NBDE Ultimate 5 — Questions and Answers
Question 1: Which nerve provides general somatic afferent (taste-independent sensory) innervation to the anterior two-thirds of the tongue?
- Glossopharyngeal nerve (CN IX)
- Chorda tympani branch of CN VII
- Lingual nerve (branch of CN V3) (Correct answer)
- Hypoglossal nerve (CN XII)
Correct answer: Lingual nerve (branch of CN V3)
The lingual nerve (a branch of the inferior alveolar nerve from V3) carries general sensation from the anterior two-thirds of the tongue; taste is carried by the chorda tympani.
Question 2: Which major salivary gland produces an almost entirely serous secretion?
- Sublingual gland
- Submandibular gland
- Parotid gland (Correct answer)
- Von Ebner's glands
Correct answer: Parotid gland
The parotid gland is composed almost exclusively of serous acini, producing watery, enzyme-rich saliva, including amylase.
Question 3: The correct chemical formula for hydroxyapatite, the principal mineral of enamel and bone, is:
- Ca3(PO4)2
- Ca10(PO4)6(OH)2 (Correct answer)
- CaHPO4·2H2O
- Ca(H2PO4)2
Correct answer: Ca10(PO4)6(OH)2
Hydroxyapatite has the formula Ca10(PO4)6(OH)2 and constitutes approximately 96% of mature enamel by weight.
Question 4: Hertwig's epithelial root sheath (HERS), which dictates root morphology and initiates cementogenesis, is derived from:
- Dental follicle mesenchyme
- Inner and outer enamel epithelium at the cervical loop (Correct answer)
- Dental papilla ectomesenchyme
- Stellate reticulum of the enamel organ
Correct answer: Inner and outer enamel epithelium at the cervical loop
HERS forms from the proliferation and fusion of the inner and outer enamel epithelium at the cervical loop, growing apically to shape the root.
Question 5: The inferior alveolar nerve, after supplying the mandibular teeth, exits the mandible as the mental nerve through the:
- Foramen ovale
- Mental foramen (Correct answer)
- Mandibular foramen
- Incisive foramen
Correct answer: Mental foramen
The terminal branch of the inferior alveolar nerve exits the mental foramen (typically between the premolar apices) as the mental nerve, supplying the chin and lower lip.
Question 6: Which type of collagen is the predominant collagen in the periodontal ligament (PDL)?
- Type I collagen (Correct answer)
- Type II collagen
- Type III collagen
- Type IV collagen
Correct answer: Type I collagen
Type I collagen constitutes approximately 74% of total PDL collagen and forms the principal Sharpey's fibers that anchor the tooth to alveolar bone.
Question 7: During glycolysis, glucose is first phosphorylated to glucose-6-phosphate by which enzyme?
- Phosphoglucose isomerase
- Pyruvate kinase
- Hexokinase (Correct answer)
- Phosphofructokinase-1
Correct answer: Hexokinase
Hexokinase (or glucokinase in hepatocytes) catalyzes the first committed step of glycolysis, phosphorylating glucose to glucose-6-phosphate using one ATP.
NBDE Ultimate 5
Which nerve provides general somatic afferent (taste-independent sensory) innervation to the anterior two-thirds of the tongue?