Epithelial

• Covers and protects internal and external surfaces of the body (every 4 days your whole intestinal lining will be replaced with new epithelial cells) and can be subdivided based on the shape and function of the cells
• Cuboidal epithelium aids absorption and mechanical support (e.g. forms the lining of kidney tubules) and columnar epithelium acts as an impermeable barrier to any possibly ingested bacteria but is permeable to any necessary ions
• Simple squamous epithelium lines the alveoli and allows transport of small molecules over the membrane and stratified squamous epithelium protects areas subject to abrasion (found in the skin), it is multi-layered