The Lymphatic System

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The Lymphatic System

• By Emily Lopez, Alejandro Campos, and Jennifer
  Leon

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What Is the Lymphatic System?

• It is the network of vessels in which lymph
  drains from the tissue into the blood
• It is composed of lymph vessels, lymph nodes, the
  spleen, the thymus, tonsils, and bone marrow.

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Functions of the Lymphatic System

• The functions of this system include
• the absorption of excess fluid and its return to
  the blood stream
• Absorption of fat (In the villi and small
  intestine)
• Its Immune System Response

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Lymph Vessels

• Thin walled, valve structures that carry lymph
• Complementary to the cardiovascular system
• Lined by endothelial cells, a thin layer of
  smooth muscles, and adventitia(binds lymph
  vessels to surrounding tissue)
• Types of vessels Afferent vessels, Efferent
  vessels, and Lymph Trunks

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Different types of Lymph Vessels

• Afferent lymph vessels Carries unfiltered lymph
  into the node
• Found only in the lymph nodes
• Efferent lymph vessels Carries filtered lymph
  out of the node
• Found in the thymus and spleen
• Lymph Trunk Carries lymph and is formed by
  confluence of many efferent lymph vessels

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Different types of Lymph Vessels(Cont)

• Lymph Trunks carry lymph and then drain them into
  either the right lymph duct, or the thoracic
  duct.
• There are four pairs and one unpaired lymph
  trunk
• Jugular Lymph Trunk
• Subclavian Lymph Trunk
• Bronchomediastinal Lymph Trunk
• Lumbar Lymph Trunk
• Intestinal Trunk(unpaired)

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Lymph Nodes

• Lymph nodes are areas of concentrated lymphocytes
  and macrophages along the lymphatic veins.
• Located in the neck, armpit, groin, center of
  chest and abdomen
• Act as filters for foreign particles and cancer
  cells
• Do NOT deal with toxicity
• They become inflamed or enlarged in various
  infections and diseases

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The Spleen

• It is a reservoir for blood
• It filters the blood and lymph fluid that flows
  through
• It sits under the rib cage in the upper left part
  of the abdomen towards the back

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The Thymus

• secretes hormone, thymosin, that causes
  pre-T-cells to mature into the T-cells

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The Bone Marrow

• contains tissue that produces lymphocytes
• All lymphocytes derive from stem cells in the
  bone marrow

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Absorption(and return) of Fluid

• The Lymphatic System returns excess interstitial
  fluid(A.K.A tissue fluid) to the blood
• Lymph capillaries pick up the excess interstitial
  fluid and proteins and return them to the venous
  blood
• When the fluid enters the lymph capillaries it is
  called lymph

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Fluid Formation

• Lymph starts as Interstitial fluid
• The interstitial fluid forms at the end of the
  arterial end of capillaries, through which
  hydrostatic pressure pushes outward, creating a
  fluid similar to plasma in terms of function.
  Interstitial fluid maintains equilibrium by
  osmotic pressure, which pushes water into the
  capillaries due to solubility.
• 90 returns to the venules. The other 10 enters
  the lymph capillaries making it now lymph

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Absorption of Fat

• The Lymphatic systems second function is the
  absorption of fats and fat-soluble vitamins from
  the digestive system, and the transport of these
  to the venous circulation
• There are lymph capillaries called lacteals in
  the villi of the small intestine that absorb fats
  and fat solubles

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Immune System Function

• Lymph nodes and other lymphatic organs filter the
  lymph to remove microorganisms and other foreign
  particles
• The nonspecific responses are the first line of
  defense
• Highly specific responses are the second line of
  defense and are tailored to an individual threat

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Non-specific vs. Specific
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Non-specific vs. Specific

• The immune response includes both specific and
  nonspecific components
• Nonspecific responses block the entry and spread
  of disease-causing agents.
• examples Physical Barriers(skin), Inflammation,
  the Complement system, and Immune Response

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Non-specific vs. Specific(cont)

• Specific responses generate to specific invaders.
• The immune system is more effective than the
  nonspecific methods, and has a memory component
  that improves response time when an invader of
  the same type (or species) is again
  encountered(antibodies)

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Specific Cells
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T-Cells

• A.K.A T lymphocytes
• Act as helpers to other immune cells or attack
  pathogens directly
• After an infection, memory T cells persist in the
  body to provide faster reaction to the same
  antigen

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B-Cells

• A.K.A B lymphocytes
• Form plasma cells to produce antibodies
• These antibodies neutralize the pathogen until
  other immune cells destroy it

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NK-Cells

• A.K.A Natural Killer Cells
• Lymphocytes that respond to a wide range of
  pathogens and cancerous cells

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Non-Specific Cells
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Macrophages

• A phagocyte that consumes pathogens, destroys
  cells, and debris by phagocytestosis

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Dendritic Cells

• They detect pathogenic antigens which activate T
  and B cells to help body fight off parasites

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Eosinophils

• granular leukocytes that reduce allergic
  inflammation and help body fight off parasites

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Basophils

• granular leukocytes that trigger inflammation by
  releasing heparin and histamine

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Neutrophils

• granular leukocytes that act as the first
  responder to the site of infection
• Neutrophils use chemotaxis to detect chemicals
  produced by the infection agents

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Inflammatory Response

1. Damaged cells release histamine, a chemical
   messenger, that increases blood flow to the
   infection site
2. Inflammation produces heat unfavorable to
   microbes promotes healing raises mobility of W.
   blood cells increases metabolic rate of cells
3. Capillaries pass fluid into interstitial areas,
   which causes swelling
4. Clotting factors trigger blood clots
5. Monocytes clean up dead microbes, cells, and
   debris

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Allergen Response

• Allergies result from immune system
  hypersensitivity to weak antigens that do not
  cause an immune response in most people
• Some allergens include dust, molds, pollen,
  certain foods and some medicines
• After an exposure to an allergen, some people
  make IgE antibodies as well as B and T memory
  cells
• Subsequent exposure to the same allergen releases
  IgE antibodies
• IgE antibodies bind to mast cells, which then
  releases histamine
• In some individuals, histamine causes
  life-threatening anaphylaxis

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The Cardiovascular System vs. The Lymphatic System
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The Cardiovascular System

• Carries oxygen throughout the body
• Flows in a continues loop
• Uses a pumping action
• Blood is filtered by kidneys

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The Lymphatic System

• collects and removes waste left behind in tissue
• Flows in an open circuit and only one direction
• Flows passively into the lymph capillaries by
  movement such as breathing, muscle movement and
  blood pumping
• Invisible and difficult to detect damage
• Filtered by lymph nodes throughout the body

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Bibliography

• Boundless. Cardiovascular and Lymphatic System
  Defenses. 1 January 2015. Webpage. 23 March 2015.
• Farabee, M.J. Lymphatic System and Immunity.
  2001. Webpage. 23 March 2015.
• Knowedgebase. Lymphatic versus Cardiovascular
  Systems. 11 December 2013. Article. 23 March
  2015.