Lymphoid Histology

Question 1

How are lymphoid organs classified?

Answer 1

Primary or secondary

Question 2

Define and name primary lymphoid organs.

Answer 2

Sites where lymphocytes develop and mature: bone marrow and thymus.

Question 3

Define and name secondary lymphoid organs.

Answer 3

Sites where mature lymphocytes are activated and respond to pathogens: lymph nodes, spleen and MALT (mucosa-associated lymphoid tissues, accessory as no capsule).

Question 4

Describe what all lymphoid organs have.

Answer 4

Capsule (outer connective tissue layer) and a compartmentalised structure (e.g., cortex, medulla).

Question 5

What are the key histological features of the thymus?

Answer 5

• Hassall’s corpuscles in the medulla
• Cortex and medulla organization with a clear boundary
• Predominantly T-cells; presence of thymic epithelial cells

Question 6

What are the key histological features of lymph nodes?

Answer 6

• Cortex with lymphoid follicles (B-cell zones, often with germinal centres in an active node)
• Paracortex rich in T-cells
• Medulla with medullary cords and sinuses

Question 7

What are the key histological features of the spleen?

Answer 7

• White pulp around central arteries (containing lymphocytes)
• Red pulp with sinusoids and splenic cords (involved in filtering blood)

Question 8

What are the key histological features of tonsils?

Answer 8

• Large lymphoid follicles with germinal centres
• Often have crypts (invaginations) surrounded by lymphoid tissue

Question 9

What colour do lymphocytes stain?

Answer 9

Usually dark blue or purple