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