Final answer:
Mechanical digestion begins in the mouth, where food is chewed and mixed with saliva. The stomach continues mechanical digestion, but the majority of fat digestion takes place in the small intestine. The large intestine moves semi-solid waste but does not play a significant role in digestion.
Step-by-step explanation:
Mechanical Digestion in the GI Tract
Mechanical digestion begins in the mouth, where food is physically broken down by the action of chewing. The mouth houses several structures specialized for digestion, including the salivary glands, tongue, and teeth. This process of breaking down food through physical means, such as chewing, is essential in preparing the food to be further digested chemically as it moves through the digestive system. The mouth, through mastication and saliva, starts the process of breaking down carbohydrates and fats.
While the esophagus is involved in moving food from the mouth to the stomach by peristalsis, it does not play a direct role in mechanical digestion.
In the stomach, mechanical digestion continues with the vigorous churning of food, but it's important to remember that it begins in the mouth.
Regarding the digestion of fats, the small intestine, with the aid of bile and lipase, is where the majority of fat digestion occurs.
As for the large intestine, while it is not a site for significant digestion, semi-solid waste is indeed moved by wave-like muscle contractions.