Department of Histology and Embryology, Faculty of Medicine MU pvanhara@med.muni.cz Tissue concept and classification Petr Vaňhara, PhD - 6  1013 CELLS of 200 different types - cells form functional, three-dimensional, organized aggregations of morphologically similar cells and their products and derivatives - TISSUES - tissues constitute ORGANS and organ systems Myocardium TISSUES AND ORGANS Parenchyma: functional component of a tissue (liver, lung, pancreatic, kidney parenchyma) Stroma: surrounding, supportive tissue Parenchyma Stroma LIVER Parenchyma: - Hepatocytes - Sinusoids and adjacent structures Stroma: - Connective tissue and adjacent structures - Vessels - Nerves - Bile ducts TISSUES AND ORGANS Epithelium Muscle Nerve Connective Based on morphology and function: Myofibrils → contraction Mesoderm – skeletal muscle, myocard, mesenchyme – smooth muscles Rarely ectoderm (eg. m. sphincter a m. dilatator pupillae) Neurons and neuroglia Reception and transmission of electric signals Ectoderm, rarely mesoderm (microglia) Dominant extracellular matrix Connective tissue, cartilage, bone… Mesenchyme Continual, avascular layers of cells with different function, oriented to open space, with specific junctions and minimum of ECM and intercellular space. Derivates of all three germ layers CONTEMPORARY TISSUE CLASSIFICATION CONNECTIVE TISSUE Not just a tissue glue… Mechanical and biological properties → surrounds other tissues, allows compartmentalization, provides support, defines physicochemical environment, brings immunological support, provides storage of energy, ... CONNECTIVE TISSUE Cells and extracellular matrix (ECM) • Matrix – fibrous and amorphous • Fibrous component ‒ collagen ‒ reticular ‒ elastic • Amorphous component (amorphous ground substance) Complex matrix consisting of ‒ glycosaminoglycans ‒ glycoproteins ‒ proteoglycans composition dependent on tissue type (connective  ligament  cartilage  bone) • Cells • Connective tissue – permanent and transient cell populations (e.g. fibroblasts/myofibroblasts, immune cells, adipocytes, adult stem cells) • Cartilage – chondroblasts/chondrocytes • Bone – osteoblasts/osteocytes/osteoclasts GENERAL COMPOSITION OF CONNECTIVE TISSUE Collagen fibers - family of fibrous proteins encoded by >35 genes (2013) - polymer – subunit = tropocollagen; triple helix - different structural and mechanical properties (strength, elasticity, pliability…) - most abundant protein in human body ( 30% dry weight) EXTRACELLULAR MATRIX – FIBROUS COMPONENT COLLAGEN further study: https://www.ncbi.nlm.nih.gov/books/NBK507709/ Type Localization Structure Main function I Bone, tendons, meniscus, dentin, dermis, capsules of organs, loose CT 90% of type I Fibrils (75nm) – fibers (1-20m) Resilience in pull II Hyaline and elastic cartilage Fibrils (20nm) Resilience in pressure III Skin, veins, smooth muscles, uterus, liver, spleen, kidney, lung Like I, high content of proteoglycans and glycoprotiens, reticular network Shape formation IV Basal lamina of epithelium and endtohelium, basal membranes No fibrils or fibers Mechanical support V Lamina of muscle cells and adipocytes, fetal membranes Like IV VI Interstitial tissue, chondrocytes – adhesion Connecting dermis and epidermis VII Basal membrane of epithelium VIII Some endothelia (Cornea) IX, X Growth plate, hypertrophic and mineralized cartilage Growth of bones, mineralization COLLAGEN AZAN HES HE COLLAGEN IN LIGHT MICROSCOPE • less abundant than collagen • polymer – tropoelastin • minimal tensile resistance, loss of elasticity if overstretched • reduction of hysteresis = allow return back to original state after mechanic change ELASTIC FIBERS • collagen 3D meshwork • bone marrow, spleen, lymphatic nodules • microenvironment for e.g. hematopoietic stem cells and progenitors RETICULAR FIBERS RETICULAR CONNECTIVE TISSUE Amorphous extracellular matrix Colorless, transparent, homogenous substance consisting of glycosaminglycans, proteoglycans and structural glycoproteins EXTRACELLULAR MATRIX – GROUND SUBSTANCE linear polysaccharides composed of two disaccharide subunits – uronic acid and hexosamine glucosamin or galactosamin glucuronic or iduronic acid polysaccharides rich in hexosamines = acid mukopolysaccharides GLYCOSAMINOGLYCANS Glycosaminoglycan Localization Hyaluronic acid Umbilical cord, synovial fluid, fluid of corpus vitreum, cartilage Chondroitinsulphate Cartilage, bone, cornea, skin, notochord, aorta Dermatansulphate Skin, ligaments, adventitia of aorta Heparansulphate Aorta, lungs, liver, basal membranes Keratansulphate Iris, cartilage, nucleus pulposus, anulus fibrosus They bind to protein structures (except for hyaluronic acid) GLYCOSAMINOGLYCANS — protein + dominant linear saccharide component — proteoglycan aggregates — water-binding, volume dependent of hydratation — aggrecan (cartilage) — syndecan — fibroglycan PROTEOGLYCANS • dominant protein + branched saccharide component • interaction between cells and ECM ― fibronectin – connects collagen fibers and glykosaminoglycans, cell adhesion and migration ― laminin – basal lamina – epithelial integrity ― chondronectin – cartilage – adhesion of chondrocytes to collagen (J. Nutr. 136:2123-2126, 2006) STRUCTURAL GLYCOPROTEINS COMPOSITION OF ECM CLASSSIFICATION OF CONNECTIVE TISSUE Collagen Structure Function and distribution Loose collagen CT Abundant ground substance, few collagen fibers with random arrangement Microvascularisation Innervation Irregular dense collagen CT Few ground substance, few cells, many collagen fibers, random arrangement Mechanically resistant organ capsules Regular dense collagen CT Tightly arranged collagen fibers with fibroblasts intercalated between them Part of musculoskeletal system. Tendons, ligaments Embryonic Mesenchyme Undifferentiated cells uniformly dispersed in the ground substance, few collagen fibers Undifferentiated progenitors Wharton’s jelly Viscous amorphous matrix with collagen fibers. Fibroblasts. Matrix of umbilical cord Special Reticular CT Network of collagen III fibers and reticular cells Support of hematopoietic and lymphatic cells Elastic Rich in elastic fibers Flexible support to the elastic arteries and aorta Adipose Adipocytes Energy storage (white fat), heat production (brown fat) Cartilage Chondroblasts, chondrocytes Mechanical support Bone Osteoblasts, ostecoytes, osteoclasts Mechanical support, calcium and phospate metabolism Blood See lecture on blood & hematopoiesis this semester Cells - Fibroblasts/fibrocytes/myofibroblasts - Heparinocytes - Macrophages of CT = histiocytes - Plasma cells - Lymphocytes - Adipocytes - Adult stem cells Extracellular matrix - Fibrous compound - Amorphous ground substance LOOSE COLLAGEN CONNECTIVE TISSUE Mesenchymal (adult) stem cells CELLS OF LOOSE COLLAGEN CONNECTIVE TISSUE DENSE COLLAGEN CONNECTIVE TISSUE • Adipocytes, fibroblasts, reticular, collagen and elastic fibers, capillaries • White and brown adipose tissue ADIPOSE TISSUE • adipocytes are actively formed until 2nd year of life • no innervations, but rich vascularisation • adipocytes with only one lipid droplet • leptin (adipokinins) WHITE ADIPOSE TISSUE • fetus and children up to 1st year of life • fast source of energy • typical localization – between shoulder blades, axilla, mediastinum, around kidneys, pancreas, small intestine • small cells with numerous fat droplets BROWN ADIPOSE TISSUE • Mesenchyme = loose tissue between germ layers • Complex network of star- or spindle-shaped cells • Jelly-like amorphous ground substance http://www.mun.ca/biology/desmid/brian/BIOL3530/DB_Ch02/DBNModel.html DAY 12 of embryonic development EMBRYONIC ORIGIN OF CONNECTIVE TISSUE Connective BoneCartilage Mesenchyme DEVELOPMENT OF CONNECTIVE TISSUES FURTHER STUDY http://www.histology.med.muni.cz Thank you for attention pvanhara@med.muni.cz