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 Placoid scales are found in the
 <a alt="Cartilaginous_fish" class="mw-redirect gcloudimg" href="https://storage.googleapis.com/microcosmosdelta.appspot.com/images/transfer_54448/Cartilaginous_fish" title="Cartilaginous fish">
 cartilaginous fishes
 </a>
 . They are also called
 
 dermal denticles
 
 . Placoid scales are structurally
 <a alt="Homology_(biology)" class="gcloudimg" href="https://storage.googleapis.com/microcosmosdelta.appspot.com/images/transfer_54448/Homology_%28biology%29" title="Homology (biology)">
 homologous
 </a>
 with
 <a alt="Vertebrate" class="gcloudimg" href="https://storage.googleapis.com/microcosmosdelta.appspot.com/images/transfer_54448/Vertebrate" title="Vertebrate">
 vertebrate
 </a>
 <a alt="Tooth_(animal)" class="mw-redirect gcloudimg" href="https://storage.googleapis.com/microcosmosdelta.appspot.com/images/transfer_54448/Tooth_%28animal%29" title="Tooth (animal)">
 teeth
 </a>
 , having a central
 <a alt="Pulp_(tooth)" class="gcloudimg" href="https://storage.googleapis.com/microcosmosdelta.appspot.com/images/transfer_54448/Pulp_%28tooth%29" title="Pulp (tooth)">
 pulp cavity
 </a>
 supplied with
 <a alt="Blood_vessel" class="gcloudimg" href="https://storage.googleapis.com/microcosmosdelta.appspot.com/images/transfer_54448/Blood_vessel" title="Blood vessel">
 blood vessels
 </a>
 , surrounded by a conical layer of
 <a alt="Dentine" class="mw-redirect gcloudimg" href="https://storage.googleapis.com/microcosmosdelta.appspot.com/images/transfer_54448/Dentine" title="Dentine">
 dentine
 </a>
 , all of which sits on top of a rectangular basal plate that rests on the
 <a alt="Dermis" class="gcloudimg" href="https://storage.googleapis.com/microcosmosdelta.appspot.com/images/transfer_54448/Dermis" title="Dermis">
 dermis
 </a>
 . The outermost layer is composed of
 <a alt="Vitrodentine" class="gcloudimg" href="https://storage.googleapis.com/microcosmosdelta.appspot.com/images/transfer_54448/Vitrodentine" title="Vitrodentine">
 vitrodentine
 </a>
 , a largely inorganic
 <a alt="Tooth_enamel" class="gcloudimg" href="https://storage.googleapis.com/microcosmosdelta.appspot.com/images/transfer_54448/Tooth_enamel" title="Tooth enamel">
 enamel
 </a>
 -like substance. Placoid scales cannot grow in size, but rather more scales are added as the fish increases in size.

Placoid scales

New foliage of rose plant

Euglena

Pollen of Copper pod flower

Onion peel &#8211; the inner and outer layer

Pollen of Wild almond flower

Brine shrimp

Jaw of Leech

T.S of Leech

Mosquito larvae

T.S. of Root

Pollen grain of Lily flower

Wing of Carpenter Bee

Human Cheek Cell

Placoid scales

Shifa

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