Question

Describe the general function of teeth. Diagram the general structure of a tooth. Describe the different kinds of specialized teeth found in mammals. For each type of tooth provide the type of diet it is associated with.

Answer 1

Answer :fuction of teeth :

Incisor – to cut food like a pair of scissors.

Canine – to tear food like a fork.

First molars – can grind food.

Second molar – larger than first molars, can grind food like first molars do.

Types of tooth in mammales:

The number of teeth in an animals jaw depend on its life history. Teeth are expensive to grow so no animal wants more than it needs. Most placental mammals are happy with between 20 and 40, while most marsupials have 30 to 50. As a general rule animals that feed on insects have more teeth than either herbivores or the larger carnivores. There are some funny exceptions though.

Several groups of mammals have decided to do without teeth altogether. The 10 species of Whales in the order Mysticeti, the 8 species of Pangolins family Manidae, and the 3 species of Anteaters in the family Myrmecophagidae and order Edentata have all given up on teeth completely and have none.

An interesting tooth oddity is the Narwhale Monodon monocerus , order Odontoceti. This has two teeth in its upper jaw, one of these, normally the left one, grows out long and forward as a tusk while the other remains rudimentary.

Looking the other way to see who has the most teeth we have to visit two of the 3 orders that gave us the mammals with the least teeth. On land the mammal with the most teeth is the Giant Armadillo Priodontes giganteus order Edentata, which can as many 100 teeth in its jaws. In the oceans the real master of teeth comes from the order Odontoceti. The Long-snouted Spinner Dolphin can have as many as 252 teeth in its long thin jaws. These teeth are more like reptile teeth in that they are all the same basic shape, thin sharp little spears. This makes them good for catching and holding the slippery little fishes that dolphins live on.

Teeth in mammals come in four different sorts: Incisors, Canines, Premolars and Molars. Not all mammals have all, or even any of them and the roles any particular sort of teeth play in an animal's life can be quite diverse. The arrangement of teeth in any given mammals mouth can be expressed as a 'dental formula'. This formula gives the arrangement of one side of an animal's jaw such that incisors are always written first then canines then premolars and then molars.

For humans 2123-2123 is upper and lower jaws respectively signifying 2 incisors, 1 canine, 2 premolars and 3 molars on each side in both the upper and lower jaw.

In total this adds up to 8 incisors, 4 canines, 8 premolars and 12 molars = 32 teeth in humans. Other mammals have different numbers of each sort of teeth in their upper and lower jaws. Hence Smoky Bats (family Furipteridae) have the dental formula 2123-3133 whilst Hyenas have 3141-3131 normally.

Incisors = Cutting teeth - these are the front most teeth in the jaw primarily used for the initial biting of food. They have a straight, sharp cutting edge and one root. In many Rodents they grow continually throughout the animals life, this is because they get warn down gnawing through things.

Canines = Stabbing teeth - normally only 2 pairs (one each side) per jaw. They have a sharp, pointed edge and are used with the incisors to bite into food and or to kill prey. Like incisors they have one root. The tusks of many animals such as elephants are modified canines. They are missing in rodents and most large herbivores (Perissodactyls and Artiodactyls). The gap where the canines would have been is often enlarged and is called a 'diastema'.

Premolars = Next back from the canines. They are generally similar to molars in form and function in both herbivores and omnivores, but in carnivores some of them at least are slimmer and are used to cut flesh. When they (the first lower premolar and last upper premolar) are modified like this they are called the carnassials. Otherwise premolars are teeth we use to crush and grind our food. Their upper surfaces have a broad, lumpy top instead of a sharp biting edge. These small irregular lumps are called cusps. Premolars are called bicuspids in some books, this is because, in most cases, they have two cusps. The prefix bi meaning two. The first upper premolars normally have two roots. The other premolars have one root.

Molars = These are larger than premolars and extremely variable depending on the animal's diet. Like premolars they are used for crushing and grinding food, and like premolars their upper surfaces have ridges called cusps on them. Molars normally have three to five cusps and two or three roots. In humans we call the third molars, those closest to the back of the mouth 'Wisdom Teeth'. If the jaw bone is not large enough to accommodate all the teeth in it, as sometimes happens with humans, these wisdom teeth can become painfully wedged between the back of the jaw bone and the 2nd molars. This condition is known as 'impacted wisdom teeth'.