The parents of a newborn with a congenital heart disease ask the nurse what is meant by the diagnosis patent ductus arteriosus. The nurse's best explanation includes that this structure is a shunt between the:

Correct Answer: B

Rationale: The ductus arteriosus is a shunt that allows blood to bypass the undeveloped lungs of the fetus by allowing blood to pass between the pulmonary trunk and the aorta (great vessels). This structure closes soon after birth and is replaced by the ligamentum arteriosum. The foramen ovale is the bypass that allows blood to pass through the atria. There is no shunt within the ventricles. (Source: Document, Pretest Answer 3, p. 76)

Correct Answer: D

Rationale: Vitamin K is essential for the liver to synthesize clotting factors (e.g., II, VII, IX, X). Heparin inactivation aids but isn’t required, vitamin C is unrelated, and tissue damage triggers extrinsic clotting but isn’t always necessary.

Correct Answer: D

Rationale: Hemostasis is the process of stopping blood loss via vasoconstriction, platelet plugs, and clotting. Homeostasis is broader (body equilibrium), and syneresis is clot shrinkage, not the full process.

Correct Answer: D

Rationale: The Purkinje fibers deliver impulses directly to ventricular myocardium, causing rapid, coordinated contraction. The AV node delays the signal, the Bundle of His splits it, and bundle branches distribute it, but Purkinje fibers are the final step to the muscle.

Correct Answer: D

Rationale: Vascular resistance is primarily determined by vessel diameter (D), as per Poiseuille’s law (resistance ∝ 1/r⁴), where small changes in radius greatly affect resistance. Length (A) and viscosity (B) contribute but are less dynamic, C is vague, and E (blood pressure) is an outcome, not a determinant.