What does the mouth and stomach do in mechanical digestion?

Mouth:

The mouth plays a crucial role in the mechanical digestion of food. Here's what happens in the mouth during mechanical digestion:

- Mastication (Chewing): The primary function of the mouth in mechanical digestion is chewing. Teeth, which come in various shapes and sizes, help grind and break down solid food into smaller pieces. Mastication increases the surface area of the food, making it easier for digestive enzymes to work on it.

- Saliva and Mixing: The mouth also produces saliva, which contains digestive enzymes like salivary amylase and lingual lipase. Salivary amylase begins the chemical digestion of carbohydrates by breaking down starches into simpler sugars. Lingual lipase, found in the tongue, helps in the initial breakdown of dietary fats. Saliva also moistens and lubricates food, making it easier to swallow.

Stomach:

After chewing and mixing with saliva, food moves down the esophagus into the stomach, which continues the process of mechanical digestion. Here's what happens in the stomach:

- Muscular Contractions (Peristalsis): The stomach's muscular walls contract rhythmically in a process called peristalsis. These contractions help mix the food with gastric juices and break down larger food particles into smaller ones.

- Stomach Acid: The stomach secretes hydrochloric acid (HCl) as a part of gastric juices. This acidic environment helps kill harmful microorganisms and creates an optimal pH for the activity of digestive enzymes.

- Mechanical Grinding: The stomach has thick muscular walls that churn the food, creating friction and further breaking it down into a semi-liquid substance known as chyme. This mechanical grinding action helps reduce food particles to sizes suitable for further digestion in the small intestine.

Overall, the mouth and stomach play crucial roles in mechanical digestion. Chewing in the mouth increases surface area and initiates chemical digestion, while the muscular contractions and acidic environment of the stomach further break down food particles into a form that can be efficiently processed in subsequent stages of digestion.