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Chapter 3

Anatomy Chapter 3.docx

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Department
Psychology
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Psychology 2720A/B
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Prof

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Chapter 3 – Tissues  Tissue – group of cells that have a common origin and function to carry out an activity  Tissues may be hard, semisolid or liquid Types of Tissues  Four basic types of tissues: o Epithelial – covers body surfaces and lines hollow organs, body cavities, and ducts; forms glands; allows body to interact with both the external and internal environments o Connective tissues – protects and supports the body; stores energy reserves as fat and provides immunity for the body o Muscular tissue – for contraction and generation of force, generates heat that warms the body o Nervous tissue – detects changes in the body and sends action potentials Cell Junctions  Cell junctions – contact points between the plasma membranes of tissue cells  5 types of junctions (pg. 64 Figure 3.2) o Tight junctions  Transmembrane proteins fuse together the outer surfaces of adjacent plasma membranes  Create fluid-tight seals o Adherens junctions  Plaque (dense layer of protein) attaches to membrane proteins and to microfilaments of the cytoskeleton  Cadherins insert into the plaque from the opposite side of the plasma membrane, partially crosses the intercellular space and connects to a cadherin of an adjacent cell  Anchor cells to one another o Desmosomes  Contain plaque, have transmembrane glycoproteins that extend into the intercellular space between adjacent cell membranes and attach cells to one another  Plaque doesn’t attach to microfilaments, it attaches to elements of the cytoskeleton called intermediate filaments  Intermediate filaments extend from desmosomes on one side of the cell across the cytosol to desmosomes on the opposite side of the cell  Structural arrangement helps the stability of the cell  Prevent epidermal cells from separating under tension and cardiac muscles from pulling apart during contraction  Anchor cells to one another o Hemidesmosomes  Don’t link adjacent cells  Transmembrane glycoproteins are integrins (rather than cadherins)  Integrins attachs to intermediate filaments on the inside of the plasma membrane  On the outside of the plasma membrane, integrins attach to protein laminin (in the basement membrane)  Hemidesmosomes anchor cells to the basement membrane, not to each other o Gap junctions  Membrane protein connexins form fluid-filled tunnels that connect neighbouring cells  Plasma membranes are separated by a narrow intercellular space  Small molecules can diffuse through the passage, but the movement of larger molecules is prevented  Transfer of nutrients and wastes occur in gap junctions  Allow nerve or muscle impulses to spread among tissues Epithelial Tissue  Consists mostly of cells with little extracellular material between adjacent plasma membranes  Has three major functions: o Serve as selective barriers to limit or aid the transfer of substances into and out of the body o Release products produced by the cells onto their free surfaces o Protect against the abrasive influences of the environment  The apical, lateral, and basal surfaces of epithelial cells are modified in various ways to carry out specific functions  Epithelium is arranged in sheets and attached to the basement membrane  Basement membrane has two layers, the basal lamina and the reticular lamina  Avascular (no direct blood supply), but has nerve supply  Epithelia have high capacity for renewal  Layers of cells can be simple (one layer, secretion and absorption), pseudostratified (appears to have several layers but actually only has one), or stratified (several layers)  The cells can have different shapes: squamous (flat while bumps; rigid), cuboidal (square, secretion and absorption), columnar (tall rectangles, secretion or absorption), or transitional (variable)  There are two subtypes of epithelia: lining (covering) and glandular (secreting portion of glands)  Simple squamous epithelium = single layer of cells and flat shape o Found in parts of the body where filtration or diffusion are priority processes o Endothelium lines the heart and blood vessels o Mesothelium forms the serous membranes that line the thoracic and abdominopelvic cavities  Simple cuboidal epithelium = single layer of cube-shaped cells o Function in secretion and absorption o Covers the ovaries, in the kidneys and eyes, lines some glandular ducts  Nonciliated simple columnar epithelium = single layer of nonciliated rectangular cells o Lines most of the gastrointestinal tract o Contains specialized cells that perform absorption and secrete mucus o No goblet cells  Ciliated simple colu
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