The Function of Arterioles in Blood Pressure

How the Specialized Vessels Regulate Blood Pressure

A blood pressure monitor.
PhotoAlto/Eric Audras / Getty Images

The specialized blood vessels known as arterioles may be small in stature, but they play a big role in heart health. As you might suspect, they're related to arteries, the blood vessels that carry oxygenated blood away from the heart and to the body's tissues. As you move down through the arterial network, these vessels get smaller and smaller like the branches of a tree. When arteries have decreased in size to less than 300 micrometers, or one-hundredth of an inch, they're referred to as arterioles.

Arterioles share many of the properties of arteries. They're strong, have relatively thick walls, and contain a high percentage of smooth muscle, which means they're not under voluntary control. As the most highly regulated blood vessels in the body, arterioles also have the distinction of contributing the most to the rise and fall of blood pressure.

Tracing the Blood Flow

The circulatory system is a "closed" system, which means the blood never leaves the confines of the vascular network. At its most basic, the system is a loop which starts and ends at the heart, distributing oxygen molecules on the outward journey and carrying carbon dioxide back on the inward journey.

The outward route begins as the heart pumps blood through the aorta and continues pumping as the blood makes it way to the smallest of blood vessels called the capillaries.

Before this, the blood must pass through the arterioles where its speed is constantly being adjusted. These adjustments can occur for any number of reasons, including a rise or fall in temperature, changes in physical activity, food, stress, or exposure to toxins or medications.

The function of the arterioles, therefore, is to regulate blood pressure so that it remains steady and less prone to fluctuation. By doing so, the blood will no longer be pulsing as it reaches the capillaries. Instead, the flow will be more continuous, allowing for the steady exchange of oxygen and carbon dioxide molecules.

Once the exchange is complete, the blood will make the inward journey through the network of veins, finally returning to the heart through the inferior and superior vena cava.

Arteriole Disorders

When the body is functioning as it should, the arterioles help ensure that the blood pressure remains within normal, healthy limits. However, there are conditions that may affect or impede their performance. Among them:

  • Arteriosclerosis is the thickening, hardening, and loss of elasticity of the arterial walls. This process restricts the arteriole’s ability to regulate blood flow and allows for the progressive buildup of plaque and cholesterol on the arterial walls. The main causes of arteriosclerosis are high cholesterol, high triglycerides, cigarette smoking, and even high blood pressure itself.
  • Arterial stenosis is the abnormal narrowing of the arteries. This can be caused by any number of things, including pollution, smoking, diabetes, infection, and birth defects. The persistent constriction of blood vessels due to pollutants or chronic infection can lead to the progressive scarring (fibrosis) of arterial tissue.
  • Arteritis, the inflammation of the arterial walls in and around the scalp, is often associated with autoimmune diseases. The inflammation of the arterial walls leads to a decrease in blood flow. A prime example is giant cell arteritis (GCA), which affects the branches of the external carotid artery of the neck. With GCA, the impaired blood flow can cause symptoms like headaches, vision changes, vision loss, and jaw pain when chewing.

    A Word From Verywell

    If you've been diagnosed with high blood pressure, you need to seek the care of a doctor. While you may feel well and have no symptoms, the very presence of high blood pressure can increase your risk of heart attack and stroke. It's why high blood pressure is rightly called the "silent killer."

    Was this page helpful?
    View Article Sources
    • Lehmann, M. and Schmieder, R. "Remodeling of retinal small arteries in hypertension," Am J Hypertens. 2011; 24(12):1267-73. DOI: 10.1038/ajh.2011.166.
    • Nobel, A.; Johnson, R.; Bass, P. et al. (2010) The Cardiovascular System (Second Ed.). London: Churchill Livingstone/Elsevier. ISBN: 9780702050824.