Arteries carry blood away from your heart and deliver it to every organ, tissue, and cell in your body. They form a high-pressure network that keeps oxygen and nutrients constantly flowing, and they actively adjust their diameter to control how much blood reaches different areas depending on what your body needs at any given moment.
How Arteries Move Blood Through Your Body
Each time your heart beats, the left ventricle contracts with enough force to push blood into the aorta, the largest artery in your body. From there, blood branches into progressively smaller arteries that reach your brain, kidneys, muscles, skin, and every other organ. The blood flowing through most arteries is rich in oxygen and nutrients, freshly loaded up after passing through your lungs.
There is one notable exception. Your pulmonary arteries carry oxygen-poor blood from the right side of your heart to your lungs, where it picks up a fresh supply of oxygen and drops off carbon dioxide. These are the only arteries in your body that transport deoxygenated blood. Every other artery delivers the oxygen-rich blood your tissues depend on to function.
Your heart also needs its own blood supply. The coronary arteries branch directly off the aorta and wrap around the surface of the heart muscle. The left anterior descending artery feeds the front of the heart, the circumflex artery supplies the left atrium and the back-left portion, and the right coronary artery serves the right side. When one of these arteries gets blocked, the section of heart muscle it feeds begins to die. That’s a heart attack.
What Arterial Walls Are Made Of
Arteries need to handle serious pressure with every heartbeat, and their three-layered wall structure is built for exactly that. The innermost layer is a smooth, single-cell-thick lining that directly contacts flowing blood. These cells do more than just provide a slick surface. They sense changes in blood flow and release chemical signals that tell the surrounding muscle to relax or tighten, fine-tuning how wide the artery opens.
The middle layer is the thickest part of an artery wall. It contains rings of smooth muscle wrapped around the vessel, along with sheets of elastic tissue. The muscle can contract to narrow the artery or relax to widen it. The elastic fibers stretch when a surge of blood arrives and snap back between beats, helping to smooth out the pulsing flow into something more continuous. The outermost layer is made mostly of collagen, which anchors the artery to surrounding tissues and keeps it from over-expanding. This layer also contains tiny blood vessels and nerves that supply the wall itself.
How Arteries Control Blood Pressure
Blood pressure is the force your blood exerts against arterial walls. A healthy reading is below 120/80 mmHg. The first number (systolic) reflects the pressure when your heart pumps; the second (diastolic) measures the pressure between beats when the heart is refilling. Arteries are central to maintaining both numbers.
The smallest arteries, called arterioles, are responsible for roughly 80% of the total resistance to blood flow in your body. By widening or narrowing even slightly, they raise or lower blood pressure system-wide. This isn’t random. Your body uses arterioles to direct blood where it’s needed most. During exercise, arterioles in your muscles open wide while those in your digestive tract narrow. In your lungs, arterioles constrict around poorly ventilated air sacs to redirect blood toward areas getting better airflow. In your brain, arterioles widen when carbon dioxide levels rise, increasing blood flow to flush out waste and deliver more oxygen.
The Pulse You Feel
When your heart ejects blood into the aorta, it creates a pressure wave that stretches the elastic arterial wall outward. As the heart relaxes, the wall snaps back. This compression-and-rebound wave travels along every artery in your body, which is why you can feel a pulse at your wrist, neck, or ankle even though those spots are far from your heart. The pulse is not blood itself arriving at your wrist. It’s the pressure wave rippling through the arterial wall at a speed much faster than the blood is actually traveling.
How Arteries Differ From Veins
Arteries and veins have fundamentally different jobs, and their structure reflects that. Arteries handle high-pressure blood coming directly from the heart, so their walls are thicker and their internal openings (lumens) are smaller. In cross-section, an artery looks round and firm. Veins carry blood back to the heart under much lower pressure, so they have thinner walls and wider lumens that allow blood to flow with less resistance.
One key structural difference: veins contain one-way valves, especially in the legs, that prevent blood from pooling or flowing backward. Arteries don’t need valves because the constant forward pressure from the heart keeps blood moving in the right direction.
What Happens to Arteries as You Age
Arterial stiffening is one of the most predictable changes in the cardiovascular system over a lifetime. The elastic fibers in artery walls have an extremely low turnover rate, meaning your body barely replaces them. Over decades, these fibers fragment, calcify, and break down. As elastin deteriorates, the load shifts onto stiffer collagen fibers, and the collagen concentration in all three wall layers increases with age. On top of that, sugar molecules in the blood can form chemical bonds between collagen fibers, further rigidifying the wall.
The practical effect is measurable. Pulse wave velocity through the aorta, a direct indicator of stiffness, rises from about 4.1 meters per second in children to 6.4 m/s by the mid-30s to mid-40s and reaches 10.5 m/s in people over 65. Pulse pressure (the gap between systolic and diastolic readings) increases by about 25% between ages 30 and 60. Stiffer arteries force the heart to work harder with every beat, which over time can lead to heart failure. They also become more permeable, making it easier for cholesterol to enter the wall and trigger plaque buildup, the process behind atherosclerosis.
Staying physically active, managing blood sugar, and keeping blood pressure in a healthy range all slow the rate at which arteries stiffen. The elastic fibers you were born with are largely the ones you’ll have for life, so protecting them early matters more than trying to reverse damage later.