This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Physiology
Ohopnea in hea failure develops due to: 
Select and explain. 
A. Reservoir function of pulmonary veins, B. Reservoir function of leg veins, C. Reservoir function of pulmonary aeries, D. Reservoir function of leg aeries
B: Reservoir function of leg veins
Answer: B: Reservoir function of leg veins 
Explanation: Ohopnea is shoness of breath that occurs when a person is supine. Gravitational forces cause fluid to become sequestrated in the lower legs and feet when the person is standing or sitting. When the person assumes a recumbent position fluid from the legs (leg veins) and dependent pas of the body is mobilized and redistributed to an already distended pulmonary circulation. Ref: Hea failure: a clinician's guide to ambulatory diagnosis and treatment By Mariell L. Jessup, Evan Loh, Page 28