Tissues- Epithelial (covers)- Connective (supports)- Nervous (controls)- Muscular (movement)To view tissues1. Fixed (preserved)2. Cut into pieces (slices)3. Stained (enhance)-Artifacts- minor distortions -Electron microscope stain- acidic/negatively charged; basic/positively charged-TEM- heavy metal salts-SEM- takes 3D image of unsliced tissueEpithelial Tissue-Sheets of cells that line or cover surface-Covering- lines skin, organs-Glandular epithelial- lines glands of body-Mitotic throughout life-Functions (6)(all things that enter and leave the body contact epithelial tissue)1. Protect2. Absorb3. Filtrate 4. Excrete5. Secrete6. Sensory receptors-Characteristics (5)1. Polarity-Apical-basal polarity- upper free surface (apical) exposed to body exterior, or cavity of internal organ and a lower attached (basal)-Apical- smooth and slick, most have microvilli-Microvilli- increase surface area-Cilia- hair like projections that propel substances along -Basal-Basal lamina- thin supporting sheet-Consists of glycoproteins and collagen fibers-Selective filter to underlying connective tissue-Repair wounds2. Specialized contacts-Tight junctions and desmosomes- bind adjacent cells together at many points-Help keep apical region of membrane from diffusing to basal region (maintains polarity)3. Supported by connective tissues-Reticular lamina- layer of extracellular material containing a network of fibers that belongs to connective tissue-Basement membrane- formed by the two lamina-Reinforces epithelial sheet-Helps resist stretching and tearing-Defines epithelial border4. Avascular but innervated-Avascular- contains no blood vessels-Innervated- supplied by nerve fibers-Nourished by substances that diffuse from underlying connective tissue blood supply5. Regeneration-Reproduce rapidly-As long as receive adequate nutrition-Classification-Two names: 1st indicates number of call layers present, 2nd describes shape of cell-Simple epithelia- single cell layer, thin (absorption, secretion, and filtration)-Cells usually have same shape-Not for protection-Stratified epithelia- two or more cell layers, stacked. High abrasion areas (protection)-Cells differ at different layers-Named according to shape if cells in apical layer-Common shapes-Squamous cells- flattened and scale like-Nucleus-flat disc-Cuboidal cells- boxlike, as tall as they are wide-Nucleus- spherical -Columnar cells- tall and column shaped-Nucleus- elongated from top to bottom, closed to cell base` -Shape of nucleus conforms to shape of cellSimple Squamous Epithelium-Flattened laterally-Cytoplasm sparse-Thin and permeable-Endothelium- provides slick, friction-reducing lining-Lymphatic vessels and in hollow organs-Mesothelium- found in ventral body cavity, and covering organsSimple Cuboidal Epithelium-Single layer cells-Nuclei stain dark (cells appear like stream of beads)-Secretion and absorption -Forms small ducts and glands, kidney tubulesSingle Columnar Epithelium-Single layer, tall and packed-Lines digestive tract (stomach rectum)-Absorption and secretion-Dual function:-Dense microvilli on apical surface of absorptive cells-Tubular glands made primarily of cells that secrete mucus-Cilia on free surfacesPseudostratified Columnar Epithelium-Vary in height-All cells rest in basement membrane-Only tallest cells reach free surface of epithelium-Tissues give false (pseudo) impressions that several cell layers are present-Secretes and absorbs-Cilia version containing mucus-secreting glands line respiratory tract-Dust trapping mucusStratified Epithelia-Composed of two cell layers-Regenerate from basal cells and push apically to replace older cells-Durable, protection-Stratified Squamous Epithelium -Most widespread of stratified-Composed of several layers thick-Free surface is squamous, deeper layer cuboidal and columnar-Forms outer layer of skin (which is keratinized)-Stratified cuboidal epithelium- rare in body, mainly in larger gland ducts-Two layers of cuboidal cells-Stratified columnar epithelium- found in pharynx, male urethrae, and some glandular ducts-Often in junction areas (in-between two types of epithelia)-Only apical layer columnar-Transitional Epithelium- lining of urinary organs, stretching-Basal layer- cuboidal or columnar-Apical layer varies based on stretching of organ-When organ stretches- epithelium thins from 6 layers to 3-Allows more urine to flow/store-Glandular epithelia-Gland- consists of one or more cells that make and secrete a particular product-Secretion- aqueous fluid that contains proteins in variation-Some release a lipid or steroid based secretion-Classification:1. Where they release their product- endocrine or exocrine2. Relative cell number- unicellular or multicellular-Unicellular- scattered within epithelial sheets-Most have ducts connected to epithelial sheets-Endocrine Glands-Eventually lose their ducts (ductless glands)-Produce hormones-Structurally diverse-Exocrine Glands-Secrete products onto body surfaces (skin) or in body cavities-Unicellular glands directly secrete (exocytosis)-Mucus cells and goblet cells-Mucin- complex glycoprotein, dissolves in water-Goblet cells- cuplike accumulation of mucin, causes cell to look like glass stem-Multicellular by epithelium-walled duct-Diverse (mucus, sweat, oil, salivary glands, liver…)-Multicellular Exocrine Glands- complex-Two parts- duct and secretory unit-Supportive connective tissue surrounds the secretory unit and supplies it with blood -Classified by structure:-Simple Glands- unbranched ducts-Compound Glands- branched ducts Secretory units:-Tubular- if secretory cells form tubes-Alveolar (acinar)- if small flask-like sacsformed-Tubuloaveolar- both form tubes and flask sacs -Modes of secretion-Merocrine- secrete by exocytosis-Holocrine- accumulate product within until rupture; include synthesized product and dead cells-Apocrine- accumulate product, cell eventually pinches off, cell then repairs self-Controversy on whether humans have this glandConnective Tissue-Most abundant and widely distributed tissue in the bodyFour main types Major functions1. Connective tissue proper2. Cartilage3. Bone4. Blood1. Bind and support2. Protecting3. Insulating4. Storing reserve fuels5. TransportingCommon Characteristics:-Common origin- all arise from mesenchyme-Degrees of vascularity-Extracellular matrix- largely nonlivingThree main elements: make up extracellular matrix1. Ground substance-Unstructured material that fills space between cells-Composed of …1. Tissue