Bones and Skeletal Tissues: Structure, Types, and Functions Presentationn

Bones and Skeletal Tissues

Introduction

The human skeleton is initially composed almost entirely of cartilage, which is gradually replaced by bone as development proceeds. However, cartilage remains in areas where flexibility is required. Understanding the structure and types of skeletal tissues is fundamental to anatomy and physiology.

Skeletal Cartilages

Basic Structure and Properties

• Skeletal cartilage is a highly resilient, moldable tissue consisting primarily of water.

• It contains no blood vessels or nerves, making it avascular and reliant on diffusion for nutrient delivery.

• The perichondrium is a layer of dense connective tissue that surrounds cartilage, acting like a girdle.

• The perichondrium helps cartilage resist outward expansion and contains blood vessels for nutrient delivery to cartilage via diffusion.

• Cartilage is composed of chondrocytes, which are cells encased in small cavities called lacunae within a jelly-like extracellular matrix.

Key Features of Skeletal Cartilage

• Not vascularized (no direct blood supply).

• Mostly water, contributing to its resilience and ability to withstand compression.

• Surrounded by a thin layer of dense connective tissue (perichondrium).

• Growth is limited by diffusion, as nutrients must diffuse through the matrix from the perichondrium.

Types of Cartilage

Classification and Locations

There are three main types of cartilage found in the human body, each with distinct structural and functional properties:

• Hyaline cartilage

  • Provides support, flexibility, and resilience.

  • Most abundant type; contains only collagen fibers.

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

• Elastic cartilage

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

  • Locations: external ear and epiglottis.

• Fibrocartilage

  • Contains thick collagen fibers, providing great tensile strength.

  • Locations: menisci of the knee and intervertebral discs.

Examples and Applications

• Articular cartilage covers the ends of bones in movable joints, reducing friction and absorbing shock.

• Costal cartilage connects ribs to the sternum, allowing for flexibility during breathing.

• Menisci and intervertebral discs provide cushioning and support in joints and the spine.

Distribution of Cartilage in the Human Skeleton

Major Locations

Cartilage is distributed throughout the skeleton in specific regions where flexibility, support, or cushioning is required.

Cartilage Type	Location	Function
Hyaline	Articular surfaces of joints, costal cartilage, nose, respiratory tract	Support, flexibility, smooth movement
Elastic	External ear, epiglottis	Flexibility, maintains shape
Fibrocartilage	Intervertebral discs, menisci of knee, pubic symphysis	Shock absorption, tensile strength

Visual Overview

• Cartilage is found in the nose, external ear, joints, ribs, vertebral discs, and respiratory tubes (larynx, trachea).

• Each type of cartilage is color-coded in anatomical diagrams for clarity: hyaline (blue), elastic (green), fibrocartilage (red).

Summary Table: Cartilage Types and Locations

Type	Main Fiber	Key Locations	Function
Hyaline	Collagen	Joints, ribs, nose, larynx, trachea	Support, flexibility
Elastic	Elastic fibers	Ear, epiglottis	Flexible support
Fibrocartilage	Thick collagen	Knee, spine	Strength, shock absorption

Key Terms

• Chondrocyte: Cartilage cell found in lacunae.

• Perichondrium: Dense connective tissue surrounding cartilage.

• Lacuna: Small cavity within cartilage or bone matrix housing a cell.

• Extracellular matrix: Non-cellular component providing structural support.

Additional info:

• Cartilage is essential for skeletal development, joint function, and flexibility throughout life.

• Damage to cartilage is difficult to repair due to its avascular nature.