Cartilage and Bone Tissues

Overview

This section introduces the structure and function of cartilage and bone tissues, highlighting their differences, types, and roles in the human body. Understanding these tissues is fundamental for studying the skeletal system in Anatomy & Physiology.

Differences Between Bone and Cartilage

General Comparison

• Bone is a rigid, mineralized tissue providing structural support, protection, and movement.

• Cartilage is a flexible, avascular tissue that cushions joints and maintains shape in certain structures.

• Bone contains blood vessels and nerves; cartilage is avascular and lacks nerve fibers.

• Bone matrix is rich in calcium salts; cartilage matrix contains glycosaminoglycans (GAGs) and collagen fibers.

Structure of Cartilage

General Features

• Cartilage is tough but flexible, with a structure intermediate between dense connective tissue and bone.

• It is avascular (lacks blood vessels) and devoid of nerve fibers.

• The ground substance contains high levels of glycosaminoglycans (GAGs) such as chondroitin sulfate and hyaluronic acid, and proteins like chondronectin.

• Matrix contains collagen fibers and sometimes elastic fibers.

• Cartilage is composed of up to 80% water, contributing to its resilience.

Key Terms Relating to Cartilage

• Perichondrium: Dense connective tissue layer surrounding cartilage; provides nutrients and can form scar tissue in damaged areas.

• Chondroblasts: Immature cartilage cells that actively form cartilage.

• Chondrocytes: Mature cartilage cells that maintain cartilage; found in clusters called lacunae.

Types of Cartilage

Hyaline Cartilage

• Most abundant type; provides firm support and pliability.

• Matrix contains lots of collagen; appears glassy blue-white.

• Chondrocytes make up only 1-10% of volume.

• Locations: Embryonic skeleton, ends of long bones (epiphyseal plates), costal cartilages of ribs, nose, trachea, larynx.

• Functions: Supports and reinforces, cushions, resists compressive stress.

Elastic Cartilage

• Similar to hyaline cartilage but with more elastic fibers.

• Locations: External ear, epiglottis.

• Functions: Maintains shape while providing flexibility.

Fibrocartilage

• Rows of chondrocytes alternate with rows of thick collagen fibers.

• Intermediate structure between hyaline cartilage and dense regular connective tissue.

• Locations: Intervertebral discs, pubic symphysis, discs of knee joints (where cartilage meets ligament or tendon).

• Functions: Provides tensile strength and absorbs compressive shock.

Functions of Bone Tissue

Overview

Bones are living, dynamic tissues that respond to mechanical stress and play multiple roles in the body.

• Support: Provides structural framework for the body.

• Protection: Shields vital organs (e.g., skull protects brain, ribs protect heart and lungs).

• Anchorage & Movement: Serves as attachment points for muscles, enabling movement.

• Mineral Storage: Stores minerals, especially calcium and phosphorus; releases them into the bloodstream as needed.

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

• Fat Storage: Yellow marrow stores fat as an energy reserve.

• Hormone Production: Produces osteocalcin, a hormone involved in bone metabolism and regulation of blood sugar.

Bone Remodeling

• Bones adapt to the amount of force applied by increasing density and roughening, or decreasing density when force is eliminated (e.g., paralysis).

• Processes: Deposition (formation of new bone) vs Resorption (breakdown of bone).

Example

• When calcium levels in the blood drop, bone tissue is resorbed to release calcium into the bloodstream.

*Additional info: The notes reference textbook readings and provide a foundational overview suitable for college-level Anatomy & Physiology students. More detailed mechanisms of bone growth, repair, and hormonal regulation are covered in subsequent sections.*