Recording-2025-02-25T01:48:44.516Z

Cunei and Chondrocytes

Definition: Cunei refers to structures in cartilage, while chondrocytes are the cells present within them.

Cartilage Structure

• Maximal Composition: The purplish-stained material in hyaline cartilage is the extracellular matrix produced by chondroblasts.

• Lacunae: These small openings house the chondrocytes, which embed themselves within after forming cartilage.

Types of Cartilage

• General Types: There are three main types of cartilage: hyaline, fibrocartilage, and elastic cartilage.

  • Hyaline Cartilage: Contains few collagen fibers and is largely composed of chondrin (gel-like, with 30% water).

  • Properties: Its gelatinous nature permits elasticity and nutrient diffusion, despite being avascular.

• Functions of Cartilage:

  • Roles: Cartilage's avascular nature and high water content facilitate nutrient diffusion and waste removal.

  • Examples:

    • Costal Cartilages: Connect ribs to sternum.

    • Tracheal Rings: Prevent trachea from collapsing.

    • Joints: Hyaline cartilage offers cushioning in areas like elbows and knees.

Hyaline Cartilage Characteristics

• Microscopic View: Appears as a uniform ground substance with minimal fibers, making it weaker than fibrocartilage and elastic cartilage.

Elastic Cartilage

• Elasticity: Contains more elastic fibers, enabling return to original shape (found in the external ear and epiglottis).

• Epiglottis Function: Covers the glottis during swallowing to prevent food from entering the respiratory tract.

Fibrocartilage

• Strength and Composition: Contains many collagen fibers, offering high stress resistance.

• Examples:

  • Intervertebral Discs: Absorb stress from body weight and movement.

  • Pubic Symphysis: Stabilizes hip bones during movement.

Bone Formation and Types

• Bone Cells:

  • Osteoprogenitor Cells: Precursor cells for osteoblasts, capable of mitosis.

  • Osteoblasts: Form new bone material but cannot undergo mitosis.

  • Osteocytes: Mature osteoblasts that maintain bone tissue, trapped in lacunae.

  • Osteoclasts: Resorb bone; derived from hematopoietic lineage.

Bone Remodeling

• Continuous Process: New bone creation and old bone breakdown is regulated to maintain calcium balance.

• Calcium Regulation: Osteoblasts and osteoclasts maintain blood calcium levels.

Bone Structure

• Composition: Bone matrix has organic (collagen fibers) and inorganic (hydroxyapatite) components for strength.

• Types of Bone Tissue:

  • Compact Bone: Dense outer layer, made of osteons.

  • Spongy Bone: Lightweight, internal structure with trabeculae.

Bone Classification by Shape

• Flat Bones: Skull, ribs, sternum.

• Long Bones: Femur, humerus, phalanges.

• Short Bones: Carpals, tarsals.

• Irregular Bones: Vertebrae, some facial bones.

• Sesamoid Bones: Form in tendons (e.g., patella).

• Pneumatized Bones: Containing air pockets (e.g., maxilla with sinuses).

Bone Architecture and Remodeling

• Mechanostimulation: Muscle force on bones attracts osteoclasts and osteoblasts to fix microfractures.

• Adaptation Based on Use: High-stress areas experience increased bone density and architectural changes.

Summary of Developmental Anatomy

• Bone classification can be challenging due to diverse shapes that reflect functional adaptations.

• Suture Bones: Extra bones along skull sutures due to incomplete fusion during development.