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
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
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
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
The Leg Pump depends on two factors
to pump the blood back up from the foot and into the
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
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.
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
The Leg Pump - Failing due to Abnormal
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
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.