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HISTOLOGY 1.9.: SUPPORTIVE TISSUESHISTOLOGY 1.9.: SUPPORTIVE TISSUES

Supportive tissues are connective tissues specialized for supportive role.Supportive tissues are connective tissues specialized for supportive role.Types:Types:

Embryonic:Embryonic: notochord (see earlier)notochord (see earlier)Adult:Adult: cartilage:cartilage: hyaline cartilagehyaline cartilage

elastic cartilageelastic cartilagefibrocartilagefibrocartilage

bone:bone: spongy, or trabecularspongy, or trabecularlamellarlamellar

Please note: due to their supportive function, according to certain Please note: due to their supportive function, according to certain classification, adipose tissues may also be classified into the group of classification, adipose tissues may also be classified into the group of supportive tissuessupportive tissues

White adipose tissue Brown adipose tissueBrown adipose tissue

CARTILAGECARTILAGE

Cartilage is a supportive tissue with firm ECM. The consistency Cartilage is a supportive tissue with firm ECM. The consistency of the tissue is hard, but bending.of the tissue is hard, but bending.

In the adult this tissue is normally avascular, aneural and alymphatic. In the adult this tissue is normally avascular, aneural and alymphatic.

It exists in the form of pieces of varied shape covered by It exists in the form of pieces of varied shape covered by the perichondrium.the perichondrium.The perichondrium supplies the piece of cartilage with nutrients The perichondrium supplies the piece of cartilage with nutrients and oxygen via diffusion.and oxygen via diffusion.

Tissue components:Tissue components: cells (chondrocytes)cells (chondrocytes)ECM: fibers, ground substanceECM: fibers, ground substance

Types:Types: hyaline cartilagehyaline cartilageelastic cartilageelastic cartilagefibrocartilagefibrocartilage

Hyalin cartilage:Hyalin cartilage:

Development of the hyaline cartilage:Development of the hyaline cartilage:Clusters of mesenchymal cellsClusters of mesenchymal cells chondroblastschondroblasts chondrocyteschondrocytes(center of chondrification)(center of chondrification) (produce ground subst.)(produce ground subst.) (in lacunae)(in lacunae)

Microscopic structure:Microscopic structure:

Chondron (cell nests with isogenousChondron (cell nests with isogenouscell groups)cell groups)

Pericellular matrixPericellular matrix

Territorial matrixTerritorial matrix

Interterritorial matrixInterterritorial matrix

LM TEM

Components of the ECM: Components of the ECM:

Firm gel laced with collagen fibrils (same refraction index – non-visible)Firm gel laced with collagen fibrils (same refraction index – non-visible)Ground substance contains GAGs: chondroitin sulphate, keratan sulphate,Ground substance contains GAGs: chondroitin sulphate, keratan sulphate,

hyaluronic acid.hyaluronic acid.Chondrocyte: lightly stained resting rounded cellChondrocyte: lightly stained resting rounded cell

Nutrition of the tissue: Nutrition of the tissue: via diffusion from the perichondrium.via diffusion from the perichondrium.Perichondrium:Perichondrium: inner vascular, or cellular layerinner vascular, or cellular layer

outer fibrous layerouter fibrous layer

FPch: fibrousFPch: fibrousperichondriumperichondrium

ChL:cellular layerChL:cellular layerof perichondriumof perichondrium(appositional growth)(appositional growth)

ChB: chondroblastChB: chondroblast

ChC:chondrocyteChC:chondrocyte

CN: chondronCN: chondron

Lac: lacunaLac: lacuna

Consequence of avascularity:Consequence of avascularity:low metabolic rate (bradtroph tissue)low metabolic rate (bradtroph tissue)prone to degeneration (calcification, asbest prone to degeneration (calcification, asbest degeneration)degeneration)heals with persistent scarheals with persistent scartransplantation only with perichondriumtransplantation only with perichondrium

Occurrence of hyalin cartilage:Occurrence of hyalin cartilage:

articulating surfaces of bonesarticulating surfaces of bonesnosenosepharynxpharynxtracheatracheabronchibronchiappendicular and axial skeleton of embryoappendicular and axial skeleton of embryo

Elastic cartilage:Elastic cartilage:Occurrence:Occurrence: external earexternal ear

epiglottisepiglottisexternal auditory canalexternal auditory canalcorniculate and cuneiform cartilages of the larynxcorniculate and cuneiform cartilages of the larynx

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Dense network of elastic fibers around the chondrons visible bothDense network of elastic fibers around the chondrons visible bothwith H.E. staining (Fig.1) and resorcin-fuchsin or orcein staining (Fig.2)with H.E. staining (Fig.1) and resorcin-fuchsin or orcein staining (Fig.2)

FibrocartilageFibrocartilage

Occurrence:Occurrence: intervertebral disksintervertebral disksmenisci of stifle jointsmenisci of stifle jointsmeeting of tendons and ligaments with the cartilagemeeting of tendons and ligaments with the cartilagedog: between the atrial and ventricular heart musclesdog: between the atrial and ventricular heart muscles

Collagen fiber bundle(rich in type I. collagen)

Chondrocyte

Comparison of the three cartilage-types:Comparison of the three cartilage-types:

Dominating tissue component:Dominating tissue component: Physical property:Physical property:

1. Hyaline cartilage:1. Hyaline cartilage: ground substance tensile strengthchondrons with many cells

2. Elastic cartilage:2. Elastic cartilage: elastic fibers elasticitychondrons with single cells

3. Fibrocartilage:3. Fibrocartilage: collagen fibers great tensile strengthvery few chondrocytes against pulling forces

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BONEBONE

Connective tissue with cells and fibers embedded in a hard Connective tissue with cells and fibers embedded in a hard non-bending ground substance.non-bending ground substance.

Functions: Functions: gives internal support for the bodygives internal support for the bodyattachment for the muscles and tendonsattachment for the muscles and tendonsprotects the brain and organs in the thoracic cavityprotects the brain and organs in the thoracic cavitycontains the bone marrowcontains the bone marrowmain source of calcium for the organismmain source of calcium for the organism

Differences from the cartilage:Differences from the cartilage:canalicular system within the bonecanalicular system within the bonedirect vascular supplydirect vascular supplyappositional growth onlyappositional growth only

It is a highly dynamic tissue that is renewed and remodeled throughout It is a highly dynamic tissue that is renewed and remodeled throughout the whole life.the whole life.

Structure of a long bone:Structure of a long bone:

Nutritive artery and vein

Tissue components of the bone:Tissue components of the bone:Cells: Cells: osteoblastsosteoblasts

osteocytesosteocytesosteoclastsosteoclasts

Bone matrix – osteoid: ECM: organic: collagen fibers (flexibility)Bone matrix – osteoid: ECM: organic: collagen fibers (flexibility) GAGsGAGs

inorganic: hydroxyapatite crystals (firmness)inorganic: hydroxyapatite crystals (firmness) (CA, CO(CA, CO33,PO,PO44,OH, Na, Mg, Fe),OH, Na, Mg, Fe)

Demineralized bone: looses firmness

The mature lamellar bone is The mature lamellar bone is built up by several osteons built up by several osteons

Light microscopic structure of the Light microscopic structure of the lamellar bonelamellar bone

Concentric lamellae (C): around Haversian canals (H)Interstitial lamellae (I): remnants of old osteons (space-filling)Circumferential lamellae (not shown): outer and inner surface of the bone

V: Volkmann-canal

CC

II

HH

Cross-sectionCross-section

Longitudinal sectionLongitudinal section

VV

Osteon

H

Osteoblast:Osteoblast:

LMLM

SEMSEM

TEMTEM

Osteocyta:Osteocyta:

LMLM

TEMTEM

OsteoclastOsteoclast

LMLM

TEMTEM

LMLM

OsteoclastOsteoclast

Bone matrix (osteoid)Bone matrix (osteoid)

Howship-lacunaHowship-lacuna

Periosteum:Periosteum:Two layers:Two layers: inner vascular and cellular osteogenic layerinner vascular and cellular osteogenic layer

outer fibrous layer of collagen fibers and blood vesselsouter fibrous layer of collagen fibers and blood vesselsSharpey-fibers:Sharpey-fibers: collagen fibers continuous with the collagen fiber collagen fibers continuous with the collagen fiber

system of lamellae, fix the periosteum to the bonesystem of lamellae, fix the periosteum to the bone

Endosteum:Endosteum: delicate layer of squamous cells lining the bone insidedelicate layer of squamous cells lining the bone insideion barrier ion barrier plays role in the mineral homeostasis plays role in the mineral homeostasis

Bone marrowBone marrow

EndosteumEndosteum

BoneBone


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