This document discusses the histology of cartilage. It defines cartilage and its main functions, which include bearing mechanical stresses, forming frameworks, and facilitating bone movement. The document then describes the three main types of cartilage - hyaline, elastic, and fibrocartilage - and discusses their composition, distribution in the body, and characteristics. It also addresses cartilage growth and repair mechanisms as well as common conditions that affect cartilage.

1. Histology of cartilage
Dr. Marwa Gaffar Faki Ali
M.B.B.S, M.Sc. clinical anatomy

2. By the end of this session, the student is
able to:
• Define cartilage and its functions.
• Identify the components of cartilage.
• Classify the different types of cartilage.
• Identify the properties of each type of cartilage.
• Identify the growth and repair mechanisms of
cartilage.

3. Introduction:
• Tough, flexible form of connective tissue.
• Firm in consistency to allow bearing of mechanical
stresses.
• Extracellular matrix enriched with ground
substances that interact with collagen and elastic
fibers.
• Avascular.

4. Introduction:
Functions:
• Bearing mechanical stresses without permanent
distortion.
• Forms framework that supports soft tissues.
• Provision of shock absorbing and sliding regions
(joints) and facilitates bone movement.
• Guides development and growth of long bones.

5. cells:
Chondroblasts
&
Chondrocytes.
Ground substances:
Proteoglycans
(proteins,aggrecan
and carbohydrates,
GAG; chondroitin
sulphate, keratan
sulphate and
hyaluronic acid).
Fibers:
Collagen.
Elastic.
Cartilage

6. Perichondrium:
• Dense irregularly arranged fibrous tissue.
• Covers the free surface of cartilage (exception).
• Forms an interface between the cartilage and the tissue supported
by the cartilage.
• Harbors the vascular and nerve supply for the avascular cartilage.

7. Perichondrium:
• Composition: Collagen fibers and spindle-shaped cells.
• Cells have the capacity to transform into chondroblasts
and form new cartilage.

8. According to different functional requirements and variation
in matrix composition
3 Types of cartilage:
- Hyaline cartilage.
- Elastic cartilage.
- Fibrocartilage.

9. Hyaline cartilage
Fibrocartilage
Elastic cartilage
Distribution of cartilage in adults

10. Distribution of cartilage in adults

11. Hyaline cartilage
• Most common form of cartilage.
• Homogeneous and semitransparent (fresh state).

12. Hyaline cartilage
Distribution:
1. Costal Cartilages.
2. Articular Cartilage.
3. Other sites:
a. The skeletal framework of the larynx (thyroid,
cricoid & arytenoid).
b. The walls of the trachea and large bronchi.
c. Parts of the nasal septum, and of the lateral wall
of the nose.
d. The epiphyseal plate of growing long bones.

13. Hyaline cartilage
Chondrocytes:
- Presents in groups of two or more cells (cell-nests
or isogenous cell groups).
Matrix: homogenous and glassy.
- Fibers: Collagen II.
- Ground substances: Aggrecan & chondronectin
glycoproteins.
Perichondrium:
- Present, except at the hyaline cartilage of articular
surfaces or the epiphyses of growing long bones.

14. Osteoarthritis:
• A chronic condition with gradual loss or changed
physical properties of the hyaline cartilage that
covers the articular ends in joints.
• Degenerated cartilage fragments released by wear-
and-tear trigger damage and cause pain and
inflammation within the joint.

15. Elastic cartilage
• Yellow in color in fresh state (elastin).
• Similar in many ways to hyaline cartilage.
• Has greater flexibility than hyaline cartilage.
• Recovers its shape after being deformed.

16. Elastic cartilage
Distribution:
1. Auricle of the ear.
2. Walls of the external auditory canals.
3. Auditory (eustachian) tubes.
4. Epiglottis and the cuneiform cartilage in the
larynx.

17. Elastic cartilage
• Chondrocytes:
- Similar to those of hyaline cartilage.
• Matrix:
- Fibers: abundant elastic fibers in addition to collagen type II.
- Ground substances: Same as those in hyaline cartilage.
• Perichondrium:
- Always present.

18. Fibrocartilage
• Combination of hyaline cartilage and dense connective tissue.
• looks very much like dense fibrous tissue.
• Has great tensile strength combined with considerable
elasticity.

19. Fibrocartilage
Distribution:
1. Secondary cartilaginous joints or symphyses.
2. Some synovial joints (e.g temporo-mandibular
and sternoclavicular joints, and menisci of the knee
joint).
3. The glenoidal labrum of the shoulder joint and
the acetabular labrum of the hip joint.
4. Where tendons run in deep grooves on bone,
grooves are lined by fibrocartilage.
5. Where tendons are inserted into bone.

20. Fibrocartilage
• Chondrocytes:
- Either singly or in isogenous groups, usually arranged in long rows
separated by collagen fibers.
• Matrix:
- Fibers: Collagen type I.
- Ground substances: scarcity of proteoglycans.
• Perichondrium:
- No present.

21. Intervertebral disk
• Act as a lubricated cushion that prevents adjacent
vertebrae from being eroded by abrasive forces
during movement.
• Two major components:
1. Annulus fibrosus (prepheral): Overlapping
laminae of fibrocartilage.
2. Nucleus pulposus (central): gel-like matrix rich in
hyaluronic acid and type II collagen.

22. Herniation of the Intervertebral Disk
• Expulsion of the nucleus pulposus due to rupture of
the annulus fibrosus.
• Concomitant flattening of the disk.
• Then, disk frequently dislocates or slips from its
position between the vertebrae compressing the
spinal nerves .

23. Cartilage Formation, Growth, & Repair
• All forms of cartilage are of mesenchyme origin.
• Cartilaginous structures grow by:
- Interstitial growth: Mitosis of existing
chondroblasts in lacunae (Increase the length of
long bones).
- Appositional growth: Formation of new
chondroblasts peripherally from progenitor cells in
the perichondrium (grow in width).

24. Cartilage Formation, Growth, & Repair
• Repair or replacement of injured cartilage is very
slow and ineffective (avascularity and low metabolic
rate ).