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5.1 Anatomy & Physiology Study Guide.docx - Anatomy &...

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Anatomy & Physiology Study Guide 5.1 Characteristics of Epithelial TissueEpithelium- Also referred to as epithelial tissue, is composed of one or more layers of closely packed cells, and it contains little to no extracellular matrix between these cells. Cellularity- Epithelial tissue is composed almost entirely of tightly packed cells. There is a minimal amount of extracellular matrix between cells. Polarity- An epithelium has an Apical Surface, which is exposed to the external environment or to some internal body space. The apical surface may have either microvilli or cilia. Basal Surface- Where the epithelium is attached to a basement membrane with underlying connective tissue. Basement Membrane- Has three molecular layers that can be viewed using an electron microscope: the lamina lucida, the lamina densa, and the reticular lamina. Avascularity- All epithelial tissues lack blood vessels. Nutrients are obtained either directly across the apical surface or by diffusion across the basal surface from blood vessels within the underlying connective tissue. Extension Innervation- Epithelia are richly innervated to detect changes in the environment at that body or organ region. High Regeneration Capacity- Epithelial cells undergo division frequently. This allows this tissue to regenerate itself at a high rate, a necessary condition for a tissue that is often exposed to the environment and lost by abrasion and damage. Physical Protection- Epithelial tissues protect both external and internal surfaces from dehydration, abrasion, and destruction by physical, chemical, or biological agents. Selective Permeability- An epithelium typically exhibits a range of permeability; it may be relatively non-permeable to some substances, while protecting and assisting the passage of other ions and molecules. Epithelial cells act as “gatekeepers”. Secretions- Some epithelial cells are specialized to produce and release secretions. These cellsform glands. Glands may be individual cells scattered among other cell types in an epithelium. Sensations- Epithelial tissues are innervated by sensory nerve endings to detect or respond to astimulus. The underlying connective tissue- continuously relay sensory input to the central nervous system concerning touch, pressure, temperature, and pain. Simple Epithelium- Is one layer of epithelial cells, and all of the epithelial cells are in direct contact with the basement membrane. Found in areas where stress is minimal and filtrations, absorption, or secretion is the primary function. Stratified Epithelium- Contains two or more layers of epithelial cells. Only the cells in the deepest (basel) layer are in direct contact with the basement membrane. Found in areas with abrasive activities or mechanical stresses, as multiple layers of cells are better able to resist the wear and tear.

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Term
Fall
Professor
Nolan
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