All MCQs

Stomach acid kills many swallowed microbes and is a chemical innate defense. It acts nonspecifically before pathogens enter tissues.

Valve incompetence permits blood to flow backward, reducing pumping efficiency and increasing workload on the heart.

Heart valves prevent backflow during the cardiac cycle. They maintain directional flow from veins to atria, ventricles, and arteries.

Severe blood loss reduces circulating volume, blood pressure, and oxygen transport. This can lead to shock and organ failure.

Inflammatory mediators increase capillary permeability. Fluid and proteins move into tissues, causing swelling and helping defense molecules reach the area.

Hemolymph is a primary circulatory fluid in open systems. Vertebrate lymph is tissue fluid collected by lymphatic vessels and returned to blood.

Lymphocytes, especially B and T cells, are central to adaptive immunity. Defects can weaken antibody and cell-mediated responses.

Immune defense involves detecting danger, signaling between cells, recruiting responses, eliminating threats, repairing tissues, and sometimes forming memory.

Active muscles need more oxygen and produce more carbon dioxide. Respiratory and circulatory systems work together to match gas exchange with demand.

Veins have thin walls and large lumens, allowing them to store much of the blood volume. They operate at low pressure.

Blood pressure results from cardiac pumping and resistance in blood vessels. It is regulated by heart rate, vessel diameter, blood volume, and hormones.

Complete ventricular separation prevents mixing and supports efficient oxygen delivery, which is important for endothermy and sustained activity.