1 Lymphatic System

2 Functions Return fluid to general circulation Production of WBCs Immunity

3 Lymphatic Vessels Open circulatory system Originate blindly in tissue interstices throughout the body except CNS and those without blood supply Thin walled - endothelium only Permeable

4 Lymphatic Vessels

5 Parallel venous flow Asymmetrical distribution Two major junctions with cardiovascular system –Thoracic duct into left subclavian vein –Right lymphatic duct into right subclavian vein

6 Ducts

7 Lymphatic Vessels

8 Lymphatic Physiology Movement into lymphatic capillaries function of osmotic pressure Valves and muscular activity assist return flow

9 Lymphatic Organs Lymph nodes Spleen Tonsils Thymus Diffuse tissue

10 Lymph Nodes Distributed along vascular pathway Filter lymph Encapsulated by dense CT stroma/framework of reticular fibers, trabeculae Parenchyma of cortex and medulla Lymphocytes/t cells

11 Lymph Nodes

12 Lymph Nodes Macrophages B lymphocytes/b cells Multiple afferent lymphatics Usually a single efferent exiting at hilus/hilum Size variable 1-25 mm, change with infection Secondary tumor sites via metastasis

13 Spleen Functions Fetal blood development Store and release blood during stress Recycle old blood cells B cell maturation into plasma cells

14 Spleen Structure 12 cm oval body in left hypochondriac region Splenic artery and vein enter at hilus Covered with peritoneum Structure similar to lymph node Parenchyma of two types

15 Spleen Structure Red pulp Blood filled venous sinuses Splenic cords/Billroth’s cords White pulp Lymphocyte production

16 Tonsils Aggregated lymph nodes Concentrated in Waldeyer’s tonsilar ring –Lingual –Palatine –Pharyngeal/adenoid

17 Thymus In superior mediastinum Two lobes Surrounded by CT capsule Cortex = reticular fibers + lymphocytes Medulla - epithelial cells produce thymosin stimulating maturation of T cells, form Hassall’s corpuscles Maximum size yrs old ~ 40 grams, degenerates with age

18 Diffuse Lymphatic Tissue Not encapsulated Widely distributed throughout body Found in lamina propria of digestive tract, respiratory, urinary and reproductive systems

19 Pathology Lymphangitis Lymphadenopathy Edema