0-1 Chapter 21 Lymphatic and immune system Flashcards Preview

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Flashcards in 0-1 Chapter 21 Lymphatic and immune system Deck (277)
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1

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

2

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

3

Lymphatic and Immune Systems

functions

maintain fluid balance
•protect body from infection and disease

4

Functions of Lymphatic System

fluid recovery
immunity
lipid absorption

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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

6

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

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lipid absorption

lacteals in small intestine absorb dietary lipids that are not absorbed by the blood capillaries

8

Components of the Lymphatic System

lymph
lymphatic vessels
lymphatic tissues
lymphatic organs

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lymph

–the recovered fluid

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lymphatic vessels

–transport the lymph

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lymphatic tissues

composed of aggregates of lymphocytes and macrophages that populate many organs in the body

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lymphatic organs

–defense cells are especially concentrated in these organs
–separated from surrounding organs by connective tissue capsules

13

lymph

–clear, colorless fluid, similar to plasma, but much less protein
–extracellular fluid drawn into lymphatic capillaries

14

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

15

Lymphatic Vessels

larger ones composed of three layers

–tunica interna:
–tunica media:
–tunica externa:
•converge into larger and larger vessels

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tunica interna

endothelium and valves

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tunica media

elastic fibers, smooth muscle

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tunica externa

thin outer layer

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Route of Lymph Flow

•lymphatic capillaries
•collecting vessels
•six lymphatic trunks:
•two collecting ducts:
•subclavian veins

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two collecting ducts:

right lymphatic duct
thoracic duct

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right lymphatic duct

receives lymph from right arm, right side of head and thorax; empties into right subclavian vein

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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

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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

24

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

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T lymphocytes (T cells)

–mature in thymus

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B lymphocytes (B cells)

–activation causes proliferation and differentiation into plasma cells that produce antibodies

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macrophages

–very large, avidly phagocytic cells of the connective tissue
–develop from monocytes
–phagocytize tissue debris, dead neutrophils, bacteria, and other foreign matter
–process foreign matter and display antigenic fragments to certain T cells alerting the immune system to the presence of the enemy
–antigen presenting cells (APCs)

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dendritic cells

–branched, mobile APCs found in epidermis, mucous membranes, and lymphatic organs
–alert immune system to pathogens that have breached their surface

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reticular cells

–branched stationary cells that contribute to the stroma of a lymphatic organ
–act as APCs in the thymus

30

lymphatic (lymphoid) tissue

aggregations of lymphocytes in the connective tissues of mucous membranes and various organs