Questions & Answers

Which dental formula represents a heterodont in placental draught and tough animals?
A. I\[\dfrac{3}{3}\]​, C\[\dfrac{1}{1}\]​, PM​\[\dfrac{4}{4}\], M​\[\dfrac{3}{2}\]
B. l​\[\dfrac{3}{3}\], C​\[\dfrac{1}{1}\], PM​\[\dfrac{2}{3}\], M​\[\dfrac{1}{1}\]
C. l​\[\dfrac{1}{1}\], C​\[\dfrac{0}{0}\], PM​\[\dfrac{2}{3}\], M​\[\dfrac{3}{3}\]
D. l​\[\dfrac{3}{3}\], C​\[\dfrac{1}{1}\], PM​\[\dfrac{4}{4}\], M​\[\dfrac{3}{3}\]

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Hint: An animal with more than one dent is a heterodont in anatomy. Heterodont refers to animals where teeth are separated into various types in vertebrates. A draught animal is a domesticated animal, which is kept and trained to perform tasks by people.

Complete answer: The hard chewing surface of the teeth is composed of enamel that helps to chew food. This enamel, secreted by ameloblast cells (ectodermal in origin), is the toughest material in the human body. Each tooth has three parts, including the crown, neck and root. Crown remains capped with hard enamel, made predominantly of phosphate of calcium; it forms the tooth's chewing surface. Dentin, secreted by odontoblast cells (mesodermal in origin), is composed of both the crown and the root, within which there is a central pulp cavity with nerve and blood supply.
Dental formula l​\[\dfrac{3}{3}\], C​\[\dfrac{1}{1}\], PM​\[\dfrac{4}{4}\], M​\[\dfrac{3}{3}\] $\times 2 =$ ​\[\dfrac{11}{11}\] $\times 2 =$ $44$ are part of the draught animal horse. Among Heterodontus placental species, the animal has the highest number of teeth. The remaining three dental formulas are: cat, dog, and rabbit.
During their lives, the majority of animals, including humans, have two sets of teeth, i.e., one temporary and one permanent set. A collection of temporary milk or deciduous teeth that will be replaced by a set of permanent or adult teeth. Diphyodont is this type of denture.
Hence, the correct answer is option D, i.e.,l​\[\dfrac{3}{3}\], C​\[\dfrac{1}{1}\], PM​\[\dfrac{4}{4}\], M​\[\dfrac{3}{3}\]

Note: Humans also have Bunodont teeth. They're thin, they're blunt and they've got rounded cusps. They are called acrodont teeth when teeth are fixed to the free surface or summit of the jaw bone. Fish, amphibians and reptiles are seen in them.