The lymphoid system

Question 1

Where do B cells mature?

Answer 1

In the bone marrow

Question 2

Where do T cells mature?

Answer 2

In the thymus

Question 3

What are the primary/central lymphoid organs?

Answer 3

The bone marrow and the thymus

Question 4

What are the secondary/peripheral lymphoid tissues/organs?

Answer 4

Lymph nodes
Spleen
Tonsils (Waldeyer's ring)
Epithelio-lymphoid tissues
Bone marrow

Question 5

What are the functions of the lymphoid system?

Answer 5

Return lymph to the circulation (fluid homeostasis)
Filtration of circulatory fluids - bring lymph into contact with immune system
Location for cells of the immune system

Question 6

How large may normal lymph nodes be?

Answer 6

Up to 2.5cm

Question 7

What ensures the direction of flow in lymph vessels?

Answer 7

Valves

Question 8

What cell populations are found in lymph nodes?

Answer 8

Lymphocytes
Macrophages and dendritic cells (antigen presenting cells)
Endothelial cells

Question 9

Where in the lymph node are B cells found?

Where are T cells found?

Answer 9

B cells: In the follicles

T cells: the remainder of the lymph node

Question 10

What causes lymphadenopathy?

Answer 10

Local inflammation
Systemic inflammation
Malignancy
Others

Question 11

How can internal lymph node groups be viewed?

Answer 11

Radiologically

Question 12

What are the likely causes of a predominant B-cell reactive response in a lymph node?

Answer 12

Autoimmune conditions

Infections

Question 13

What is a likely causes of a predominant phagocytic response in a lymph node?

Answer 13

Draining a tumour site

Question 14

What is a likely cause of a predominant T cell response in a lymphocyte?

Answer 14

Viral infections

Drugs e.g. phenytoin

Question 15

What investigation should you do when you find generalised lymphadenopathy?

Answer 15

FBC

This may give the diagnosis and you may not need to do a biopsy

Question 16

How big is the spleen normally?

Answer 16

up to 150-200g

12x7x3 cm

Question 17

what vessels supply and drain the spleen?

Answer 17

The splenic artery (branch of coeliac trunk) and splenic vein (forms the portal vein with the superior mesenteric vein)

Question 18

When might a spleen rupture?

Answer 18

Trauma or if it is diseased (more prone to rupture)

Question 19

Briefly describe the structure of the spleen

Answer 19

Encapsulated
White and red pulp separated by marginal zone
White pulp: lymphoid tissue composed of periarterial lymphatic sheath containing T cells (CD4+) and lymphatic nodule/follicle containing B cells
Red pulp: contains blood. Made of sinusoids and cords containing macrophages, fibroblasts and cells in transit.
Marginal zone: mainly non-circulating B cells, also specialised macrophages which take up CHO antigens

Question 20

What is the function of the spleen?

Answer 20

Removal of old cells, cellular debris and microorganisms from the blood
Response to bacterial and fungal infections

Question 21

List three ways in which the spleen can remove old cells, debris and microorganisms from the blood

Answer 21

Phagocytosis
Removal of red cells which are not sufficiently deformable to pass through sinusoids
Removal of intracellular debris or organisms when the cell passes through the inter-endothelial slit.

Question 22

Name three conditions in which there are RBCs which are not sufficiently deformable to pass through the sinusoids in the spleen

Answer 22

Hereditary spherocytosis
Malaria
Sickle cell anaemia

Question 23

What type of red cells are removed by phagocytosis in the spleen?

Answer 23

Those coated with IgG antibody

Question 24

What is the hypersplenism triad?

Answer 24

Splenomegaly
Fall in one or more cellular components of blood
Correction of cytopenias by splenectomy