teeth Flashcards
how do we chew
We masticate, or chew, by opening and closing our jaws and moving them from side to side while continuously using our tongue and cheek muscles to keep the food between our teeth. In the process, the teeth tear and grind the food, breaking it down into smaller fragments.
By 21 what two teeth have been formed
. The first set are deciduous (de-sid′u-us) teeth, also called baby teeth or milk teeth. As the second set of teeth, the deeper permanent teeth
The first set are deciduous (de-sid′u-us) teeth, also called baby teeth or milk teeth.
The deciduous teeth begin to erupt around 6 months; the first teeth to appear are the lower central incisors. A baby has a full set (20 teeth) by the age of 2 years.
the seccond set of teeth permanent teeth,
, the deeper permanent teeth, enlarge and develop, the roots of the milk teeth are reabsorbed, and between the ages of 6 and 12 years they loosen and fall out. All of the permanent teeth but the third molars have erupted by the end of adolescence. The third molars, also called wisdom teeth, emerge between the ages of 17 and 25. Although there are 32 permanent teeth in a full set, the wisdom teeth often fail to erupt; sometimes they are completely absent.
what happens if the teeth remain embeded in jawbone
When teeth remain embedded in the jawbone, they are said to be impacted. Impacted teeth can exert pressure and cause a good deal of pain, so they usually must be removed surgically. Wisdom teeth are the most commonly impacted.
teeth classification
We classify the teeth according to shape and function as incisors, canines, premolars, and molars (see Figure 14.9). The chisel-shaped incisors are adapted for cutting; the fanglike canines (eyeteeth) are for tearing or piercing. The premolars (bicuspids) and molars have broad crowns with rounded cusps (tips) and are best suited for crushing and grinding.
A tooth consists of two major regions, the crown and the root
A tooth consists of two major regions, the crown and the root (Figure 14.10). The enamel-covered crown is the exposed part of the tooth above the gingiva (jin′-jĭvah), or gum. The crown is covered with enamel, a ceramic-like substance as thick as a dime, that directly bears the force of chewing. It is the hardest substance in the body and is fairly brittle because it is heavily mineralized with calcium salts.
what are the neck region in teeth
The portion of the tooth embedded in the jawbone is the root; the root and crown are connected by a region called the neck. The outer surface of the root is covered by a substance called cement, which attaches the tooth to the periodontal (per″e-o-don′tal) ligament. This ligament holds the tooth in place in the bony jaw. Dentin, a bonelike material, underlies the enamel and forms the bulk of the tooth. It surrounds a central pulp cavity, which contains a number of structures (connective tissue, blood vessels, and nerve fibers) collectively called pulp. Pulp supplies nutrients to the tooth tissues and provides for tooth sensations. Where the pulp cavity extends into the root, it becomes the root canal, which provides a route for blood vessels, nerves, and other pulp structures to enter the pulp cavity of the tooth.
Did You Get It?
Three pairs of salivary glands empty their secretions into the mouth.
The large parotid (pah-rot′id) glands lie anterior to the ears. Mumps, a common childhood disease, is an inflammation of the parotid glands. If you look at the location of the parotid glands (see Figure 14.1), you can readily understand why people with mumps complain that it hurts to open their mouth or chew.
The submandibular glands and the small sublingual (sub-ling′gwal) glands empty their secretions into the floor of the mouth through tiny ducts. The product of the salivary glands, saliva, is a mixture of mucus and serous fluids. The mucus moistens and helps to bind food together into a mass called a bolus (bo′lus), which makes chewing and swallowing easier. The clear serous portion contains an enzyme, salivary amylase (am′ĭ-lās), in a bicarbonate-rich (alkaline) juice that begins the process of starch digestion in the mouth. Saliva also contains substances such as lysozyme and antibodies (IgA) that inhibit bacteria; therefore, it has a protective function as well. Last but not least, saliva dissolves food chemicals so they can be tasted.
