Connective Tissue I PDF

LESSON 7 CONNECTIVE TISSUE I CONTENTS CONNECTIVE TISSUE: Introduction The term “connective” “joining together” Support and connect the other 3 tissues Forms a continuity and keep the body integrated Morphological, topographic and structural diversity CONNECTIV...

LESSON 7 CONNECTIVE TISSUE I CONTENTS CONNECTIVE TISSUE: Introduction The term “connective” “joining together” Support and connect the other 3 tissues Forms a continuity and keep the body integrated Morphological, topographic and structural diversity CONNECTIVE TISSUE: Introduction EMBRIONIC ORIGEN Ectoderm MESODERM (middle germ layer of the embrionic tissue) MESODERM MESENCHYME Mesenchymal cells Endoderm CONNECTIVE TISSUE: Classification CLASSIFICATION Embrionic connective tissue Mesenchymal and mucous connective tissue Connective tissue proper Loose (areolar) connective tissue Dense (regular and irregular) connective tissues Reticular tissue Adipose tissue Specialised connective tissues Cartilage Bone Blood CONNECTIVE TISSUE: functions JOINING TOGETHER: all 4 different tissues Providing STRUCTURAL SUPPORT Bones, cartilage, ligaments, tendons Capsules and stroma THERMAL REGULATION Adipose tissue MEDIUM FOR EXCHANGE of nutrients and waste products DEFENSE, PROTECTION and REPAIR of the body Paghocytic cells, immunocompetent cells, pharmacological substances and physical barrier FAT store Energy CONNECTIVE TISSUE: COMPONENTS EXTRACELLULAR MATRIX (ECM) Same components (change proportion) CELLS Different depend on the type EXTRACELLULAR MATRIX EXTRACELLULAR MATRIX GROUND SUBSTANCE Hydrated, gel-like material RESISTANCE TO COMPRESSION FORCES FIBRES RESISTANCE TO TRACTION FORCES & ELASTICITY COLLAGEN FIBRES RETICULAR FIBRES ELASTIC FIBRES GROUND SUBSTANCE GROUND SUBSTANCE Amorphous gel-like material where the fibres and cells are included. H&E: not seen 3 components: Glycosaminoglycans (GAGs) Proteoglycans (PGs) Adhesive glycoproteins Ground substance GROUND SUBSTANCE Glycosaminoglycans (GAGs) Mucopolysaccharides Long polysaccharides Composed of repeating DISACCHARIDE units Amino Sugar Uronic acid Inflexible and without ramifications Hydrophilic Hydrated gels RESISTANCE TO COMPRESSION FORCES GROUND SUBSTANCE Glycosaminoglycans (GAGs) GAGs SULFATED GAGs NOT SULFATED Amino Sugar Amino Sugar keratan sulfate sulfated hyaluronic acid non-sulfated heparan sulfate chondroitin sulfate dermatan sulfate heparin Negatively charged: PHYSICAL BARRIER attract cations (Na+) RETAIN LIQUID  GROUND SUBSTANCE Proteoglycans Sulfated GAGs linked to proteins AGGRECAN Functions: Resistance to compressive forces Physical barrier for microorganisms and cells spreading Molecular filters in the basal lamina Binding sites of signalling molecules ( TFGβ, FGF...)  GROUND SUBSTANCE Adhesive glycoproteins Join together the components of the extracellular matrix Types: 3 binding-domains: Fibronectin collagen fibres proteoglycans Laminin integrins of the cells Entactin Tenascin Chondronectin Osteonectin FIBRES COLLAGEN FIBRES The most abundant and present in most connective tissues MACROSCOPICALLY: Bright white colour in large accumulations MICROSCOPICALLY: 10 μm in diameter Organised in groups or bundles H&E: long, wavy, pink fibre bundles Methylene Blue/Masson Trichome: blue Van Gieson Picrofucsina Light Green technique COLLAGEN FIBRES COLLAGEN FIBRE Collagen fibril Tropocollagen triple helix 3α chains 1000 amino acids DIFERENT TYPES OF COLLAGEN  COLLAGEN FIBRES ELECTRON MICROSCOPE Cross-banding at regular intervals of 67 nm COLLAGEN FIBRES TYPE OF COLLAGEN FIBRES RETICULAR FIBRES reticulin fibres Individual fibrils of type III collagen 0.5-2 µm Ø LIGHT MICROSCOPE Not distinguised with H&E stain Silver stain Stained with SILVER techniques and PAS black magenta Flexible and delicate mesh Capilaries, muscle fibers, adipose cells, hepatocytes... PAS + stroma In many organs and tissues Basement membrane, smooth muscle, exocrine and endocrine glands, lymphoid organs... ELASTIC FIBRES Elasticity of the connective tissue Skin, lung, blood vessels, nape ligament MACROSCOPICALLY Yellowish in large quantitites MICROSCOPICALLY H&E stain Acidophilic and shiny (more than collagen fibres) Wavy bundles ELASTIC FIBRES ELECTRON MICROSCOPE 2 components: Central amorphous material: ELASTIN Fibroblasts and smooth muscle cells Sheath of fibrillin microfibrils ELASTIN FIBRILLIN MICROFIBRILS CONNECTIVE TISSUE: COMPONENTS EXTRACELLULAR MATRIX (ECM) Same components (change proportion) CELLS Different depend on the type CONNECTIVE TISSUE CELLS CELLS Fixed or resident cells Transient, free or inmigrant cells Fibroblasts and fibrocytes Plasma cells Pericytes Lymphocytes Fat cells, adipose cells and adypocytes Neutrophils Mast cells Eosinophils Some macrophages Basophils Monocytes Some macrophages CELLS Fixed or resident cells Fibroblasts and fibrocytes Fibroblast Fibrocyte The most abundant cell type in the connective tissue Origen: undifferentiated mesenchymal cells Synthesis of almost all of the extracellular matrix Fibrobast: ACTIVE FORM Fibrocyte: RESTING FORM CELLS Fixed or resident cells Fibroblasts and fibrocytes Spindle cells with pale-staining cytoplasm Darker-stained, large, granular ovoid nucleus CELLS Fixed or resident cells MICROSCOPICALLY FIBROBLASTS FIBROCYTES Big and granular nucleus with Smaller, not granular and intensely evident nucleolus basophilic nucleus  CELLS Fixed or resident cells ELECTRON MICROSCOPE FIBROBLASTS FIBROCYTES Abundant RER, Golgi complex and Scant cytoplasm mitochondria. Vimentin and actin filaments Few organelles CELLS Fixed or resident cells Fibroblasts and fibrocytes Have some motility Can enter mitosis (wound healing) MYOFIBROBLASTS Fibroblasts/smooth muscle cells Contractile activity (actin filaments) Do not have basal lamina Common in healing areas H&E: indistinguisable from fibroblasts CELLS Fixed or resident cells Pericytes Pericytes Spindle cells with numerous cytoplasmic processes Partially surround the endothelial cells of capillaries and small venules Charactacteristics of endothelial cells and smooth muscle cells Contractile activity CELLS Fixed or resident cells Fat cells, adipose cells, adipocytes Synthesize and store lipids (TRIGLYCERIDES) Origen: Undifferentiated mesenchymal cells Never divide except in the immediate postnatal period Two types Unilocular adipocyte (WHITE FAT) Multilocular adipocyte (BROWN FAT) CELLS Fixed or resident cells Unilocular adipocyte (white fat) Triglycerides in a single large droplet signet ring LIGHT MICROSCOPE Round or polyhedral cells (>120 µm Ø) Cytoplasm; large vacuole Nucleus: one side of the cytoplasm (signet ring) To see the lipids: frozen samples and special stains (Sudan III, Scarlet red...) Release glycerol and fatty acids into blood CELLS Fixed or resident cells Multilocular adipocyte (brown fat) Triglycerides in several small droplets Smaller than unilocular adipocytes LIGHT MICROSCOPE Cytoplasm; numerous vacuoles Nucleus: central position ELECTRON MICROSCOPE Abundant mitochondria Oxidation of fatty acids (thermogenin): HEAT  CELLS Fixed or resident cells Mast cells Origen: undifferentiated cells in bone marrow LIGHT MICROSCOPE Ovoid in shape and variable in size Numerous basophilic granules in the cytoplasm Metachromasia (Toluidine blue and Giemsa) Half-life of few months ELECTRON MICROSCOPE Electron-dense granules CELLS Fixed or resident cells Mast cells Function: Immediate hypersensitivity reaction or anaphylactic reaction Heparin (Anticoagulant) Histamine (increases vascular permeability) Other chemical mediators of inflammation  CELLS Fixed or resident cells Macrophages Fixed and transient cells Phagocytosis capacity Lysosomes Mononuclear phagocytic system Receptor for Fc portion Origen: Bone marrow monocytes macrophages (half-life about 2 months) Free macrophages migrate to that particular site Resident macrophages Same location, regardless of there is or not external stimuli Kupffer cells, alveolar macrophages, osteoclasts, microglia  CELLS Fixed or resident cells Macrophages LIGHT MICROSCOPE Irregular morphology, large size (10-30 µm Ø) Basophilic, pale, vacuolised cytoplasm Ovoid or kidney-shaped, eccentric and vesicular nucleus  CELLS Fixed or resident cells Macrophages ELECTRON MICROSCOPE Cytoplasmic processes (filopodia) Developed RER and Golgi complex Primary and secondary lysosomes CELLS Fixed or resident cells Macrophages Chronic inflamation Epithelioid cells Foreign body giant cells (multinucleated) Primary and secondary lysosomes  CELLS Fixed or resident cells Macrophages Functions Phagocytosis and digestion Signalling molecules: CYTOKINES Processing and presentation of antigens to lymphocytes CELLS Fixed or resident cells Transient, free or inmigrant cells Fibroblasts and fibrocytes Plasma cells Pericytes Lymphocytes Fat cells, adipose cells and adypocytes Neutrophils Mast cells Eosinophils Some macrophages Basophils Monocytes Some macrophages LESSON 7 CONNECTIVE TISSUE I