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Chapter 14

SCIE 22273 Chapter Notes - Chapter 14: Exocrine Gland, Dander, Mononuclear Phagocyte System


Department
Faculty of Applied Health and Community Studies
Course Code
SCIE 22273
Professor
Tara Hayes
Chapter
14

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Chapter 14- Lymphatic System
Lymphatic system is a vast collection of cells and biochemicals that travel in
lymphatic vessels, and organs and glands that produce them
Include a network of vessels that assist in circulating body fluids. Therefore, are
closely associated with the cardiovascular system
Lymphatic vessels transport excess fluids away from interstial spaces in tissues
into bloodstreams. Without these, fluids would accumulate
Special lymphatic capillaries called lacteals absorb fats and transport them to the
circulatory system
Lymphatic system defend against disease
Lymphatic Pathways
Start as lymphatic capillaries then merge to form larger vessels that empty out into
the circulatory system
Lymphatic capillaries
Microscopic, close-ended tubes that extend into interstial spaces.
Found everywhere, where there are blood capillaries, except the CNS
Interstial fluid inside the lymphatic capillaries are called lymph
Lymphatic Vessels
Walls of lymphatic vessels are similar to those of veins, but thinner, but thicker
than blood capillaries
Have flap-like valves that prevent back flow
Larger lymphatic vessels leads to specialized organs called lymph nodes and
merge to form larger lymphatic trunks
Lymphatic trunks and collecting ducts
Lymphatic trunks join one of two collecting ducts:
oThoracic ducts: drains out into the left subclavian duct
oRight Lymphatic duct: drains out into the right subclavian duct
After leaving the two ducts, lymph enter the venous system
Tissue Fluid and Lymph
Tissue fluid becomes lymph once it enters lymph capillaries
Tissue fluid formation
Tissue fluid originates from blood plasma
Composed of water and dissolved substances
Leave blood capillaries by filtration
Resulting fluid is very alike to plasma, exception of proteins
Osmotic effect of proteins (plasma colloid osmotic pressure) helps draw fluid
back into capillaries through osmosis

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Lymph formation and function
An increase in tissue fluid hydrostatic pressure moves tissue fluid into lymphatic
capillaries. Therefore, forming lymph
Lymph transports foreign particles to lymph nodes
Lymph Movement
Hydrostatic pressure drives lymphatic capillaries
Muscular activity largely influences movement of lymph
Lymph is under low hydrostatic pressure and may not flow readily without
muscular contraction
Contraction of muscles compresses lymphatic vessels. Therefore, moving lymph
Valves prevent backflow, so lymph can only move forward
Conditions that interfere with lymph movement can cause tissue fluid to
accumulate, resulting in edema (swelling)
Edema may result when surgery removes lymphatic tissue. Therefore, no lymph
flow
Lymphatic tissue and lymphatic organs
Lymphatic tissue contain lymphocytes, macrophages and other cells
Lymphatic tissue associated with digestive, respiratory, urinary and reproductive
system is called mucosa-associated lymphoid disease (MALT)
This part is diffused and uncapsulated
Compact masses of lymphatic tissue is called lymph nodules (compose tonsils and
appendix)
Aggregates of lymph nodules are called Peyer’s patches
Lymphatic organs are: lymph nodes, thymus and spleen
Lymph nodes
Blood vessels and nerves join a lymph node through an indented region called
hilum
Connective tissue covers lymph and divides it into compartments
Lymph nodes contain lymphocytes (B and T cells) and macrophages
Masses of B cells and macrophages are contained in lymphatic nodules
Spaces within a node are lymphatic sinuses provide channels for lymph to
circulate
Absent in CNS
Lymph nodes have 2 functions: 1. filtering potential harmful particles 2. monitor
body fluids
Centers for lymphocyte production (Along with red bone marrow)
Thymus
Located behind sternum, above heart
Larger during infancy, but shrinks after puberty
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