Blood enters the systemic circuit of blood flow by passing through the

Correct Answer: B

Rationale: The aortic valve allows blood to exit the left ventricle into the aorta, initiating the systemic circuit.

Correct Answer: A

Rationale: Potential complications of hypertension include the following: left ventricular hypertrophy; MI; heart failure; transient ischemic attacks (TIAs); cerebrovascular accident; renal insufficiency and failure; and retinal hemorrhage. Venous insufficiency and right ventricular hypertrophy are not potential complications of uncontrolled hypertension. The original question was a multiple-answer type, but it has been restructured to a single-answer format emphasizing a key consequence (TIAs) while maintaining accuracy.

Correct Answer: D

Rationale: Endothelin evokes positive inotropic and chronotropic effects on the myocardium by acting directly on cardiac muscle cells.

Correct Answer: B

Rationale: Cardiac muscle fibres are smaller than skeletal muscle fibres.

Correct Answer: D

Rationale: Valves ensuring one-way blood flow are located between the atria and ventricles (atrioventricular valves) and between the ventricles and arteries (semilunar valves).