It’s estimated that there are approximately 60,000 miles of blood vessels in the adult body. These blood vessels include arteries, veins, and capillaries. They are all protected by a microscopic inner lining of endothelial cells, which are commonly called the endothelium. It’s important to note that these cells line the entire circulatory system from the inside of your heart all the way down to your smallest capillary. When added up, the volume of these endothelial cells would cover the surface area of 4 to 8 tennis courts depending upon the size of the individual. The endothelium is only one cell thick and can’t be seen by the human eye.

Once discovered, the endothelium was classified as an inert membrane whose primary function was to keep the blood in the circulatory system and out of the body’s tissues and organs. Research over the last 25 years has shown that your endothelium is an active, multi-functional organ that plays a vital role in metabolic, immunologic, and cardiovascular health. Your endothelium is now considered to be the single largest secreting organ in the body.

Endothelial health is so important that the 1998 Nobel Prize in Medicine was awarded to three American researchers who discovered how the endothelium converts the amino acid L-arginine into nitric oxide – the master signaling molecule of your entire cardiovascular system.

  • Blood Flow – Your endothelium helps to facilitate blood flow. It does this by providing a smooth surface that inhibits platelet adhesion and clotting. It also tries to inhibit foreign substances from adhering to its cellular wall, which can lead to plaque formations. Large molecules like LDL (bad) cholesterol and/or toxic substances like nicotine damage the intercellular junctions between the endothelial cells allowing deposits to build up. This causes the smooth and flexible lining of your blood vessels to become rough and hard to directly impact endothelial health.
  • Production of the ‘miracle molecule’ nitric oxide.- The endothelial cells produce a molecule called nitric oxide, which inhibits platelet adhesion, activation, secretion and aggregation, and promotes platelet disaggregation. This is extremely important in preventing blood clots in the vascular system to lessen the risk for heart attacks and strokes.
  • Blood pressure – Not only do the endothelial cells provide a dynamically-controlled structural barrier between the circulating blood and surrounding tissues and organs but they also produce signaling molecules that influence vasodilation and vasoconstriction. Vasodilation causes blood vessels to relax allowing for greater blood flow. This reduces blood pressure.
    Vasoconstriction causes blood vessels to tighten reducing blood flow and causing blood pressure to increase. It’s currently believed that the endothelial cells are the controlling factor in the regulation of blood pressure. They produce nitric oxide, which is the most potent vasodilator. The proper production of nitric oxide is fundamental to maintaining normal blood pressures, which means that endothelial health is critical to helping you maintain normal blood pressures.
  • Specialized barrier function – Endothelial cells act as selective filters to regulate the passage of gases, fluids, and various molecules across their membranes. For example, in the brain and retina the endothelial cells are tightly linked together to create a barrier that only allows selective molecules to pass through it. In the liver, spleen, and bone marrow, the endothelial cells are loosely linked allowing for cellular trafficking between their intercellular gaps. However, in the kidneys, endocrine glands, and intestinal villi, the endothelial cells have a different type of selective permeability to allow for efficient filtering, secretion, and absorption based on that organ’s function.

Endothelial Functions

Because endothelial cells line every blood vessel they play an important role in the proper function of every organ in your body. The following is a list of the known functions of the endothelium. Each function plays an important role in endothelial health, cardiovascular health, and your overall wellness:

  • Angiogenesis – The formation of new capillaries is called angiogenesis and is regulated in part by the endothelium. It also plays a significant role in the heart’s ability to develop collateral vessels. These collateral vessels can help lessen the impact of a blood vessel blockage in the heart by providing alternative routes for blood flow.
  • Wound-healing/ muscle creation. Endothelial health is extremely important in wound healing. It also plays a significant role in muscle creation.
  • Endothelial health is also critical to the proper function of your immune system. – Your white blood cells or leucocytes are produced in the bone marrow. They travel through the blood stream where the endothelial cells facilitate their passage into your body’s tissue to allow them to destroy foreign agents or antigens. This gate-keeping role varies for each organ system but is dependent upon endothelial health and function.
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