Introduction To The Cardiovascular System In Horses

The cardiovascular system is the plumbing of the body.  This is the system that distributes food, oxygen, communication molecules (hormones), repair and maintenance molecules (enzymes) and defense cells (first responders and police investigators).  It is also responsible for taking out the trash and delivering it to the filters of the body (liver and kidneys) and returning messages from the body’s organs back to the brain or to other organs.  The system is constantly monitored so that the pressure is maintained or increased when the body is needing more materials (exercise, illness), the density is measured (hydration) and the temperature both locally (heat in a limb) or systemically (fever) is adjusted.

The heart is the pump that forces the blood through the arteries towards the organs and then through the veins back to the heart.  The materials it carries are transferred to surrounding tissue in very thin vessels called capillaries.  These are basically a bed of finely meshed vessels in any tissue.  

Fortunately for most horses this system works flawlessly their whole lives but for some horses, a problem in one system can lead to troubles.  These include swelling when the blood can’t return properly or death when the blood no longer provides fresh gasses to the individual cells.  Causes include blocked vessels (bruising, thrombi), breakage of vessels (trauma, aneurism), or a pump that doesn’t effectively pump the blood (defect or damage).  Bruising with fluid leakage doesn’t look the same in horses as it does in humans because of the darker skin color of horses but the swelling from trauma is the same.

Dependent Edema In Horses

Blood, like any liquid, falls to the lowest point. When the liquid part of blood leaks out of the blood vessels, it always gravitates to the low point. It is usually a sign of general body inflammation that caused the vessels to leak.

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Petechiae In Horses

Small red spots on the gums and mucous membranes behind the lips indicates inflammation of the blood vessels in the horse causing them to leak small patches of blood into the surrounding tissue.

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Sheath Edema In Horses

The sheath is at the farthest point from the heart and damage to the blood flow in castrated males can sometimes prevent the normal flow of blood leading to swelling (edema) of the sheath.

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Thrombosed Veins In Horses

The veins of horses normally do not have obstructions but when they become occluded either partially or fully, then the blood flow ceases and they become enlarged. the blockage is usually a blood clot called a thrombosis.

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Equine Infectious Anemia In Horses

This is the viral disease that the Coggins blood test was made to discover. A negative test is required for travel of the change of ownership in the US. It caused an anemia that can be fatal.

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