Arterioles

What are arterioles?

An arteriole (är-‘tir-ē-,ōl) is a very small blood vessel that branches off from your artery and carries blood away from your heart to your tissues and organs.

Arterioles are small arteries that link up to capillaries, which are smaller yet. With their very thin walls, your capillaries act like an exchange station where oxygen and nutrients trade places with waste from your tissues. Your smallest veins (venules), which take blood back to your heart, also link to your capillaries to make these exchanges.

What do arterioles do?

Your small but powerful arterioles control blood flow and blood pressure throughout your body.

• They supply 80% of your blood vessels’ resistance to blood flow in your body. This means they manage and control how forcefully your blood moves through your body and how much goes to your tissues at any given time. Muscles in your arterioles’ walls make this happen. Arterioles can handle the force of your blood coming from your heart, and they can squeeze blood as it travels from your heart to the rest of your body. This maintains steady blood pressure.
• They provide a connection between arteries and capillaries, acting as a “middle man” when the larger arteries and tiny capillaries want to trade oxygen, nutrients and waste. Venules (small veins) taking blood back to your heart join capillaries to take part in these exchanges.

How do arterioles help with other organs?

Since your arterioles are located all throughout your body, they can help any of your organs. Here are some examples.

• In your skin, some arterioles help keep you warmer when they constrict and keep blood closer to your body’s core. When arterioles in your skin dilate, they help cool you off by increasing blood flow to your skin and extremities.
• Afferent arterioles bring blood into your kidney’s glomerulus (blood vessels that filter your blood). Afferent arterioles can dilate, or get wider, to allow for more filtration. Efferent arterioles take blood out of your glomerulus.
• Arterioles in your lungs constrict or tighten when there’s not enough oxygen. This moves blood away from areas in your lungs without enough oxygen and toward areas of your lungs with more oxygen.
• Arterioles in your brain can dilate, or become more open, to increase blood flow.

Interesting facts about arterioles

Instead of sharing neurons (nerve cells), each smooth muscle cell in an arteriole has its own neuron that receives signals to expand or contract the size of the arteriole. That means each muscle cell has a direct line of communication when your nervous system sends a request to make arterioles’ diameter bigger or smaller to adjust blood pressure or flow.

When your arteriole makes its diameter half of what it was, that cuts the blood flow down to one-sixteenth of what it was.

Where are arterioles located?

Since arterioles are involved in getting oxygen and nutrients to your cells and tissue, they’re located all throughout your body.

How big are arterioles?

Arterioles are 100 μm (micrometers or microns) to 7 μm (or .30 to .01 millimeters) in diameter. Arteriole walls are .02 millimeters thick.

What are arterioles made of?

Arterioles are tubes with thick walls of muscle that can adjust the amount of space they have inside. This allows them to keep your blood pressure at a certain level and control how much blood flows through your arterioles.

They’re more muscular than veins because they have to be able to handle higher blood pressure when your heart pumps blood out to your body and have to be able to contract and dilate more forcefully to adjust blood flow.

Arterioles have three layers:

• Tunica intima (inner lining of epithelial cells that communicate with the muscle in the middle layer).
• Tunica media (middle layer with smooth muscle cells and elastic tissue).
• Tunica adventitia (an outer layer of connective tissue, collagen fibers and nerve endings).

What are the common conditions and disorders that affect arterioles?

Since arterioles are blood vessels, conditions that affect the cardiovascular system also affect arterioles. Conditions affecting your arterioles include:

• High blood pressure (hypertension).
• Smoking.
• High cholesterol.
• Chronic obstructive pulmonary disease (COPD).
• Inflammatory bowel disease.
• Thrombosis (blood clots).
• Arthritis.
• Cystic fibrosis.
• Atherosclerosis.
• Vasculitis or inflammation of your blood vessel walls.
• Arteriolosclerosis or protein deposits in your blood vessel walls, often in your kidneys.
• Small strokes (blocked arteriole) or aneurysms (ruptured arteriole).
• Diabetes-related microangiopathy (arterioles don’t get enough oxygen, which leads to damage).

Damage to arteriole walls makes them less able to dilate or constrict. This affects both blood pressure and blood flow.

Common signs or symptoms of arteriole conditions

Symptoms of some conditions that affect arterioles include:

Vasculitis

• Weight loss.
• Fever.
• Tiredness.
• Rashes and bruises.

COPD

• Shortness of breath.
• Wheezing.
• Coughing often.

Blood clots

• Shortness of breath (if the clot is in your lung or heart).
• Chest pain (for a blood clot in your heart).
• Difficulty speaking (for a blood clot in your brain).
• Leg swelling (most blood clots originate in your leg veins).

Inflammatory bowel disease

• Belly pain.
• Bleeding.
• Diarrhea.
• Nausea and vomiting.

Common tests to check the health of arterioles

Your healthcare provider can use the following imaging methods to check arterioles:

• CT (computed tomography) angiogram.
• MR (magnetic resonance) angiogram.
• Doppler ultrasound.

Common treatments for arterioles

Your healthcare provider may prescribe medicines that help your cardiovascular system — which includes your arterioles — work better. These include:

• Antihypertensives for high blood pressure.
• Cholesterol-lowering medicines.
• Anti-inflammatory medications for conditions such as vasculitis.
• Quitting smoking.

Simple lifestyle changes/tips to keep arterioles healthy

You can help keep your arterioles healthy with these habits:

• Eat less salt.
• Eat less saturated fat.
• Exercise regularly.
• Don’t use tobacco products.
• Stay at a weight that's healthy for you.

A note from Cleveland Clinic

You may not think about your tiny, hard-working arterioles, but they’re important for managing your body’s blood flow and blood pressure. You can keep your entire cardiovascular system at its best when you eat healthy foods and get regular physical activity. Since some cardiovascular problems don’t have symptoms early on, it’s a good idea to get regular checkups with your healthcare provider. They can catch issues before they become larger problems.