The heart is covered by:

Correct Answer: A

Rationale: The heart is covered by the pericardium, a double-layered sac (fibrous and serous layers) that encloses and protects it. The epicardium is the heart’s outer layer, not a covering sac, and 'supracardium' is not a valid term.

Correct Answer: C

Rationale: In veins, the tunica media (smooth muscle layer) is poorly developed compared to arteries, as veins rely more on valves and external forces (e.g., muscle pump) than muscle contraction for blood movement.

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: D

Rationale: Normal RBC count is 4.5-5.9 million/mm³ (men) or 4.0-5.2 million/mm³ (women). 3.8 million/mm³ is below normal (assuming male; still low for female), indicating anemia. Thrombocytes are normal (150,000-450,000), hematocrit 43% is normal (38-50%), and hemoglobin 17 g/dL is normal.

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.