Week 2- structure and function of the lymph nodes

Question 1

What is the origin of lymphoid cells? What do these then develop into?

Answer 1

Haematopoetic stem cells. Turn into precursor lymphoid cells.

Question 2

Precursor lymphoid cells can develop in two areas of the body, what are these and how do they develop from these areas further?

Answer 2

They can either go to the thymus or the bone marrow. B cells mature in the bone marrow and T cells mature in the thymus. Then they both migrate to lymphoid tissues.

Question 3

What are the central (primary) lymphoid tissues?

Answer 3

Bone marrow Thymus

Question 4

What are the secondary (peripheral) lymphoid tissues?

Answer 4

Lymph nodes Spleen Tonsils Epithelio-lymphoid tissues Bone marrow

Question 5

What is the normal size of lymph nodes?

Answer 5

Normally pea sized.

Question 6

Where are lymph nodes located?

Answer 6

Located along the course of lymphatic vessels.

Question 7

How is fluid moved within the lymph node? Where does the fluid come from and where is it returned too?

Answer 7

Passively. It takes in fluid from the tissues and returns it to the blood stream.

Question 8

What ensures direction of flow within lymph vessels?

Answer 8

Valves.

Question 9

Describe the function of the afferent channel in the lymph nodes?

Answer 9

They drain lymph through the capsule into the peripheral sinus.

Question 10

Describe the function of the efferent vessel?

Answer 10

Drains the hilum to

• cisterna chyli/thoracic duct
• Left jugular, subclavian or bronchomediastinal trunks
• Right jugular, subclavian or bronchomediastinal trunks

And then to the venous system at the junction of the left or right jugular and subclavian veins.

Question 11

Where does the blood supply (both arterial and venous) enter the lymph node?

Answer 11

at the hilum.

Question 12

Where specifically in the lymph node is the lymph filtered? What occurs to the lymph after this?

Answer 12

Lymph parenchyma.

returns to the blood stream

Question 13

NOTE- there is a traffic of cells between the lymph and the node parenchyma. There are interactions between the lymph cells and cells in the parenchyma.

Question 14

What is chylous ascites?

Answer 14

Ascitic fluid made up of lipid rich lymph fluid.

Question 15

What are the function of lymph nodes?

Answer 15

Return lymph to the circulation:

• Important function in fluid homeostasis
• Prevent excessive accumalation of fluid in the tissues-oedema.

Filter lymph before return to the circulation:

• cell traffic
• Interactions with immune competent cells

Question 16

What types of cells do the lymph nodes ‘house’? What does this allow?

Answer 16

Cells of the innate immune system- however allows communication between the innate and adaptive immune system.

Question 17

Specifically, which cells reside in the lymph nodes?

Answer 17

B cells

T cells

NK cells

Macrophages (antigen presenting cells)

Dendritic cells

Endothelial cells

Question 18

In the lymph node, what are the B cells associated with?

Answer 18

Associated with follicles and germinal centres. Plasma cells are mainly in the medulla.

Question 19

What can cause lymphadenopathy?

Answer 19

Viral causes- EBV

Bacterial causes e.g. tonsillitis.

Malignancy- especially metastatic

Lymphoma

Autoimmune causes

Sarcoidosis

Question 20

NOTE- specific groups of nodes drain specific areas.

Question 21

When a patient has a specific regional lymphadenopathy, where should you examine?

Answer 21

You should examine the area that drains to those nodes.

Question 22

What sort of stimulation (e.g. bacterial) will cause a predominant T cell response within a lymph node?

Answer 22

Viral infections

Drugs e.g. phenytoin

Question 23

What sort of stimulation (e.g. bacterial) will cause a predominant B cell response within a lymph node?

Answer 23

Auto-immune conditions

Infections

Question 24

What sort of stimulation (e.g. bacterial) will cause a predominant phagocytic response within a lymph node?

Answer 24

Draining a tumour site.

Question 25

What does generalised lymphadenopathy suggest?

Answer 25

Suggests a generalised inflammatory response or widespread malignancy.

Question 26

What is the normal weight of the spleen?

Answer 26

150-200g.

Question 27

What are the two key aspects of the spleen?

Answer 27

Diaphragmatic surface Visceral surface- left kidney, gastric fundus, tail of the pancreas, splenic flexure of the colon.

Question 28

Describe the blood supply to the spleen?

Answer 28

Splenic artery supplies it- branch of the coeliac axis. Drains via splenic vein (combines with superior mesenteric vein to form portal vein).

Question 29

Describe the structure of the spleen?

Answer 29

An encapsulated organ. The parenchyma includes red and white pulp.

Question 30

What makes up the red pulp of the spleen?

Answer 30

Contains sinusoids and cords. Sinusoids are fenestrated, lined by endothelial cells, supported by hoops of reticulin. Cords contain macrophages and some fibroblasts and cells in transit (RBC, WBC, PC and some CD8 + T cells).

Question 31

NOTE ## Footnote Fulfills the same function for blood as lymph nodes do for lymph fluid i.e. acts as a filter for the blood –Detect, retain and eliminate unwanted, foreign or damaged material –Facilitate immune responses to blood borne antigens

Question 32

What makes up white pulp?

Answer 32

It makes up the peri-artreiolar lymphoid sheath (PALS) This is expanded by lymphoid follicles- may show reactive changes. Antigen reaches the white pulp via the blood. APC's in the white pulp present antigen to immune reactive cells. When stimulated by antigen, B and T cell responses may occur.

Question 33

What may a patient with splenic enlargement feel like?

Answer 33

Not want to eat- sense of constant fullness. Pain if it has infarcted. Hypersplenism- triad of splenomegaly, fall in one or more cellular components of blood, correction of cytopenias by splenomegaly.

Question 34

What can cause splenomegaly?

Answer 34

Infection Congestion Haematological disorders Inflammatory conditions Storage diseases

Question 36

Name some causes of hyposplenism?

Answer 36

Most common- splenectomy Then Coeliac disease Sickle cell disease Sarcoidosis Iatrogenic- non surgical

Question 37

What are features of reduced red pulp function?

Answer 37

Howell Jolly bodies- small portion of DNA left in RBC's nucleus. Normally the spleen would eliminate these, however due to its hypofunction this does not occur. Other red cell abnormalities.