The innermost layer of the blood vessels is made up of:

Correct Answer: B

Rationale: The innermost layer (tunica intima) is endothelium (B), a simple squamous epithelium specialized for blood contact. Ciliated (A) and columnar (C) are not in vessels; D is a general term overlapping with B.

Correct Answer: A

Rationale: Afterload (A) is the pressure (e.g., aortic pressure) ventricles overcome to eject blood. B is preload, C is contractility, D is atrial unrelated.

Correct Answer: A

Rationale: The Purkinje system (A) directly activates ventricular muscle. Bundle of His (B) and branches (C) precede, AV node (D) delays.

Correct Answer: D

Rationale: The ductus arteriosus shunts blood from the pulmonary trunk to the aorta in the fetus, bypassing the lungs. Fossa ovalis (A) and foramen ovale (B) are atrial structures, trabeculae (C) are ventricular ridges.

Correct Answer: C

Rationale: The medulla oblongata (C) houses the cardiovascular center, regulating heart rate via autonomic nerves. Midbrain (A), cerebrum (B), and cerebellum (D) have other roles.