The Lymph System and Lymphoid

Organs and Tissues

Overview

• lymphatic vessels

• lymph

• lyphoid cells and tissues

• lymphoid organso lymph nodeso spleeno thymuso tonsilso other lymphoid tissue

lymphatic vessels

• collects excess interstitial fluid

• returns fluid to blood

• one way systemo 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 breatheo 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

• diffuseo found in every

body organo 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