The Lymph System and Lymphoid
Organs and Tissues
Overview
• lymphatic vessels• lymph• lyphoid cells and tissues• lymphoid organs
o lymph nodeso spleeno thymuso tonsilso other lymphoid tissue
lymphatic vessels• collects excess
interstitial fluid• returns fluid to blood• one way system
o flows toward the heart
lymphatic capillaries
- cells overlap
- collagen filaments anchor ends
lymphatic vessels
lacteals- specialized lymph
capillaries in lining of small intestine
- absorb fats- chyle = fatty lymph
that is milky white- moves into lymph
vessels
lymphatic vessels
lymphatic collecting vessels
- similar structure to veins- more valves- reconnect (anastamose) more often
lymphatic vessels
lymphatic trunks- formed by
union of largest vessels
lymphatic vessels
lymphatic ducts- right- thoracic
- cisterna chyli - enlarged sac where lumbar trunks meet
lymphatic vessels
• lyphangitiso when lymph vessel is
inflamed, blood vessels that feed them become congested with blood
lymphatic vessels
lymph
- similar to blood plasma
- white blood cells- debris/pathogens
lymph transport
• no pump• skeletal muscles• muscles used to breathe
o diaphragmo intercostal muscles
• smooth muscle in lymphatic trunks and thoracic duct
• valves prevent backflow• arterial pumping
lymph transport
• lymphedemao flow is blockedo lymph vessels removed
• lymph vessels can regrow!
lymphoid cells
• lymphocyteso T cellso B cells
• macrophages• dendritic cells• reticular cells
lymphoid tissue
• houses and provides a site for proliferation of lymphocytes
• surveillance point for lymphocytes and macrophages
lymphoid tissue
types• diffuse
o found in every body organ
o scattered
• lymphoid follicleso solid spherical
bodieso germinal
center
clusters- inguinal- axillary- cervical
functions- filter lymph- help activate the
immune system
lymph nodes
- average 1" bean shaped
- capsule with trabeculae
- cortex- medulla
lymph nodes
flow through node- afferent lymph
vessels- efferent lymph
vessels
lymph nodes
spleen
• size of fist• largest lymphoid
organ• site of lymphocyte
proliferation• site of immune
surveillance
spleen
• cleans the bloodo stores and releases
breakdown products of RBCs
o stores blood plateletso site of RBC production
in fetus
spleen
spleen
thymus
thymus
• many thymic lobules• cortex
o rapidly dividing lymphocytes
• medullao thymic corpuscles
development of regulatory T cells• prevent autoimmune
diseases
tonsils• palatine tonsils• lingual tonsil• pharyngeal tonsil• tubal tonsils
tonsilstonsillar crypt
other lymphoid tissue
Peyer's patches - aggregated follicles in the far end of the ileum and appendix- immune function of GI tract
other lymphoid tissue
MALT - mucosa-associated lymphatic tissue- Peyer's patches- appendix- tonsils- lymphoid follicles in bronchi- lymphoid follicles in genitourinary organs
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