Chapter 5: Histology- Study of Tissueso Primarily Tissue Class Tissue: group of similar cells that arise from the same region of theembryo & work together to perform specific functions  Extracellular Matrix: surrounds the cell- Composed of fibrous proteins & a clear gel known as ground substance, tissue fluid, extracellular fluid, or interstitial fluido Water, gases, minerals, nutrients, and hormoneso Embryonic Tissue Primary Germ Layers- Ectoderm: outer layer that gives rise to epidermis and nervous system- Mesoderm: middle layer with more loosely organized cells o Mesenchyme: fine, wispy collagen fiberso Gives rise to muscle, bone, and blood- Endoderm: gives rise to mucous membraneo Interpreting Tissue Sections Histological Sections: thin slices of tissue that are artificially colored - Preserved in a fixativeo Chemical like formalin- Cut into sections: 1 or 2 cells thick and stainedo Longitudinal, transverse, cross, oblique- Smears: rubbed or spread- Spreads: laid- Epithelial Tissue: sheet of closely adhering cells, one or more cells thick with upper surface usually exposed to the environment or an internal spaceo Protection: protects deeper tissue from invasion and injury Inner lining of stomach and epidermiso Secretion: mucous, sweat, enzymes, and hormoneso Excretion: void wastes CO2 and bileo Absorption: absorbs chemical and nutrients Small intestineo Filtration:  Blood vessels and kidneyo Sensation: nerve endings Skin and stomacho Extracellular material: very thino Avascularo High Rate of mitosiso Basement membrane: between epithelium and underlying connective tissue Contains: collagen, glycoprotein, and other carbohydrate-protein complexes Blends into connective tissue- Anchor epithelium to connective tissueo Basal surface: faces basement membraneo Apical surface: faces awayo Simple Epithelia: only one layer of cells Simple squamous: dry and scaly Simple cuboidal: squarish and round Simple columnar: tall and narrow Psuedostratified: - Goblet Cells: wine glass-shaped that produce protective mucous coating over mucous membrane o Stratified Epithelia: range from 2-20 layers of cells resting directly on top one another and only the deepest layer attached to the basement membrane  Stratified squamous: most widespread- Exfoliation: the loss or flaking of dead squamous cells- Keratinized: found in the epidermis and covered with dead compressed cellso Compact with keratin and coated with water-repellent glycolipid- Nonkeratinized: lack a layer of dead cellso Abrasion-resistant, moist & slipperyo Vagina, tongue, esophagus Stratified Cuboidal Stratified Columnar- Rare and minor importance Transitional Epithelium: Domed surface with a unique protection property- Umbrella cellso Upper surface & outer phospholipid layer is thick than usual and has dense patches (lipid raft) embedded with uroplakins (impermeable to urine)- Found only in the urinary tract- Connective Tissue: most abundant, widely distributed, and histologically variableof the primary tissueso Their cells occupy less space than the extracellular matrix Cells are not usually in direct contact with each othero Overview Binding of Organs: tendons bind muscle to bone, ligaments bind one bone to another, fat holds the kidneys and eyes in place Support: Support body and it’s parts Physical Protection: bones and fat provide most protection Immune Protection: connective tissue cells attack foreign invaders,fibers provide a battle field, & mucous provides quick mobility to immune cells Movement: Bones & cartilage Storage: fat and bone Heat production: metabolism of brown fat Transport: bloodo Fibrous Connective Tissue: most diverse type Components of Fibrous Connective Tissue: - Cellso Fibroblasts: large, fusiform or stellate cells, with branches that produce the fibers and ground substance of matrix of the tissueo Macrophage: large phagocytic cells that engulf and destroy bacteria, foreign particles, or dead cells Activate immune system when they sense antigens  They arise from white blood cells called monocyteso Leukocytes (white blood cells): spend time in the blood vessels, but most time in connective tissue  Neurophils: wander and attack bacteria  Lymphocytes: react against bacteria, toxins, and other foreign agents- Form dense patches in mucous membraneso Plasma Cells: certain lymphocytes turn into plasma cells when they detect foreign agents Synthesize antibodies  Rarely seen except in wall of intestines and inflamed tissueo Mast Cells: secrete heparin that inhibits blood clotting and histamine that increases blood flow by dilating blood vessels alongside blood vessleso Adipocytes (fat cells): small clusters in some connective tissue - Fiberso Collagenous Fibers: made of collagen and are tough & flexible and resist stretching Most abundant protein Base of gelatin, leather, glueo Reticular Fibers: thin collagen fibers coated with glycoprotein Sponge-like framework for organso Elastic Fibers: made of protein elastin that allows stretch and spring like a rubber band Thinner than collagen fibers- Ground Substance: a gelatinous to rubbery consistency resulting from glycoaminoglycans, proteoglycans, and adhesive glycoproteinso Absorbs compressive forces and protects delicate cells from mechanical injury.- Glycosaminoglycan: long polysaccharide composed of unusual disaccharides called amino sugars and uronic acid.o Negatively charged and attract sodium and potassium Causes GAGs to absorb and retain watero Play an important role in regulating water and electrolyte balance of tissues o Chondroitin Sulfate: most common Abundant in blood vessels and bones Give cartilage relative stiffnesso Hyaluronic: slippery substance that forms a lubricant in the joints and constitutes - Proteoglycan: shaped like a bottle brush with a central core of protein and bristle-like outgrowths composed of GAGso Form think colloids o Slows the spread of pathogenic organisms through the tissueso Create strong, structural bond between cells and extracellular macromolecules and help hold tissues together- Adhesive Glycoproteins: protein-carbohydrate complexes that bind plasma membrane proteins to extracellular collagen and proteoglycans o Mark the path that guides migrating embryonic cells to their tissues Types of Fibrous Tissue- Loose Connective Tissue: much of the space is occupied by ground substance which dissolves out of