1. LYMPHATIC SYSTEM
Marieb - Chapter 20

2. Lymphatic System capillaries ducts nodes lymphoid organs
diffuse cell pockets

3. Lymphatic capillaries
extremely permeable
present throughout body intermingle with blood capillaries
not in CNS or mineralized tissues

4. Lymphatic Ducts Trunks Lumbar Bronchomediastinal Subclavian Jugular
Intestinal

5. Trunks anastomose & enter veinous return at junction of subclavian & jugular veins

6. Lymph Vessel Structure
much like veins
more valves
more frequent anastomoses

7. ELEPHANTIASIS
A tropical disease caused by lymphatic obstruction. Victim is bitten by a mosquito infected with a roundworm known as a filarial worm.
The resulting edema leads to fibrosis and elephant-like thickening of the skin.

8. Lymphoid organs Lymphocytes Lymphoid tissue
Lymphatic nodule (follicle) with germinal center

9. Lymph Nodes Encapsulated by dense fibrous connective tissue
Trabeculae - capsule extends inward form compartments

10. Lymph Nodes
Clusters at junctions of vessels into trunks

12. Lymph node structure Cortex Medulla Sinuses Circulation in the node:
Figure 20.4a
Cortex
dense follicles with germinal centers
dividing B cells
Deep cortex (T cells)
Medulla
inward extensions of cortical tissue (B, T and plasma cells)
Sinuses
lymph drainage
filtered by macrophages
Circulation in the node:
afferent lymphatic vessel  subcapsular sinus  drain through tissue  hilus  efferent vessels

13. Lymphoid Organs

14. Spleen

15. Spleen

16. Thymus primary function is in early life
Secretes thymosin and thymopoietin which causes T lymphocytes to become immunocompetent
Lacks B cells (no follicles)
Atrophies with age: prominent in newborns, stops growth by adolescence, degenerates by old age

17. Thymus

18. Lymphoid Follicle Aggregates
MALT (mucosa associated lymphatic tissue) includes:
Peyer’s Patches in intestines
Appendix
Tonsils
Small bronchiolar follicles
MALT are positioned well to:
Destroy bacteria that breach the mucosal membrane from outside
Develop “memory” lymphocytes for long term immunity

19. Tonsils

20. Tonsils not encapsulated blind pouches – crypts bacteria can enter
induced immune response

21. Peyer’s Patches

22. Peyer’s Patches