20. Where does digestion begin in the digestive system?
Answer: B
Digestion begins in the oral cavity.
The process of digestion starts in the oral cavity, where food is mechanically broken down by chewing and mixed with saliva, which contains enzymes that initiate the chemical breakdown of carbohydrates.
A) Small intestine
The small intestine is primarily responsible for the absorption of nutrients after digestion has occurred. While digestion continues here, it is not the starting point of the digestive process.
B) Oral cavity
The oral cavity is the correct answer because it is where food enters the digestive system, and the process of breaking down food begins with mechanical and enzymatic actions.
C) Esophagus
The esophagus serves merely as a conduit for food to pass from the mouth to the stomach. It does not play a role in the digestion process itself, making it an incorrect choice.
D) Sternum
The sternum is a bone structure in the chest and has no function in the digestive system. It does not participate in digestion, which eliminates it as a possible answer.
Conclusion
The oral cavity is definitively the starting point of digestion due to its role in both mechanical breakdown and enzymatic action on food. Other options fail because they either occur after the initial stages of digestion or do not contribute to the digestive process at all.