MedCourseFinder

Structure

Lymph nodes

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

Lymph nodes are small, encapsulated, bean-shaped secondary lymphoid organs placed along lymphatic vessels. They filter lymph and are the main sites where lymph-borne antigens meet lymphocytes.

Terminologia Anatomica (Latin): Nodi lymphoidei · Open in the 3D atlas

Location

Several hundred nodes are distributed in groups, often at flexures and in the root of organs: cervical, axillary, inguinal, mediastinal, para-aortic and mesenteric are the clinically important groups. Normal nodes are a few millimetres to about 1 to 2 cm and are usually not palpable except small inguinal nodes.

Structure

A capsule with trabeculae surrounds a cortex (B-cell follicles), paracortex (T cells and dendritic cells) and medulla (cords of plasma cells and macrophages, with medullary sinuses). Several afferent lymphatics enter the convex surface; one or two efferent vessels leave at the hilum.

Blood supply

A small artery enters at the hilum and forms capillary networks in the cortex; blood returns through post-capillary high endothelial venules, where lymphocytes enter the node from the blood, and then a hilar vein.

Innervation

Sympathetic fibres follow the vessels and supply the smooth muscle of the capsule and trabeculae; nerve supply is mostly vasomotor and modulates local immune activity. Pain in an inflamed node results from capsular stretch.

Function

Nodes filter lymph through macrophage-lined sinuses, present antigen to naive lymphocytes, and support clonal expansion and germinal-centre antibody responses. Activated lymphocytes leave in efferent lymph to recirculate.

Clinical correlations

Lymphadenopathy may be reactive (tender, soft), infective or malignant (firm, rubbery or hard, matted, non-tender). A left supraclavicular (Virchow) node suggests abdominal or thoracic malignancy. Sentinel node biopsy stages some cancers, and node dissection can cause lymphoedema.

Common exam points

  • Describe a node by size, consistency, tenderness, mobility and site, and examine the whole drainage area.
  • Cortex: B-cell follicles; paracortex: T cells; medulla: plasma cells.
  • Afferent vessels enter the convex surface; efferent vessels leave at the hilum.
  • Axillary nodes drain the breast and upper limb; inguinal nodes drain the lower limb, perineum and lower abdominal wall.
  • Left supraclavicular node (Virchow) is a classic sign of upper abdominal malignancy.

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Moore KL, Dalley AF, Agur AMR. Clinically Oriented Anatomy. Wolters Kluwer, 8th edition (2018) — Tier 3 (textbook)
  3. Kumar V, Abbas AK, Aster JC. Robbins and Cotran Pathologic Basis of Disease. Elsevier, 10th edition (2020) — Tier 3 (textbook)

References are listed only where the article cites them. See the sources page for the full policy. How sources are chosen and credited

Back to the index