NBDHE NBDHE Scientific Basis of Practice 3 — Questions and Answers
Question 1: Which enzyme converts arachidonic acid into prostaglandins and thromboxanes?
- Lipoxygenase
- Cyclooxygenase (COX) (Correct answer)
- Phospholipase A2
- Adenylyl cyclase
Correct answer: Cyclooxygenase (COX)
Cyclooxygenase (COX-1 and COX-2) catalyzes the first steps in converting arachidonic acid to prostaglandins, prostacyclin, and thromboxane A2.
Question 2: A histologic section shows columnar cells with nuclei polarized away from the basement membrane and active secretory vesicles. Which cell type is depicted?
- Ameloblast (Correct answer)
- Odontoblast
- Osteoclast
- Cementoblast
Correct answer: Ameloblast
Ameloblasts are tall columnar cells with Tomes' processes and nuclei polarized away from the enamel-forming surface during amelogenesis.
Question 3: Which pharmacologic effect of epinephrine accounts for its use as a vasoconstrictor in local anesthetic solutions?
- Beta-2 receptor stimulation causing vasodilation
- Alpha-1 receptor stimulation causing vasoconstriction (Correct answer)
- Muscarinic receptor blockade
- Histamine H1 receptor antagonism
Correct answer: Alpha-1 receptor stimulation causing vasoconstriction
Epinephrine acts on alpha-1 adrenergic receptors in peripheral vasculature to cause vasoconstriction, reducing systemic absorption of the local anesthetic.
Question 4: Which type of hypersensitivity reaction is responsible for contact dermatitis from latex gloves?
- Type I (IgE-mediated)
- Type II (cytotoxic)
- Type III (immune complex)
- Type IV (delayed/cell-mediated) (Correct answer)
Correct answer: Type IV (delayed/cell-mediated)
Contact dermatitis from latex is a Type IV delayed hypersensitivity reaction mediated by sensitized T lymphocytes, occurring 24–72 hours after exposure.
Question 5: During embryonic development, failure of fusion of the maxillary and medial nasal processes results in which condition?
- Cleft palate only
- Cleft lip (Correct answer)
- Bifid uvula
- Ankylosis of the mandible
Correct answer: Cleft lip
Cleft lip results from failure of the maxillary process to fuse with the medial nasal process during the 5th–6th weeks of embryonic development.
Question 6: Which nutrient deficiency is associated with smooth, painful tongue (glossitis), angular cheilitis, and normocytic anemia?
- Vitamin C
- Riboflavin (B2) (Correct answer)
- Vitamin B12
- Iron
Correct answer: Riboflavin (B2)
Riboflavin (B2) deficiency causes magenta glossitis, angular cheilitis (stomatitis), and normocytic anemia alongside other mucocutaneous lesions.
Question 7: Which structure forms the floor of the nasal cavity and the roof of the oral cavity?
- Vomer
- Hard palate (Correct answer)
- Ethmoid plate
- Pterygoid plate
Correct answer: Hard palate
The hard palate, formed by the palatine processes of the maxilla and the horizontal plates of the palatine bones, separates the oral and nasal cavities.
NBDHE NBDHE Scientific Basis of Practice 3
Which enzyme converts arachidonic acid into prostaglandins and thromboxanes?