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Week/Lecture 2: Histology.pdf

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BIOL 171

Primary Tissues: Epithelial tissue (covering:skin; lining:stomach lining; secreting: sweat) Connective tissue (binds tissue together; fills in space; "glue") Muscle tissue (shortens to produce movement) Nerve tissue (conducts impulses, action potentials) Mitosis: *occurs most quickly in epithelial in connective tissue, mitosis rate varies nervous and muscle tissues rarely undergo mitosis Epithelial Tissue Functions: protects underlying structures (from bacteria, injury) synthesizes substances secretes substances (like sweat) absorbs substances (small intestines) Characteristics: cells tightly packed together to prevent bacteria from invading, and to keep substances in, like blood 2 sides to the cell: apical (unattached, free-floating) surface; basal surface attached to basement membrane to prevent moving away. not vascularized: no blood vessels Classification: 3 Shapes squamous (flat with little bulge for nucleus) cuboidal (cubical) columnar (columns) Cilia ciliated (with cilia on apical surface) non-ciliated (no cilia on apical surface) Layers simple (1 layer of cells; all attached to basement membrane) stratified (2-20 layers of cells; only deepest layer attached to basement membrane) pseudostratified (looks stratified--long/tall cells, but all attached to basement membrane; not all reach apical surface) *Pseudostratified Ciliated Columnar Epithelium location? Transitional Epithelium apical cells change shape (cuboidal to squamous) lines organs that stretch (bladder) Functional Classification: Covering covers external surfaces (epidermis, conjunctiva) Lining lines internal cavities (mucous membrane, blood vessel endothelium) Glandular composes parenchyma [functional component] of glands secretes compounds Gland: secreting structure composed of one or more cells classified as endocrine or exocrine Endocrine Glands: secrete hormones directly to blood or body fluid generally simple and cuboidal examples: thyroid gland secretes thyroxin pancreas secretes insulin ovaries secrete estrogens testes secrete testosterone Exocrine Glands: secrete to external surfaces (sweat gland, lacrimal gland), into a cavity that leads to external surface (salivary gland, mucous gland), by a duct (transports secretion to external surface) Connective Tissue cells separated by matrix (fibers, ground substance) large variety of cells (fibroblasts--most common, secrete fibres) Ground substance: hyaluronoic acid (binds cells together, facilitates phagocyte movement) chondroitin sulfate, dermatan sulfate, ketatan sulfate (all supporting molecules, trap water) fibronectin (links components of ground substance together) Fibers Collagen fibers: produced by fibroblasts composed of collagen protein strong, resistant to pulling forces give strength to bone, tendons, skin, blood vessels Elastic fibers: stretch 150% composed of elastin component of elastic structures such as the aorta, large arteries, lungs Reticular fibers: composed of collagen protein but thinner than collagen fibres form supporting framework (stroma) of organs Functions of connect
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