Lymphatic vessel

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(Redirected from
Lymphatics
)
Lymphatic vessel
Lymph capillaries in the tissue spaces.
The thoracic duct and right lymphatic duct.
Details
SystemLymphatic system
Identifiers
Latinvas lymphaticum
MeSHD042601
TA98A12.0.00.038
TA23915
THH3.09.02.0.05001
FMA30315
Anatomical terminology]
A still image from a 3D medical animation showing afferent vessels
A still image from a 3D medical animation showing afferent vessels

The lymphatic vessels (or lymph vessels or lymphatics) are thin-walled vessels (tubes), structured like

interstitial fluid from the tissues. Lymph capillaries are slightly bigger than their counterpart capillaries of the vascular system. Lymph vessels that carry lymph to a lymph node are called afferent lymph vessels, and those that carry it from a lymph node are called efferent lymph vessels, from where the lymph may travel to another lymph node, may be returned to a vein, or may travel to a larger lymph duct. Lymph ducts drain the lymph into one of the subclavian veins and thus return it to general circulation
.

The vessels that bring lymph away from the tissues and towards the lymph nodes can be classified as

afferent vessels. These afferent vessels then drain into the subcapsular sinus.[1]
The
subclavian veins
, respectively. There are far more afferent vessels bringing in lymph than efferent vessels taking it out to allow for lymphocytes and macrophages to fulfill their immune support functions. The lymphatic vessels contain valves.

Structure

The general structure of lymphatics is based on that of

lymph capillaries
) lack both the muscular layer and the outer adventitia. As they proceed forward and in their course are joined by other capillaries, they grow larger and first take on an adventitia, and then smooth muscles.

The lymphatic conducting system broadly consists of two types of channels—the initial lymphatics, the prelymphatics or lymph capillaries that specialize in collection of the lymph from the interstital fluid, and the larger lymph vessels that propel the lymph forward.

Unlike the cardiovascular system, the lymphatic system is not closed and has no central pump. Lymph movement occurs despite low pressure due to

arterial pulsation.[3]

Propulsion of lymph through lymph vessel

Lymph capillaries

The lymphatic circulation begins with blind ending (closed at one end) highly permeable superficial lymph capillaries, formed by endothelial cells with button-like junctions between them that allow fluid to pass through them when the interstitial pressure is sufficiently high.

anastomoses) between them and form a very fine network.[6]

Rhythmic contraction of the vessel walls through movements may also help draw fluid into the smallest lymphatic vessels, capillaries. If tissue fluid builds up the tissue will swell; this is called edema. As the circular path through the body's system continues, the fluid is then transported to progressively larger lymphatic vessels culminating in the right lymphatic duct (for lymph from the right upper body) and the thoracic duct (for the rest of the body); both ducts drain into the circulatory system at the right and left subclavian veins. The system collaborates with white blood cells in lymph nodes to protect the body from being infected by cancer cells, fungi, viruses or bacteria. This is known as a secondary circulatory system.

Lymph vessels

The lymph capillaries drain into larger collecting lymphatics. These are contractile lymphatics which transport lymph using a combination of smooth muscle walls, which contract to assist in transporting lymph, as well as valves to prevent the lymph from flowing backwards.

right or thoracic) lymph ducts, or may empty into another lymph node as its afferent lymph vessel.[6] Both the lymph ducts return the lymph to the blood stream by emptying into the subclavian veins

Lymph vessels consist of functional units known as lymphangions which are segments separated by semilunar valves. These segments propel or resist the flow of lymph by the contraction of the encircling smooth muscle depending upon the ratio of its length to its radius.[7]

Function

See also: Lymphatic system

Lymph vessels act as reservoirs for plasma and other substances including cells that have leaked from the vascular system and transport lymph fluid back from the tissues to the circulatory system. Without functioning lymph vessels, lymph cannot be effectively drained and lymphedema typically results.

Afferent vessels

The afferent lymph vessels enter at all parts of the periphery of the

endothelial
lining, which is continuous with a layer of similar cells lining the lymph paths.

Afferent lymphatic vessels are only found in lymph nodes. This is in contrast to efferent lymphatic vessel which are also found in the thymus and spleen.

Efferent vessels

The efferent lymphatic vessel commences from the

medullary
portion of the lymph nodes and leave the lymph nodes at the hilum, either to veins or greater nodes. It carries filtered lymph out of the node.

Efferent lymphatic vessels are also found in association with the thymus and spleen. This is in contrast to afferent lymphatic vessels, which are found only in association with lymph nodes.

Clinical significance

Lymphedema is the swelling of tissues due to insufficient fluid drainage by the lymphatic vessels. It can be the result from absent, underdeveloped or dysfunctional lymphatic vessels. In hereditary (or primary) lymphedema, the lymphatic vessels are absent, underdeveloped or dysfunctional due to genetic causes. In acquired (or secondary) lymphedema, the lymphatic vessels are damaged by injury or infection.[8][9] Lymphangiomatosis is a disease involving multiple cysts or lesions formed from lymphatic vessels.

See also

Additional images

  • Lymphatic system
    Lymphatic system
  • Section across portal canal of pig. X 250.
    Section across portal canal of pig. X 250.

References

  1. ^ "19.2B: Distribution of Lymphatic Vessels". Medicine LibreTexts. 22 July 2018. Retrieved 28 November 2021.
  2. PMID 14581448
    .
  3. ^
    PMID 16597644
    .
  4. ^
    PMID 17846148
    .
  5. PMID 23980683
    .
  6. ^
    ISBN 0-397-51256-2
    .
  7. ISBN 0-7803-8439-3
    .
  8. S2CID 5899689
    .
  9. ^ Krebs R, Jeltsch M (2013). "The lymphangiogenic growth factors VEGF-C and VEGF-D. Part 2: The role of VEGF-C and VEGF-D in lymphatic system diseases". Lymphologie in Forschung und Praxis. 17 (2): 96–104.

Further reading

External links


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