The document provides an extensive overview of cartilage, detailing its types—hyaline, elastic, and fibrocartilage—and their structural characteristics. It describes the composition of cartilage, the role of chondrocytes, and the significance of the extracellular matrix in providing mechanical support and protection. Additionally, it outlines the processes of cartilage formation, growth, and repair, emphasizing the slow recovery rate due to its avascular nature.

1. Cartilage
"Mohmmadrjab" S. Seder
Faculty of Medicine
Histology

2. Table of contents
Introduction
Types of cartilages
Hyaline cartilage
Elastic cartilage
Fibrocartilage
Cartilage formation, growth, and prepair

3. Introduction
 Cartilage is a resilient and smooth elastic
connective tissue, a rubber-like padding that
covers and protects the ends of long bones at
the joints, and is a structural component of the rib
cage, the ear, the nose, the bronchial tubes, the
intervertebral discs, and many other body
components.

4.  Cartilage is found in many areas of the body
including:
 Joints between bones e.g. the elbows, knees and ankles
 Ends of the ribs
 Between the vertebrae in the spine
 Ears and nose
 Bronchial tubes or airways

7. Cartilage:
 Important for:
 Support to softer tissues
 Formation and growth of long bones
 Consists of:
 Extracellular matrix containing mainly,
 Collagen and/or elastin fibers
 Proteoglycans
 Water

9.  Cartilage is characterized by:
 An (ECM) with high concentrations of GAGs
and proteoglycans, interacting with collagen
and elastic fibers.
 Structural features of its matrix make cartilage
ideal for a variety of mechanical and protective
roles within the adult skeleton and elsewhere.
 Cartilage is mainly (~80%) water.
 Cartilage is made up of specialized cells called
chondrocytes.

10. Extracellular matrix components of cartilage including proteoglycan
aggregates, collagen, integrins and fibronectin

12.  Unlike connective tissue proper, cartilage contains
only chondrocyte and no other cell types.
 These chondrocytes produce large amounts of
extracellular matrix composed of collagen fibres,
proteoglycan, and elastin fibers.

13.  The cartilage cells or chondrocytes are contained in
cavities in the matrix, called cartilage lacunae.

15.  All types of cartilage lack vascular supplies; and
chondrocytes receive nutrients by diffusion from
capillaries in surrounding connective tissue.

16.  Cartilage also lacks nerves.

18.  The perichondrium is a sheath of dense CT that
surrounds cartilage in most places (except articular
cartilage of joints), forming an interface between the
cartilage and the tissues supported by the cartilage.
 Perichondrium contains blood supply, nerves,
lymphatics.
 Perichondrium contains collagen fibers, fibroblasts,
chondroblasts.

22. Types of cartilages
 Variations in the composition of the matrix
characterize three main types of cartilage:
 Hyaline cartilage
 Elastic cartilage
 Fibrocartilage

23. Dense connective tissue of
perichondrium is shown here with
hyaline and elastic cartilage.

24.  Important features of the major cartilage types

26. Hyaline Cartilage Fibrocartilage
Elastic Cartilage

27. Hyaline cartilage
 Hyaline (Gr. hyalos, glass) cartilage, the most
common of the three types.
 Is homogeneous and semitransparent in the fresh
state.

28.  In adults hyaline cartilage is located in:
 Epiphyseal plate (bone growth plate)
 ​Articulate cartilage (cartilage of the joints)
 Costal cartilages (connects ribs to sternum)
 Respiratory Cartilages (larynx, reinforces air passageways)
 Nasal Cartilage (supports external structure of the nose)

30.  In the embryo, hyaline cartilage forms the temporary
skeleton that is gradually replaced by bone.

31. Matrix of Hyaline Cartilage
 The dry weight of hyaline cartilage is nearly 40%
collagen embedded in a firm, hydrated gel of
proteoglycans and structural glycoproteins.
 In routine histology preparations, the
proteoglycans make the matrix generally
basophilic and the thin collagen fibrils are barely
discernible.
 Most of the collagen in hyaline cartilage is type II,
although small amounts of minor collagens are

32.  Aggrecan is the most abundant proteoglycan of
hyaline cartilage.
 Another important component of cartilage matrix is
the structural multiadhesive glycoprotein
chondronectin.

33. Chondrocytes cells in Hyaline cartilage matrix:
 Chondrocytes cells occupy relatively little of the hyaline
cartilage mass.
 At the periphery of the cartilage, young chondrocytes or
chondroblasts have an elliptic shape, with the long axes
parallel to the surface.
 Deeper in the cartilage, they are round and may appear in
groups of up to eight cells that originate from mitotic divisions
of a single chondroblast and are called isogenous
aggregates.
 As the chondrocytes become more active in secreting
collagens and other ECM components, the aggregated cells
are pushed apart and occupy separate lacunae.

34. Isogenous Group
 Are located in the mature
cartilage zone.
 Contains from 4 to 8 mature
chondrocytes.
 Result from successive
mitotic division.
 Are surrounded by cartilage
matrix.

35. Territorial matrix vs. Interterritorial matrix
The territorial matrix is the tissue surrounding chondrocytes
(cells which produce cartilage) in cartilage.

37.  Staining variations within the matrix reflect local
differences in its molecular composition.
Immediately surrounding each chondrocyte, the
ECM is relatively richer in GAGs than collagen,
often causing these areas of territorial matrix to
stain differently from the intervening areas of
interterritorial matrix

38.  Except in the articular cartilage of joints, all hyaline
cartilage is covered by a layer of dense connective
tissue, the perichondrium, which is essential for
the growth and maintenance of cartilage. The outer
region of the perichondrium consists largely of
collagen type I fibers and fibroblasts, but an inner
layer adjoining the cartilage matrix also contains
mesenchymal stem cells which provide a source for
new chondroblasts that divide and differentiate into
chondrocytes.

39. P: Perichondrium
C: Chondrocytes & Chondroblasts
M: Matrix
Hyaline Cartilage

40. Hyaline Cartilages

41. Elastic cartilage
 Is a type of cartilage that provides
both strength and elasticity to
certain parts of the body, such as
the ears. Within the outer ear, it
provides the skeletal basis of the
pinna, as well as the lateral
region of the external auditory
meatus.

42.  Elastic cartilage is essentially similar to hyaline
cartilage except that it contains an abundant
network of elastic fibers in addition to a meshwork
of collagen type II fibrils, which give fresh elastic
cartilage a yellowish color.
 With appropriate staining the elastic fibers usually
appear as dark bundles distributed unevenly
through the matrix.

43. C: Chondrocytes
P: Perichondrium
M: Matrix

44.  Elastic Cartilage is more flexible than hyaline
cartilage, elastic cartilage is found in the auricle of
the ear, the walls of the external auditory canals,
the auditory (Eustachian) tubes, the epiglottis, and
the upper respiratory tract.

46.  Elastic cartilage function is two-fold: to change
cartilage shape in response to tension,
compression, and bending before returning to an
at-rest state, and to provide a strong but flexible
structure.

47. Hyaline vs. Elastic Cartilige
 Elastic cartilage looks very similar to hyaline
cartilage under a microscope, and special stains
must be used to show the otherwise invisible elastic
fibers that give this particular cartilage type its
name. Like hyaline, elastic cartilage also has single
or multiple chondrocytes housed within spaces
called lacunae. The extracellular matrix of elastic
cartilage contains higher levels of type II collagen.

48. Hyaline vs. Elastic Cartilige

49. Fibrocartilage
 Fibrocartilage is the tough, very strong tissue
found predominantly in the intervertebral disks and
at the insertions of ligaments and tendons.
 Fibrocartilage takes various forms in different
structures but is essentially a mingling of hyaline
cartilage and dense CT.

50. Fibrocartilage
Hyaline cartilage

51.  Chondrocytes of fibrocartilage occur singly and often
in aligned isogenous aggregates, producing type II
collagen and other ECM components, although the
matrix around these chondrocytes is typically sparse.
 Areas with chondrocytes and hyaline matrix are
separated by other regions with fibroblasts and dense
bundles of type I collagen which confer extra tensile
strength to this tissue.

52. Fibrocartilage
C: Chondrocytes

53.  Intervertebral discs of the spinal column are
composed primarily of fibrocartilage and act as
lubricated cushions and shock absorbers preventing
damage to adjacent vertebrae from abrasive forces
or impacts.

54. Fibrocartilages

55. Hyaline cartilage / Elastic cartilage / Fibrocartilage

56. Hyaline cartilage / Elastic cartilage / Fibrocartage
Hyaline cartilage Elastic cartilage
Fibrocartilage

57. Hyaline cartilage /
Elastic cartilage /
Fibrocartage

58. Hyaline cartilage / Elastic cartilage / Fibrocartage

59. Cartilage formation, growth,
and prepair
 All cartilage forms from embryonic mesenchyme in
the process of chondrogenesis.
 The first indication of cell differentiation is the
rounding up of the mesenchymal cells, which retract
their extensions, multiply rapidly, and become more
densely packed together.

60. Chondrogenesis

62.  In general the terms “chondroblasts” and
“chondrocytes” respectively refer to the
cartilage cells during and after the period of rapid
proliferation.
 At both stages the cells have basophilic
cytoplasm rich in RER for collagen synthesis.
Chondrocytes in growing cartilage

63.  Cartilaginous structures grow by mitosis of existing
chondroblasts in lacunae (interstitial growth) or
formation of new chondroblasts peripherally from
progenitor cells in the perichondrium (appositional
growth).
 Repair or replacement of injured cartilage is very
slow and ineffective, due in part to the tissue’s
avascularity and low metabolic rate.

64. Growth of epiphyseal plate

65. Epiohyseal plate (interstatial growth)

67. THANK YOU
THE END