Mucosa is a wet, pink tissue that covers the tongue. The rough texture of the tongue is caused by tiny bumps called papillae. Thousands of taste buds cover the papillae's surfaces. When you eat or drink something sour (such as lemon juice), your mouth reacts to these acids by producing more acid itself. This self-correcting mechanism is what gives sour foods their characteristic flavor. The tongue is also where we speak language. It has two main parts: the tip (known as the tongue tip) and the back (known as the tongue base). The muscles that control the movement of the tongue are also responsible for some of our expressions. For example, the muscle at the top of the tongue helps pronounce words like "pen" and "ate". The muscle at the back of the tongue helps make sounds like "s", "f", and "sh". The surface of the tongue is covered with microscopic folds called fricatives that help break down food as it passes through from the mouth to the stomach. The tongue is also home to hundreds of bacteria that play an important role in our digestion. Some of these bacteria feed on the sugars in our food while others produce enzymes that aid in the breakdown of carbohydrates, proteins, and fats. The tongue is very sensitive and can be used to tell us about our body's health.