"Arteries always carry oxygenated blood." FALSE — Pulmonary arteries carry DEOXYGENATED blood from right ventricle to lungs.

"Veins always carry deoxygenated blood." FALSE — Pulmonary veins carry OXYGENATED blood from lungs to left atrium.

"AVN is the pacemaker of the heart." FALSE — SAN is the primary pacemaker. AVN is the secondary pacemaker (backup only).

"QRS complex represents ventricular contraction." FALSE — QRS represents ventricular DEPOLARIZATION (electrical). Contraction is the mechanical event that follows.

"Atrial repolarization appears as a distinct wave on ECG." FALSE — Atrial repolarization is MASKED by the QRS complex occurring simultaneously.

"RBCs are formed in the spleen." FALSE — RBCs are formed in RED BONE MARROW. Spleen is the site of RBC destruction.

"Blood group AB is the universal donor." FALSE — O (O-negative) is the universal donor. AB (AB-positive) is the universal RECIPIENT.

"Erythroblastosis fetalis occurs in the first pregnancy." FALSE (usually) — It occurs in the SECOND or later pregnancies (first pregnancy sensitizes the mother; disease manifests in subsequent pregnancies).

"Basophils perform phagocytosis." FALSE — Neutrophils and monocytes/macrophages perform phagocytosis. Basophils SECRETE histamine and heparin.

"Plasma and serum are the same thing." FALSE — Serum is plasma MINUS fibrinogen and clotting factors (removed after clot formation).

"The bicuspid valve is on the right side of the heart." FALSE — Bicuspid (mitral) valve is on the LEFT side. Tricuspid valve is on the right side.

"Joint diastole is the shortest phase of the cardiac cycle." FALSE — Joint diastole (0.4 s) is the LONGEST phase. Atrial systole (0.1 s) is the shortest.

"Stroke volume multiplied by blood pressure gives cardiac output." FALSE — Cardiac Output = Stroke Volume × HEART RATE (CO = SV × HR).

"T-lymphocytes produce antibodies." FALSE — B-lymphocytes produce antibodies (humoral immunity). T-lymphocytes provide CELL-MEDIATED immunity.

"All blood cells are nucleated." FALSE — Mature RBCs and platelets LACK nuclei. WBCs are nucleated.

"Platelets are complete cells derived from lymphocytes." FALSE — Platelets are cell FRAGMENTS (not complete cells), derived from MEGAKARYOCYTES.

"Normal resting cardiac output is 10 L/min." FALSE — Normal resting cardiac output is approximately 5 L/min (CO = 70 mL × 72 bpm).