The Lymphatic System: Objectives

What are the primary lymphatic organs

thymus and red bone marrow

Primary Lymphoid Organs

the site where stem cells divide and become immunocompetent (t and b cells make an army to fight infections)

What are the secondary lymphoid organs

lymph nodes, spleen, lymphoid nodules

Seconday Lymphoid Nodules

where most immune responses occur

Contrast of Lymph

• Filters pathogens through lymph nodes

• itransporter of absorbed dietary fats (chyle)

• moves in a one-way flow propelled by muscle contractions, not a central pump.

Contrast of Interstital Fluid

• Exists outside vessels

• directly bathes all body cells

• direct exchange between blood and cells

Contrast of Blood

• Contains red blood cells and platelets

• has the highest concentration of proteins

• circulated by the heart in a closed loop

How are lymph, blood and interstitial fluid similar

water is the main component

transport and circulatory system

• Blood and Interstitial Fluid: Both are involved in the exchange of water, nutrients, oxygen, and waste across the capillary walls. Interstitial fluid is a "leak" from blood plasma.

• Interstitial Fluid and Lymph: Lymph is formed directly from interstitial fluid. Both have very low protein content (compared to blood), and both contain cellular debris and waste materials.

• Blood and Lymph: Both are crucial components of the immune system and contain white blood cells (specifically lymphocytes). Lymphatics return fluid to the large veins of the bloodstream.

Lymph Capillaries

Pickup: Blind-ended tubes that collect excess interstitial fluid (making it lymph) from tissues.

Lymphatic Vessels

Transport & Filter: Carry lymph toward the heart, passing it through lymph nodes for filtration and immune surveillance.

Lymph Trunks

Regional Collection: Large vessels that drain lymph from major body regions

Right Lymphatic Duct

Minor Drainage: Drains lymph into the right subclavian vein from the upper-right quarter of the body

Thoracic Duct 

Major Drainage: The largest duct; drains lymph from the rest of the body into the left subclavian vein.

Lymphatic Capillaries Lacteals

Lymphatic capillaries in the small intestine villi.

Absorb large dietary fats (chylomicrons) and fat-soluble vitamins.

chyle

explain how lymph is pressurized to cause it to circulate from lymph capillaries through lymphatic vessels trunks and ducts to the blood at the right and left subclavian vein

1. Fluid Pressure: Excess interstitial fluid (tissue fluid) builds up, forcing open mini-valves on lymph capillaries and flowing inside.

2. Skeletal Muscle Pump: Contraction of surrounding muscles (walking, moving) squeezes the lymphatic vessels.

3. Smooth Muscle Contraction: The walls of the lymphatic vessels themselves contract rhythmically (peristalsis) to push lymph along.

4. Respiratory Pump: Pressure changes in the chest and abdomen from breathing "suck" lymph up toward the neck.

5. One-Way Valves: Valves inside the vessels snap shut after each squeeze, preventing lymph from flowing backward.

6. Venous Entry: Lymph finally flows from the high-pressure ducts into the low-pressure subclavian veins.