This document summarizes the key features of cartilage and bone. It describes the main types of cartilage - hyaline, elastic, and fibrocartilage - and their characteristic cells, extracellular matrix, and fiber components. Hyaline cartilage is found in various locations like the epiphyseal plate and nasal septum. Elastic cartilage contains elastic fibers and is flexible. Fibrocartilage contains collagen fibers and is found at sites of tendon insertion. Bone is summarized as being either compact or cancellous, and its histological features like osteons, Haversian canals, and lamellae are outlined. The process of endochondral ossification by which cartilage is replaced by bone is also mentioned.

1. CARTILAGE
DR. SUNDIP CHARMODE
ASSOCIATE PROFESSOR
DEPARTMENT OF ANATOMY
AIIMS RAJKOT

2. INTRODUCTION
• It is a specialized connective tissue.

3. CHARATERISTIC FEATURES
• Chondroblasts – cartilage forming cells differentiate from
mesenchymal cells. It has very limited ability for regeneration.
• During fetal life, cartilage is much more widely distributed than in
adult. Hence, the greater part of skeleton is cartilaginous in early fetal
life.
• Presence of Cartilage canals in the cartilage is well established.
• Cartilage canals – small artery surrounded with numerous venules
and capillaries.

4. CHARATERISTIC FEATURES
• Replacement of cartilage by bone is Endochondral ossification.
• Cartilage canals also play a role in ossification of cartilage by carrying
bone forming cells into it.
• Calcification is the process in which matrix hardens because of
deposition of calcium salts in it.
• It is an avascular tissue. Nutrition is via diffusion from vessels in the
perichondrium or in cartilage canals.

5. GROWTH OF CARTILAGE
• Interstitial growth -
• Appositional growth -

6. COMPONENTS OF CARTILAGE
 Cells – Chondrocytes
 Ground substance / Inter-cellular / Extra-cellular matrix
 Fibres – Collagen fibers and elastic fibers

7. CARTILAGE CELLS
• Cells of cartilage – Chondrocytes which lie in spaces / Lacunae present in
matrix
• Chondroblasts: Mesenchymal progenitor cells- Small, immature and
metabolically active.
• Chondrocytes: Mature, large (dia. – 40 um) and produced from
chondroblasts. Cytoplasm of chondrocytes contains glycogen and lipids.
• Chondroblasts – secrete components of extracellular matrix
• Chondrocytes – nourishment and maintenance of cartilage

8. GROUND SUBSTANCE
• It is rich in proteins and carbohydrates i.e. Proteo-gylcans and
Glycoproteins (chondronectin)
• Proteogylcan – Complex formed by protein and long chain
polysaccharides (glycosaminoglycans).
• Glycosaminoglycans – Chondroitin sulphate,, Hyaluronic acid,
Keratan sulphate
• The core protein - Aggrecan

9. GROUND SUBSTANCE - PROTEOGYLCANS
• Tightly bound - negatively charged – attracts water and sodium ions -
firm gel like consistency.
High water content confers following abilities:
1. Maintains hydration of matrix
2. Allows diffusion of molecules to and from the chondrocytes
3. Confers cartilage the ability to resist compression

10. GROUND SUBSTANCE - GLYCOPROTEINS
• Glycoproteins (Chondronectin) – Macromolecules which bind to GAG
and collagen fibres.
• Facilitate adhesion of Chondroblasts and Chondrocytes to collagen
fibres of matrix.

11. GROUND SUBSTANCE – GENERAL FUNCTIONS
• Facilitate adhesion between various elements of connective tissue.
• Fibroblasts - Intercellular ground substance
• Osteoblasts, Chondrocytes, Chondroblasts and smooth muscle cells
also produce ground substance.

12. FIBRES
• Collagen fibres are chemically distinct from the usual fibres – Type II
collagen
• Fibrocartilage and Perichondrium – Type I collagen
• The collagen /elastin fibres give cartilage its firmness and resilience.
• Collagen fibres not seen in routine stains – same RI to that of GS.

13. HYALINE CARTILAGE
• Hyalos – glass – transparent
• Inter-cellular substance appears homogenous (basophilic).
• Special stains – can visualise Collagen Fibers – type II
• Fibres – resist tensile strength , Matrix – resist compressive forces
• H and E stain:
I. Matrix – blue (basophilic)
II. Matrix just beneath perichondrium – acidophilic

14. HYALINE CARTILAGE
• Towards the centre – chondrocytes are large, in groups (2-4)
• The cells tend to remain together due to surrounding dense matrix.
• Groups of cells – Cell nests / Iso-genous cell groups.
• Cell nests are formed by division of a single parent cell.
• Towards the periphery, the cells become small and flattened, parallel
to the perichondrium. (Differentiating Chondrobasts)

15. HYALINE CARTILAGE
• Lacunae
• Territorial matrix / Lacunar capsule – deeper stained
• Inter-territorial matrix – pale stained
• Calcification of hyaline cartilage occurs in old age.
• With advancing age, Collagen fibres become much more prominent in
hyaline cartilage

16. HYALINE CARTILAGE
• Conversion of Hyaline cartilage to Fibro-cartilage – sign of ageing in
body.
• E.g. Costal cartilages, articular cartilages, thyroid, cricoid, arytenoid
cartilage, tracheal rings, large bronchi, epiphyseal plate, parts of nasal
septum, lateral wall of nose.

24. PERICHONDRIUM
• Peripheral layer of vascularised, dense, irregular connective tissue
surrounding hyaline and elastic cartilage.
• Outer fibrous layer – Type I collagen fibres and fibroblasts
• Inner cellular layer – contains chondrogenic cells – differentiate to
form – chondroblasts – secrete matrix. Chondroblasts differentiate
into chondrocytes.

26. ELASTIC CARTILAGE
• Yellow fibro-cartilage
• In addition to Collagen fibres (type –II), numerous elastic fibres are present
which branch and anastomose.
• Elastic fibres difficult to visualise in H and E stains.
• Special stains used are Resorcin – fuschin, Orcein, Verhoeff’s method –
bluish black
• Surface is covered by perichondrium containing fibrocytes, venules.
• Large chondrocytes in the lacunae – centre, small and flat cells – periphery.

27. ELASTIC CARTILAGE
• Chondrocytes larger than those in hyaline cartilage. Found in single
or in twos in lacunae.
• Other features similar to hyaline cartilage. Do not undergo
calcification. Presence of perichondrium
• It has greater flexibility than hyaline cartilage.
• Examples : Auricle, lateral part of external acoustic meatus, wall of
medial part of auditory tube, epiglottis, corniculate and cuneiform
cartilage.

34. FIBROCARTILAGE
• White fibro-cartilage.
• Combination of dense regular connective tissue and hyaline cartilage.
• Numerous parallel running bundles of collagen fibers (type I , II)
• Rows of chondrocytes (round nucleus) intervening between the
bundles. No cell nests / cell groups. All cells – same size.
• In sections, Chondrocytes in lacunae are seen surrounded by
capsules. Fibroblasts are seen with flat nucleus

35. FIBROCARTILAGE
• Chondrocytes are similar to that of hyaline, but they have
considerably less cartilage matrix material.
• Collagen fibres – Type I, II
• Fibro-cartilage unlike Hyaline cartilage does not undergo
calcification
• Absent perichondrium

36. FIBROCARTILAGE
• Examples :
i. Secondary cartilaginous joints, articular disc, menisci
ii. Disc of Temporo-mandibular jt, sterno-clavicular jt, knee joint
iii. Glenoidal labrum, acetabular labrum
iv. Bony Grooves lodging tendons are lined by fibro-cartilage
v. Sites where tendons insert into bone are covered by fibro-cartilage.

40. BONE
DR. SUNDIP CHARMODE
ASSOCIATE PROFESSOR
DEPARTMENT OF ANATOMY
AIIMS RAJKOT

41. SLIDES
1. Compact bone -
• Transverse section
• Longitudinal section
2. Cancellous bone – T.S.

42. TYPES OF BONE
 Based of histology:
• Compact bone
• Cancellous / Spongy bone
 Base on maturity:
• Mature/ Lamellar bone
• Immature / Woven bone
 Based on manner of development:
• Cartilage bone
• Membranous bone

43. COMPACT BONE
• Made up of Lamellae
• Lacunae
• Canaliculi
• Types of lamellae
• Haversian canal
• Osteon / Haversian
system
• Volkmann’s canal
• Osteocytes and its
processes

45. COMPACT, DRIED BONE –
TRANSVERSE SECTION

51. COMPACT, DRIED BONE –
LONGITUDINAL SECTION

53. CANCELLOUS BONE – TRANSVERSE
SECTION
 Made up of layers / lamellae

56. SUMMARY

57. THANK YOU