Lymph capillaries or lymphatic capillaries are tiny, thin-walled
microvessel
The microcirculation is the circulation of the blood in the smallest blood vessels, the microvessels of the microvasculature present within organ tissues. The microvessels include terminal arterioles, metarterioles, capillaries, and venule ...
s located in the spaces between
cells
Cell most often refers to:
* Cell (biology), the functional basic unit of life
Cell may also refer to:
Locations
* Monastic cell, a small room, hut, or cave in which a religious recluse lives, alternatively the small precursor of a monastery w ...
(except in the
central nervous system
The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all par ...
and non-vascular
tissues) which serve to drain and process
extracellular fluid. Upon entering the
lumen of a lymphatic capillary, the collected fluid is known as
lymph. Each lymphatic capillary carries lymph into a
lymphatic vessel
The lymphatic vessels (or lymph vessels or lymphatics) are thin-walled vessels (tubes), structured like blood vessels, that carry lymph. As part of the lymphatic system, lymph vessels are complementary to the cardiovascular system. Lymph vessel ...
, which in turn connects to a
lymph node, a small bean-shaped gland that filters and monitors the lymphatic fluid for infections.
Lymph is ultimately returned to the
venous circulation.
Lymphatic capillaries are slightly larger in diameter than
blood capillaries
A capillary is a small blood vessel from 5 to 10 micrometres (μm) in diameter. Capillaries are composed of only the tunica intima, consisting of a thin wall of simple squamous endothelial cells. They are the smallest blood vessels in the body: ...
, and have closed ends (unlike the loop structure of blood capillaries). Lymph capillaries are strategically placed among the blood-related capillaries in order to have efficient and effective uptake from the interstitial fluid during capillary exchange. This intentional formation allows for a more rapid and continuous collection. Their unique structure permits
interstitial fluid to flow into them but not out. The ends of the
endothelial cells
The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vesse ...
that make up the wall of a lymphatic capillary overlap. When pressure is greater in the interstitial fluid than in lymph, the cells separate slightly, like the opening of a one-way swinging door, and interstitial fluid enters the lymphatic capillary. When pressure is greater inside the lymphatic capillary, the cells adhere more closely, and lymph cannot escape back into the interstitial fluid. Attached to the lymphatic capillaries are anchoring filaments, which contain elastic fibers. They extend out from the lymphatic capillary, attaching lymphatic endothelial cells to surrounding tissues. When excess
interstitial fluid accumulates and causes tissue swelling, the anchoring filaments are pulled, making the openings between cells even larger so that more fluid can flow into the lymphatic capillary.
[Tortora, Gerard J.: "Principles of Human Anatomy - 10th edition", page 512. John Wiley and Sons, Inc., 2005. lymph enters the lymph capillaries by osmosis]
Lymph capillaries have a greater internal
ncoticressure than blood capillaries, due to the greater concentration of
plasma proteins in the lymph.
References
{{DEFAULTSORT:Lymph Capillary
Lymphatic organ anatomy
Angiology