Digestive Enzyme - Oral Cavity

Oral Cavity

Complex food substances that are taken by animals and humans must be broken down into simple, soluble, and diffusible substances before they can be absorbed. In the oral cavity, salivary glands secrete an array of enzymes and substances that aid in digestion and also disinfection. They include the following:

Potassium bicarbonate (KHCO3): The major role of bicarbonate is to neutralize acidity mainly in an attempt to preserve the dentin and tooth enamel and also to neutralize bacterial toxins. Bicarbonate also prevents acid damage to the esophageal lining before food enters the stomach.

• lingual lipase: Lipid digestion initiates in the mouth. Lingual lipase starts the digestion of the lipids/fats.
• amylase: Carbohydrate digestion also initiates in the mouth. Amylase produced by the salivary glands breaks complex carbohydrates to smaller chains, or even simple sugars. It is sometimes referred to as ptyalin.
• Mucin: Mucin functions to make food more pliable and also covers it facilitating its transfer in the esophagus to the stomach, by lubricating the content.
• lysozyme: Considering that food contains more than just the essential nutrients and bacteria or viruses, the lysozome offers a limited and non-specific, yet beneficial antiseptic function in digestion.
• IgA: This is a dimeric form of antibodies produced by the body. Gastrointestinal tract produces only IgA mainly to battle bacterial toxins, and also to tag certain recognizable molecular patterns in viruses and bacteria. IgA-coated pathogens are digested by white cells lining the gastrointestinal tract.
• Haptocorrin (also known as R-factor): Helps with the absorption of Vitamin B12. After Vitamin B12 igs released from its original carrier protein in the stomach, it gets bound to Haptocorrin. Haptocorrin protects it from acidic conditions of the stomach but is cleaved in the duodenum by pancreatic proteases. Vitamin B12 can then bind to intrinsic factor (IF) that has been produced by parietal cells. Finally, the IF-Vitamin B12 complex is taken up by in ileum via the cubam receptor.

Of note is the diversity of the salivary glands. There are two types of salivary glands:

• serous glands: These glands produce a secretion rich in water, electrolytes, and enzymes. A great example of a serous oral gland is the parotid gland.
• Mixed glands: These glands have both serous cells and mucous cells, and include sublingual and submandibular glands. Their secretion is mucinous and high in viscosity.

In addition, all salivary secretions are hypotonic with respect to the plasma concentration. This is because the duct cells of salivary cells are impermeable to water, yet there is a continuous abstraction of electrolytes such as sodium (Na) and potassium (K) from the initially secreted juice, causing it to be very dilute (hypotonic) by the time it is released into the mo