The Types of Blood Vessels in Your Body

Blood vessels are intricate networks of hollow tubes that transport blood throughout the entire body. This is an essential function as blood delivers valuable nutrients to and removes wastes from our cells. Blood vessels are constructed of layers of connective tissue and muscle. The inner blood vessel layer is formed of endothelium. In capillaries and sinusoids, endothelium comprises the majority of the vessel. Blood vessel endothelium is continuous with the inner tissue lining of organs such as the brainlungsskin, and heart. In the heart, this inner layer is called the endocardium.

Types of Blood Vessels

Colored scanning electron micrograph (SEM) of a resin cast of blood vessels in human tissue
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There are four main types of blood vessels:

  • Arteries
    Arteries are elastic vessels that transport blood away from the heart. Pulmonary arteries carry blood from the heart to the lungs where oxygen is picked up by red blood cells. Systemic arteries deliver blood to the rest of the body.
  • Veins
    Veins are elastic vessels that transport blood to the heart. Veins can be categorized into four main types: pulmonary, systemic, superficial, and deep veins.
  • Capillaries
    Capillaries are extremely small vessels located within the tissues of the body that transport blood from the arteries to the veins. Fluid and gas exchange between capillaries and body tissues takes place at capillary beds.
  • Sinusoids
    Sinusoids are extremely small vessels located within the liver, spleen, and bone marrow.

Blood Vessels and Circulation

Blood is circulated through the body via the cardiovascular system. This system is comprised of the heart and the circulatory system. Blood vessels carry blood from the heart to all areas of the body. Blood travels from the heart via arteries to smaller arterioles, then to capillaries or sinusoids, then to venules, to veins, and back to the heart. Blood is circulated along pulmonary and systemic circuits. The path of circulation between the heart and the lungs is called the pulmonary circuit. Blood is circulated between the heart and the rest of the body along systemic circuits.

Microcirculation deals with the flow of blood from arterioles to capillaries or sinusoids to venules. As blood moves through the capillaries, substances such as oxygen, carbon dioxide, nutrients, and wastes are exchanged between the blood and the fluid that surrounds cells.

Blood Vessel Problems

An illustration of how hardening of the arteries can restrict blood flow
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Blood vessel problems and vascular diseases inhibit the proper functioning of blood vessels. One of the most common diseases of the arteries is atherosclerosis. In atherosclerosis, cholesterol and fatty deposits accumulate inside arterial walls. This can lead to the formation of plaque, which inhibits blood flow to organs and tissues. Atherosclerosis may also result in blood clots that can become dislodged blocking blood flow. Elasticity is a characteristic of blood vessels that enable them to perform the function of circulating blood. Hardened plaque in arterial walls causes vessels to become stiff. These vessels may rupture under pressure due to the loss of elasticity. Atherosclerosis may also cause a bulging in a weakened area of an artery known as an aneurysm. This enlargement can cause problems by pressing against organs or may rupture causing internal bleeding and excessive blood loss.

Problems in veins are typically due to inflammation resulting from an injury, blockage, defect, or infection. The formation of blood clots in superficial veins can cause superficial thrombophlebitis. Blood clots in deep veins can result in deep vein thrombosis. Damage to vein valves can cause the accumulation of blood in veins. This may result in the development of varicose veins.