Epithelium tissues

Tissues form all the organs in the body and work together to accomplish a physiological function. Many organs form a system.

 There are 4 types of tissue;

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  • Epithelial
  • Connective
  • Muscle
  • Nervous

There are 2 types of epithelium tissue:

• Membranous epithelium:
  • Found: skin, lining cavities, tubes, ducts and the viscera
  • Role: protection from pathogens, physical injury, toxins and dehydration
  • Always has a free surface exposed to; gases (in lungs), liquids (blood vessels), semi solids (in the gut) and urine (bladder)
  • Cells continually regenerate to replace dead or damaged cells
• Glandular epithelium:
  • Found in the secretion portion of glands (thyroid, adrenal and sweat glands)

Features of epithelial tissue

•  
  • Closely packed cells forming continuous sheets
  • Cells sit on a basement membrane
  • Have an apical (upper) free surface
  • Avascular (without blood vessels) so nutrients diffuse in from underlying connective tissue
  • Good nerve supply
  • Rapid cell division

Naming epithelium

• Number of cell layers:
  • Simple = 1
  • Stratified = more than 1
  • Pseudostratified = single layer that looks like more as the cells all reach the apical surface and nuclei are found at different levels
• Shape of cells
  • Squamous= flat squares
  • Cuboidal = cube like
  • Columnar = tall and thin columns
  • Transitional = shape varies with stretching tissue
• …