Question

question
pertaining to the heart, what substance acts as a lubricant by reducing friction between opposing surfaces?
answer
parietal pericardium
fibrous pericardium
visceral pericardium
pericardial fluid
i dont know yet

Explanation:

The parietal pericardium, fibrous pericardium, and visceral pericardium are layers of the pericardium (a sac around the heart), not lubricants. Pericardial fluid is the fluid within the pericardial cavity that reduces friction between the opposing surfaces (the parietal and visceral pericardium) as the heart beats.

Answer:

Pericardial fluid