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.
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
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