BIOL&253Ch22NotesFall11

BIOL&253Ch22NotesFall11 - Ch. 22 The Lymphoid...

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1 Ch. 22 – The Lymphoid System and Immunity Above : macrophage (gray), T lymphocyte (pink), and bacteria (orange) Fig. 22-1, p. 778 The lymphoid system General functions : It acts with other organ systems to prevent and fight disease It returns “lost” plasma (= interstitial fluid) to the blood It transports dietary lipids from the digestive tract to the blood (more in Ch. 24) Components : Lymph = interstitial fluid that gets absorbed and transported by… Lymphatic vessels = low pressure tubes that ultimately return lymph to the blood Lymphoid tissues and organs Lymphocytes and supporting cells
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2 Fig. 22-2, p. 779 Lymphatic capillaries •A r e a . k . a . terminal lymphatics Are different than blood capillaries because they: – Are blind-ended – Have larger diameters – Have thinner walls – Have an incomplete basal lamina (or none at all) – Are composed of loosely bound, overlapping endothelial cells… • Which act as one-way valves for entry Fig. 22-3, p. 780 Lymphatic vessels • Are a.k.a. lymphatics
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3 Lymphatic trunks and ducts Fig. 22-4, p. 781 Lymphatic vessels merge to form lymphatic trunks, which drain into either the… Thoracic duct – which empties into the left subclavian vein, or the… Right lymphatic duct – which empties into the right subclavian vein Fig. 22-5, p. 769 Lymphocytes Total in the body: ~ 1 trillion = 1 kg = 2.2 pounds!
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4 Lymphocytes – NK and T cells 1. NK cells (n atural k iller cells) • Make up 5-10% of circulating lymphocytes • Are responsible for “immunological surveillance” – Function : nonspecifically attack foreign, virus-infected, and cancerous cells 2. T cells (t hymus-dependent cells) • Make up ~ 80% of circulating lymphocytes • Are responsible for cell-mediated immunity • There are 3 main types of T cells: –A . Cytotoxic T cells (T C cells) • Function : specifically attack foreign, virus-infected, and cancerous cells –B . Helper T cells (T H cells) • Function : stimulate T and B cells; coordinate cell- and antibody-mediated immunity –C . Suppressor T cells (T S cells) • Function : inhibit T and B cells Lymphocytes – B cells 3. B cells (b one marrow-derived cells) • Make up 10-15% of circulating lymphocytes • Are responsible for antibody-mediated (humoral) immunity – Function: when stimulated, they differentiate into plasma cells which secrete specific antibodies (immunoglobulins) • Effects of antibodies include : – Neutralizing toxins – Agglutinating and precipitating antigens – Activating complement proteins – Attracting phagocytes Opsonizing (which means “to make tasty”) antigens to enhance phagocytosis
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5 Fig. 22-6, p. 784 Lymphoid tissues
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BIOL&253Ch22NotesFall11 - Ch. 22 The Lymphoid...

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