The mouth is the start of the gastrointestinal tract. It is the site of both mechanical and chemical digestion via chewing, and saliva, respectively. Saliva contains the enzyme amylase that breaks down carbohydrates.

Saliva contains the enzyme alpha amylase. This enzyme is responsible for breaking down starch and carbohydrates into smaller polysaccharide chains.

Later, in the small intestine, pancreatic beta amylase further digests the carbohydrates until they can be absorbed into the blood. Most chemical digestion occurs in the small intestine, where enzymes to digest proteins, lipids, and carbohydrates are introduced to the digestive tract.

The correct answer is mouth. While each answer choice has a part in the digestion process, carbohydrate digestion begins in the mouth, which provides enzymes required for starch (amylase) and sugar (lactase, maltase, sucrase) digestion.

Carbohydrate digestion (starches and sugars) begins in the mouth with the enzyme salivary amylase. Amylase, which is also found in the small intestine, is responsible for breaking apart starches. Sugars are also digested (broken down) by three major enzymes located in the mouth and small intestine (lactase, maltase, sucrase). The carbohydrates are broken down along the gastrointestinal tract (mouth, pharynx, esophagus, stomach) and are absorbed while moving through the small intestine.

"Deglutition" is the scientific term for swallowing. In contrast, the scientific term for chewing is "mastication." The scientific term for urination is "micturition." Lastly, "voiding" is also another word for urination.

Proteins need pepsin in order to begin digestion, and that enzyme is only produced in the stomach — not the mouth.

Styloglossus: elevates and retracts tongue

Hyoglossus: depresses and retracts the tongue

Palatoglossus: elevates the tongue

Vertical muscles: this is an intrinsic muscle of the tongue