Lymphatics and secondary lymphoid organs

Question 1

What are the two primary lymphoid tissues?

Answer 1

bone marrow and thymus

Question 2

What are 4 secondary lymphoid tissues?

Answer 2

– Lymph nodes
– Spleen
– Tonsils, adenoids
– Payer’s patches

Question 3

What is the generalized flow of the lymphatic system?

Answer 3

1. efferent lymph vesels carry lymphocytes and macrophages away from the lymph node
2. Efferent vessels empty into the thoracic duct at the left subclavian vein
3. Normal blood flow through the heart and arteries
4. Some fluid leaks out as interstitial fluid at the capillary bed and is taken up by the lymphatic capillaries
5. Afferent lymphatic vessels carry lymph to local nodes

Question 4

Afferent vessels bring..? what does it contain ?

Answer 4

lymph fluid from tissues to lymph nodes.

contains antigen carrying dendritic cells, particulate antigen and few lymphocytes

Question 5

Efferent vessels bring…

Answer 5

lymph fluid from lymph nodes via thoracic duct into blood circulation.

Question 6

What are blind-ended lymphatic capillaries ?

Answer 6

the blunt ended capillaries of the lymphatic system that have no physical connection to the normal capillary system

Question 7

tissue fluid management in the lymphatic system is dependent upon which 5 things?

Answer 7

• Capillary hydrostatic pressure
• Capillary permeability
• Effective oncotic pressure (difference between plasma and
interstitium)
• Lymphatic drainage
• Tissue tension

Question 8

which two forces act in opposition at both the arterial and venous sides of the capillary bed? what is the result

Answer 8

Oncotic pressure which is mediated by albumin present in the blood forces fluid back into the capillary

Both the arterial (higher) and venous (lower) BP pushes fluid out

there is always a greater net efflux of fluid at the arterial end than there is influx at the venous end
- results in loss of fluid as interstitium

Question 9

What causes lymphadema?

Answer 9

Blockage or damage of lymphatic vessels leading to accumulation of interstitial fluid, due primarily to impaired
lymphatic drainage

Question 10

lymphadema of the leg often occurs in association with which infection? what causes it?

Answer 10

with filariasis caused by the worm W. bancrofti

Question 11

lymphadema in the arms often occurs after..?

Answer 11

a mastectomy

Question 12

What two things occur in the lymph nodes?

Answer 12

1. lymphocytes encounter and interact with particulate antigen and antigen presenting cells
2. Phagocytosis of particulate matter and microorganisms that enter the lymph
   - prevents spread to bloodstream

Question 13

What is the parenchyma of the lymph node? what is it subdivided into?

Answer 13

tissue part of the lymph node

subdivided into the cortex, paracortex, and medulla

Question 14

What two structures are located in the cortex?

Answer 14

primary and secondary follicles

Question 15

What are in the primary follicles?

Answer 15

naive, non activated B cells

Question 16

What are in the secondary follicles?

Answer 16

Activated B cells in germinal centres

Question 17

What is the paracortex home to?

Answer 17

the T cells

Question 18

What things are located in the medulla?

Answer 18

– Plasma cells secreting antibody

– few activated/memory T cells and B cells transiting into efferent lymph.

Question 19

What kind of epithelial cells are present in high endothelial venules?

Answer 19

simple Cuboidal

Question 20

What is the role of follicular dendritic cells? what is different about them compared to normal dendritic cells?

Answer 20

concentrate particular antigen on the dendrites

• don’t present it in the context of MHC
• b cells can interact with this antigen and potentiate their differentiation

Question 21

What kind of maturation do the B cells in germinal centres undergo?

Answer 21

within the germinal centre there is lots of proliferation of antigen specific B cells

• during this process, the B cell receptor (variable region) will undergo somatic hypermutation to make the receptor potentially better to respond to antigen
• the B cells now better at responding to antigen will be stimulated and proliferate
• those that don’t will be neglected/apoptosed (there is a lot of cell death in the germinal centre)

Question 22

What do the medullary cords contain?

Answer 22

plasma cells that secrete antibodies into medullary sinuses

Question 23

Where do the medullary sinuses empty into?

Answer 23

empty into efferent lymphatic vessels

Question 24

What cells are numerous in the medullary sinuses? what do they do?

Answer 24

macrophages that phagocytose particulate matter and microorganisms in lymph to prevent their entry into blood stream

Question 25

the high endothelial venules are located in which section of the parenchyma?

Answer 25

the paracortex

Question 26

What two things are carried in the efferent lymphatics?

Answer 26

1. antibodies secreted by plasma cells in the lymph node

2. activated/memory T cells and B cells

Question 27

What is the function of the white pulp of the spleen?

Answer 27

generation of T cell responses and B cell responses (antibodies) against blood borne pathogens

Question 28

What is the/are the function(s) of the red pulp of the spleen?

Answer 28

– phagocytosis of blood borne pathogens by
macrophages in splenic cords.
– grooming of red cells as well as phagocytosis of old red cells.

Question 29

What are post-splenectomy patients susceptible to?

Answer 29

blood borne infections such as:
– pneumonia (Streptococcus pneumoniae)
– meningitis (Neisseria meningitidis)

Question 30

What are two characteristic inclusions that appear in the RBCs of post splenectomy patients?

Answer 30

1. Howell Jolly bodies

2. Pappenheimer bodies

Question 31

What are Howell Jolly bodies?

Answer 31

small nuclear remnants (erythroblast nucleus).

Question 32

What are Pappenheimer bodies?

Answer 32

Abnormal granules of iron