Splanchnic vessels and venules contain- % of blood volume:

Under normal resting conditions splanchnic circulation receives 25-28% of the cardiac output. It is also a large reservoir of blood containing about 20-25% of total blood volume. The splanchnic circulation consists of the vascular beds of spleen, GIT and liver. Splanchnic blood flow curses through Control over the splanchnic bed in response to stress is central. Stimulation of carotid and aoic baroreceptors cause causes sympathetic neural stimulation of splanchnic resistance and capacitance vessels and a large decrease in venous capacitance size. Ref: Moss and Adams' Hea Disease in Infants, Children, and Adolescents page 62.