Bone and Skeletal Tissues

Overview

This chapter introduces the structure and function of bone and skeletal tissues, focusing on cartilage types, bone classification, and the organization of bone at both gross and microscopic levels. Understanding these tissues is fundamental to the study of the musculoskeletal system in Anatomy & Physiology.

Cartilage

General Characteristics of Cartilage

• Cartilage is a specialized connective tissue.

• Cells: The primary cells are chondroblasts (immature, matrix-producing) and chondrocytes (mature, maintain matrix).

• Extracellular Matrix (ECM):

  • Composed of fibers embedded in a firm, rubbery gel.

  • High water content provides resiliency and allows cartilage to act as a shock absorber.

  • Gristle-like nature supports flexibility and cushioning.

• Avascular: Cartilage lacks blood vessels and nerves.

• Perichondrium: A connective tissue covering that supports cartilage physically and supplies nutrients via diffusion. The perichondrium contains blood vessels and nerves.

Types of Cartilage

There are three main types of cartilage, each with distinct structural and functional properties:

• Hyaline Cartilage

  • Contains very fine collagen fibers in its matrix, providing flexible support.

  • Locations: Articular surfaces of joints, trachea, bronchi, ribs (costal cartilage), and nose.

  • Function: Reduces friction and absorbs shock in joints; forms the embryonic skeleton.

• Elastic Cartilage

  • Contains a large number of elastic fibers, conferring elasticity and resiliency.

  • Locations: External ear (auricle/pinna) and epiglottis.

  • Function: Maintains shape while allowing flexibility.

• Fibrocartilage

  • Contains abundant thick collagen fibers, providing strength and the ability to withstand compression.

  • Locations: Symphysis pubis, menisci of knees, and intervertebral discs.

  • Function: Acts as a shock absorber in high-pressure areas.

Distribution of Cartilage Types in the Human Body

Cartilage as a Component of Bone Organs

• Bones are organs composed of multiple tissue types, including:

  • Cartilage

  • Bone tissue

  • Fibrous connective tissue

  • Blood (myeloid tissue)

  • Adipose tissue

• These components contribute to the structure, function, and metabolic activity of bones.

Key Terms

• Chondroblast: Immature cartilage cell that produces the matrix.

• Chondrocyte: Mature cartilage cell that maintains the matrix, found in lacunae.

• Perichondrium: Dense irregular connective tissue membrane surrounding cartilage (except at articular surfaces).

Example: Articular Cartilage in Joints

Articular cartilage, a type of hyaline cartilage, covers the ends of bones in synovial joints. It provides a smooth, lubricated surface for articulation and facilitates the transmission of loads with a low frictional coefficient, protecting the underlying bone from wear and tear.