[quote author=diamond link=topic=24419.msg280951#msg280951 date=1268172695]
When I went to college I took a zoology course where the professor stressed one particular item of biological anatomy. He said if we didn't get anything else out of the course to remember that the inside of the alimentary track (of which the colon is part) is made up of epithelial cells the same as comprise the skin on the "outside" of our bodies. Ego, what's good for the outside must then be OK for the inside. That, plus all the other reasons already mentioned is why I use soap (ivory) in my enemas. I just leave a bar in my bag (open top) add some water, shake vigorously and then fill to the top. Very soapy, very big, and very very warm. Ah, what bliss. Just had three and feel wonderful.
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Your professor was wrong wrong wrong and greatly oversimplified the truth.
The outside and inside of the body are both comprised of epithelial cells, BUT did he tell you that there are at least seven, and up to a dozen distinct types, depending on how you classify epithelial cells.
Simple squamous epithelium, simple cuboidal epi, simple columnar epi, transitional epi, stratified cuboidal epi, pseudostratified epi, ciliated columnar, ciliated pseudostratified and stratified squamous epi. Glandular tissue is an eighth type of epithelium. Stratified epi can be further divided into keratinized and non-keratinized.
The "outside" of the body (skin) is almost all keratinized stratified squamous epi. There are some parts which are further specialized, like the cornea and tympanic membrane are further specialized.
The "inside" of the body, and there who could correctly argue that the entire alimentary tract is OUTSIDE the body, the epithelial types are non-keratinized and mostly simple squamous, simple cuboidal, simple columnar (the stomach, small and large intestines). The mouth has several different types of epithelium.
Without giving a years worth of histology lectures, the "inside" IS NOT AT ALL like the outside, and what is alright for the skin on the outside is not necessarily good for the inside of the colon.