BIOL&251Ch4NotesSpr11

BIOL&251Ch4NotesSpr11 - Ch. 4 Tissues = groups of...

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1 Ch. 4 – Tissues • = groups of specialized cells (and cell products) that perform specific functions Histology = the study of tissues • 4 basic tissue types : – 1. Epithelial tissue – 2. Connective tissue – 3. Muscle (muscular) tissue – 4. Neural (nervous) tissue • Since we’ve done a lot with tissues in lab already, information on slides marked “FYI” is NOT fair game for Lecture Exam 2 – The parts of Ch. 4 that further discuss info on the “FYI” slides are also not fair game for Lecture Exam 2…there will be a complete list of specifically excluded portions of Ch. 4 on the next Lecture Exam Prep Guide Fig. 4-1, p. 113 Characteristics of epithelia Epithelia : – Are mostly made up of cells that are closely packed together –H a v e polarity – i.e., there are structural differences between the exposed (free or apical) and basal surfaces – Sit on a basal lamina (basement membrane) – Are avascular – Rapidly regenerate from stem (germinative) cells , which have a high mitotic rate Locations : – Covering body surfaces – Lining hollow body cavities – Glands Functions : – Physical protection – Permeability control/barrier – Sensation – Specialized secretion (via glands)
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2 Fig. 4-2, p. 115 Epithelial intercellular connections • Are via integral proteins, some of which are called cell adhesion molecules (CAMs) – And are sometimes also via intercellular cement = proteoglycans • Specialized cell junctions : Occluding (tight) junctions – seal and prevent the leakage of fluids between cells Gap junctions = connexon channels for ion communication and coordination of activity Spot desmosomes = strong attachments to resist mechanical stress Fig. 4-2ae, p. 115 Attaching epithelium to underlying tissue Hemidesmosomes attach epithelial cells to the basal lamina – The basal lamina has 2 layers : •1 . Clear layer (lamina lucida) –is next to and made by the epithelium – It restricts the entry of large molecules into the epithelium from the underlying CT •2 . Dense layer ( l amina densa) next to and made by the underlying CT – It’s a strong, anchoring attachment point for hemidesmosomes – It filters/determines what substances can diffuse from other adjacent tissues into the epithelium
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3 Classification of epithelia
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BIOL&251Ch4NotesSpr11 - Ch. 4 Tissues = groups of...

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