Histology Notes

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HISTOLOGY: EPITHELIAL TISSUE
oHuman body composed of 4 basic types of tissue: epithelial, connective, nervous and muscular oFormed by cells and molecules of the extracellular matrix
oConnective tissue: characterized by the abundance of extracellular fluid oOrgans can be divided by parenchyma (composed of cells for main function of organ) and stroma ( supporting tissue) oExcept in brain and spinal cord stroma made of connective tissue oEpithelial tissue: covering, lining protecting surfaces ex: skin, absorption (intestines), secretion (epithelial cells of glands), contractility (myoepithelial cells) oCharacteristic features of epithelial cells:

oForms and dimensions range from high columnar to cuboidal to low squamous oEpithelial cells have distinctu nuclei from spherical to elongated or elliptic oMost epithelial lay on connective tissue

oIn epithelia that line cavity of internal organs, layer of connective tissue called lamina propina. Lamina propina serves to support epithelial tissue and provide nutrition oConnective tissues has small evaginations called papillae. Occur most frequently in epithelial tissues subject to friction ex: covering of skin/tongue oPolarity in epithelial cells

Region of cell facing connective tissue: basal pole
Region facing open space: apical side
Regions on the side called: lateral sides
oBasal laminae and basement membrane:
oBasal lamina: sheet of extracellular material on basal surface of cells (where it comes into contact with connective tissue) oConsists of dense layer or lamina dense
oBasal lamina may have electron lucent layers or lamina lucida owhere epithelia are w/o connective tissue basal lamina is thicker due to fusion of basal laminae from each epithelial layer ocomponents of basal lamina:

laminin: large glycoproteins. Form lace like sheet below basal cells where they are held in place by transmembrane integrins type IV collagen: form felt like sheet associated with laminin...
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