Lymph Node Development

Introduction

Basic structure of an adult lymph node.

Schematic of lymph node.

Lymphatic vasculature drains lymph fluid from the organ tissue space and returns it to the blood vasculature for recirculation. Lymph nodes lie on the path of lymph vessels and these structures monitor and carry out immune surveillance of this fluid for antigens and pathogens, trapping them within the lymph nodes and generating immune responses.

Some Recent Findings

Lymph sacs are not required for the initiation of lymph node formation "As proposed by Florence Sabin more than a century ago and recently validated, the mammalian lymphatic vasculature has a venous origin and is derived from primitive lymph sacs scattered along the embryonic body axis. Also as proposed by Sabin, it has been generally accepted that lymph nodes originate from those embryonic primitive lymph sacs. However, we now demonstrate that the initiation of lymph node development does not require lymph sacs."

Adult Lymph Node

• Encapsulated organ (1 mm - 2 cm)
• In lymph vessel pathways “filter”
• Afferent- towards node
• Efferent- away from node
• Location throughout the entire body - Concentrated in axilla, groin, mesenteries
• Antigen transformed lymphocytes from the blood

Lymph Node Cartoon Gallery

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  Detailed structure

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  Detailed structure

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  Simple structure

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  Wiki image

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  internal structure

Links: Immunobiology - Figure 1.8. Organization of a lymph node | MBoC Figure 24-16. A simplified drawing of a human lymph node

Schematic representation of the organization of a lymph node. Afferent lymphatics enter lymph nodes and deliver lymph to the subcapsular sinus (SCS), which forms a channel around the periphery of the lymph node. Lymphatic sinuses run from the SCS through the cortex to the medulla, and exit the lymph node via efferent lymphatic vessels on the opposite, hilar, side of the organ. B cell follicles containing follicular dendritic cell (FDC) networks are arranged in the lymph node cortex and are separated from the SCS by a layer of marginal reticular cells (MRC). T cells zones in the paracortex, which contain many fibroblastic reticular cells (FRC), are separated by the cortical ridge, an area rich in T cells, dendritic cells (DCs), blood vessels, and FRC. Blood vessels enter and exit the lymph node on the hilar side, and snake through the lymph node like the branches of a tree. Specialized high endothelial venules (HEVs) in the paracortex and cortical ridge allow entry of leukocytes from the blood.

Adult Lymph Node Structure

• Capsule - dense connective tissue
• Trabeculae - dense connective tissue
• Reticular Tissue - Reticular cells and fibers, supporting meshwork
• Macrophages - process antigen, difficult to distinguish from the reticular cells.

Lymph

• enters the node through afferent vessels
• filters through the sinuses
• leaves through efferent vessels

Subcapsular sinus = marginal sinus

Continuation of trabecular sinus

Adult Lymphocytes

The following data is from a recent article and review of live adult mouse lymphocytes (T and B cells) imaged within a lymph node.

Both lymphocyte types:

• Spend 8 to 24 h in the lymph node interstitium.
• Transit across a lymphatic endothelium to exit.
• Enter a network of medullary sinuses.
• Drain from sinuses into efferent lymphatic vessels.

Lymphocyte Migration Speeds

T cells - 10–12 μm/min in the follicle diffuse cortex, peak velocities up to 30 μm/min. (move more slowly in the medullary region near the hilus of the lymph node than in the paracortex)

B cells - 6 μm/min in the follicle diffuse cortex, peak velocities up to 20 μm/min.

Both cortical T cells and follicular B cells move in random directions following "guide cells".

Lymphocyte Guide Cells

FDC - Follicular Dendritic Cells, may guide B cells in the follicle.

FRC - Fibroblastic Reticular Cells, may guide T cells in the follicle.

Lymphocyte Movies

Adult Mouse Lymph Node - T cell motility

Transendothelial migration Quicktime | Flash	T cell zone Quicktime | Flash	Medullary sinus Quicktime | Flash
Sinus endothelial barrier Quicktime | Flash	Bi-directional traffic Quicktime | Flash	Cross the sinus endothelial barrier Quicktime | Flash

References

Reviews

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Articles

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Glossary Links

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Cite this page: Hill, M.A. (2026, March 10) Embryology Lymph Node Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Lymph_Node_Development

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© Dr Mark Hill 2026, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G