First we should define these terms. A "chemical" aspect of the digestive system is one that employs molecules, typically ones secreted by the body, in order to break down and absorb food. "Mechanical" aspects are those which use macroscopic force or muscle action to break down the food. Typically, these terms refer specifically to the process of nutrient absorption, and exclude the excretion of waste. Additionally, mechanical digestion typically refers to digestion of food on...
First we should define these terms. A "chemical" aspect of the digestive system is one that employs molecules, typically ones secreted by the body, in order to break down and absorb food. "Mechanical" aspects are those which use macroscopic force or muscle action to break down the food. Typically, these terms refer specifically to the process of nutrient absorption, and exclude the excretion of waste. Additionally, mechanical digestion typically refers to digestion of food on a macroscopic scale, while chemical digestion is microscopic.
The three primary mechanical-digestion organs are the teeth, tongue and stomach. The teeth are the only ones which can be considered entirely mechanical, because they secrete no chemicals and do not aid in digestion beyond physically smashing the food into smaller pieces.
The tongue and stomach are also considered chemical digesters because they excrete chemicals; saliva is an enzyme that helps break down starch, and the stomach secretes hydrochloric acid which chemically tears apart the food as well as destroying contaminants.
The liver, gall bladder and pancreas are the other primarily chemical digestion organs, as they secrete a variety of chemicals that aid in the breakdown of food, particularly bile, which aids in digesting fats.
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