A client admitted from home is diagnosed with community-acquired pneumonia. Which organism does the nurse suspect is the cause of this infection?

Correct Answer: C

Rationale: Pneumococcus (C), or Streptococcus pneumoniae, is the most common cause of community-acquired pneumonia (CAP) in adults, accounting for 20-60% of cases per CDC guidelines. Escherichia coli (A) is a gram-negative rod linked to nosocomial or aspiration pneumonia, not typical CAP from home. Staphylococcus aureus (B) causes severe CAP, often post-viral (e.g., influenza), but is less frequent than Pneumococcus. Pneumocystis jiroveci (D) affects immunocompromised patients (e.g., HIV), not typical home-acquired cases. The document's answer (C) aligns with CAP epidemiology S. pneumoniae's polysaccharide capsule drives lobar consolidation, fever, and cough in healthy individuals, distinguishing it from A's hospital association or D's opportunistic nature.

Correct Answer: D

Rationale: Involuntary breathing is regulated by neurons in the medulla and pons, brain stem regions that set the respiratory rhythm. The medulla's dorsal respiratory group initiates inspiration, while the pons fine-tunes it, responding to CO2 levels via chemoreceptors, ensuring automatic breathing without conscious effort. Bronchioles adjust airflow but don't control rhythm. Pulmonary arterioles regulate blood flow, not breathing. The alveolar-capillary network facilitates gas exchange, not its initiation. This neural control, via the phrenic nerve to the diaphragm, underscores breathing's autonomic nature, vital for survival, distinguishing it from voluntary overrides like holding breath, a key concept in respiratory neuroscience.

Correct Answer: B

Rationale: Internal respiration is the exchange of gases oxygen from blood to tissues, carbon dioxide from tissues to blood occurring at the cellular level via diffusion across capillaries. ATP production is cellular respiration's outcome, not the exchange itself. Alveolar-blood exchange is external respiration, not internal. Breathing from atmosphere to alveoli is ventilation, not respiration's tissue phase. This process sustains metabolism, delivering oxygen for energy and removing CO2 waste, distinct from lung-based external respiration, a vital concept in understanding systemic oxygen transport and tissue oxygenation in physiology.

Correct Answer: D

Rationale: Pericardial fluid, a serous secretion between the pericardium's parietal and visceral (epicardium) layers, reduces friction as the heart beats, ensuring smooth motion within the sac. Synovial fluid lubricates joints, not the heart. The endocardium lines heart chambers, not reducing external friction. Pleural fluid lubricates lung pleura, not the pericardium. This fluid's role about 15-50 mL prevents adhesion during cardiac cycles, a vital mechanism for uninterrupted pumping, central to cardiac physiology and relevant in pericardial effusion where excess fluid disrupts function.

Correct Answer: C

Rationale: The pulmonary semilunar valve prevents blood from flowing back into the right ventricle, closing after systole as pulmonary artery pressure exceeds ventricular pressure, ensuring one-way flow to the lungs. The tricuspid valve stops backflow into the right atrium, not ventricle. The bicuspid (mitral) serves the left side. The aortic semilunar valve guards the left ventricle. This valve's role in pulmonary circulation is crucial, maintaining forward flow, key in right heart dynamics and conditions like pulmonary regurgitation affecting lung perfusion.