005 - cartilage histology

7/31/2019 005 - Cartilage Histology

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1. Hyaline cartilage (collagen II +matrix)

2. Fibrous connective tissue(Collagen I) (perichondrium)

3. Respiratory epithelium

4. Mucous-secreting glands -stained turquoise, indicatingpresence ofglycosaminoglycans (GAGs)

5. Goblet cells in respiratoryepithelium, stained turquoise,indicating presence ofglycosaminoglycans

6. Adipocytes

Hyaline cartilage

1. Cartilage matrix. Consists oftype II collagen (tiny fibrilsnot visible by light microscopy)and proteoglycans (PGs):Appears homogeneousNote absence of blood vesselsin this simple tissue

2. Chondrocytes in smallclusters. Note territorial

turquoise staining around cells- indicates glycosaminoglycansynthesis by chondrocytes - i.e.locally higher concentrations

3. Perichondrium - containingchondrocyte precursors, type 1collagen. Small blood vesselsalso present (not clearlyvisible).


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This is a synovial joint

The ends of two long bones connected by a cruciate ligamentcan be seen.

The articular surface is indicated by the boxed area at theupper left


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Articular surface and subchondral bone of adult cat

1. Articular cartilage2. Subchondral bone

3. Adipocytes in marrow cavity

Note: there are no epiphyseal growth plates in mature bones asthere is no longer any growth and endochondral ossification.


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Articular surface and subchondral bone of adult cat

1. Articular surface2. Synovial space3. Articular cartilage

4. Subchondral bone5. Adipocytes in marrow cavity

Note the smooth articular surface charcteristic of young, healthyanimals (& humans)

1. Hyaline cartilagematrix

2. Chondrocytes arranged insmall clusters, reflectinglimited intersitialproliferation

3. Mineralised articularcartilage - chondrocytesalso present, but lessdistinctThe white arrows showthe "tidemark zone" ofadvancing mineralisation

4. Subchondral bone(stained brightred/orange). The wavyjunction between thebone and the mineralisedcartilage is indicated bythe white arrow heads.

5. Osteocytes insubchondral bone

Note: there are extensive blood vessels in the bone, but as soon asthey reach the cartilage they stop cartilage remains avascular.


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This is a section cut from a decalcified knee joint from agrowing animal (kitten)

Diagonal black box links to the region of the synovial jointbetween the two bones

Large black box links to growing long bone

Small black box links to higher magnification of articularcartilage


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Thick, cellular hyaline cartilage covering articular surface ofgrowingknee joint

1. Articular surface (white arrow heads)

2. Complex of blood vessels deep in growing cartilageBlood vessels are occasionally present in rapidly growingcartilage, reflecting the relatively high metabolic demands ofsuch tissue, but are essentially absent from adult cartilage.

NOTE 3 key differences between the cartilage of growing and maturelong bones:

Growing long bones have epiphyseal plates

Rapidly growing cartilage may have some blood vessels.

Rapidly growing cartilage is more cellular


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Growing long bone:

1. Epiphyseal growth plate cartilage

2. Secondary ossification centre3. Diaphyseal marrow cavity

Features 1 and 2 both contain rapidly modelling / remodellingbony trabeculae and haemopoietic marrow


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Immature knee: Overview of epiphyseal growth plate andendochondral ossification

This image illustrates the highly organised structure of the epiphysealgrowth plate

1. Chondrocytesproliferate to generate columns of progeny cellsthat secrete cartilage matrix (stained grey / pale mauve).

2. The chondrocytes then hypertrophy progressively3. The cartilage matrix around them begins to mineralise

(staining becomes more purple).4. At the edge (r.) of the growth plate blood vessels attackthe

mineralised cartilage: the hypertrophic chondrocytes seem todisappear (most probably die by apoptosis) but the mineralisedcartilage matrix around them persists.

5. Osteoblasts (bone forming cells) immediately start to depositnew bone matrix on the 'scaffolding' provided by the extrudedribbons of mineralised cartilage. Thus, the growth plate effectivelyadvances in the direction of the large white arrow.

This provides a mechanism for the rapid, controlled elongation of thelong bones. The newly forming ribbons of trabecular bone providethe necessary structural strength to enable the bone to fulfil itsmechanical functions during growth. Most of this bone is quiterapidly remodelled as growth proceeds, to accomodate thecontinually changing mechanical requirements


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At the edge (r.) of the growth plate blood vessels attack themineralised cartilage (white arrowheads)

1. Zone ofresting (reserve) cartilage2. Zone ofproliferating chondrocytes (5. Proliferating

chondrocytes secreting (initially unmineralised) cartilagematrix)

3. Zone ofhypertrophy4. Mineralising cartilage matrix around hypertrophic

chondrocytes

Endochondral ossification

Intense cellular activity is evident in this complex, rapidly evolvingtissue:

1. Zone ofhypertrophy2. Ribbons ofmineralised cartilage matrix3. New bone matrix (stained orange) being deposited on

mineralised cartilage "scaffolding" (stained purple) byosteoblasts (bone forming cells).


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Neonatal Human Pinna: Verhoeff's stain for elastic fibres(very low power) -fibrocartilage

Pinna is the outer ear

The central plate of cartilage isvery cellular, and the matrix isstained darkly because of theabundant elastic fibres(black) it contains

The surface of the section iscovered by typical thin skin, with

hairs and sebaceous glands


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1. Elastic cartilageThis is essentially hyaline cartilage, with the addition of elasticfibres to make the tissue more springy

2. Perichondrium (collagen I)

3. Thin stratified squamous epithelium

4. Sebaceous glands

1. Elastic cartilage

2. Chondrocytes - note similar appearance to those insimple hyaline cartilage. This cartilage is more cellularthan hyaline cartilage.3. Perichondrium, consisting of coarse type 1 collagenfibres (pink) and elastic fibres (black)4. Elastic fibres


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Hyaline cartilage in human fetal rib

1. Cartilage2. Muscle

Hyaline cartilage in humanfetal rib

1. Cartilage. White arrowheads indicate chondrocytes;this immature (ie growing)

hyaline cartilage isrelatively cellular.

o Can you identifycollagen fibres in thematrix?

o What is the matrixcomposed of?

2. Chondrogenic layer ofperichondriumEnables appositional growth


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3. Fibrous tissue (type 1 collagen fibres)4. Blocks ofskeletal muscle cut in various orientations.5. Adipose tissue (clusters of adipocytes)

005 - cartilage histology

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