A newborn has a congenital defect in which the fetal opening between the right atrium and left atrium did not close after birth. The nurse knows that this structure is called the:

Correct Answer: A

Rationale: The foramen ovale is a fetal opening between the right and left atria, allowing blood to bypass the lungs. It normally closes after birth. The ductus arteriosus connects pulmonary artery to aorta, ligamentum arteriosum is its remnant, and Tetralogy of Fallot is a different defect.

Correct Answer: B

Rationale: In adults, RBC production (erythropoiesis) occurs in red bone marrow of flat bones (sternum, skull, vertebrae) and proximal ends of long bones. The femur’s shaft in adults is mostly yellow marrow, not active in erythropoiesis.

Correct Answer: C

Rationale: The carotid sinus baroreceptors detect increased pressure, triggering a reflex via the vagus nerve (parasympathetic) to slow heart rate (bradycardia) and reduce blood pressure. Hypercapnia (high CO₂) and hyperpnea (increased breathing) are unrelated, and tachycardia would counter the response.

Correct Answer: A

Rationale: The EKG shows inverted T-waves, a hallmark of hypokalemia (low potassium, A), which affects repolarization. Calcium (B) impacts rate/contractility, not T-waves, and chloride (C) and sodium (D) abnormalities don’t typically cause this pattern. (Source: Document, p. 10-11; assumes image context)

Correct Answer: D

Rationale: Cardiac output (CO, D) is the volume of blood ejected by the heart per minute (CO = HR × SV, ~5 L/min at rest). EDV (A) is pre-contraction volume, SV (B) is per beat, HR (C) is beats per minute, and BP (E) is pressure, not volume.