Bean-shaped bodies strung along lymph vessels, with several vessels entering the convex side and one leaving at the hilum
Lymph node â afferent vessels in, efferent vessel out.
Anatomy · Heart & blood vessels
Lymph node
Bean-shaped filter of lymph
Lymphatic system · immune surveillance
A small, bean-shaped organ, typically 1â25 mm long, that lies along lymphatic vessels and filters lymph. Several afferent lymphatics enter its convex surface and a single efferent vessel leaves at the hilum. Inside, macrophages and dendritic cells present antigens to B and T lymphocytes, so nodes swell during infection. Clusters are found in the neck, armpit and groin.
How to spot them
- âļBean shape with a convex surface (afferent vessels enter) and an indented hilum (efferent vessel, artery and vein)
- âļFibrous capsule with trabeculae dividing it
- âļOuter cortex with B-cell follicles, paracortex of T cells, inner medulla with cords and sinuses
- âļMany afferent lymphatics in, one efferent out, so flow slows through the node
What to know
Roughly 500â600 exist in the body, clustered in the neck, armpit and groin
Lymph node â cervical, axillary and inguinal groups.
When you have a sore throat, the tender swellings you feel beneath the jaw are these organs enlarging
Lymph node â reactive lymphadenopathy.
Their cortex holds follicles with germinal centres where B cells multiply, while the paracortex is rich in T cells
Lymph node â cortex, paracortex and medulla.
The first of these to receive drainage from a tumour is biopsied to see whether cancer has spread, e.g. in breast cancer and melanoma
Lymph node â the sentinel node.
A hard one above the left collarbone can signal abdominal cancer, and is named after a German pathologist
Lymph node â Virchow's node (Troisier's sign).
Lymph passes through sinuses lined by macrophages that trap bacteria and debris before it returns to the blood
Lymph node â subcapsular, cortical and medullary sinuses.
Key ideas
- Function: filtration of lymph plus a meeting place where antigen-presenting cells show antigens to circulating lymphocytes.
- Afferent vessels are more numerous than efferent ones, so lymph slows and macrophages get time to clear it.
Quick-fire facts
- âĒCommonly quoted total is about 500â600 nodes, with large groups in the head and neck, axilla and groin.
- âĒNormal size is up to about 1 cm; up to 2.5 cm in the groin.
- âĒAfferent lymphatics have valves and enter via the capsule; the efferent vessel leaves the hilum.
- âĒB cells are concentrated in cortical follicles; T cells in the paracortex.
- âĒVirchow's node lies in the left supraclavicular fossa and receives drainage from the thoracic duct.
- âĒThe spleen and thymus are lymphoid organs but, unlike nodes, the spleen filters blood, not lymph.
- âĒSentinel lymph node biopsy is used in breast cancer and melanoma staging.
- âĒIn infectious mononucleosis (glandular fever), nodes in the neck enlarge and become tender.
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Sources
- OpenStax â 21.1 Anatomy of the Lymphatic and Immune Systems â Anatomy and Physiology 2e
- TeachMeAnatomy â The Lymphatic System