Overview of the Vascular System

What is the vascular system?

The vascular system, also called the circulatory system, is made up of the vessels that carry blood and lymph through the body. The arteries and veins carry blood throughout the body, delivering oxygen and nutrients to the body tissues and taking away tissue waste matter. The lymph vessels carry lymphatic fluid (a clear, colorless fluid containing water and blood cells). The lymphatic system helps to protect and maintain the fluid environment of the body by filtering and draining lymph away from each region of the body.

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The vessels of the blood circulatory system are:

• arteries - blood vessels that carry oxygenated blood away from the heart to the body.
• veins - blood vessels that carry blood from the body back into the heart.
• capillaries - tiny blood vessels between arteries and veins that distribute oxygen-rich blood to the body.

Blood moves through the circulatory system as a result of being pumped out by the heart. Blood leaving the heart through the arteries is saturated with oxygen. The arteries break down into smaller and smaller branches in order to bring oxygen and other nutrients to the cells of the body's tissues and organs. As blood moves through the capillaries, the oxygen and other nutrients move out into the cells, and waste matter from the cells moves into the capillaries. As the blood leaves the capillaries, it moves through the veins, which become larger and larger to carry the blood back to the heart.

In addition to circulating blood and lymph throughout the body, the vascular system functions as an important component of other body systems. Examples include:

• respiratory system
  As blood flows through the capillaries in the lungs, carbon dioxide is given up and oxygen is picked up. The carbon dioxide is expelled from the body through the lungs, and the oxygen is taken to the body tissues by the blood.
• digestive system
  As food is digested, blood flows through the intestinal capillaries and picks up nutrients, such as glucose (sugar), vitamins, and minerals. These nutrients are delivered to the body tissues by the blood.
• kidneys and urinary system
  Waste materials from the body tissues are filtered out from the blood as it flows through the kidneys. The waste material then leaves the body in the form of urine.
• temperature control
  Regulation of the body's temperature is assisted by the flow of blood among the different parts of the body. Heat is produced by the body's tissues as they go through the processes of breaking down nutrients for energy, making new tissue, and giving up waste matter.

What is vascular disease?

A vascular disease is a condition that affects the arteries and/or veins. Most often, vascular disease affects blood flow, either by blocking or weakening blood vessels, or by damaging the valves that are found in veins. Organs and other body structures may be damaged by vascular disease as a result of decreased or completely blocked blood flow.

What causes vascular disease?

Causes of vascular disease include:

• atherosclerosis
  Atherosclerosis (a build-up of plaque, which is a deposit of fatty substances, cholesterol, cellular waste products, calcium, and fibrin in the inner lining of an artery) is the most common cause of vascular disease.
  
  It is unknown exactly how atherosclerosis begins or what causes it. Atherosclerosis is a slow, progressive, vascular disease that may start as early as childhood. However, the disease has the potential to progress rapidly. It is generally characterized by the accumulation of fatty deposits along the innermost layer of the arteries. If the disease process progresses, plaque formation may take place. This thickening narrows the arteries and can decrease blood flow or completely block the flow of blood to organs and other body tissues and structures.
• embolus/thrombus
  A blood vessel may be blocked by an embolus (a tiny mass of debris that moves through the bloodstream) or a thrombus (a blood clot).
• inflammation
  In general, inflammation of blood vessels is referred to as vasculitis, which includes a range of disorders. Inflammation may lead to narrowing and/or blockage of blood vessels.
• trauma/injury
  Trauma or injury involving the blood vessels may lead to inflammation or infection, which can damage the blood vessels and lead to narrowing and/or blockage.

What are the effects of vascular disease?

Because the functions of the blood vessels include supplying all organs and tissues of the body with oxygen and nutrients, removal of waste products, fluid balance, and other functions, conditions that affect the vascular system may affect the part(s) of the body supplied by a particular vascular network, such as the coronary arteries of the heart.

Examples of the effects of vascular disease include:

• coronary vascular disease - heart attack, angina (chest pain)
• cerebrovascular disease - stroke, transient ischemic attack (a sudden or a temporary loss of blood flow to an area of the brain, usually lasting less than five minutes but not longer than 24 hours, with complete recovery)
• peripheral arterial disease - claudication (limping because of pain in the thigh, calf, and/or buttocks that occurs when walking), critical limb ischemia (lack of oxygen to the limb/leg at rest)
• vascular disease of the great vessels - aortic aneurysm (a bulging, weakened area in the wall of a blood vessel resulting in an abnormal widening or ballooning), coarctation of the aorta (narrowing of the aorta, the largest artery in the body), Takayasu's arteritis (a rare inflammatory disease affecting the aorta and its branches)
• thoracic vascular disease - thoracic aortic aneurysm (a bulging, weakened area in the wall of a blood vessel resulting in an abnormal widening or ballooning in the thoracic, or chest, portion of the aorta)
• abdominal vascular disease - abdominal aortic aneurysm (a bulging, weakened area in the wall of a blood vessel resulting in an abnormal widening or ballooning in the abdominal portion of the aorta)
• peripheral vascular disease - deep vein thrombosis (Also called DVT; a blood clot in a deep vein located within the muscles of the leg), varicose veins
• lymphatic vascular diseases - lymphedema (swelling caused by interruption of the normal drainage pattern in the lymph nodes)
• vascular diseases of the lungs - Wegener's granulomatosis (an uncommon disease in which the blood vessels are inflamed; mainly affects the respiratory tract and the kidneys), angiitis (inflammation of blood vessels), hypertensive pulmonary vascular disease (high blood pressure in the lungs' blood circulation due to vascular conditions)
• renal (kidney) vascular diseases - renal artery stenosis (blockage of a renal artery), fibromuscular dysplasia (a condition that weakens the walls of medium-sized arteries and occurs predominantly in young women of childbearing age)
• genitourinary vascular diseases - vascular erectile dysfunction (impotence)

Because vascular conditions and diseases may involve more than one of the body's systems at a time, many types of physicians treat vascular problems. Specialists in vascular medicine and/or surgery work closely with physicians in other specialties, such as internal medicine, interventional radiology, cardiology, and others to ensure comprehensive care of patients with vascular conditions.

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