The Lymphatic System
Another of the amazing systems in our beautiful bodies is the Lymphatic System.
This System is a network of vessels lying adjacent to the capillaries. It aids the circulatory system in transporting fluids and is a very important part of the body's Immune System.
In and around the cells of the body extracellular fluid collects waste products and carries nutrients and oxygen to the cells.
Some of the fluid travels through the capillaries. Some, especially if it contains proteins too large to enter the capillary membranes, circulates through the lymphatic vessels.
The lymphatic vessels flow through several lymph nodes. These lymph nodes contain concentrations of white blood cells which kill bacteria and other harmful agents trapped in the nodes.
The tissue fluids return to the circulatory system through the large veins near the heart.
The Lymphatic System is comprised of several organs which include:
- the thymus
- the tonsils
- the spleen
- the adenoids
- and the bone marrow.
- There are hundreds of lymph nodes located at various points in the body, particularly
in the neck, arm pits, groin and behind the knees.
- There is also a vast network of vessels,
very similar to blood vessels. Their movement is even the same - accomplished not by a pump
(as in the arteries), but by muscle activity.
When I was young, my brother use to catch large garter snakes and make me watch as he fed
them eggs or small animals. Though a little scary to a small girl, it was still interesting
to watch the muscles of the snake push the item down into the body through parastaltic movement.
This is very much the
way that the lymph system as well as the blood vessels, or venal vascular system, push the
lymph (or the blood in the case of the vessels) back towards the heart. Respiration or
breathing also helps move the lymph.
What is the Function of This System?
The Lymphatic System actually has four different functions.
- It removes interstitial
fluid, sometimes referred to as lymph, from the area around the cells. This fluid comes from blood plasma which is forced
out of the capillaries into the open space, or the interstitial space.
- It picks up and brings to the venous system many fatty acids from the digestive tract.
- It transports immune cells to and from the lymph nodes.
- It creates and circulates the
In spite of the effectiveness of the lymphatic system and the selective semi-permeable nature of
the capillaries as well as the presence of other forces, there is still a net loss of fluid and
proteins from the blood into the interstitial space.
In activities such as extreme exercise,
trauma, or in some diseases, this net loss can be greatly increased.
The Lymphatic System is a separate system from the arterial and venal vascular systems. It's
function is to return any plasma proteins and fluids that are not picked up by the venous system
from the interstitial space and return it to the circulating blood.
If there was not another way of removing this excess material, edema (swelling) due to fluid and
protein retention in those tissues, would take place. The normal operation of the lymphatic
system keeps edema from developing.
It is also important that any residual metabolites or
toxins produced from trauma or disease be removed including excess fluid, waste products,
bacteria, fats, dead cells, viruses and proteins.
Also, any process that blocks the lymphatic system and its flow will result in edema or swelling.
These obstructions may occur from injury, disease processes, parasites, inflammation, and surgery
to mention a few.
There may also be an excessive leakage from the arterial vessels and if it
exceeds the rate of venous and lymphatic removal, edema will result.
Heart failures can also cause a backup in the venous and lymphatic flow resulting in edema.
The lymphatic vessels at the capillary area are made up of a single layer of epithelial cells.
This system begins with a series of sacs with large endothelial pores and relatively low
This facilitates the movement of both fluid and protein into the lymphatic chain. These lymphatic capillaries drain into larger vessels (similar to following a bush from the small twigs at the leaves and going toward its trunk) which eventually drain back into the blood stream at the subclavian veins near the heart.
Lymph flow towards the heart is propelled along its path similar to the way venous blood moves toward the heart. There is an extensive series of one-way valves in both the veins and the lymphatic vessels. The pumping action is a result of smooth muscle activity around the vessels as well as skeletal muscle activity (this includes the core muscles) and breathing.
This is one of the reasons that exercise is so important. It becomes one of the major pumps for returning both venous blood and lymph back to the circulatory system near the heart.
The lymphatic system is efficient enough to return approximately 5 liters of fluid back to the circulatory system every 24 hours. In addition, about one fourth to one half of the total plasma protein is returned back to the blood stream via this system!
The lymphatic system also moves substances absorbed from the gastrointestinal tract, generally fats, and moves them to the blood stream. At strategic points along the path of the lymphatic chain are lymph nodes.
I have heard the lymph nodes referred to as the post office of the body. All parcels must pass through it and are then sent to where they need to be.
These nodes remove microorganisms such as cells that have been damaged through both physical and disease activities, as well as cellular debris and pathogens like bacteria and viruses. It also removes other foreign material.
When the body is actively fighting infections, allergic antigens, or ridding itself of excess toxins and cellular debris, swollen glands may result.
It is primarily in these lymph nodes that lymphocytes (a type of white blood cell that defends the body against infection by producing chemicals to destroy foreign molecules,) along with macrophages (a type of white blood cell which eats foreign material in the body), destroy the waste materials that have been filtered by the lymph nodes.
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