HISTOLOGY OF CARTILAGE & BONE Dr Punita Manik Department of
Anatomy K G Medical Univesity U P Lucknow
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Cartilage Is a firm and flexible type of connective tissue in
which the extracellular matrix has a firm consistency
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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.
Foetal Skeleton- predominantly cartilaginous.
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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)
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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
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Types of cartilage Depending on the Number and Variety of
fibres in the matrix, classified 1 Hyaline cartilage 2
Fibrocartilage 3 Elastic Cartilage
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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, Inner-
Cellular-chondrogenic cells,undifferentiated flat cells,
proliferating and differentiating into chondroblasts
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
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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
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Hyaline Cartilage Examples: 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
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Hyaline Cartilage
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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
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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
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Hyaline Cartilage
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Matrix appears Homogeneous : WHY? Collagen fibrils present in
the matrix have same refractive index as that of the ground
substance.
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Hyaline cartilage has been compared to a TYRE! Ground Substance
=Corresponds to the RUBBER of the tyre resisting Compressive forces
Fibres= corrresponds to the treads of the tyre resisting tensional
forces
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?
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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
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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
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Branching Elastic fibres give FLEXIBILITY & SUPPORT
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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
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Fibrocatilage
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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.
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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
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MCQ Hyaline cartilage is present in 1.Tracheal ring
2.Epiglottis 3.Intervertebral disc 4.Glenoidal Labrum
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MCQ Perichondrium is absent in 1.Elastic and Hyaline Cartilage
2.Hyaline Cartilage 3.Fibrocartilage and articular cartilage Costal
Cartilage and Ear Pinna
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MCQ Which of the following features is NOT TRUE about
cartilage? 1.Firm and flexible 2.Highly vascular 3.Insensitive
4.Poor in regeneration
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Histology of Bone
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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
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Functions Attachment to muscles Serves as lever for muscular
actions Bears body weight Protects vital organs Stores calciuum,
phoshate and other ions Contains haemopoietic tissue, the bone
marrow
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Types of Bones Morphologically: Compact Bone Spongy or
cancellous Bone
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Bone Membranes Periosteum Endosteum
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Bone Composition Cells Fibres Ground Substance
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Structure of Compact Bone Circumferential System Periosteal
Endosteal Haversian System Interstitial System
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Compact and Spongy bone
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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
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Compact Bone
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MCQ Periosteum is absent over the following EXCEPT 1.Articular
surface of bone 2.Sesamoid bone 3.Site of attachment of tendons and
ligaments to the bone 4.Shaft of long bones
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MCQ Osteocytes may b identified by the presence of 1.Many
Nuclei 2.Lacuna around the cell 3.Lysosomes 4.Ingested
particles
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MCQ Alkaline phosphatase activity can be demonstrated in
1.Osteoblasts 2.Osteocytes 3.Osteoclasts 4.Osteoprogenitor
cells
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MCQ Spongy bone can be identified histologically by the
presence of 1.Haversian canal and concentric bony lamellae 2.Bony
trabeculae and marrow cavity 3.Interstitial Lamellae 4.Volkmanns
Canal
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MCQ The vitamin necessary for the absorption of calcium from
small intestine is 1.A 2.B 3.C 4.D
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MCQ The epiphyseal plate of a growing bone is made up of
1.Elastic Cartilage 2.Hyaline Cartilage 3.Spongy Bone 4.Compact
Bone