Spleen how does it look and how do i identify white red pukp and other parts of it in histology

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Spleen Histology: Complete Guide

Overview & Low-Power Appearance

At low magnification (scanning power), the spleen is the only major lymphoid organ with no cortex/medulla distinction. Instead you see two intermingled regions flooding the entire section:

A thick dense connective tissue capsule on the outer surface
Trabeculae — thick bands of connective tissue projecting inward from the capsule, carrying trabecular arteries and veins
White pulp — scattered dark blue/purple islands
Red pulp — the dominant pink background filling everything between

Spleen schematic and low-power photomicrograph showing capsule, trabeculae, white pulp nodules, and red pulp

How to Identify Each Part

1. Capsule & Trabeculae

Feature	What you see in H&E
Capsule	Thick eosinophilic (pink) band of dense connective tissue at the periphery; contains scattered myofibroblast nuclei
Trabeculae	Dense pink connective tissue bundles radiating inward; large vessels (trabecular arteries/veins) run inside them — the trabecular vein is thin-walled and lumen is wide

Key clue: Trabeculae are the only pink dense structures that contain a large vascular lumen. They connect the capsule to the interior and are your anchor point when orienting a spleen section.

2. White Pulp

Color in H&E: Dark blue-purple (basophilic), because the densely packed lymphocyte nuclei stain intensely with hematoxylin.

In fresh tissue: Whitish-gray islands.

White pulp has two components:

a) Periarteriolar Lymphatic Sheath (PALS)

A cuff of T lymphocytes surrounding the central artery (a small arteriole that has left the trabecula)
The central artery sits roughly in the middle of the sheath — this is the defining feature
Appears as a dark blue elongated sleeve around a small artery in longitudinal section

b) Splenic Nodules (Malpighian corpuscles)

Compact spherical or oval dark blue masses = B-lymphocyte follicles
When activated: show a paler germinal center (large, proliferating B cells with vesicular nuclei) surrounded by a dark mantle of small lymphocytes
The central artery is pushed eccentrically to the periphery of the nodule (no longer central!) — this is a classic exam point

White pulp (W) and red pulp (R) in H&E — note the central arteriole (arrowhead) within the PALS, surrounded by the pink-red pulp

Quick identification rule: Find a small artery → look for the blue lymphocyte cuff around it → that is white pulp.

3. Marginal Zone

The transition zone between white and red pulp
Contains a mix of B cells, macrophages, and small sinusoid-like vascular spaces
Slightly less densely blue than the PALS/nodule core
Important site for trapping blood-borne antigens and first-responder B cells

4. Red Pulp

Color in H&E: Pink (eosinophilic) — filled with erythrocytes.

Red pulp has two components that alternate throughout:

a) Splenic Sinusoids (Venous Sinuses)

Irregular elongated pale/clear spaces or spaces filled with RBCs
Lined by unique "stave cells" — rod-shaped endothelial cells whose nuclei bulge into the lumen (look like barrel staves)
The basal lamina is discontinuous (fenestrated barrel-hoop pattern), allowing RBCs to squeeze through

b) Splenic Cords (Cords of Billroth)

The tissue between the sinusoids
Contains RBCs, platelets, macrophages, lymphocytes in a reticular framework
Macrophages here phagocytose old/damaged RBCs — you may see macrophages with engulfed erythrocytes (deeply eosinophilic inclusions)

Red pulp at high magnification — sinusoids (S) with stave-cell endothelium (arrows) and splenic cords (C)

Quick identification rule: The red pulp = alternating pattern of pale slit-like sinusoids + RBC-filled cords. The stave-cell nuclei poking into the sinus lumen are distinctive at high power.

H&E Summary Table

Structure	Color (H&E)	Key identifying feature
Capsule	Pink	Thick outer band, myofibroblasts
Trabeculae	Pink	Inward projections, contain blood vessels
White pulp (PALS)	Dark blue-purple	Sleeve of lymphocytes around central artery
Splenic nodule	Dark blue-purple with pale center	Round B-cell follicle; central artery eccentric
Marginal zone	Intermediate	Thin transitional band at WP/RP border
Red pulp cords	Pink	Reticular meshwork, macrophages, RBCs
Splenic sinusoids	Pale/clear to pink	Stave-cell nuclei bulging into lumen

Normal H&E section — recognizing white vs. red pulp at a glance

H&E section of normal spleen showing blue-purple white pulp nodules scattered throughout the pink-red red pulp

In this image you can immediately spot:

Dark violet-blue round/oval masses = white pulp (lymphoid nodules/PALS)
Diffuse pink background = red pulp (cords + sinusoids)
The proportion is approximately 80% red pulp, 20% white pulp

Blood Flow Recap (helps understand the architecture)

Splenic artery → trabecular artery → central arteriole (enters white pulp, acquires PALS) → penicillar arterioles → sheathed capillaries → open circulation into splenic cords (RBCs squeeze through sinusoid walls to return to blood) → sinusoids → trabecular veins → splenic vein.

Sources: Histology: A Text and Atlas (Ross & Pawlina), 9th ed.; Junqueira's Basic Histology, 17th ed.

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