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Wednesday, April 15, 2020

Dentition in Mammals:By. Dr. Vidhin Kamble Sangola College, Sangola


Dentition in Mammals:
Usually, heard and pointed structure present into the buccal cavity, attached to the jaw is called as dentation or teeth.  Teeth are found in fishes, amphibians, and mammals. In birds, teeth are absent and are reported in ancient/fossil birds.


Structure of tooth
The typical tooth of mammal shows the following parts.
a.       Crown
b.      Neck
c.      Root.




Crown : it is exposed part of the tooth, covered by relatively hard enamel. the enamel is a white glistening part composed of hydroxyapatite covering dentine. Enamel is folded with sharp cutting edges. On the basis of cavity or cusp formed by enamel, teeth are mono-cuspid, di-cuspid, poly-cuspid.

Dentine: Dentine is softer than enamel but harder than bone. dentine encloses the cavity called pulp cavity filled with pulp consist of the blood vessel, lymph vessels, nerve, connective tissue, etc. enervate through the opening of the pulp cavity.  The pulp cavity project into numerous treelike branched process called dentine forming odontoblast.

Neck- it is the middle part of tooth surrounded by the fleshy fold of the mucus membrane called gum. 

Root:It is the lower part of the tooth, fitted into the socket of the jaw bone.  The incisor and canines have a single root, pre-molar has two roots and molar teeth have two to three roots. The tooth is fitted into the socket or alveolus by cellular cement.  

There are several kinds of dentation which are as follows.
a.       Kinds of teeth on the basis of attachment to the jaw bone
b.      Kinds of teeth on the basis of succession or replacement
c.       Kinds of teeth on the basis of structure.

a.       Kinds of teeth on the basis of attachment to the jaw bone.
On the basis of attachment following are the kinds of teeth
i)                    Acrodont teeth
ii)                  Pleurodont teeth
iii)                Thecodont teeth




I.         Acrodont teeth: In this type, the teeth are not directly attached to the jaw bone. But simply embedded into the socket of jaw bone are present at the free edge of the jaw bone.  eg. Scoliodon

ii.        Pleurodont teeth : in this kind, teeth are present on the inner side of jaw bone are also embedded into the mucus membrane of the jaw bone. eg. lizard

iii.       Thecodont teeth:  in this kind, the teeth are fitted into the socket of the jaw bone. e g. Mammals

b.   Kinds of teeth on the basis of succession or replacement
On the basis of succession or replacement of teeth in a lifetime, there are three kinds of teeth in animals, which are as follows.
i.                   Polyphyodont
ii.                 Monophydont
iii.                Diphyodont Polyphyodont


i.          Polyphyodont:
In this type, there are several sets of teeth during a lifetime. If teeth are destroyed of ware off are replace by new rows of teeth. This condition is known as polphyodont condition.
Eg. Lower vertebrates such as fishes, amphibians, reptiles, etc.

ii.         Monophyodont: In some mammals, there is a single set of teeth during a lifetime known as a monophyodont condition. In duckbill platypus, teeth are present in embryonic conditions, which are replaced by horny epidermal plate.  In spiny anteater, teeth are absent in all stages of life forms.
Eg. Duckbill platypus, whales, marsupials, etc.

iii.        Diphyodont : in this type, there are two sets of teeth during a lifetime. Such types of teeth are present in mammals. The condition is called as diphyodont. The first set of teeth is called lacteals or milk teeth or deciduous teeth. These teeth are replaced by permanent teeth. 
Eg. Man, monkey, etc.

c.       Kinds of teeth on the basis of structure:
On the basis of the structure following are the kinds of teeth.
i.                    Homodont
ii.                  Heterodont


i. Homodont:
In this type, all the teeth are similar in shape and structure, called homodont dentition of isodont dentition.  Such types of teeth are present lower vertebrates, such as fishes, amphibians, reptiles and in certain mammals such as whales, dolphins, armadillo, etc. 


2. Heterodont Teeth:
The presence of heterodont is the characteristics of mammals. In this type, teeth are dissimilar in shape and structure. The variation in the dentition is on the basis of food and manner of eating food. The heterodont teeth include four kinds of teeth which are as follows
1.      Incisor
2.      Canines
3.      Pre-molar
4.      Molar teeth

1.   Incisors: These are front or anterior teeth situated at the tip of the dentary in the upper jaw and lower jaw. The incisors are with a single root and monocuspid crown. In the case of rat (Rodents) incisors are open rooted and continue to grow throughout life. In the case of ox and sheep on the upper jaw, the incisors are absent.
Function: Incisors are used for cutting and copping.

2.   Canines: Incisors the canines are followed by canines are also single-rooted. The crown is ling and pointed..  The canines are absent in the jaws of some herbivores animals leaving the toothless region between incisor and premolar. This toothless region is called diastema.  In carnivore, canines are long and sharply pointed used for piercing and tearing the animal flesh.
Functions: To tear the animal flesh and it acts as an organ of offense and defense.

3.   Premolars:
In the buccal cavity, canines are followed by pre-molars.  The premolars are with a bi-cuspid crown and two roots.
Function:  Gridding or crushing of food particles.

4.   Molar: The molar teeth lie behind pre-molars. The molar tooth has a two to three roots and enamel is with several cavity or cusps. In humans, the last molar tooth is called Wisdom tooth.
      Function:  Gridding or crushing of food particles.

The pre-molar and molar teeth are together called cheek teeth.

Cheek teeth: On the basis of structure and numberscof the cusp, there are various kinds of cheek teeth are present, which are as follows,
i.                 Triconodont-                    - Fossil mammals
ii.                Tri-tuberculate                - Fossil mammals
iii.               Bunodont                         -Man Monkey
iv.               Selenodont                       - Cattles
v.                Secodont                           - Carnivore
vi.               Lophodont                       - Elephant

i.       Triconodont: In this type, the crow shows the presence of three conical projections arranged linearly. Ex. Fossil mammals.



ii.    Trituberculate: The crown shows the presence of three tuberosity arranged separately in the form of a triangle. Ex. Fossil mammals


iii.     Bunodont: in this type the crow is polycuspid. The cusp are separate and remain rounded, called bunodont used for grinding of food.
Ex. Man, Monkey, primate, etc.

iv.      Selenodont: The selenodont teeth are present in cattle.  There are two types of selenodont teeth, includes
1.      Brachydont:
2.      Hypsodont

1.  Brachydont:: In this type, the enamel is poly-cuspid with sharp cutting edges. These teeth are deeply rooted. Ex. Ruminants (Cow)


2.  Hypsodont: The crown is tall prism-like and low rooted. The enamel is poly-cuspid with sharp cutting edges. Ex. Horse


Functions: Selenodont teeth are used for crushing plant material.  
v.         Secodont: In this type, the crown is poly-cuspid. The enamel shows the presence of sharp cutting edges. such types of teeth are used to crack the bones and for cutting sharing tendons. Such types of teeth are also called carnassial teeth.
            Eg.   Carnivore.


vi.        Lophodont: In this type of cheek teeth, the enamel is much folded, these folds are called lophs.  Hence, the tooth is called lophodont.  Such type of lophodont is found in elephants, measures about 30X10 cm.  such types of teeth are used for grinding of all kinds of plants and grasses.
Ex. Elephant.

Dental formula:
The method of expressing the total number of teeth in animals according to the arrangement is termed as the Dental Formula. The dental formula expresses the number of each type of tooth into the buccal cavity for a given species.
Thus, the dental formula represents the arrangement of teeth in each half of the upper and lower jaw multiplied by two, which represents the total number of teeth in the buccal cavity. The dental formula is represented as follows.

Dental formula   
In the above formula
I – Incisor
C- Canines
Pm- Pre-molar
M- Molar
From half of the upper and lower jaws.

For Ex.
     
                        The dental formula of  Man        -2123/2123X2= 32 Teeth


For instance, a man has 2 incisor, 1 canine, 2 premolars and 3 molars on one side of the upper jaw and 2 incisor, 1 canine, 2 premolars and 3 molars on one side of the lower jaw. The number of teeth is multiplied by 2 which gives the total number of teeth in the buccal cavity that is 32
          

  The dental formula of Dog   =        3142/3143 X 2 =42 Teeth 

For instance, a dog has 3 incisors, 1 canine, 4 premolars and 2 molars on one side of the upper jaw and 3 incisors, 1 canine, 4 premolars and 3 molars on one side of the lower jaw. The total number of teeth is 42



The dental formula of elephant =        1003/0003 X 2 =14

In elephant, 1 incisors, 0 canine, 3 premolars and 3 molars on one side of the upper jaw and 0 incisors, 0 canines, 3 premolars and 3 molars on one side of the lower jaw are present.  ‘0’ indicates the absence of teeth.  The Ivory tusk in the elephant are nothing but the modified incisors of the upper jaw. 

Some dental formulas:   

 The dental formula of  Rat         -1003/1003X2= 14 Teeth

The dental formula of cattle        -0033/4033X2= 32 Teeth

The dental formula of  sheep       -0033/3133X2= 32 Teeth


Significance of Dentition :
1.      For the taxonomic classification of animals.
2.      To calculate the approximate edge of the animal.
3.      To illustrate the pedigree of certain animals.  
4.      To understand the diet of the animal.

Functions of dentition :
In the life of the animal, dentition performs the following functions
1.      Chewing or crushing of food particles.
2.      Teeth help in the process of speech and pronunciation
3.      It acts as an organ of offense and defense.
4.      Tearing the animal flesh.


Dentition in Mammals:
By, Dr. Vidhin Kamble
Sangola College, Sangola


Friday, April 10, 2020

B. Sc. I - Semester - I,CBCS Syllabus,wef -June -2019 as per Punyashlok Ahilyadevi Holkar Solapur University, Solapur -


 B. Sc. I -  CBCS Syllabus,wef -June -2019 as per 
Punyashlok Ahilyadevi Holkar Solapur University, Solapur -

SEMESTER – I

PAPER I: Animal Diversity- I
Unit 1: Kingdom Protista
General characters and classification up to classes; locomotory organelle and locomotion in
protozoa ,nutrition in protozoa.
Unit 2: Phylum Porifera
General characters and classification up to classes; canal system in Sycon
Unit 3: Phylum Cnidaria
General characters and classification up to classes; polymorphism in hydrozoa
Unit 4: Phylum Platyhelminthes
General characters and classification up to classes; life history of Taenia solium
Unit 5: Phylum Nemathelminthes
General characters and classification up to classes; life history of Ascaris lumbricoides and
its parasitic adaptations
Unit 6: Phylum Annelida
General characters and classification up to classes; metamerism in annelid, economic
importance of annelids with reference to earthworm and leech
Unit 7: Phylum Arthropoda
General characters and classification up to classes; vision in arthropoda, metamorphosis in
insects, economic importance of insects.
Unit 8: Phylum Mollusca
General characters and classification up to classes; torsion in gastropods. Economic importance of molluscs
Unit 9: Phylum Echinodermata
General characters and classification up to classes; water-vascular system in Asteroidea

SEMESTER – I
Paper-II Animal Diversity- II

Unit 1: Protochordates
General features and phylogeny of protochordata
Unit 2: Agnatha
General features of agnatha and classification of cyclostomes up to classes
Unit 3: Pisces
General features and classification up to orders; economic importance of fishes
Unit 4: Amphibia
General features and classification up to orders; parental care
Unit 5: Reptiles
General features and classification up to orders; poisonous and non-poisonous snakes,
types of snake venom, symptoms and treatments of snake bite
Unit 6: Aves
General features and classification up to orders; flight adaptations in birds
Unit 7: Mammals
General features and classification up to orders; adaptive radiation in mammals

Mouth Parts of Insects