ATI LPN
Questions on the Respiratory System Questions
Question 1 of 5
The total number of alveoli present in the human lungs is estimated to be around ______.
Correct Answer: C
Rationale: The human lungs contain about 500 million alveoli, a figure derived from anatomical studies estimating 480-600 million across both lungs. These sacs provide a massive surface area (around 100 m²) for gas exchange, vital for oxygenating blood efficiently. One billion or 1.5 billion overestimate this such numbers exceed histological counts. Eight hundred million is closer but still high. This 500 million estimate balances lung capacity with microscopic reality, supporting respiration's demands. Understanding this scale is key in physiology and pathology, like in COPD, where alveolar loss reduces exchange capacity, affecting oxygen delivery.
Question 2 of 5
Through which structure does blood pass from the right atrium to the right ventricle?
Correct Answer: C
Rationale: The tricuspid valve allows blood to pass from the right atrium to the right ventricle, opening during diastole and closing during systole to prevent backflow its three cusps ensure one-way flow. The bicuspid (mitral) valve serves the left side. The interventricular septum separates ventricles, not a passage. The mitral valve is left-sided, not right. Named for its three leaflets, the tricuspid's role is pivotal in right heart circulation, a fundamental valve in cardiac flow, critical in conditions like tricuspid regurgitation affecting pulmonary return.
Question 3 of 5
Which network of specialized cardiac muscle fibers provide a path for each cycle of cardiac excitation to progress through the heart?
Correct Answer: D
Rationale: The cardiac conduction system sinoatrial (SA) node, atrioventricular (AV) node, bundle of His, and Purkinje fibers provides the path for electrical excitation, pacing the heartbeat from SA node initiation through ventricular contraction. The systemic circuit is blood flow, not conduction. Intercalated discs connect fibers, not a network. The cardiovascular center in the medulla regulates rate, not the path. This system's specialized fibers ensure rapid, orderly spread, critical for synchronized pumping, a cornerstone of cardiac physiology and target in conduction disorders like heart block.
Question 4 of 5
Which wave in an electrocardiogram represents repolarization of the ventricles?
Correct Answer: B
Rationale: The T wave on an ECG represents ventricular repolarization, when potassium exits cells, relaxing the myocardium after systole key to resetting for the next beat. The R wave, part of the QRS complex, shows ventricular depolarization and contraction. The S wave completes QRS, not repolarization. The P wave is atrial depolarization. The T wave's shape and timing reflect recovery, critical in diagnostics e.g., inverted T waves signal ischemia making it a cornerstone of ECG interpretation and cardiac health assessment.
Question 5 of 5
The saclike structure around the heart is the:
Correct Answer: D
Rationale: The pericardium, a saclike structure, encases the heart fibrous pericardium anchors it, serous layers (parietal, visceral/epicardium) reduce friction. The epicardium is the heart's outer layer within this sac, myocardium the muscle, endocardium the inner lining. This sac's dual role protection, lubrication is vital, key in pericardial diseases like tamponade, a fundamental cardiac enclosure in anatomy.