The Circulatory System

The circulatory system is responsible for delivering oxygen to cells. It is made up of the heart, arteries, veins, capillaries, and blood. The heart’s pumping action forces oxygenated blood from the heart and lungs to millions of cells throughout the body via arteries and capillaries.
Function of the Cardiac Pump Blood from the heart takes oxygen and food to the tissues in blood vessels called Arteries. Blood then returns to the heart through the Veins.

The heart pumps the blood through the arteries at high pressure, and so it moves quickly down the leg and into the tissues. When you are lying down, your heart pumps blood to your legs. However getting blood back from the legs isn't so easy. There is no "heart" in the leg and so the body needs a different way to get blood back to the heart. After the blood has been through the tissues, delivering oxygen and food to keep the cells alive, it collects together in the veins.

When you are lying down, there is just enough pressure left in the blood to get flow back to the heart. 

However, as soon as you sit up or stand, things change

Standing up:

When you stand up, the heart is raised above the feet. This increases the pressure in the blood because of the weight of the column of blood from the heart to feet. This is called "Gravitational" or "Hydrostatic" pressure. This extra pressure from standing helps the blood to flow from the heart to the legs, in the arteries. But, this same "Gravitational" or "Hydrostatic" pressure means that there is NOT enough pressure in the blood in the veins to get back to the heart. This is the reason that that people who have to stand still (such as soldiers on parade) faint. They cannot get the blood out of their legs and so they cannot get it pumped to their brains, and so they faint. 

So, to stop this happening, blood needs to be pumped out of the legs and get back to the heart.












Function of Leg Pump or Muscle Pump or "Peripheral Heart"

The fact that we do not usually faint when we sit up or stand up shows that the blood does usually get back to the heart. With the gravitational pressure pushing down on the blood in the leg, there needs to be a pump that pushes the blood back from the ankle and lower leg into the pelvis from where it can be helped back to the heart by breathing. The Peripheral Heart is a system of muscles, veins, and valves in the calf and foot that work together to push deoxygenated blood back up to the heart and lungs. Veins are equipped with one-way valves that prevent backflow during the return of blood from the toes to the heart. These valves act as trap doors that open with each muscle contraction and close when the muscle relaxes in order to prevent the backflow of blood.

The Leg Pump depends on two factors to pump the blood back up from the foot and into the pelvis:


Movement

The movement of the muscles in the leg push on the veins and squash them. The most important of these movements is the calf muscle moving the ankle joint.

The picture on the left shows the calf muscle moving the ankle joint - watch how it squashes the vein within it when the muscle contracts




Valves - situated in the veins

Pressure from the muscles squashing the veins will make the blood move. But without valves the blood moves without  direction and so the blood is not pumped out of the leg.  The prevention of this reflux by the valves is the key to how veins protect the legs in normal people. When the valves are working the vein is said to be "competent”. When valves become defective or weak they cannot function properly. In turn, the second heart becomes overwhelmed and blood is allowed to pool in the veins.

The picture on the right shows what would happen if there were no valves at all in veins but the muscle contracted as normal


There are 2 systems of veins at work in the legs: the deep system and the superficial system. The deep system contains the big veins that are approximately 1 inch in diameter and are situated close to the bone, surrounded by muscle. The superficial system contains the veins that are visible directly under the surface of the skin. The systems meet at 2 junctions and through a series of connecting veins called perforators


 

Functioning Valves in Veins	Leg Pump with No Valves	Failing Valves

The Leg Pump - Failing due to Abnormal Valves:

When the valves in a vein do not work, they are called "incompetent".
The muscle squeezes the vein and the blood is forced up and out of the vein, as in normal veins. However, when the pressure eases and the veins open up, the blood is allowed to fall back down the leg as the valves are not able to prevent it. This is called venous "reflux".
Virtually every problem associated with venous disease ie: varicose veins, leg aching, venous eczema, lipodermatosclerosis and venous leg ulcers, are caused by a FAILURE OF THE LEG PUMP and subsequent Venous reflux.