HISTOLOGY OF CARTILAGE
& BONE
Cartilage
• Is a firm and flexible type of
connective tissue in which the
extracellular matrix has a firm
consistency
Cartilage
• Modified Connective tissue.
• Firm, not rigid
• Embryologically derived from Mesenchyme.
• Cells are widely separated by intercellular
substance.
• Firmness of Cartilage and the hardness of bone
is because of the nature of ground substance in
them.
• Fetal Skeleton- predominantly cartilaginous.
Functions
• Forms the skeletal framework
• Supports regions of the body which require
varying degree of flexibility
• Provides gliding area for the joint, facilitating
movements (in Hyaline Cartilage)
• Essential for the growth of long bones (In
Hyaline Cartilage)
Cartilage
• Avascular
• Nourished by diffusion
• Limited ability for
regeneration
• Defects replaced by
fibrous tissue
• No nerves
• No lymphatics
• Covered by dense
connective tissue sheath
-Perichondrium
Types of cartilage
• Depending on the Number and Variety of
fibres in the matrix, classified
• 1 Hyaline cartilage
• 2 Fibrocartilage
• 3 Elastic Cartilage
Perichondrium
• Mesenchymal cells surrounding the developing
cartilage form- Perichondrium
• Special form of dense irregular connective tissue
• Covers the free surface of the cartilage
• Rich in fibres, fibroblasts and blood vessels
• Since hyaline cartilage is avascular, it gets its nutrition
from the perichondrium by simple diffusion
• Perichondrium: 2 layers: Outer – Fibrous, InnerCellular-chondrogenic cells,undifferentiated flat cells,
proliferating and differentiating into chondroblasts
Components
• Cells : Chondrogenic cells, Chondroblasts
& Chondrocytes
• Fibres: Collagen and Elastic
• Ground Substance: Acid
Mucopolysaccharides (Chondroitin
Sulphate)
Cells
• Embryonically Cartilage cells- Chondroblasts
derived from mesenchymal cells, lie very close
to the perichondrium, rich in cell organellae
• Chondroblasts- intercellular matrix & Collagen
fibres
• Chondrocytes are mature chondroblasts –
imprisoned within the matrix, seen away from
the perichondrium
• Old cells are incapable of multiplication, but
secrete an enzyme , Alkaline phosphatase,
resulting in calcification of cartilage in old age.
• Fibres: Collagen and elastic
• Ground Substance: basophilic, metachromatic
and PAS positive. Chemically:
Mucopolysaccharides, Collagen Type II,
electrolytes and Water
• Examples:
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Hyaline Cartilage
Costal Cartilage
Tracheal and Bronchial Rings
Thyroid and Cricoid Cartilages
Articular Cartilage
Epiphyseal plates
Parts of nasal Septum
Parts of Lateral wall of nose
Skeletal framework of fetus
Articular surface of sesamoid
bones
ARTICULAR CARTILAGES ARE NOT
COVERED BY PERICHONDRIUM
Hyaline Cartilage
Hyaline Cartilage
• Hyalos=glass like
• Transparent,
homogeneous
• H/E: Bluish, basophilic
matrix
• Chondrocytes: large & in
isogenous groups
• Territorial matrix
• Interstitial matrix
• Rich in Type II Collagen
fibres
Hyaline Cartilage
• Chondroblasts: short,
small, elongated cells,
rich in all cell organellae,
usually occuring singly,
covered by asac like
structure known as
Lacunae
• Chondrocytes: matured
cells , large, less cell
organellae, in isogenous
groups, seen away from
the perichondrium
Hyaline Cartilage
Hyaline Cartilage
Matrix appears
Homogeneous : WHY?
• Collagen fibrils present in
the matrix have same
refractive index as that of
the ground substance.
Elastic cartilage(Yellow Elastic
Cartilage)
• Similar to Hyaline Cartilage
• Matrix rich in Elastic fibres
hence the name Elastic
Cartilage
• H/E: elastic fibres difficult to
see.
• Clearly visualized on special
staining
• Surface covered by
Perichondrium
• Better flexibility than
hyaline cartilage, readily
recovers its shape
Sites of Elastic Cartilage
• Pinna
• Lateral part of External
Auditory meatus
• Medial part of Auditory
tube
• Epiglottis
• Corniculate &
Cunneiforms
• Apical part of arytenoid
• ALL THE SITES
MENTIONED ARE
CONCERNED EITHER
WITH PRODUCTION OR
PERCEPTION OF SOUND
Branching Elastic fibres give FLEXIBILITY &
SUPPORT
Fibrocartilage(White Fibrocartilage)
Great Tensile strength with
considersable elasticity
• Numerous dense
collagen bundles
oriented in the
direction of functional
stress with some
fibroblastsn
• No perichondrium
• Type I Collagen
Fibrocatilage
Sites of Fibrocartilage
• Intervertebral discs
• Symphysis pubis
• Manubriosternal joints
• Articular discs in temporo-mandibular joints
,Sterno-clavicular joints & Menisci of Knee
joints
• Glenoidal labrum & Acetabular labrum
• Deep groves of bone, where tendons ru.
MCQ
• A section of Hyaline cartilage can be identified
by the presence of
• 1.Homogenous matrix
• 2.Elastic fibres
• 3.Collagen fibres
• 4.Chondrocytes arranged in row
MCQ
• Hyaline cartilage is present in
• 1.Tracheal ring
• 2.Epiglottis
• 3.Intervertebral disc
• 4.Glenoidal Labrum
MCQ
• Perichondrium is absent in
• 1.Elastic and Hyaline Cartilage
• 2.Hyaline Cartilage
• 3.Fibrocartilage and articular cartilage
• Costal Cartilage and Ear Pinna
MCQ
• Which of the following features is NOT TRUE
about cartilage?
• 1.Firm and flexible
• 2.Highly vascular
• 3.Insensitive
• 4.Poor in regeneration
Histology of Bone
Bone
• Is a rigid form of scleral connective tissue in
which the extracellular matrix is impregnated
with inorganic salts mainly calcium, phosphate
and carbonate, providing hardness
Rigidity and hardness is provided by the matrix which is
impregnated with inorganic salts
Functions
• Attachment to muscles
• Serves as lever for muscular actions
• Bears body weight
• Protects vital organs
• Stores calcium, phoshate and other ions
• Contains hemopoietic tissue, the bone
marrow
Types of Bones
• Morphologically:
• Compact Bone
• Spongy or cancellous Bone
Bone Membranes
• Periosteum
• Endosteum
Bone Composition
• Cells
• Fibres and Ground substance–
– organic
– inorganic
Compact and Spongy bone
Cancellous or Spongy Bone
• Slender bony trabeculae
that branch and
anastomose with one
another.
• Enclose irregular marrow
spaces containing blood
vessels and
haemopoietic tissue that
give rise to new blood
vessels.
• They receive nutrition
from blood vessels in the
bone marrow
Compact Bone
Compact Bone
Endochondral ossification
Intramembranous ossfication
BONE FRACTURE REPAIR
SUMMARY OF BONE TYPE AND
ORGANIZATION
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