Science, Tech, Math › Science The Types of Blood Vessels in Your Body Share Flipboard Email Print Science Biology Anatomy Basics Cell Biology Genetics Organisms Physiology Botany Ecology Chemistry Physics Geology Astronomy Weather & Climate By Regina Bailey Biology Expert B.A., Biology, Emory University A.S., Nursing, Chattahoochee Technical College Regina Bailey is a board-certified registered nurse, science writer and educator. Her work has been featured in "Kaplan AP Biology" and "The Internet for Cellular and Molecular Biologists." our editorial process Regina Bailey Updated October 10, 2019 Blood vessels are intricate networks of hollow tubes that transport blood throughout the entire body so that it can deliver valuable nutrients to and remove waste from cells. These tubes are constructed of layers of connective tissue and muscle with an inner layer formed of endothelial cells. 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 brain, lungs, skin, and heart. In the heart, this inner layer is called the endocardium. Blood Vessels and Circulation Blood is circulated through the body by blood vessels via the cardiovascular system which is comprised of the heart and the circulatory system. Arteries move blood from the heart first to smaller arterioles, then capillaries or sinusoids, venules, veins, and back to the heart. Blood travels through pulmonary and systemic circuits, the pulmonary circuit being the path between the heart and lungs and the rest of the body the systemic circuit. Microcirculation is the flow of blood from arterioles to capillaries or sinusoids to venules—the smallest vessels of the circulatory systemic. As blood moves through capillaries, oxygen, carbon dioxide, nutrients, and waste are exchanged between blood and the fluid between cells. Types of Blood Vessels Susumu Nishinaga / Getty Images There are four main types of blood vessels that each play their own role: Arteries: These 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: These are also elastic vessels but they transport blood to the heart. The four types of veins are pulmonary, systemic, superficial, and deep veins.Capillaries: These 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: These narrow vessels are located within the liver, spleen, and bone marrow. Like capillaries, they deliver blood from larger arteries to veins. Unlike capillaries, sinusoids are permeable and leaky to allow for quick nutrient absorption. Blood Vessel Complications Science Picture Co / Collection Mix: Subjects / Getty Images Blood vessels cannot function properly when inhibited by vascular diseases. One of the most common diseases of the arteries is called atherosclerosis. In atherosclerosis, cholesterol and fatty deposits accumulate inside arterial walls leading to the formation of plaque. This inhibits blood flow to organs and tissues and can lead to further complications such as blood clots. The elasticity of blood vessels enables them to circulate blood but hardened plaque in arterial walls makes them too stiff to do this. Stiffened vessels may even rupture under pressure. Atherosclerosis can also cause the bulging of a weakened artery known as an aneurysm. Aneurysms create complications by pressing against organs and may rupture and cause internal bleeding if left untreated. Other vascular diseases include stroke, chronic venous insufficiency, and carotid artery disease. Most venous problems are due to inflammation that results from an injury, blockage, defect, or infection—blood clots are commonly triggered by these. The formation of blood clots in superficial veins can cause superficial thrombophlebitis, which is characterized by clotted veins just beneath the surface of the skin. Blood clots in deep veins lead to a condition known as deep vein thrombosis. Varicose veins, which are enlarged veins that can lead to blood clots, may develop when damage to vein valves causes blood to accumulate.