Which one of the following characterizes a poal system of blood vessels?
A poal system of blood circulation is defined as two capillary beds that are joined by an aerial or venous blood vessel. An example is the poal vein connecting the mucosal capillaries of the small intestine to the sinusoids (i.e., capillaries) of the liver. While capillary beds may connect pas of an organ (e.g., adrenal coex, pancreatic islet), capillaries do not extend between organs. Ref: Moon D.A., Foreman K.B., Albeine K.H. (2011). Chapter 10. Midgut and Hindgut. In D.A. Moon, K.B. Foreman, K.H. Albeine (Eds), The Big Picture: Gross Anatomy.
The absence of a capillary bed, thus shunting aerial blood directly to venules
A capillary bed supplied and drained by a larger, non capillary vessel
Two capillary beds connected by a larger blood vessel
A continuous capillary bed that extends from one organ to another