In intravascular clotting or thrombosis the one factor which is not important is:

Correct Answer: C

Rationale: Intravascular thrombosis Virchow's triad: vessel injury (A), stasis (B), hypercoagulability (D) plus infection promote clots. Lack of vitamin C (C) causes scurvy, not thrombosis collagen weakness bleeds, not clots. C's irrelevance is key, guiding nursing for anticoagulation focus, not nutritional correction.

Correct Answer: A

Rationale: Abruptio placentae (A) placental detachment triggers defibrination (DIC) via tissue factor release, consuming fibrinogen (e.g., <100 mg/dL), causing bleeding. Liver (B), surgery (C), cancers (D) contribute, but abruptio's acute proteolysis is frequent, key in nursing for FFP and obstetric emergency care.

Correct Answer: C

Rationale: Dead space refers to the portion of the tidal volume that does not participate in gas exchange. Anatomical dead space includes the conducting airways (e.g., trachea, bronchi), while physiological dead space includes both anatomical dead space and any alveolar dead space (alveoli that are ventilated but not perfused). The statement that physiological dead space is the same as alveolar dead space is false because physiological dead space encompasses both anatomical and alveolar components, not just the latter. Measuring physiological dead space involves the Bohr method, which uses mixed expired PCO2, arterial PCO2, and tidal volume, so that statement is true. Mechanical ventilation can increase dead space by adding apparatus dead space (e.g., tubing), and an increased ventilation/perfusion (V/Q) ratio can occur in conditions like pulmonary embolism, where ventilation exceeds perfusion, both of which are accurate. The false statement hinges on the incorrect equivalence of physiological and alveolar dead space, as physiological dead space is a broader concept that includes all non-gas-exchanging volumes, not limited to poorly perfused alveoli.

Correct Answer: B

Rationale: Airway resistance is inversely proportional to the fourth power of the radius (Poiseuille's law), but total cross-sectional area also determines resistance across the respiratory tree. The trachea has a large diameter (~2 cm), but as a single tube, its cross-sectional area is limited (e.g., ~3-4 cm²). Bronchioles, though individually small (~1 mm), number in the thousands by the terminal stage, yet their collective area is still less than the alveoli. The alveoli, numbering ~300 million in adult lungs, have a tiny individual diameter (~0.2 mm) but an enormous total cross-sectional area (~70-100 m² during inspiration), vastly exceeding other structures. This massive area reduces airflow velocity and resistance to negligible levels at the alveolar level, where gas exchange occurs by diffusion, not flow. While resistance is highest in medium-sized bronchi due to turbulent flow, the alveoli's collective area minimizes overall resistance to air movement, making them the site of lowest resistance, contrasting with the trachea or bronchioles, which handle bulk airflow with higher resistance despite larger individual diameters.

Correct Answer: B

Rationale: The percentage of CO2 in a structure reflects its PCO2, tied to metabolic production and gas exchange. Pulmonary arteries carry deoxygenated blood from the right heart to the lungs, with a PCO2 of ~45-46 mmHg (venous blood), the highest among options, as it's loaded with CO2 from systemic tissues. Alveolar air has a PCO2 of ~40 mmHg, equilibrated with arterial blood after CO2 diffuses out during respiration. Pulmonary veins, post-gas exchange, carry oxygenated blood with a PCO2 of ~40 mmHg, matching arterial levels. Interstitial fluid's PCO2 varies but approximates venous blood (~45 mmHg) or slightly less, depending on local metabolism, though it's not a standard respiratory measure. Systemic arteries, not listed, also have ~40 mmHg. Pulmonary arteries stand out with the highest CO2 due to their role in transporting metabolically produced CO2 to the lungs for excretion, before alveolar ventilation lowers it, making them the site of peak CO2 concentration.