavities called lacunae within a jelly-like extracellular matrix.

Types of Cartilage

Type	Main Features	Locations
Hyaline Cartilage	Most abundant; provides support, flexibility, and resilience; contains fine collagen fibers	Articular (joints), costal (ribs), respiratory (larynx), nasal cartilage (nose)
Elastic Cartilage	Similar to hyaline cartilage but contains elastic fibers	External ear, epiglottis
Fibrocartilage	Thick collagen fibers; has great tensile strength	Menisci of knee, intervertebral discs

Growth of Cartilage

• Appositional Growth: Cartilage-forming cells in the perichondrium secrete new matrix on the external surface of existing cartilage.

• Interstitial Growth: Chondrocytes within lacunae divide and secrete new matrix, expanding cartilage from within.

Example: The flexibility of the external ear is due to the presence of elastic cartilage, while the menisci in the knee joint are composed of fibrocartilage, providing shock absorption.

Key Terms

• Chondrocyte: A mature cartilage cell that maintains the cartilage matrix.

• Perichondrium: Dense connective tissue layer surrounding cartilage.

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

Additional info: Cartilage is avascular, so nutrients diffuse through the matrix to reach chondrocytes, which limits its ability to heal after injury.