Lymphatics and Secondary LOs

Question 1

Secondary LOs

Answer 1

Lymph nodes
Spleen
Tonsils, adenoids
Peyer's patches
Where mature lymphocytes generate immune responses

Question 2

Afferent versus efferent lymphatic vessels

Answer 2

Afferent: bring lymph fluid from tissues to lymph nodes - contains antigen carrying DCs, particulate antigen and a few lymphocytes
Efferent: take lymph fluid from lymph nodes via thoracic duct into blood circulation

Question 3

Tissue fluid management depends on…

Answer 3

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

Question 4

Lymphedema

Answer 4

Blockage or damage of lymphatic vessels
Net accumulation of interstitial fluid due to poor damage
Because of reduced removal of protein from interstitium, there is a lowering of colloid osmotic pressure differential

Question 5

Elephantiasis

Answer 5

Lymphedema of the leg, which may occur in association with filariasis
W. bancrofti migrates through lymphatic system and causes regional lymphatic obstruction

Question 6

Lymph node function

Answer 6

Generation of T and B cell immune responses
Provides a location where lymphocytes can encounter and interact with particulate antigen and APCs
Phagocytosis of particulate matter and microorganisms that enter lymph to prevent their entry into blood stream
Elegant system that allows for lymphocyte activation and provides a barrier to spread of infection

Question 7

Lymph node structure

Answer 7

Capsule
Sinuses (subcapsular, cortical, medullary)
Afferent and efferent lymphatics
Blood vessels
Parenchyma (cortex, paracortex, medulla)

Question 8

3 regions of the lymph node

Answer 8

Cortex: primary follicles (naive B cells, not activated), and secondary follicles (activated B cells in germinal centers)
Paracortex: T cell areas, also some B and DC cells
Medulla: plasma cells secreting antibody, few activated/memory T cells and B cells transiting into efferent lymph

Question 9

High endothelial venules

Answer 9

Cuboidal cells

Express specific adhesion molecules that allow lymphocytes to adhere and migrate out

Question 10

Follicular dendritic cell

Answer 10

Stay in the follicles
Concentrate particulate antigen in their dendrites
B cells can interact

Question 11

Medullary chords

Answer 11

Medullary chords contain plasma cells that secrete antibodies into medullary sinuses

Question 12

Medullary sinuses

Answer 12

Empty into efferent lymph vessels
Contain numerous macrophages that phagocytose particulate matter and microorganisms in lymph to prevent their entry into blood stream

Question 13

Efferent lymphatic

Answer 13

Carry antibodies secreted by plasma cells in the lymph node
Carry activated/memory T and B cells into thoracic duct, which empties into venous circulation
Facilitates distribution of antibodies and effector cells throughout the body to fight infection

Question 14

2 areas of the spleen and their function

Answer 14

1. White pulp: generation of T cell responses and B cell responses (antibodies) against blood borne pathogens
2. Red pulp: phagocytosis of blood borne pathogens by macrophages in splenic chords, grooming of red cells and phagocytosis of old ones

Question 15

Post-splenectomy

Answer 15

Patients are susceptible to blood borne infections like pneumonia (strep pneumoniae) and meningitis (Neisseria meningitidis)
Such infections can be fatal
Have to be immunized against these pathogens and treated promptly

Question 16

2 red cell inclusions post splenectomy

Answer 16

1. Howell Jolly bodies (small nuclear remnants - purple)

2. Pappenheimer bodies (abnormal granules of iron - blue, not as round and smaller than above)