1. The Lymphatic System
and Immunity

2. Functions Draining excess interstitial fluid
Transporting dietary lipids

3. Lymphatic vessels:
In spaces between cells
Closed at one end,
converge to form larger
vessels (like veins) to trunks
to right and left duct to
venous blood
Contain valves to ensure one
way movement
Flow through lymph nodes
(masses of B and T cells)
Lymphatic capillaries:
Anchored by elastic
filaments
Open and close with
pressure differences

5. Thymus:
Located between sternum and aorta
Two lobes divided into lobules
Cortex (outer layer) of immature cells
-T cells: antigenic activity:
-dendritic cells: assist maturation
-epithelial cells: “educate” pre-T cells by positive selection
-macrophages: clear debris and dead cells
Medulla (inner layer) of mature T cells, epithelial cells, dendritic cells, and macrophages

6. Lymph nodes:
Lymph flows in
through afferent
vessels and out
through efferent
vessels
Made up of nodules
-Primary nodules: B cells
-Secondary nodules: plasma cell and memory B cell formation

7. Spleen:
Located between stomach and
diaphragm
Contains white and red pulp
-White pulp: lymphocytes and macrophages around central arteries
-Red pulp: red blood cells, macrophages, lymphocytes, plasma cells, and granulocytes
Removes worn out or defective
RBCs
Stores platelet
Produces blood cells in fetus

8. MALT Lymphatic nodules: no capsule
Throughout mucus membranes (MALT= mucosa-associated lymphatic tissue)
Tonsils
MALT

9. Nonspecific Resistance/
Innate Defenses: born with and offer immediate protection
First line of defense-
skin and mucus
membranes
Physical and chemical
barrier

10. Nonspecific Immunity
Barriers

11. Phagocyte NK

12. Helper T Cell
Cytotoxin T Cell

18. Active immunity

19. Passive immunity