Mouth and Teeth
A smile is the facial expression that most engages others. With the help of the teeth — which provide structural support for the face muscles — the mouth also forms a frown and other expressions that show on your face.
The mouth also plays a key role in the digestive system, but it does much more than get digestion started. The mouth — especially the teeth, lips, and tongue — is essential for speech. The tongue, which allows us to taste, also helps form words when we speak. The lips that line the outside of the mouth both help hold food in while we chew and pronounce words when we talk.
With the lips and tongue, teeth help form words by controlling air flow out of the mouth. The tongue strikes the teeth as certain sounds are made.
The hardest substances in the body, the teeth are also necessary for chewing (or mastication) — the process by which we tear, cut, and grind food in preparation for swallowing. Chewing allows enzymes and lubricants released in the mouth to further digest food.
Here's how each aspect of the mouth and teeth plays an important role in our daily lives.
Basic Anatomy of the Mouth and Teeth
The entrance to the digestive tract, the mouth is lined with mucous membranes. The membrane-covered roof of the mouth is called the palate. The front part consists of a bony portion called the hard palate, with a fleshy rear part called the soft palate. The hard palate divides the mouth and the nasal passages above. The soft palate forms a curtain between the mouth and the throat, or pharynx, to the rear. The soft palate contains the uvula, the dangling flesh at the back of the mouth. The tonsils are located on either side of the uvula and look like twin pillars holding up the opening to the pharynx.
A bundle of muscles extends from the floor of the mouth to form the tongue. The upper surface of the tongue is covered with tiny bumps called papillae. These contain tiny pores that are our taste buds. Four main kinds of taste buds are found on the tongue — those that sense sweet, salty, sour, and bitter tastes. Three pairs of salivary glands secrete saliva, which contains a digestive enzyme called amylase that starts the breakdown of carbohydrates even before food enters the stomach.
The lips are covered with skin on the outside and with slippery mucous membranes on the inside of the mouth. The major lip muscle, called the orbicularis oris, allows for the lips' mobility. The reddish tint of the lips comes from underlying blood vessels. The inside portion of both lips is connected to the gums.
There are several types of teeth. Incisors are the squarish, sharp-edged teeth in the front of the mouth. There are four on the bottom and four on the top. On either side of the incisors are the sharp canines. The upper canines are sometimes called eyeteeth or cuspids. Behind the canines are the premolars, or bicuspids. There are two sets, or four premolars, in each jaw.
The molars, situated behind the premolars, have points and grooves. There are 12 molars — three sets in each jaw called the first, second, and third molars. The third molars are the wisdom teeth, thought by some to have evolved thousands of years ago when human diets consisted of mostly raw foods that required extra chewing power. But because they can crowd out the other teeth or cause problems like pain or infection, a dentist might need to remove them.
Human teeth are made up of four different types of tissue: pulp, dentin, enamel, and cementum. The pulp is the innermost portion of the tooth and consists of connective tissue, nerves, and blood vessels, which nourish the tooth. The pulp has two parts — the pulp chamber, which lies in the crown, and the root canal, which is in the root of the tooth. Blood vessels and nerves enter the root through a small hole in its tip and extend through the canal into the pulp chamber.
Dentin surrounds the pulp. A hard yellow substance, it makes up most of the tooth and is as hard as bone. It's the dentin that gives teeth their yellowish tint.
Enamel, the hardest tissue in the body, covers the dentin and forms the outermost layer of the crown. It enables the tooth to withstand the pressure of chewing and protects it from harmful bacteria and changes in temperature from hot and cold foods. Both the dentin and pulp extend into the root.
A layer of cementum covers the outside of the root, under the gum line, and holds the tooth in place within the jawbone. Cementum is also as hard as bone.
Note: All information is for educational purposes only. For specific medical advice, diagnoses, and treatment, consult your doctor.
© 1995-2009 The Nemours Foundation. All rights reserved.
Add your own comment
Today on Education.com
- Kindergarten Sight Words List
- The Five Warning Signs of Asperger's Syndrome
- What Makes a School Effective?
- Child Development Theories
- Why is Play Important? Social and Emotional Development, Physical Development, Creative Development
- 10 Fun Activities for Children with Autism
- Test Problems: Seven Reasons Why Standardized Tests Are Not Working
- Bullying in Schools
- A Teacher's Guide to Differentiating Instruction
- Steps in the IEP Process