In which vascular bed does hypoxia primarily induce vasoconstriction?

In pulmonary circulation, hypoxia primarily induces vasoconstriction as a mechanism known as hypoxic pulmonary vasoconstriction (HPV). This response is unique to the lungs and serves a protective function. When areas of the lung are poorly ventilated and do not receive adequate oxygen, the blood vessels in that region constrict. This reduces blood flow to the hypoxic areas and diverts blood to better-ventilated regions of the lung, facilitating more efficient gas exchange.

In contrast, other vascular beds, such as in the systemic, cerebral, and coronary circulations, typically respond to hypoxia with vasodilation to increase blood flow and enhance oxygen delivery to tissues that are in need. Thus, the pulmonary circulation's unique response of vasoconstriction during hypoxic conditions stands out among the various vascular systems in the body.