Saliva plays several important roles in the digestion of foodDigestion of food is the process by which the body breaks down food into smaller components that can be absorbed into the bloodstream and used by the body. It involves both mechanical actions, like chewing, and chemical processes, using enzymes to break down complex molecules like proteins, fats, and carbohydrates., starting from the moment food enters the mouth. Its functions include:
Moistening and Lubrication
Saliva moistens food, which helps in the formation of a soft, easily swallowable bolus. This lubrication is essential for comfortable swallowing and preventing damage to the esophagusThe esophagus is a muscular tube that connects the throat (pharynx) to the stomach. It’s about 8 inches long in adults and functions as a conduit for food and liquids that have been swallowed. The esophagus uses rhythmic muscle contractions, known as peristalsis, to propel food to the stomach..
Initiation of Starch Digestion:
Saliva contains an enzyme called salivary amylase (also known as ptyalin), which begins the chemical digestion of starches (complex carbohydrates) into simpler sugars like maltose and dextrin. This enzymatic process starts in the mouth and continues until the food reaches the acidic environment of the stomach, where salivary amylase is inactivated.
Taste and Food Selection
Saliva dissolves certain food particles, which is essential for the sensation of taste. Taste receptors on the tongue can only detect flavors when substances are dissolved in saliva.
This also plays a role in food selection, as taste helps identify foods that are palatable and safe to eat.
Oral Hygiene and Protection
Saliva helps in maintaining oral hygiene. It has antibacterial properties and can neutralize acids produced by bacteria in the mouth, thus protecting teeth from decay.
It also washes away food particles and debris from the teeth and gums, reducing the risk of tooth decay and gum disease.
Saliva acts as a buffer, helping to neutralize the acidic or basic nature of foods. This is important for protecting the mouth and esophagus from extreme pH levels.
pH levels: pH levels measure the acidity or alkalinity of a substance on a scale from 0 to 14. This scale is logarithmic, meaning each whole number change represents a tenfold increase or decrease in acidity. A pH of 7 is considered neutral, like pure water. Values below 7 indicate acidity, with lower numbers being more acidic, while values above 7 indicate alkalinity, with higher numbers being more alkaline. The pH level is crucial in many contexts, from chemistry to environmental science, and in our bodies, where a stable pH is vital for proper physiological function. For instance, human blood typically maintains a slightly alkaline pH around 7.4.
Speech, Chewing and Enzymatic Activity
Speech and Chewing:
Saliva facilitates speech by lubricating the mouth, allowing for the smooth movement of the tongue and lips.
It also aids in chewing, making the process of grinding food easier and more efficient.
Besides salivary amylase, saliva also contains other enzymes, such as lingual lipase, which begins the digestion of fats, although its role in fat digestion is more significant in some animals than in humans.
Saliva contains compounds that can aid in the healing of minor oral wounds and sores.
Overall, saliva is essential for the initial stages of digestion, oral health, and the overall eating experience. Its production is typically a reflex response to the sight, smell, or thought of food, as well as the presence of food in the mouth.