The Lymphatic System
Chapter 20
Major Functions
• Drain interstital fluid.
• Protect against invasion by
foreign cells or substances.
– The specific immune
response is performed by
the lymph tissue.
• Transport dietary lipid from
gastrointestinal tract.
Where does lymph come from
and how does it circulate?
• Lymph originates as
extracellular fluid in the
interstitial space (interstitial
fluid).
• Become lymph when it
enters the lymph capillaries.
• Mainly consists of water,
foreign particles (bacteria,
virus), lymphocytes, and
lipids.
Lymph Vessels and Nodes
• Lymph capillaries merge to form
the afferent lymphatic vessels
leading to lymph nodes.
– Valves prevent backflow
• At lymph nodes, lymph is filtered
(to remove foreign material) and
leaves via the efferent lymph
vessels.
• Merging of other vessels form
the lymphatic trunk that joins
the lymph duct and drains into
the left subclavian vein.
Primary organs: bone marrow and thymus
Secondary organs: spleen, lymph nodes, other
Components of the Lymphatic System
• Primary organs – bone marrow production
• Secondary organs – spleen, lymph nodes,
mucosal associated lymphoid tissue (MALT)
– Spleen and lymph nodes are encapsulated, complex
structures that represent satellite sites for lymphatic
activation when challenged by antigen.
• Primary cells – B & T lymphocytes, killer cells
and phagocytes (macrophages)
– B lymphocytes become plasma cells
• Secrete antibodies
– T lymphocytes regulate immune rxns
Clinical Terms of the
Lymphatic System
• AIDS (acquired immunodeficiency syndrome)
– body's immune system breaks down and is
unable to fight off many infections.
• HIV (human immunodeficiency virus)
– Virus that causes AIDS.
– A member of a group of viruses called
retroviruses, HIV infects human cells and
uses the energy and nutrients provided by
those cells to grow and reproduce.
Clinical Terms of the
Lymphatic System
• Virus enters the body and lives and multiplies
primarily in the white blood cells.
• The hallmark of HIV infection is the progressive
loss of a specific type of immune cells called Thelper.
• Compromised T-cells lead to weakening of the
immune system and leaving the individual
vulnerable to various opportunistic infections
and other illnesses, ranging from pneumonia to
cancer.
Clinical Terms of the
Lymphatic System
• Lymphoma
– Any neoplasm of the lymphoid tissue, whether
malignant or benign.
• Mononucleosis
– the presence of an abnormally large number of
mononuclear leukocytes (monocytes) in the blood.
– Viral disease caused by EBV and passed by saliva.
– EBV (Epstein-Barr virus), causes glandular fever and
other nasty diseases, herpes family.
– Symptoms include fatigue, sore throat, swollen lymph
nodes and can last up to 6 weeks.
– B-cells are attacked by EBV and a T-cell response
ensues.
Clinical Terms of the
Lymphatic System
• Tonsillitis
– Swollen tonsils that become red and sore,
due to bacterial infection or other infections.