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, and enable movement, while also serving as sites for blood cell formation and mineral storage.

Structure and Composition of Cartilage

General Features of Cartilage

• Cartilage is a resilient, molded connective tissue primarily composed of water, which allows it to withstand compression and return to its original shape.

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

• It is surrounded by a layer of dense connective tissue called the perichondrium, which acts as a girdle to resist outward expansion and contains blood vessels for nutrient delivery.

• The main cell type in cartilage is the chondrocyte, which resides in small cavities called lacunae within a jelly-like extracellular matrix.

Types of Cartilage

• Hyaline Cartilage

  • Most abundant type; provides support, flexibility, and resilience.

  • Contains only collagen fibers.

  • Locations: articular surfaces of joints, costal cartilage (ribs), respiratory structures (larynx), and nasal cartilage (nose tip).

• Elastic Cartilage

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

  • Locations: external ear and epiglottis.

• Fibrocartilage

  • Contains thick collagen fibers, providing great tensile strength.

  • Locations: intervertebral discs, menisci of the knee, and pubic symphysis.

Microscopic Structure of Cartilage

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

• The perichondrium is a dense connective tissue layer that encases the cartilage, providing nutrients via diffusion.

• Example: A histological section at 400X magnification shows chondrocytes within lacunae and the perichondrium at the periphery.

Summary Table: Types of Cartilage

Type	Main Fibers	Key Properties	Locations
Hyaline	Collagen (Type II)	Support, flexibility, resilience	Joints, ribs, larynx, nose
Elastic	Collagen & Elastic fibers	Flexible, maintains shape	Ear, epiglottis
Fibrocartilage	Thick collagen fibers	Strong, resists compression	Intervertebral discs, knee menisci

Key Terms and Definitions

• Chondrocyte: Mature cartilage cell that maintains the cartilage matrix.

• Lacuna (plural: lacunae): Small cavity within the matrix that houses a chondrocyte.

• Perichondrium: Dense connective tissue membrane surrounding cartilage, providing nutrients and limiting expansion.

• Extracellular Matrix: Network of fibers and ground substance in which cells are embedded; provides structural support.

Applications and Clinical Relevance

• Cartilage injuries heal slowly due to lack of blood supply.

• Degeneration of articular cartilage leads to conditions such as osteoarthritis.

Additional info: The notes above are based on standard content for introductory Anatomy & Physiology courses, with inferred details to fill in gaps from the provided slides.