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Connective tissue 2009

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Connective tissue

2009

Connective tissue

Connective tissue consists of cells and extracellular matrix

• Connective tissue proper• Cartilage• Bone• Adipose tissue

Connective tissue

Mechanical (structural) role – supportive and connecting

Defence – immune response and physical barrier

Nutrition – vessels (blood supply) Storage of metabolites – Ca, fat Tissue repair after injury

Connective tissue proper Cells:

Fixed: fibroblasts, reticular cells, adipocytes

Blood derived: macrophages, plasma cells, mast cells, leucocytes

Fibres: collagen, reticular and elastic

Ground substance: glycoproteins and proteoglycans

Fibroblast

Spindle -shaped cell with elliptic nucleus

Proteosynthesis (GER and GA): collagen, elastin, proteoglycans and glycoproteins

Synthesis of collagen Preprocollagen with signal peptide – into RER Procollagen – hydroxylation of lysine and proline

(RER) GA – packing nad secretion of procollagen,

glycosylation, formation of disulphidic bounds Removal of nonhelical endings Tropocollagen Polymeration outside of cell Periodicity 64 nm

Types of collagens

I. Bone, tendon, dentin, skin II. Hyalinne and elastic cartilage III. Reticular lamina (BM) and

reticular fibres IV. Basale lamina V. Chorion and amnion

Elastin

Proelastin – secretion of tropoelastin Interaction with fibrillin to organize

immature elastic fibers Aggregation – mature elastic fibers Content of desmosin and

isodesmosin (AA)- cross-linking of elastic fibers

EM: microfibrils+MAGPs+fibrillin

Fibres

Collagen fibres Reticular fibres

(AgNO3) Elastic fibres

(resorcin fuchsin, orcein)

Clinical significance:

Vitamine C – necessary for hydroxylation of collagen (hydroxyproline and hydroxylysine)

Ehlers-Danlos syndrome – hyperelasticity of skin and hypermobility of joints – defect of procollagen peptidase or lysyl hydroxylase – impairment of cross-linking formation in collagen fibres

Clinical significance

Marfan syndrome – autosomal dominant – defect of fibrillin

– Myopy, lens ectopy, skeletal defects

arachnodactyly, prolapse of the mitral

valve, dilatation of aorta ascendens.

Ground substance

Glycoproteins – fibronectin, chondronectin, laminin etc.

Proteoglycans – Glycosaminoglycans – polysaccharides

formed from hexosamine and uronic acide: chondroitin sulphate, heparan sulphate, dermatan suphate keratan sulphate

Core protein, linker protein, hyaluronan molecule

Interaction between cells and matrix

Integrins – receptors for molecules of extracellular matrix (hemidesmosomes and focal adhesions)

Intracellular attachment to the cytoskeleton (paxilin, vinculin, talin, β-catenin)

Ground substance

Hydratation of glycosaminoglycan molecules, presence of growth factors

Degradation – metalloproteinases – collagenase, kathepsin, stromelysin, gelatinase,

Significance : tumor invasion – degradation of basement membrane

Cells decrease expression of integrines – attachment to BL

Regeneration

After injury or impairment of tissue Cell division – scar formation Myofibroblasts – wound healing -

wound contraction characteristics of both, fibroblast and smooth muscle cell

Synthesis of growth factors (during development, too)

Macrophages

Phagocytic cells, derived from monocytes Contain of lysosomes, phagosomes

(vacuoles) Stainable by vital dyes – trypan blue Function: turn over the senescent fibers and

ECM Antigen presenting cells (MHC) Production of cytokines – interleukin 1, TNFα

Macrophages Monocytes Histiocytes Osteoclasts Dendritic cells Mikroglia Kupffer cells Langerhans cells Epiteliod cells, multinuclear giant cells –

segregation of foreign bodies

Mast cells Derives from bone

marrow Vasoactive

mediators: histamine, heparin, chemotactic mediators – leukotrienes

Metachromasia

Mast cells Mucosal mast cells (lungs and gut) Connective tissue mast cells Activation – antigen - bounds to two IgE

receptors Release – histamine, proteases,

proteoglycans Synthesis of mediators derived from

arachidonic acid- prostaglandins and leukotrienes

Plasma cells Activated B-

lymphocytes – immunoblasts – plasma cells

Proteosynthesis -GER and GA

Cartwheel nucleus

Connective tissue

Embryonic – mesenchyme, mucoid connective tissue – Wharton´s jelly

Adult – loose and dense collagen connective tissue, reticular connective tissue, elastic connective tissue

Special – white and brown adipose tissue

Connective tissue

Collagen connective tissue Loose Dense

Elastic Reticular White adipose tissue Brown adipose tissue

Embryonic connectives

Mesenchyme – embryonic tissue starlike cells with little amount of ECM – allow cells to migrate

Mucoid connective tissue – fetal – fibroblasts, collagen V, hyaluronic acid – umbilical cord (Warthon´s jelly), chorion

Collagen connective tissue

Loose – many cells (blood deriveds, too) less fibers. Occurence in lamina propria, muscles ect.

Dense – more fibres and less cells Regular (tendon, fascia, aponeurosis) Irregular (dermis)

Elastic connective tissue

Bundles of elastic fibers, thin collagen fibers and fibroblasts

Yellow ligament Suspensory

ligament of the penis

Reticular connective tissue Three-dimensional

network - reticular cells and fibers – microenvironment for haemopoesis and lymphatic organs: bone marrow, spleen, lymph nodes

Unilocular adipose tissue 50-150um, signet ring cell Excentric nuclei Only one big lipid droplet, it is not

surrounded by membrane - triglycerids (Glut-4)

Surrounded by basal lamina Hormone: insulin,GH, thyroxin,

katecholamins, glucocorticods, prostaglandins,

Function:

Insulator agains heat loss Reserve of energy Fills spaces and cushions Shock absorber in soles and

mechanic support (kidney, eye). Synthesis: leptin, adiponectin,

estrogens

Multilocular adipose tissue Multilocular Nucleus in the

centra of cell, many mitochondria

Present in fetuses and newborns

Multilocular adipose tissue

Many vessels, sympathetic adrenergic inervation

Function: thermogenesis – thermoregulation in newborns

Uncoupling protein = thermogenin - in mitochondria - mitochondria produce heat instead of ATP