KAAP220 Lecture Notes - Lecture 8: Thyroid, Adrenal Gland, Extracellular Fluid
23 Oct 2018
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Document Summary
Levels of organization up to the tissue level. Relies on diffusion of substances from the connective tissue below. Often contain secretory or gland cells scattered among other cell types. Secrete onto external surfaces or into ducts. Protect surfaces from abrasion, dehydration, or destruction by chemical or biological agents. Most epithelia are capable of selective absorption or secretion. Epithelial barrier can be modified in response to stimuli. Ex. calluses - repeated depression or abrasion will cause epithelium to thicken. Specialized epithelial cells detect changes in environment (ex. Sensory epithelium found in special sense organs. Faces exterior of body or internal space. Includes base and sides (lateral surfaces) attached to neighboring cells. If lining a tube, apical surface is exposed to space inside the tube, called lumen. Microvilli found on the surface in digestive, urinary, and reproductive tracts (absorption) Cilia found on this surface in parts of the respiratory and reproductive tracts (motility)
