Cardiovascular, Lymphatic and Nervous Systems MCQs

Right coronary dominance is present in about 85% of hearts, where the posterior interventricular artery arises from the right coronary artery. In left dominance (about 8-10%), it arises from the circumflex artery.

The thoracic duct, the largest lymphatic vessel, ascends from the cisterna chyli, crosses to the left at about T5, and drains at the left venous angle, the junction of the left internal jugular and left subclavian veins.

The middle meningeal artery, a branch of the maxillary artery, enters the skull through the foramen spinosum. Its rupture, often from a fracture at the pterion, causes an extradural hematoma.

About 75% of breast lymph drains to the axillary nodes, especially the anterior (pectoral) group. The remainder drains mainly to the internal mammary and supraclavicular nodes.

The cisterna chyli is a sac-like dilation at the origin of the thoracic duct, lying anterior to the L1-L2 vertebrae and to the right of the abdominal aorta. It receives lymph from the intestinal and lumbar trunks.

The sinoatrial node is supplied by the right coronary artery in about 60-65% of people and by the circumflex artery in the remainder. The atrioventricular node is supplied by the right coronary artery in about 80%.

The left supraclavicular node receives lymph via the thoracic duct from the abdomen, so enlargement (Troisier sign) classically indicates an abdominal or gastrointestinal malignancy, most famously gastric cancer.

The posterior communicating artery connects the internal carotid artery to the posterior cerebral artery on each side, completing the posterior part of the circle of Willis and linking the carotid and vertebrobasilar systems.