THE GROUND TISSUESTHE GROUND TISSUES

EPITHELIAL TISSUESEPITHELIAL TISSUES

CONNECTIVE AND CONNECTIVE AND SUPPORTIVE TISSUESSUPPORTIVE TISSUES

MUSCLE TISSUESMUSCLE TISSUES

NERVOUS TISSUENERVOUS TISSUE

HISTOLOGY 1.5.:HISTOLOGY 1.5.:CONNECTIVE AND SUPPORTIVE TISSUESCONNECTIVE AND SUPPORTIVE TISSUES

A diverse group of tissues that share a common origin from the A diverse group of tissues that share a common origin from the mesenchyme of the embryo.mesenchyme of the embryo.They provide structural and metabolic support for other tissues andThey provide structural and metabolic support for other tissues andorgans throughout the body, bind the tissues to form organs, and theorgans throughout the body, bind the tissues to form organs, and theorgans to form organ systems and organism. organs to form organ systems and organism. They contain blood vessels and mediate the exchange of nutrients, They contain blood vessels and mediate the exchange of nutrients, metabolites and waste products between tissues and metabolites and waste products between tissues and the circulatory system.the circulatory system.

THUS:THUS:

•Origin: from the mesodermOrigin: from the mesoderm•Blood supply: densely vascularizedBlood supply: densely vascularized•Nerve supply: densely innervatedNerve supply: densely innervated

Tissue components of the connective and supportive tissues:Tissue components of the connective and supportive tissues:

• Cells of great variety (fixed and free cell types, Cells of great variety (fixed and free cell types, see latersee later))• Extracellular matrix (ECM)Extracellular matrix (ECM) - ground substance- ground substance

- fibers (collagen, elastic, reticular)- fibers (collagen, elastic, reticular)

Extracellular matrix (ECM)Extracellular matrix (ECM)I. THE GROUND SUBSTANCEI. THE GROUND SUBSTANCE

A highly hydrated gel in which the cells and fibers are embeddedA highly hydrated gel in which the cells and fibers are embeddedMolecular components: Molecular components: Proteoglycan consisting of dimericProteoglycan consisting of dimeric glycosaminoglycans (GAGs)glycosaminoglycans (GAGs)bound to a protein core:bound to a protein core:

chondroitin sulphate chondroitin sulphate (cartilage, arteries, skin, cornea)(cartilage, arteries, skin, cornea)keratane sulphate keratane sulphate (cartilage, bone, cornea)(cartilage, bone, cornea)heparane sulphate heparane sulphate (arteries, lung)(arteries, lung)dermatan sulphate dermatan sulphate (skin, tendon,ligaments, sclera, lung)(skin, tendon,ligaments, sclera, lung)hyaluronic acid hyaluronic acid (vitreous humor of eye, synovial fluid, loose CT,(vitreous humor of eye, synovial fluid, loose CT,

skin, cartilage, umbilical cord)skin, cartilage, umbilical cord)Hydrophilic side chains of GAGs bind a considerable amount Hydrophilic side chains of GAGs bind a considerable amount of extracellular fluid – water reservoir of the organism.of extracellular fluid – water reservoir of the organism.

It is a part of the connective and supportive tissues not visible in It is a part of the connective and supportive tissues not visible in histological preparates, unless special staining methods are applied:histological preparates, unless special staining methods are applied:• Toluidine-blueToluidine-blue• PAS stainingPAS staining• Alcian-blue stainingAlcian-blue staining

Extracellular matrix (ECM)Extracellular matrix (ECM)II. CONNECTIVE TISSUE FIBERSII. CONNECTIVE TISSUE FIBERS

1.1. COLLAGEN fibersCOLLAGEN fibersThe most abundant protein in the body.The most abundant protein in the body.H.E-stained light micrographH.E-stained light micrograph Scanning electron micrographScanning electron micrograph

Two isolated fibersTwo isolated fibersartificially colouredartificially colouredin the computerin the computer(SEM)(SEM)

Cross-striationCross-striationobserved in theobserved in thetransmissiontransmissionelectron micro-electron micro-scopescope

Synthesis of collagen fibersSynthesis of collagen fibers:

• Takes place in the rER of fibroblasts: Takes place in the rER of fibroblasts: pro-pro--chains form triple helices-chains form triple helices

• These procollagen molecules are transferred to the Golgi These procollagen molecules are transferred to the Golgi complexcomplex• Tropocollagen molecules are released Tropocollagen molecules are released

via exocytosis from Golgi-vesiclesvia exocytosis from Golgi-vesicles• Tropocollagen molecules are assembled to form Tropocollagen molecules are assembled to form

collagen fibers in ECMcollagen fibers in ECM

Properties of collagen fibersProperties of collagen fibers

• Non-branching bundles of changing thicknessNon-branching bundles of changing thickness• High tensile strengthHigh tensile strength• Poor sheer strengthPoor sheer strength• They can be stretched to approximately 5 % of their initial lengthThey can be stretched to approximately 5 % of their initial length

SYNTHESIS OF COLLAGEN FIBERS BY FIBROBLASTSSYNTHESIS OF COLLAGEN FIBERS BY FIBROBLASTS

Specific staining for the visualization of collagen fibers:Specific staining for the visualization of collagen fibers:Azan staining stains the collagen fibers selectively in blue colourAzan staining stains the collagen fibers selectively in blue colour

other tissue componenst are stained redother tissue componenst are stained red

TYPES OF COLLAGEN FIBERSTYPES OF COLLAGEN FIBERS

Type I.:Type I.: 2 2 1 chains + 1 1 chains + 1 2 chain2 chainthe most common (bone, skin,tendon, ligaments)the most common (bone, skin,tendon, ligaments)

Type II.:Type II.: 3 3 1 chains1 chainspredominates in cartilagepredominates in cartilage

Type III.:Type III.: 3 3 1 chains1 chains in embryonic CT and skinin embryonic CT and skin

Type IV.:Type IV.: still unknown composition still unknown compositionin the basal laminae of adultsin the basal laminae of adults

Type V.:Type V.: still unknown composition still unknown composition mainly in the embryomainly in the embryo

2. ELASTIC FIBERS2. ELASTIC FIBERSThey are present in organs whose normal function requires elasticityThey are present in organs whose normal function requires elasticity

in addition to tensile strengthin addition to tensile strength

Wall of the aorta stained with H.E.Wall of the aorta stained with H.E. andand resorcin fuchsin,resorcin fuchsin,specific staining for elastic fibresspecific staining for elastic fibres

SYNTHESIS OF ELASTIC FIBERS:SYNTHESIS OF ELASTIC FIBERS:

• Takes place in the rER of fibroblasts (and smooth muscle cells):Takes place in the rER of fibroblasts (and smooth muscle cells):tropoelastin moleculestropoelastin molecules

• Transformed to elastin, cross-linked and assembled in the Transformed to elastin, cross-linked and assembled in the extracellular spaceextracellular space

• Microfibrils secreted prior to elastin provide scaffolding on which Microfibrils secreted prior to elastin provide scaffolding on which elastin forms fibers and sheetselastin forms fibers and sheets

PROPERTIES OF ELASTIC FIBERSPROPERTIES OF ELASTIC FIBERS

• Occur in the form of individual, branching and anastomosing fibersOccur in the form of individual, branching and anastomosing fibers

•They can be stretched 2.5 times of their original length They can be stretched 2.5 times of their original length to which they return when releasedto which they return when released

SYNTHESIS OF ELASTIC FIBRES BY FIBROBLASTSSYNTHESIS OF ELASTIC FIBRES BY FIBROBLASTS

3. RETICULAR FIBERS3. RETICULAR FIBERSIndividual collagen fibers coated by proteoglycans and glycoproteins.Individual collagen fibers coated by proteoglycans and glycoproteins.This coating causes their affinity for silver salts.This coating causes their affinity for silver salts.They form delicate flexible networks around capillaries, muscle fibers,They form delicate flexible networks around capillaries, muscle fibers,nerves, adipose cells and hepatocytes.nerves, adipose cells and hepatocytes.Serve as scaffolding in endocrine, lymphatic and blood cell-forming Serve as scaffolding in endocrine, lymphatic and blood cell-forming organs.organs.

Reticular fibers around hepatocytes and around kidney tubules (as part of basement membrane)

SYNTHESIS OF RETICULAR FIBRES BY FIBROBLASTSSYNTHESIS OF RETICULAR FIBRES BY FIBROBLASTS

CELL TYPES OF THE CONNECTIVE TISSUESCELL TYPES OF THE CONNECTIVE TISSUES

I.I. Fixed cells:Fixed cells: fibrocytesfibrocytesfibroblastsfibroblastsmesenchymal cellsmesenchymal cellsadipose cellsadipose cells

II. Free cells:II. Free cells: macrophagesmacrophagesmast cellsmast cellsplasma cellsplasma cellsmelanocytesmelanocytesblood-derived cellsblood-derived cells((lymphocytes, monocytes,lymphocytes, monocytes,

eosinophils,neutrophils)eosinophils,neutrophils)

I.I. FIXED CELLSFIXED CELLSI.1. Fibrocytes, fibroblasts:I.1. Fibrocytes, fibroblasts:

The most common fixed cell types.Fibroblast: metabolically more active(see before: synthesis of ECM components)(purple arrows).Fibrocyte: metabolically less active,more slender cell and nucleus, less cellorganelles (green arrows)

I.I. FIXED CELLSFIXED CELLSI.2. Mesenchymal cellsI.2. Mesenchymal cellsPluripotent undifferentiated cells around blood vessels: Pluripotent undifferentiated cells around blood vessels: Serve as a reservoir of cells that can differentiate into other Serve as a reservoir of cells that can differentiate into other connective tissue cell types.connective tissue cell types.

I. FIXED CELLS:I. FIXED CELLS:I.3. Adipose cells:I.3. Adipose cells:

LM

TEM

SEM

Adipose cells, single or in groups are normal components of the connective tissue (they mayform a separate tissue: adipose tissue).Spherical or polyhedral cells with a large lipid droplet surrounded by a thin cytoplasmic rim.

II. FREE CELLS:II. FREE CELLS:II.1. MACROPHAGES (histiocytes): II.1. MACROPHAGES (histiocytes): in non-reactive CT are fixed, in non-reactive CT are fixed,

upon stimulation they become motile. upon stimulation they become motile. Phagocytotic cell type, rich in hydrolytic enzymes.Phagocytotic cell type, rich in hydrolytic enzymes.

LM

TEMSEM

THE MONONUCLEAR PHAGOCYTE SYSTEMTHE MONONUCLEAR PHAGOCYTE SYSTEM

Connective tissue:Connective tissue: histiocyteshistiocytesLiver:Liver: Kupffer-cellKupffer-cellLung:Lung: alveolar macrophagealveolar macrophageLymph nodes:Lymph nodes: free and fixed macrophagesfree and fixed macrophagesSpleen:Spleen: free and fixed macrophagesfree and fixed macrophagesBone marrow:Bone marrow: fixed macrophagesfixed macrophagesSerous cavities:Serous cavities: pleural and peritoneal macrophagespleural and peritoneal macrophagesBone:Bone: osteoclastsosteoclastsCentral nervous system:Central nervous system: microglial cellsmicroglial cellsSkin: Skin: histiocyteshistiocytesSynovia:Synovia: type A cellstype A cells

II.FREE CELLS:II.FREE CELLS:II.2. Mast cells: II.2. Mast cells: around blood vessels in skin and intestine.around blood vessels in skin and intestine.

TEM

LM

LM

Large metachromatic granules: histamine, heparin, serotonin

II. FREE CELLS:II. FREE CELLS:II.3. Plasma cells:II.3. Plasma cells:In the loose CT of gastrointestinal tract,In the loose CT of gastrointestinal tract,respiratory system and female respiratory system and female reproductive system, in the lymphaticreproductive system, in the lymphatictissue.tissue.They develop from B-lymphocytes, They develop from B-lymphocytes, produce antibodies.produce antibodies.

LMLM TEMTEM

II. FREE CELLSII. FREE CELLSII.4. MelanocytesII.4. Melanocytes

Large pigmented cells of neural crest-origin. They occur in the dermis Large pigmented cells of neural crest-origin. They occur in the dermis of skin, meninges, choroid and iris.of skin, meninges, choroid and iris.

II. FREE CELLS:II. FREE CELLS:II.5. Other free cells temporarily occurring in the CTII.5. Other free cells temporarily occurring in the CT

Lymphocytes, Lymphocytes, monocytes, granulocytes monocytes, granulocytes

(in details see the chapter „Blood” later)(in details see the chapter „Blood” later)