DAANCE Basic Sciences and Anatomy 5 — Questions and Answers
Question 1: The circle of Willis is formed by which set of arteries?
- Internal carotid, anterior cerebral, posterior cerebral, anterior and posterior communicating arteries (Correct answer)
- External carotid, vertebral, basilar, and middle cerebral arteries
- Internal carotid, external carotid, vertebral, and posterior communicating arteries
- Anterior cerebral, middle cerebral, posterior cerebral, and subclavian arteries
Correct answer: Internal carotid, anterior cerebral, posterior cerebral, anterior and posterior communicating arteries
The circle of Willis is an anastomotic ring formed by the internal carotid arteries, anterior and posterior cerebral arteries, and the anterior and posterior communicating arteries.
Question 2: Which phase of the cardiac cycle corresponds to ventricular filling?
- Systole
- Isovolumetric contraction
- Diastole (Correct answer)
- Isovolumetric relaxation
Correct answer: Diastole
Diastole is the phase when ventricular muscle relaxes and the ventricles fill with blood from the atria.
Question 3: In the context of dental sedation, which muscle is the primary muscle of mastication responsible for elevating the mandible?
- Buccinator
- Masseter (Correct answer)
- Digastric
- Geniohyoid
Correct answer: Masseter
The masseter is the primary elevator of the mandible and one of the most powerful muscles of mastication.
Question 4: Which electrolyte imbalance is most likely to cause cardiac arrhythmias during anesthesia?
- Hypernatremia
- Hypokalemia (Correct answer)
- Hypercalcemia
- Hypermagnesemia
Correct answer: Hypokalemia
Hypokalemia (low serum potassium) destabilizes myocardial cell membranes and can precipitate life-threatening arrhythmias including ventricular fibrillation.
Question 5: The trachea bifurcates into the right and left main bronchi at the level of which anatomical landmark?
- Angle of Louis (sternal angle) at T4-T5 (Correct answer)
- Jugular notch at T1
- Xiphoid process at T9
- Cricoid cartilage at C6
Correct answer: Angle of Louis (sternal angle) at T4-T5
The trachea bifurcates at the carina, located at the level of the sternal angle (angle of Louis), which corresponds to the T4-T5 vertebral level.
Question 6: Which of the following correctly describes the blood-brain barrier?
- It is formed by fenestrated capillary endothelium and allows free passage of most drugs
- It consists of tight junctions between capillary endothelial cells, limiting passage of polar molecules (Correct answer)
- It is primarily composed of astrocytes that actively pump drugs into the brain
- It breaks down during normal aging, allowing most sedative drugs unrestricted access
Correct answer: It consists of tight junctions between capillary endothelial cells, limiting passage of polar molecules
The blood-brain barrier is formed by tight junctions between cerebral capillary endothelial cells, restricting passage of polar, ionized, or large molecules.
Question 7: The phrenic nerve, which innervates the diaphragm, originates from which cervical nerve roots?
- C1-C2
- C3-C5 (Correct answer)
- C6-C8
- C4-C6
Correct answer: C3-C5
The phrenic nerve arises from cervical nerve roots C3, C4, and C5, which is summarized by the mnemonic 'C3, 4, 5 keeps the diaphragm alive.'
DAANCE Basic Sciences and Anatomy 5
The circle of Willis is formed by which set of arteries?