Lymphatic Tissues and Organs February 15, 2010

Lymphatic System Lymphatic vessels: Removes extracellular fluid (lymph) from the lamina propria. Absorb fat and transport as chyle. Transport lymphocytes and other cells, such as tumor cells. Lymphatic tissues: Diffuse lymphatic tissues and cells Solitary nodules Aggregates of nodules (Peyer’s patches) Tonsils Lymph nodes (filters lymph) Spleen (filters blood) Thymus (T cell differentiation) Bone marrow (source of lymphocytes) Ross and Pawlina, p.397

Ross and Pawlina, p. 417 #27 Lymph node Cortex Medulla Hilus

#26 Lymph Node also #142 Subcapsular sinus Trabecular sinus Medullary sinuses Hilus Efferent lymphatic ducts Blood vessels Secondary follicles Medullary cords

Direction of lymph flow through a lymph node Afferent lymphatic vessel Subcapsular sinus Trabecular or perinodular sinus Medullary sinus Efferent lymphatic vessel Thoracic duct Left subclavian vein General circulation Ross and Pawlina, p. 419 To lymph nodes (Left side) Another lymph node….

#26 Lymph Node: secondary follicle Germinal center: lymphoblasts HEV Subcapsular sinus

#26 Lymph Node: Medullary cords and sinuses (also #142) M. Cord: lymphocytes plasma cells M. sinus reticular cells lymphocytes macrophages

#30 Lymph Node Afferent lymphatic ducts

#30 Lymph Node: deep cortex High Endothelial Venules

High endothelial venules: longitudinal sections

#142 Lymph Node H&E

#28: silver stain Reticular fibers in medullary sinus

Solitary nodules #161 &157 Aggregates of nodules #175, UCSF 261, 168 #161 #261

#168 (jejunum) Intraepithelial lymphocytes

Palatine tonsil: covered with stratified squamous epithelium which invaginates to line the surface of the crypts Ross and Pawlina, p. 415

#138L Palatine tonsil crypt Stratified squamous epithelium

#138 Palatine tonsil: starry sky Macrophages

Lingual Tonsils

Spleen: red and white pulp #147B #148, #301 #301

Splenic Circulation Splenic artery Splenic vein PALS: Periarterial (periarteriolar) lymphatic sheath Ross, et al

#301 Splenic nodule ( 2 o ) and central artery Germinal center

#148 PALS and Marginal zone Green arrows: macrophage

#148 Splenic sinuses

Splenic sinuses Ross and Pawlina, p. 427

Pulp vein trabecular vein splenic vein #301

#147B Human Spleen, H&E

#26 Lymph Nodes #140 Thymus Incomplete lobules: The medulla of adjacent lobules merges.

#27 Lymph Node #140 Thymus No follicles in the cortex

#140 Thymus: medulla Epithelial reticular cells Hassall’s corpuscle Blood vessel

#140 Young Thymus#141 Involuting Thymus