Cartilage Flashcards
Where does cartilage develop from?
Mesenchyme
Characteristics of cartilage
Consists of cells, tissue fibers and ground substance
Nonvascular (diffusion)
Strong, rigid and flexible
What cells are within cartilage?
Chondrogenic –> chondroblasts and chondrocytes
What are the 3 types of cartilage?
Elastic, hyaline and fibrocartilage
What is the function of cartilage?
Forms the supporting framework of organs
Lines the surface of articulating bones
Forms the template for growth and development of long bones
What is the ECM of cartilage composed of?
Glycoanimoglycans (GAGs) and proteoglycans
Collagen and elastic fibers
This makes the ECM firm and resistant to mechanical forces
Hyaline Cartilage
Most common and the skeletal model for most bones
Type II collagen fibers that cannot be seen
Covered by perichondrium
Found in trachea
Hyaline cartilage in adults
In adults it’s replaced by bone except for articular surfaces, costal cartilage, larynx, nose, trachea and bronchi
Does not calcify under normal conditions in the adult
Perichondrium
Covers the surface of hyaline and elastic cartilage
Dense CT composed of fibroblasts and type I collagen fibers
Contains blood vessels
Outer fibrous layer, inner cellular layer (chondrogenic)
What does each chondroblast give rise to?
A group of isogenous chondrocytes all derived from one chondroblast
Where do chondrocytes lie?
Cell nests in lacuna
Why are collagen II fibers invisible in cartilage?
Because of similarity in refractive index with the ground substance
Why is ground substance basophilic?
Because of chondroitin sulfate content
What happens to mesenchymal stem cells in cartilage?
reach the inner perichondrial layer differentiate into chondroblasts
Chondroblasts
Mature and secrete cartilaginous matrix and get trapped in it and become chondrocytes
Chondroclasts
Multinucleated cells that may be involved in lysis of cartilage, not commonly seen
Appositional Growth
Cartilage grows from outside (growing up)
Interstitial growth
New tissue is created within the matrix of existing cartilage
Cartilage grows within (gets thicker)
Appositional Growth process
1) Mesenchymal cells found in chondrogenic centers
2) Chondroblasts form from those centers
3) Chondroblasts differentiate into chondrocytes
4)Chondrocytes deposit matrix
5) Includes new matrix formation on existing cartilage
Interstitial growth process
1) chondrocytes in matrix divide
2) Lacunae may possess 2, 4, 8 daughter chondrocytes (isogenous or nest cells)
3) increase in matrix volume
Elastic Cartilage
Has Elastic fibers, perichondrium highly flexible
Yellow, more resilient
Identical to hyaline cartilage except for the presence of elastic fibers
Where is elastic cartilage found?
External ear, canal, laryngeal cartilages
How are chondrocytes arranged in elastic cartilage?
Cell nests
Fibrocartilage
Irregular layers of collagenous type I fibers
Acts as an intermediate between tendon and cartilage
Chondrocytes lie in the lacunae
Where is fibrocartilage found?
Intervertebral discs (mechanical shock absorbers)
Ligaments, tendon bone junctions, cardiac skeleton, menisci
Cartilage formation
- Mesenchyme is the precursor tissue of all types of cartilage
- Mitotic proliferation of mesenchymal cells gives rise to a highly cellular tissue
- Chondroblast are separated from one another by the formation of great amount of matrix
- Multiplication of cartilage cells gives rise to isogenous groups, each surrounded by a condensation of territorial (capsular) matrix
Degeneration of Cartilage
Chondrocytes hypertrophy and matrix becomes calcified
Normal process in endochondral ossification
When does degernation of cartilage abnormally occur?
Abnormally occur in an environment of hypercalcemia
Cartilage Regeneration
Very poor except in young animals
Results from the activity of chondrogenic cells in the perichondrium
