The Lymphatic System

Lymph

15% of substances filter out of the blood capillaries moves into lymphatic capillaries due to the pressure gradient

Flow Of Lymph

1. Lymph

2. Lymphatic capillaries

3. Vessels

4. Trunks

5. Ducts

6. Venous blood circulation

Lymphatic Capillaries

• Body’s drainage system, absorbing excess interstitial fluid to form lymph

• Microscopic and close-ended, fluids can enter but not exit

Lymphatic Vessels

• Contain all 3 layers (tunica intima, media, externa) but thinner

• Valves prevent lymph backflow and pooling

• No pump, moved by contraction of surrounding skeletal muscles in the limbs and torso

Lymphatic Ducts

• Right lymphatic duct: drains upper right quadrant, empties into junction between right subclavian and right internal jugulars

• Thoracic duct: drains left side of head/neck, left upper extremity, left thorax, and all abdomen plus lower extremity

Lymphedema

Accumulation of interstitial fluid due to poor lymphatic dranage

Lymphatic Tissue & Organs

• Primary lymphatic structures: formation and maturation of lymphocytes. RBM and thymus

• Secondary lymphatic structures: store lymphocytes and other immune cells

Red Bone Marrow

Produce all formed elements through hemopoiesis

Thymus

T-lymphocyte maturation

Secondary Lymphatic Structures

Where matured lymphocytes stay and fight infections

Lymph Node

• Filtering lymph and removing unwanted substances

• As the lymph passes through the node, macrophages remove foreign materials before proceeding into the next node

Spleen

• Filters blood

• Phagocytize defective erythrocytes and platelets

• Reservoir for 30% of platelets

Tonsils

Protect against inhaled or ingested foreign materials

Innate Immunity

All body structures and processes that prevent entry of potentially harmful substances

Adaptive Immunity

• Initiated after entry of foreign substance

• Takes longer than innate immunity

Function of Lymphatic System

• Return fluid from interstitial space back into the blood to maintain fluid balance, BP, and blood volume

• Assist the immune system in the body’s defense