Average duration of function of primary dentition is:

 # Average duration of function of primary dentition is:

A. 6 years

B. 8 years

C. 10 years

D. 12 years

The correct answer is A. 6 years.

The primary or deciduous dentition is considered to be completed by about 30 months or when the second primary molars are in occlusion. The dentition period includes the time when no apparent changes occur intraorally, i.e. from about 30 months to about 6 years of age.

The primary dentition may be in use from age 2 to 7 or older or about five or more years in all. Some of the teeth are in use from six months until 12 years of age, or a total of eleven and half years. 

Hence, average duration of function of primary dentition is 6 years while the maximum duration is 10 years.

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Intended target cells of H2 histamine receptor blockers

 # Which of the following is the intended target of H2 histamine receptor blockers?

A. Juxtaglomerular cells

B. Basophils

C. Arterial endothelial cells

D. Parietal cells

E. Mast cells

The correct answer is D. Parietal cells.

Histamine stimulates the H2 receptor of the parietal cells of the stomach and is released by basophils and mast cells. 

H2 receptor stimulation induces a proton release into the stomach lumen, decreasing the pH.

H2 receptor blockers reduce the amount of acid in the stomach.

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FALSE regarding biotransformation of drugs is:

 # FALSE regarding biotransformation of drugs is:

A. It usually converts a drug into its lipid soluble non ionized form

B. It generally involves modifications of the chemical structure of the drug

C. It principally occurs in the microsomal enzyme system of the liver

D. The rate may vary significantly between species

The correct answer is A.  It usually converts a drug into its lipid soluble non ionized form.

Biotransformation involves the conversion of a lipid soluble non ionized form of a drug into its more water soluble metabolites.

Biotransformation increases the absorption of the drug into the bloodstream, enhancing the bioavailability of the drug. Water soluble drugs are also easily excreted in the urine.

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Globulomaxillary cyst is found between:

 # Globulomaxillary cyst is found between:

A. Central incisors

B. Central incisor and lateral incisor

C. Lateral incisor and canine

D. Canine and premolar

The correct answer is C. Lateral incisor and canine.

The globulomaxillary cyst has traditionally been described as a fissural cyst found within the bone between the maxillary lateral incisor and canine teeth. Radiographically, it is a well-defined radiolucency which frequently causes the roots of the adjacent teeth to diverge.

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The name of the second visceral arch is:

# The name of the second visceral arch is:

A. Mandibular

B. Hyoid

C. Maxillary

D. None of the above

The correct answer is B. Hyoid.

There is no specific name for each branchial arch except the first and second. The first one is called as the Mandibular and the second one is the hyoid arch.

The nerve fibers from the mandibular division of the trigeminal nerve are derived from the mandibular arch. The seventh, ninth and tenth cranial nerves are derived from the second, third and fourth branchial arches respectively.

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The name of the first visceral arch is:

 # The name of the first visceral arch is:

A. Mandibular

B. Hyoid

C. Maxillary

D. None of the above

The correct answer is A. Mandibular.

There is no specific name for each branchial arch except the first and second. The first one is called as the Mandibular and the second one is the hyoid arch.

The nerve fibers from the mandibular division of the trigeminal nerve are derived from the mandibular arch. The seventh, ninth and tenth cranial nerves are derived from the second, third and fourth branchial arches respectively.

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Which type of RNA directs protein synthesis?

 # Which type of RNA directs protein synthesis?

A. Ribosomal RNA

B. Transfer RNA

C. Messenger RNA

D. Sender RNA

The correct answer is C. Messenger RNA

Messenger RNA (mRNA) is the RNA that carries information from DNA to the ribosome, the sites of protein synthesis (translation) in the cell. The mRNA is a copy of DNA. The coding sequence of the mRNA determines the amino acid sequence in the protein that is produced. However, many RNAs do not code for protein (about 97% of the transcriptional output is non-protein-coding in eukaryotes. 

Transfer RNA (tRNA) is a small RNA chain of about 80 nucleotides that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. It has sites for amino acid attachment and an anticodon region for codon recognition that binds to a specific sequence on the messenger RNA chain through hydrogen bonding.

Ribosomal RNA (rRNA) is the catalytic component of the ribosomes. The rRNA is the component of the ribosome that hosts translation. Eukaryotic ribosomes contain four different rRNA molecules: 18S, 5.8S, 28S and 5S rRNA. Three of the rRNA molecules are synthesized in the nucleolus, and one is synthesized elsewhere. In the cytoplasm, ribosomal RNA and protein combine to form a nucleoprotein called a ribosome. The ribosome binds mRNA and carries out protein synthesis. Several ribosomes may be attached to a single mRNA at any time. Nearly all the RNA found in a typical eukaryotic cell is rRNA.

Transfer-messenger RNA (tmRNA) is found in many bacteria and plastids. It tags proteins encoded by mRNAs that lack stop codons for degradation and prevents the ribosome from stalling.

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