Lymphoid Structures

Question 1

broad structure of a lymph node

Answer 1

capsule with interior projections called trabeculae;

cortex (B cells in follicles), paracortex (T cells & HEV), medulla (cords & sinuses)

Question 2

medullary cord

Answer 2

in the medulla of the lymph node, packed lymphocytes & plasma cells

Question 3

medullary sinus

Answer 3

in the medulla of the lymph node, reticular cells & macrophages; communicates with efferent lymphatics

Question 4

which part of the lymph node enlarges in viral infection?

Answer 4

paracortex

Question 5

which part of the lymph node is underdeveloped in DiGeorge syndrome? (22q11.2 deletion syndrome)

Answer 5

paracortex

Question 6

primary vs secondary follicles in lymph nodes

Answer 6

primary = dormant, denser in outer cortex
secondary = active, have a mantle and a paler germinal center

Question 7

HEV

Answer 7

high endothelial venule; in the lymph node paracortex, allows T & B cells to arrive via blood

Question 8

what occurs in a LN germinal center?

Answer 8

broadly, B cells become high affinity

1) B cells & Th cells join to enter the dark zone
2) in the dark zone, B cells proliferate, then move to the light zone
3) In the light zone, Tfh cells help B cells undergo somatic hypermutation, affinity maturation, and isotype/class switching based on antigens presented by follicular dendritic cells
4) B cells then exit the germinal center as high-affinity B cells

Question 9

13 sets of LNs

Answer 9

Cervical, Supravclavicular, Mediastinal, Hilar, Axillary, Celiac, Superior Mesenteric, Inferior Mesenteric, Para-Aortic, External Iliac, Internal Iliac, Superficial Inguinal, Popliteal

Question 10

Cervical/Supraclavicular LNs- drainage area & assoc disease

Answer 10

Head & neck;

Kawasaki, URIs, mono

Question 11

Mediastinal LNs- drainage area & assoc disease

Answer 11

Trachea & esophagus;

primary lung cancer & granulomatous disease

Question 12

Hilar LNs- drainage area & assoc disease

Answer 12

lungs;

granulomatous disease

Question 13

Axillary LNs- drainage area & assoc disease

Answer 13

skin above umbilicus, upper limbs, breasts;

mastitis & metastasis (esp breast)

Question 14

Celiac LNs- drainage area & assoc disease

Answer 14

spleen, liver, pancreas, stomach, upper duodenum; mesenteric lymphadenitis, typhoid fever, ulcerative colitis, Crohn’s

Question 15

Superior Mesenteric LNs- drainage area & assoc disease

Answer 15

lower duodenum, jejunum, ileum, colon to the splenic flexure;
mesenteric lymphadenitis, typhoid fever, ulcerative colitis, Crohn’s

Question 16

Inferior Mesenteric LNs- drainage area & assoc disease

Answer 16

colon from the splenic flexure to the upper rectum;

mesenteric lymphadenitis, typhoid fever, ulcerative colitis, Crohn’s

Question 17

Para-Aortic LNs- drainage area & assoc disease

Answer 17

kidneys, testes, ovaries, uterus;

metastasis

Question 18

External Iliac LNs- drainage area & assoc disease

Answer 18

superior bladder, body of uterus, cervix;

STIs & medial foot/leg cellulitis

Question 19

Internal Iliac LNs- drainage area & assoc disease

Answer 19

bladder, cervix, middle 3rd of vagina, prostate, anal canal (above the pectinate line);
STIs & medial foot/leg cellulitis

Question 20

Superficial Inguinal LNs - drainage area & assoc disease

Answer 20

skin above umbilicus (other than popliteal area), anal canal (below pectinate line), scrotum, vulva;
STIs & medial foot/leg cellulitis

Question 21

Popliteal LNs- drainage area & assoc disease

Answer 21

dorsolateral foot, posterior calf;

lateral foot/leg cellulitis

Question 22

Which LN clusters are palpable?

Answer 22

Cervical, supraclavicular, axillary, and superficial inguinal

Question 23

where do the lymphatic ducts join the blood system?

Answer 23

At the junction of the subclavian & internal jugular veins

Question 24

possible cause of chylothorax

Answer 24

rupture of thoracic duct

Question 25

2 main lymphatic ducts & their drainage areas

Answer 25

1) Right (right side of body above diaphragm)

2) Thoracic (everything else)

Question 26

main areas of the spleen

Answer 26

red pulp (outer, splenic cords/cords of Billroth & venous sinuses), marginal zone ( middle, macrophages, specialized B cells, APCs catch antigens from the blood), white pulp (B cells in follicles & T cells in PALS)

Question 27

result of splenic dysfunction (splenectomy, sickle cell)

Answer 27

Decreased IgM => decreased complement activation & C3b opsonization => greater susceptibility to encapsulated organisms

Question 28

vaccines for splenectomy patients

Answer 28

pneumococcal, Hib, meningococcus (encapsulated organisms)

Question 29

specific sorts of bacteria that splenic macrophages are good for

Answer 29

encapsulated bacteria

Question 30

splenic cords (cords of Billroth)

Answer 30

in red pulp, composed of reticulin & fibrils (structural)

Question 31

reticular cell

Answer 31

fibroblast that makes collagen alpha-1, produces reticular fibers (makes network in lymphoid organs)

Question 32

spleen location

Answer 32

anterolateral to kidney, posterolateral to stomach, LUQ, 9th-11th ribs protect it

Question 33

thymus location

Answer 33

anterosuperior mediastinum

Question 34

neonatal thymus

Answer 34

sail-shaped on CXR, involutes with age

Question 35

thymic cortex

Answer 35

immature T cells, dense; site of “positive selection” in thymic education

Question 36

thymic medulla

Answer 36

mature T cells & Hassall corpuscles (epithelial reticular cells), pale; site of “negative selection” in thymic education

Question 37

thymic education

Answer 37

1. Double negative (CD4-, CD8-) T cells arrive to cortex, become double positive (CD4+CD8+)
2. Positive selection in cortex (recognize self-MHC => saved from apoptosis)
3. Negative selection in medulla (apoptosis if recognize self-antigens) to develop “central tolerance”
4. Become single positive (CD8+ or CD4+), exit to secondary lymphoid tissues