0-1 Chapter 21 Lymphatic and immune system Flashcards
(277 cards)
immune system
not an organ system, but a population of cells that inhabit all of our organs and defend the body from agents of disease
lymphatic system
- network of organs and vein-like vessels that recover fluid
- inspect it for disease agents
- activate immune responses
- return the fluid to the bloodstream
Lymphatic and Immune Systems
functions
maintain fluid balance
•protect body from infection and disease
Functions of Lymphatic System
fluid recovery
immunity
lipid absorption
fluid recovery
–fluid continually filters from the blood capillaries into the tissue spaces
•blood capillaries reabsorb 85%
•15% (2 –4 L/day) of the water and about half of the plasma proteins enters lymphatic system and then returned to the blood
immunity
excess filtered fluid picks up foreign cells and chemicals from the tissues
•passes through lymph nodes where immune cells stand guard against foreign matter
•activate a protective immune response
lipid absorption
lacteals in small intestine absorb dietary lipids that are not absorbed by the blood capillaries
Components of the Lymphatic System
lymph
lymphatic vessels
lymphatic tissues
lymphatic organs
lymph
–the recovered fluid
lymphatic vessels
–transport the lymph
lymphatic tissues
composed of aggregates of lymphocytes and macrophages that populate many organs in the body
lymphatic organs
–defense cells are especially concentrated in these organs
–separated from surrounding organs by connective tissue capsules
lymph
–clear, colorless fluid, similar to plasma, but much less protein
–extracellular fluid drawn into lymphatic capillaries
lymphatic capillaries
(terminal lymphatics)
–sacs of thin endothelial cells that loosely overlap each other
–closed at one end
–cells tethered to surrounding tissue by protein filaments
–endothelium creates valve-like flaps that open when interstitial fluid pressure is high, and close when it is low
Lymphatic Vessels
larger ones composed of three layers
–tunica interna:
–tunica media:
–tunica externa:
•converge into larger and larger vessels
tunica interna
endothelium and valves
tunica media
elastic fibers, smooth muscle
tunica externa
thin outer layer
Route of Lymph Flow
- lymphatic capillaries
- collecting vessels
- six lymphatic trunks:
- two collecting ducts:
- subclavian veins
two collecting ducts:
right lymphatic duct
thoracic duct
right lymphatic duct
receives lymph from right arm, right side of head and thorax; empties into right subclavian vein
thoracic duct
larger and longer, begins as a prominent sac in abdomen called the cisterna chyli; receives lymph from below diaphragm, left arm, left side of head, neck, and thorax; empties into left subclavian vein
Mechanisms of Lymph Flow
- lymph flows under forces similar to those that govern venous return, except no pump (heart)
- lymph flows at low pressure and slower speed than venous blood
- moved along by rhythmic contractions of lymphatic vessels
- flow aided by skeletal muscle pump
- arterial pulsation rhythmically squeeze lymphatic vessels
- thoracic pump aids flow from abdominal to thoracic cavity
- valves prevent backward flow
- rapidly flowing blood in subclavian veins, draws lymph into it
- exercise significantly increases lymphatic return
natural killer (NK) cells
–large lymphocytes that attack and destroy bacteria, transplanted tissue, host cells infected with viruses or have turned cancerous
–responsible for immune surveillance