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Chapter 14 (Lymphatic System and Immunity (14-2 (Identify the major…
Chapter 14 (Lymphatic System and Immunity
14-1
(Distinguish between nonspecific and specific defense mechanisms
Pathogens
various microorganisms that cause disease in humans including viruses, bacteria, fungi, and parasites
Nonspecific defenses
do not distinguish between one potential threat from another
Specific defense
Lymphocytes organize a defense against a particular type of pathogen
14-2
(Identify the major components of the lymphoid system, and explain the functions of each)
Major components
Lymphatic vessels
Lymph
Lymphocytes
Lymphoid tissues
nodules (tonsils)
Lymphoid organs
spleen, thymus, and nodes
Major functions
Production, maintenance, and distribution of lymphocytes
Return fluid and solutes from peripheral tissues to the blood
Distribution of hormones, nutrients, and waste products from their tissues of origin to the general circulation
Lymphatic Vessels
lymphatic capillaries
are microscopic closed-ended tubes that extend into interstitial spaces
receive lymph through their thin walls
are associated with anchoring filaments, which serve an important function during edema
are located throughout the body, except in:
avascular tissue
cns
splenic pulp
bone marrow
include lacteals that are lymphatic capillaries within villi of the small intestine
Lymphatic vessels
are formed by the merging of the lymphatic capillaries
have walls similar to veins and possess valves that prevent backflow of lymph
lead to lymph nodes as "afferent" LVs, leave lymph nodes as "efferent" LVs, and then merge into lymphatic trunks
Lymphatic trunks
drain lymph from relatively large body regions
Principal lymphatic trunks include the following
lumbar
intestinal
bronchomediastinal
subclavian
jugular
intercostal
pass their lymph into venous blood by joining one of two collecting ducts
Collecting ducts
two within the thoracic cavity
right lymphatic duct drains the right upper body (25% of total body fat)
right subclavian veins
thoracic (left lymphatic) duct drains the remaning 75% of the body lymph
between left subclavian and left internal jugular veins
Tissue Fluid Formation
Tissue fluid is blood plasma that has passed through cardiovascular capillary walls into intestinal spaces, minus large plasma proteins
recall the constituents of plasma
primarily water
dissolved substances including small plasma proteins, nutrients, wastes, gases, electrolytes, enzymes, and hormones
Lymph formation
as protein concentration in interstitial spaces increases, its pressure increases
Increasing pressure forces tissue fluid into lymphatic capillaries
this fluid is now called lymph
lymph formation prevents accumulation of excess tissue fluid
Lymph Function
returns small leaked plasma proteins back to the blood stream
transports foreign particles to the lymph nodes
transports lipids and lipid souluable vitamins absorbed in GI tract to bloodstream
Lymph movement
Lymph flow
Lymph is under low pressure and may not flow readily without aid from external forces (similar to venous return)
the squeezing action of skeletal muscles aids movement
the low pressure in the thoracic cavity created by breathing movements, moves lymph up from abdominal to thoracic region
recall the precense of one-way valves
obstruction of lymph movement
any condition that interferes with the flow of lymph results in edema
edema = accumulation of excess interstitial fluid leading to swelling of tissues
tissue swelling pulls on anchoring filaments making openings between cells even larger so that more fluid can move into the lymphatic capillary
the surgical removal of lymph nodes causes obstruction and results in edema
Lymphocytes
Types of circulating lymphocytes
T cells (thymus dependent) 80%
cytotoxic Tcells (cell mediated immunity)
helper T cells stimulate both T and B cells
suppresor T cells inhibit both T & B cells
B cells (bone marrow derived) 10-15%
differntiate into plasma cells (produce)
immunoglobulins (antibodies) bind to antigens
Antibody-antigen complex
antibody-mediated immunity (humoral immunity)
antibodies function in body fluids
NK cells (natural killers) 5-10%