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Human biology lecture notes about the lymphatic system and immunity.
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Lecture 7The Lymphatic System and
Immunity II
B Curr II HUB228 2022
Dept. Medical Biosciences
University of the Western Cape
,Roles of the lymphatic system in body defenses
•body defenses provide resistance to fight infection, illness, and disease
•two categories of defenses:
1. Nonspecific defenses
-don’t distinguish between one threat and another; are present at birth
-incl. physical barriers, phagocytic cells, immunological surveillance, interferons, inflammat
fever
-provide nonspecific resistance
2. Specific defenses
-protect against particular threats; develop after birth after exposure to environmental haza
infections
-dependent on lymphocyte activity
-provide specific resistance
•nonspecific and specific defenses operate together to provide resistance to infection and d
,Nonspecific Defenses
1. Physical barriers
-keep hazardous organisms and materials outside the body
-epithelial covering has: keratin coating, multiple layers, dense network of desmosomes
-hairs provide some protection against mechanical abrasion (esp. on scalp), and preven
materials or insects from contacting skin
-secretions from sebaceous and sweat glands flush the surface to wash away microorg
chemical agents, also contain lysozymes (destructive enzymes that contain microbe-killing
and antibodies
-think about how the epithelial lining of the digestive, respiratory, urinary and reproductiv
defended?
, Nonspecific Defenses
2. Phagocytes
-attack and remove dangerous microorganisms
-represent the “first line” of cellular defense, often removing organisms before lymphocyte invol
-two general classes: microphages and macrophages
-microphages leave the bloodstream and enter peripheral tissues that are injured or infected
o neutrophils (more abundant) phagocytize cellular debris or invading bacteria
o eosinophils (less abundant) attack foreign compounds or pathogens that have been coated with an
-macrophages (fixed or free) are actively phagocytic cells derived from circulating monocytes
-mobile macrophages and microphages can move through capillary wall by a process called di
and may also be attracted/repelled by chemicals in surrounding fluids through chemotaxis
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