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Transcript
Epithelial and Connective Tissues • Epithelial tissues – Classes – Junctions – Glands • Connective Tissues – Matrix – Cells – Types Human Anatomy, Larry M. Frolich, Ph.D. 4 Types of Tissue 1)Epithelium 2)Connective 3)Muscle 4)Nervous Human Anatomy, Larry M. Frolich, Ph.D. Tissues: groups of cells closely associated that have a similar structure and perform a related function • Four types of tissue – Epithelial = covering – Connective = support – Muscle = movement – Nervous = control • Most organs contain all 4 types • Connective tissue has non-living extra-cellular material (matrix) between its cells Human Anatomy, Larry M. Frolich, Ph.D. EPITHELIAL TISSUES • Sheets of cells • Specialized contacts/cell junctions (see below) • Basal lamina: protein scaffolding secreted by epithelial cells • Basement membrane: reticular fibers (crossed collagen network) that supports epithelium-really associated connective tissue • Connective tissue support • Nutrients from capillaries in underlying connective tissue • Nerves pass through • Easily regenerates • E.g. skin, lining of gut, mucous membranes Human Anatomy, Larry M. Frolich, Ph.D. Classes of Epithelia • Simple: just one layer or cell shape • Stratified: multiple layers and cell shapes Human Anatomy, Larry M. Frolich, Ph.D. Simple Epithelia Type Cell shape Example Squamous Squashed Cuboidal Cubed Endotheliu m (lin es blood vessels), mesothelium (serous lining of celom) Walls of glands Columnar Columns Pseudo-stratified Flat cells give rise to columns Linin g of gut tube; sometimes with cilia lik e lining of uterine tube With cilia in respiratory tubes to move mucous/particles out of lungs Human Anatomy, Larry M. Frolich, Ph.D. Stratified Epithelia • Squamous – E.g. epidermis • Transitional epithelium – E.g. urinary structures--bladder – Stretches from 6 cells to 3 cells thick as bladder fills and expands Human Anatomy, Larry M. Frolich, Ph.D. Human Anatomy, Larry M. Frolich, Ph.D. Quiz!! E Can You Identify the Classes of Epithelium? D A B C Human Anatomy, Larry M. Frolich, Ph.D. Cell Junctions • Desmosome: binding spots between cells with proteins called cadherins • Tight junctions: impermeable – E.g. gut tube, doesn’t let enzymes from gut into blood stream • Gap junctions: tubes that let small molecules pass between cells Human Anatomy, Larry M. Frolich, Ph.D. Human Anatomy, Larry M. Frolich, Ph.D. Features of Apical Surface of Epithelium Microvilli: (ex) in small intestine Finger-like extensions of the plasma membrane of apical epithelial cell Increase surface area for absorption Cilia: (ex) respiratory tubes Whip-like, motile extensions Moves mucus, etc. over epithelial surface 1-way Flagella: (ex) spermatoza Extra long cilia Moves cell Human Anatomy, Larry M. Frolich, Ph.D. Features of Lateral Surface of Epithelium • Cells are connected to neighboring cells via: – Proteins-link cells together, interdigitate – Contour of cells-wavy contour fits together – Cell Junctions • Desmosomes-adhesive spots on lateral sides • Tight Junctions-at apical area, plasma membrane of adjacent cells fuse, nothing passes • Gap junction-spot-like junction occurring anywhere, lets small molecules pass Human Anatomy, Larry M. Frolich, Ph.D. Features of the Basal Surface of Epithelium • Basal lamina: supportive sheet between epithelium and underlying connective tissue – Selective filter • Basement membrane = basal lamina plus underlying reticular fiber layer – Attaches epithelium to connective tissue below • Sometimes the two are used interchangeably Human Anatomy, Larry M. Frolich, Ph.D. Name that Epithelial Feature! (name and location on cell) 3 1 2 • Cilia 3 • Tight 1 junction • Microvilli 2 • Basement 4 membrane 4 Human Anatomy, Larry M. Frolich, Ph.D. Glands: epithelial cells that make and secrete a water-based substance • Exocrine Glands – Secrete substance onto body surface or into body cavity – Have ducts – E.G., salivary, mammary, pancreas, liver • Endocrine Glands – Secrete product into blood stream – Either stored in secretory cells or in follicle surrounded by secretory cells – Hormones travel to target organ to increase response – No ducts Human Anatomy, Larry M. Frolich, Ph.D. CONNECTIVE TISSUES • “Areolar tissue” as model • Universal in body • Underlies epithelium, supports capillaries, small nn. • Always originates from mesenchyme • CELLS in MATRIX Human Anatomy, Larry M. Frolich, Ph.D. Extracellular matrix • Fibers – Collagen gives structure – Reticular fibers (crossed collagen) gives order – Elastin gives elasticity • Ground substance – Jelly-like material made of sugarprotein molecules (proteoglycans) Human Anatomy, Larry M. Frolich, Ph.D. Cells of Connective Tissues • Fibroblasts make fibers • Immune cells in areolar tissue – – – – Macrophages Plasma cells Mast cells Neutrophils, Lymphocytes Human Anatomy, Larry M. Frolich, Ph.D. Human Anatomy, Larry M. Frolich, Ph.D. “Loose” connective tissues • Adipose tissue mostly under skin and in mesenteries • Reticular: organized 3-D network of fibers that support lots of cells – E.g. marrow, spleen, lymph nodes Human Anatomy, Larry M. Frolich, Ph.D. “Dense” Connective tissues • Irregular – Thick fibers running in many planes – E.g. dermis, fibrous capsules around organs • Regular – – – – Aligned parallel fibers Resists tension E.g. tendon, ligaments, aponeuroses Sometimes with elastic fibers (e.g. ligamentum nuchae) Human Anatomy, Larry M. Frolich, Ph.D. Other Connective Tissues • Bone • Cartilage • Blood Human Anatomy, Larry M. Frolich, Ph.D.