Digestion in Mouth

Submitted by Manjula on Sat, 11/19/2011
Digestion in Mouth

Mouth constitutes of teeth, tongue, and lips, which all together perform physical digestion by masticating food, and begins the digestion process.

Oral cavity (Mouth – teeth, tongue & lips)

Human mouth constitutes of teeth, tongue, and lips, which are all together helping in masticating the food.

The hardest part of the body, the teeth chew (or mastication) the food; tear, cut, and grind food and helps ease swallowing.

Teeth - There are four types of teeth, they are Incisor, Canines, Premolars & Molars.

  • Incisors are the chisel-shaped teeth in the front of the mouth, there are four incisors in each jaw totally 8, used for biting or cutting.
  • Canines located on either side of the incisors, two canines in each jaw totally 4, used for stabbing and tearing.
  • Premolars located behind the canines, there are four premolars in each jaw totally 8, used for grinding and chewing.
  • Molars located behind the premolars, there are 12 molars as three sets in each jaw called the first, second, and third molars.

Tongue’s upper surface contains tiny bumps called papillae, with tiny pores, which are the taste buds. There are four types of taste buds to sense sweet, salty, sour, and bitter tastes. The tongue is a vital organ for chewing & swallowing foods and for speech. The tongue has many nerves to sense taste and signaling to the brain.

Saliva is secreting in large quantities, about 1 to 1.5 liters/day by the salivary glands in the oral cavity, and is mixing by the tongue with the chewed food. Saliva is of two types; they are thinner one (watery nature) is to wet the food and thicker one (mucous nature) is for lubricating and to stick foods together to form a bolus.

Salivary gland of human consists of three glands:

  • Parotid glands - largest salivary gland secretes saliva of thin and watery in nature like serum.
  • Submandibular glands - pair of glands underneath lower jaws, secretes saliva of thin as well as thick mucus. This gland secretes 70 % of all the saliva.
  • Sublingual glands - pair of glands underneath tongue, secret’s saliva of mucus nature. This gland secretes 5 % of all the saliva.

Saliva secreted by the salivary glands contains digestive enzymes – salivary amylase, which breakdown polysaccharides (Starch) into disaccharides (Maltose). Saliva contains another enzyme, lingual lipase breakdown fat into di & mono glycerides.

Soft palate (also called as velum or muscular palate) is the soft tissue located at the back of the mouth roof, play important roles in swallowing and breathing. It helps to close the nasal passages during the swallowing of food. When sneezing, it protects the nasal passage by diverting the excreted substance to the mouth.

Pharynx is located immediately after mouth & nasal cavity, and before the esophagus. The pharynx is associated with digestion system, respiratory system, and vocalization. It is a thick fibrous muscle helps to push food to the esophagus. In addition, it prevents air from the nose to swallow or prevent food to enter respiratory system by closing the nasal path during swallowing.

Epiglottis is the flap at the back of the tongue that keeps the chewed food from going down the windpipe to the lungs. When you swallow, the epiglottis automatically closes. When you breathe, the epiglottis opens so that air can go in and out of the windpipe.

The epiglottis is the flap of cartilage lying behind the tongue and in front of the entrance to the larynx (voice box). At rest, the epiglottis is upright and allows air to pass through the larynx and into the rest of the respiratory system. During swallowing, it folds back to cover the entrance to the larynx, preventing food and drink from entering the windpipe. The throat contains both an air passage (the windpipe) and a food passage (the esophagus). If these passages were both open when a person swallowed, air could enter the stomach, and food could enter the lungs. Part of the safety hatch that seals off the windpipe is the "epiglottis," a little valve like cartilage, which works with the larynx to act as a lid every time we swallow. The larynx draws upward and forward to close the windpipe. This keeps solid food and liquid out of the respiratory tract. At the end of each swallow, the epiglottis moves up again; the larynx returns to rest, and the flow of air into the windpipe continues. The uvula (Latin for "little grape") is a fleshy piece of muscle, tissue and mucous membrane that hangs down from the palate. The part moves upward when we say, "Ah!" It flips up and helps close off the nasal passages when we swallow. Contrary to the depictions seen in cartoons, the uvula does not vibrate during singing and shouting and, in fact, has nothing to do with the voice.

Oral cavity (Mouth) – Digestion Process

The digestion process begins by the secretion of saliva even before the food reaches the mouth when stimulated by thought-of-food or smell-of-food or feel-hungry. Human digestion begins in the mouth where food is chewed and masticated.

When food is dropping in the mouth, the tongue helps to move it around and the saliva coats, stick-together and lubricates the food for easier chewing and swallowing.

Saliva contains the amylase enzymes that help to break down chemically of carbohydrates in the food. Teeth help physical breakdown of the food into smaller pieces by tearing and chewing it that aids further digestion.

The jaw and tongue movement assist chewing and swallowing of the food. The food then pushes down into the esophagus for further digestion.