Referat Dintii

Iintroduction teeth, hard, bony structures in the mouths of humans and animals used primarily to chew food, but also for gnawing, digging, fighting, and catching and killing prey. teeth are the bodys hardest, most durable organlong after bones and flesh have dissolved, archaeologists find well-preserved teeth from humans and other animals that lived thousands of years ago.
humans use teeth to tear, grind, and chew food in the first step of digestion, enabling enzymes and lubricants released in the mouth to further break down food. teeth also play a role in human speechthe teeth, lips, and tongue are used to form words by controlling airflow through the mouth. additionally, teeth provide structural support to muscles in the face and form the human smile.
like humans, most animals use their teeth to chew food, although many animals have evolved teeth that perform other specialized tasks. for example, many carnivorous meat-eating animals, such as tigers, have developed long, sharp teeth for clamping down on and killing prey. beavers have chisel-like front teeth that they use to cut down large trees for building dams.
iihuman teeth human teeth are made of four distinct types of tissue enamel, dentin, pulp, and cementum. enamel, the clear outer layer of the tooth above the gum line, is the hardest substance in the human body. in human teeth, the enamel layer is about 0.16 cm about 0.06 in thick and protects the inner layers of the teeth from harmful bacteria and changes in temperature from hot or cold food. directly beneath the enamel is dentin, a hard, mineral material that is similar to human bone, only stronger. dentin surrounds and protects the pulp, or core of the tooth. pulp contains blood vessels, which carry oxygen and nutrients to the tooth, and nerves, which transmit pain and temperature sensations to the brain. the outer layer of the tooth that lies below the gum line is cementum, a bonelike substance that anchors the tooth to the jawbone.
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Adaugat la data : 2009-09-17 Nume referat: Dintii Categorie: Biologie Afisari: 55 Download Word Download Zip

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