Introduction to the Lymphatic System Flashcards
What is the lymphatic system?
If the heart circulates blood containing oxygen, nutrients and fluid to all tissues of the body then the lymphatic system acts as a countercurrent system, draining from the tissues all the waste materials and recycling surplus fluid, salts, proteins, fat and immune cell back to the body.
What are the components of the lymphatic system?
LYMPHATIC CAPILLARIES:
- blind-ended
- no smooth muscle
- incontinuous basement membrane
COLLECTING VESSELS:
- smooth muscle coverage
- luminal valves (to ensure the direction of fluid)
- basement membrane
LYMPH NODES
How does the fluid in the lymphatic system move about?
The lymphatic system requires the contraction of the muscle around to move the fluid through it. The fluid moving along is much like the movement of peristalsis.
What is lymph?
Lymph is interstitial (tissue) fluid containing salts, proteins and cells, originally formed from a plasma ultrafiltrate.
Describe lymph nodes (glands).
Lymph nodes are filter stations positioned at intervals along the lymph drainage route. They perform two basic functions:
- to clean up the lymph before it re-enters the bloodstream by sieving it out, trapping and destroying (inorganic) foreign bodies
- monitoring the lymph for telltale signs of (organic) predators, eg. infection, so playing a vital role in our immune system responses
Describe the process of lymph drainage.
1) Lymph drainage begins with the absorption of fluid from the tissues.
2) Lymph is transported through larger collecting lymphatic vessels to lymph nodes
3) Lymph nodes filter the lymph where there is also interaction with the immune system.
4) After passing through a series of lymph nodes, large lymphatic vessels eventually discharge lymph into the great veins of the neck.
What are the three main functions of the lymphatic system?
- fluid balance (homeostasis)
- tissue immunity
- fat homeostasis
Describe fluid balance (homeostasis).
Tissue fluid homeostasis is simple: the blood vessels supply fluid and the lymph has to drain it away.
There are forces called Starling forces acting on the fluid, altering the rate at which it enters the lymphatic system. Both the Starling forces acting on the fluid and the tissue are considered.
Describe tissue immunity.
The lymphatic system houses the immune system and is responsible for tissue immunosurveillance (when the fluid flows through lymph nodes, it gets checked for any unwanted organisms).
A common complication of impaired lymph drainage is disturbed immune cell trafficking and infections.
Describe fat homeostasis.
The lymphatic system is responsible for gut fat absorption and peripheral fat reabsorption. There is a close relationship between fat and lymphatics.
When does a lymphoedema occur?
Lymphoedema occurs when the lymphatic system fails.
A lymphoedema results in swelling, such as a leg with a build-up of fluid, cells and fat, as well as a predisposition to infections.
Lymphoedema’s can occur after breast cancer treatment surgery (removing lymph nodes) or treating heart failure, for example.
When does a chronic oedema occur?
A chronic oedema occurs when there is lymphatic failure.
Either the lymph drainage is insufficient, or the lymph load (vascular fluid filtration) exceeds the lymph drainage capacity.
What are the three mechanisms for chronic oedema?
- Lymphatic failure with increased capillary filtration (high lymph load that is overwhelming lymph drainage capacity) results in RELATIVE LYMPHATIC FAILURE
- Lymphatic failure with no increased capillary filtration (normal lymph load) results in ABSOLUTE LYMPHATIC FAILURE (LYMPHOEDEMA)
- Lymphatic failure resulting from sustained increased capillary function exhausting lymph drainage capacity results in ABSOLUTE LYMPHATIC FAILURE (LYMPHOEDEMA)
What is primary lymphoedema?
It is the intrinsic failure of the lymphatic system. It’s caused by alterations (mutations) in genes responsible for the development of the lymphatic system.
The phenotypes vary in age of onset, site, inheritance patterns, associated features, genetic causes, etc.
What is the management of lymphoedema/chronic oedema?
Because there is not one drug or one operation that is known to improve lymph drainage, treatment has to be physically based, intended to stimulate lymph drainage and reduce blood vascular filtration (lymph load). Examples of this would be compression of the affected area, and performing exercise.
