[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Histology](https://durgical.com/en/histology/) › [Lymphoid organs](https://durgical.com/en/histology/#a-lymphoid) › Lymph node and spleen under the microscope

[Histology](https://durgical.com/en/histology/) · [Lymphoid organs](https://durgical.com/en/histology/#a-lymphoid)

# Lymph node and spleen under the microscope

- Organ

The lymph node filters lymph and the spleen filters blood. Under the microscope the node has a cortex and medulla; the spleen has white and red pulp.

Updated 2026-11-01

**See it in 3D:** [Spleen](https://durgical.com/en/anatomy/spleen/) · [Neck lymph nodes](https://durgical.com/en/anatomy/lymph-nodes-of-neck/)

## Key points

- Node: B cells in the cortical follicles, T cells in the paracortex, plasma cells in the medullary cords.
- High endothelial venules in the paracortex are where lymphocytes enter from the blood.
- Spleen: the periarteriolar sheath (T) and follicles (B) make up the white pulp; cords and sinusoids make up the red pulp.
- Metastatic cells arriving in lymph lodge first in the subcapsular sinus.
- Without a spleen, Howell-Jolly bodies appear on the smear and the risk of infection by encapsulated bacteria rises.

## What it is

The lymph node and the spleen are secondary lymphoid organs built on a mesh of reticular fibres, but they filter different fluids and so look different. The node receives lymph through afferent vessels and passes it along sinuses between a cortex with follicles and a medulla with cords; the spleen receives no lymph and organizes its tissue around arteries. This page covers the microscopic structure; immune function is covered in the Immunology section.

## Structure

- Node: a connective tissue capsule with trabeculae; afferent vessels enter on the convex side and the efferent leaves at the hilum, with the artery and vein.
- Node, path of lymph: subcapsular sinus → trabecular (cortical) sinuses → medullary sinuses → efferent vessel.
- Node, outer cortex: B-cell follicles; primary follicles have no germinal centre, secondary follicles have a pale germinal centre ringed by a dark mantle zone.
- Node, paracortex: a T-cell zone with high endothelial venules, where lymphocytes leave the blood to enter the node.
- Node, medulla: medullary cords with plasma cells and macrophages, separated by medullary sinuses.
- Spleen: capsule and trabeculae, no cortex or medulla and no afferent lymphatics.
- Spleen, white pulp: the periarteriolar lymphoid sheath (T cells) around the central artery and B-cell follicles; the marginal zone surrounds it.
- Spleen, red pulp: splenic cords (of Billroth) and venous sinusoids lined by elongated «barrel-stave» endothelium on a discontinuous basal lamina, which red cells must squeeze through.

## How to tell the lymphoid organs apart under the microscope

| Organ | Layout | Giveaway feature | Epithelium and lymphatics |
| --- | --- | --- | --- |
| Lymph node | Complete capsule; cortex with follicles, paracortex and medulla with cords | Subcapsular sinus under the capsule and high endothelial venules in the paracortex | No epithelium; afferent lymphatics on the convex side, efferent at the hilum |
| Spleen | Capsule with trabeculae; scattered white pulp in abundant red pulp | Follicles with an off-centre central artery and lots of blood around them | No epithelium; no afferent lymphatics, efferent only |
| Thymus | Lobules with a dark cortex and a pale medulla | Hassall's corpuscles in the medulla; no follicles or germinal centres | Mesh of thymic epithelial cells; no afferent lymphatics |
| Palatine tonsil | No complete capsule; follicles with germinal centres under an epithelium | Deep crypts lined by non-keratinized stratified squamous epithelium | Surface epithelium; no afferent lymphatics, efferent only |

## Markers

- Silver stain: reticular fibres (type III collagen)
- CD20: B follicles
- CD3: paracortex and periarteriolar sheath
- CD138: medullary plasma cells

## Clinical notes

- Viral infections tend to expand the paracortex; antibody responses expand the follicles and their germinal centres.
- In sickle cell disease, repeated infarcts leave a small, scarred spleen (autosplenectomy).
- Traumatic rupture of the spleen bleeds heavily because the red pulp is a large blood reservoir.

## Memory aid

The node is a lymph sieve with «B outside, T in the middle, plasma cells at the bottom»; the spleen is a blood sieve where the white hugs the artery and the red is the mesh.

## Test yourself

Think of the answer, then tap the question to see it.

## Which zone of the lymph node is rich in T cells?

The paracortex, between the cortical follicles and the medulla.

## Why does the spleen have no subcapsular sinus?

It receives no lymph through afferent vessels: it filters blood, not lymph.

## What surrounds the central artery in the splenic white pulp?

The periarteriolar lymphoid sheath, made mostly of T cells.

## What feature of splenic sinusoids forces red cells to deform?

Elongated endothelial cells with slits between them and a discontinuous, ring-like basal lamina.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/histology/lymph-node-and-spleen-under-the-microscope/)

## See it in 3D

The structures of Durgical's 3D anatomy where it is found.

- [Spleen](https://durgical.com/en/anatomy/spleen/)
- [Neck lymph nodes](https://durgical.com/en/anatomy/lymph-nodes-of-neck/)

## Related

- [Thymus and tonsils under the microscope](https://durgical.com/en/histology/thymus-and-tonsils-under-the-microscope/)
- [Lymphatic vessels](https://durgical.com/en/histology/lymphatic-vessels/)
- [Blood cells on a smear: erythrocytes, leukocytes, platelets](https://durgical.com/en/histology/blood-cells-on-a-smear-erythrocytes-leukocytes-platelets/)
- [Hematopoiesis and bone marrow](https://durgical.com/en/histology/hematopoiesis-and-bone-marrow/)
- [Connective tissue proper: cells and fibres](https://durgical.com/en/histology/connective-tissue-proper-cells-and-fibres/)

## Related conditions

- [Sickle cell disease](https://durgical.com/en/conditions/sickle-cell-disease/)
- [Splenic injury](https://durgical.com/en/conditions/splenic-injury/)

## Microorganisms

- [Streptococcus pneumoniae](https://durgical.com/en/microbiology/streptococcus-pneumoniae/)
- [Neisseria meningitidis](https://durgical.com/en/microbiology/neisseria-meningitidis/)
- [Haemophilus influenzae](https://durgical.com/en/microbiology/haemophilus-influenzae/)

[← All of histology](https://durgical.com/en/histology/)

Educational content on normal microscopic structure and its clinical relevance; no substitute for studying slides or for a health professional's advice.

Sources: [21.1 Anatomy of the Lymphatic and Immune Systems](https://openstax.org/books/anatomy-and-physiology-2e/pages/21-1-anatomy-of-the-lymphatic-and-immune-systems) (OpenStax, Anatomy and Physiology 2e, 2022); [Lymph Nodes](https://training.seer.cancer.gov/anatomy/lymphatic/components/nodes.html) (NCI SEER Training Modules, 2026); [Spleen](https://training.seer.cancer.gov/anatomy/lymphatic/components/spleen.html) (NCI SEER Training Modules, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/histology/lymph-node-and-spleen-under-the-microscope/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/histology/lymph-node-and-spleen-under-the-microscope/