DOH Anatomy & Physiology 2 — Questions and Answers
Question 1: The Circle of Willis provides collateral circulation to the brain. Which artery connects the two anterior cerebral arteries?
- Posterior communicating artery
- Anterior communicating artery (Correct answer)
- Middle cerebral artery
- Basilar artery
Correct answer: Anterior communicating artery
The anterior communicating artery is a short vessel connecting the left and right anterior cerebral arteries, completing the anterior part of the Circle of Willis.
Question 2: Which enzyme converts angiotensin I to angiotensin II in the renin-angiotensin-aldosterone system?
- Renin
- Angiotensin-converting enzyme (ACE) (Correct answer)
- Aldosterone synthase
- Neprilysin
Correct answer: Angiotensin-converting enzyme (ACE)
ACE (Angiotensin-Converting Enzyme), found predominantly in pulmonary endothelium, cleaves angiotensin I to produce the active vasoconstrictor angiotensin II.
Question 3: What is the primary function of surfactant produced by type II pneumocytes in the alveoli?
- To increase alveolar surface tension
- To reduce alveolar surface tension and prevent collapse (Correct answer)
- To filter airborne pathogens
- To facilitate oxygen binding to haemoglobin
Correct answer: To reduce alveolar surface tension and prevent collapse
Pulmonary surfactant reduces alveolar surface tension, preventing alveolar collapse (atelectasis) at end-expiration, and is critical for normal lung compliance.
Question 4: The hepatic portal vein drains venous blood to the liver from which organs?
- Kidneys and adrenal glands
- Gastrointestinal tract and spleen (Correct answer)
- Lungs and heart
- Brain and spinal cord
Correct answer: Gastrointestinal tract and spleen
The hepatic portal vein carries nutrient-rich and potentially toxic venous blood from the gastrointestinal tract (stomach to rectum) and spleen to the liver for processing.
Question 5: Which nerve innervates the diaphragm and originates from cervical spinal levels C3, C4, and C5?
- Vagus nerve
- Phrenic nerve (Correct answer)
- Intercostal nerves
- Accessory nerve
Correct answer: Phrenic nerve
The phrenic nerve (C3, C4, C5 — 'keeps the diaphragm alive') provides motor and sensory innervation to the diaphragm, the primary muscle of respiration.
Question 6: In the cardiac cycle, what does the P wave on an ECG represent?
- Ventricular depolarisation
- Atrial depolarisation (Correct answer)
- Ventricular repolarisation
- Bundle of His conduction
Correct answer: Atrial depolarisation
The P wave on an ECG reflects the electrical depolarisation of the atria, which triggers atrial contraction and occurs just before the PR interval and QRS complex.
DOH Anatomy & Physiology 2
The Circle of Willis provides collateral circulation to the brain.
Which artery connects the two anterior cerebral arteries?