Small arteries that are dilated or constricted to control peripheral resistance, and thus blood pressure, are .
a) blood flow into a capillary bed is regulated by the sphincter.
b) the , or inner-most layer of blood vessels, is made of endothelial tissue.
c) the pressure of nondiffusible molecules pulling water to them is called colloid .
d) reduction in the diameter of a blood vessel is called , and typically results in an increase in blood pressure.

B) The , or inner-most layer of blood vessels, is made of endothelial tissue.

Explanation:

Small dilated or contracted arteries to control peripheral resistance and therefore blood pressure are the innermost layer of blood vessels that is made of endothelial tissue and is called arteriole. Arterioles consist of arterial branches with a diameter of less than 0.1mm, and the triple wall constitution observed in the elastic and muscular arteries is highly reduced in arterioles. These structures act by regulating, in particular, the resistance to blood flow and, consequently, the peripheral blood pressure.

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