What Is the Function of Arterioles?

How Arterioles Play a Role In Your Blood Pressure

Illustration of a capillary system with metarterioles and precapillary sphincters, as is present in the mesenteric microcirculation.
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Arteries get smaller as they get further away from the heart. When they have decreased in size to a certain point, they are then referred to as arterioles.

Arterioles share many of the properties of arteries – they are strong, have a relatively thick wall for their size, and contain a high percentage of smooth muscle.

Just like arteries, arterioles carry blood away from the heart and out to the tissues of the body.

In addition to this "supply train" function, arterioles are very important in blood pressure regulation.

Special Properties

Arterioles, as a group, are the most highly regulated blood vessels in the body and contribute the most to overall blood pressure. Arterioles respond to a wide variety of chemical and electrical messages and are constantly changing size to speed up or slow down blood flow.

Arterioles are an integral part of the circulatory system, which is a closed system in the sense that blood does not enter or leave the system during its journey from the heart, to the body, and back again. In such a system, a continuous flow of the same liquid can be pumped through the loop again and again.

Circulation Begins in the Heart

The circulatory system can be thought of as beginning in the right atrium. In its most basic form, the circulatory system is a simple loop which starts, and ends, at the heart.

It is also a closed system in the sense that blood does not enter or leave the system during its journey from the heart to the body and back again. In such a system, a continuous flow of the same liquid can be pumped through the loop again and again.

How Does Blood Reach the Arterioles?

Blood travels from the aorta through a series of smaller and smaller blood vessels until it reaches the capillaries.

Before reaching the capillaries, however, blood must travel through the arterioles, where its speed and pressure are constantly adjusted as different segments of the arterioles change diameter in response to pressure and chemical sensors positioned nearby. These sensors adjust blood flow via the arterioles in response to changing conditions in the body.

Capillary Flow

Because of arteriole action, by the time blood reaches the capillaries it is no longer traveling in a pulsing fashion. Blood flows continuously through the capillaries; it does not "squirt" and "pause" along with the beating of the heart. This continuous flow is necessary because there is a constant exchange of oxygen and nutrients happening through the walls of the capillaries. No cell in the body is very far away from a capillary.

As blood travels through the capillaries, its supply of oxygen is reduced and it acquires waste products. From the capillaries, blood enters the venules and then veins, and travels back to the heart to be refreshed and sent out once again.

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