Where does digestion begin in the digestive system?
A.
Stomach
B.
Esophagus
C.
Small intestine
D.
Oral cavity
The correct answer and Explanation is :
The correct answer is D. Oral cavity.
Explanation:
Digestion is the process by which food is broken down into smaller components that the body can absorb and use. This complex process starts in the oral cavity (mouth), where both mechanical and chemical digestion occur.
- Mechanical Digestion:
- The first step in digestion is the physical breakdown of food, which happens in the mouth through mastication (chewing). The teeth cut, grind, and crush food into smaller pieces, increasing its surface area, making it easier for digestive enzymes to act on.
- The tongue helps mix the food with saliva and pushes it to the back of the mouth for swallowing.
- Chemical Digestion:
- Along with chewing, the salivary glands secrete saliva, which contains water, mucus, and digestive enzymes, primarily amylase and lipase.
- Salivary amylase begins the breakdown of carbohydrates (starches) into simpler sugars (maltose).
- Lingual lipase starts the digestion of fats, although it is more active later in the digestive process.
- The saliva also moistens the food, forming a bolus, which is a soft mass that can be easily swallowed and transported down the esophagus.
- Swallowing:
- After chewing, the tongue pushes the bolus toward the back of the mouth and into the pharynx (throat). The swallowing reflex is initiated, which directs the bolus into the esophagus.
- The food then travels down the esophagus through a wave-like motion called peristalsis, moving toward the stomach for further digestion.
Thus, the oral cavity plays a crucial role in preparing food for the digestive processes that occur later in the stomach and small intestine. Without the mechanical and chemical digestion in the mouth, the efficiency of digestion further along the tract would be reduced.