1

Lymphatic SystemLymphatic System

2

Lymphatic SystemLymphatic System

• Functions

• Return fluid to general circulation

• Production of WBCs

• Immunity

3

Lymphatic VesselsLymphatic 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 VesselsLymphatic Vessels

5

Lymphatic VesselsLymphatic Vessels

• 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

DuctsDucts

7

Lymphatic Lymphatic VesselsVessels

8

Lymphatic PhysiologyLymphatic Physiology

• Movement into lymphatic capillaries function of osmotic pressure

• Valves and muscular activity assist return flow

9

Lymphatic OrgansLymphatic Organs

• Lymph nodes

• Spleen

• Tonsils

• Thymus

• Diffuse tissue

10

Lymph NodesLymph 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 Lymph NodesNodes

12

Lymph NodesLymph 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

SpleenSpleen

• Functions

• Fetal blood development

• Store and release blood during stress

• Recycle old blood cells

• B cell maturation into plasma cells

14

Spleen StructureSpleen 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 StructureSpleen Structure

• Red pulp

• Blood filled venous sinuses

• Splenic cords/Billroth’s cords

• White pulp

• Lymphocyte production

16

TonsilsTonsils

• Aggregated lymph nodes

• Concentrated in Waldeyer’s tonsilar ring– Lingual– Palatine– Pharyngeal/adenoid

17

ThymusThymus

• 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 10-12 yrs old ~ 40 grams, degenerates with age

18

Diffuse Lymphatic TissueDiffuse Lymphatic Tissue

• Not encapsulated

• Widely distributed throughout body

• Found in lamina propria of digestive tract, respiratory, urinary and reproductive systems

19

PathologyPathology

• Lymphangitis

• Lymphadenopathy

• Edema