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Lymphatic System

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on 24 June 2015

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Transcript of Lymphatic System

Lymphatic System
By: Kevin, Arthur, Jacob
Adaptive Body Defenses
We have a specific defense system
1. It is antigen specific
2. It is systemic
3. It has “memory”

Known as the Third Line of Defense, it seeks and destroys specific hostile antigens.
It is designed to more powerful and effective after first exposures to a pathogen

There are two types of immunity
1. Humoral (antibody-mediated immunity)
2. Cellular (Cell-mediated immunity)

What are Antigens?
Our body has
that don't trigger an immune response

Haptens are special antigens responsible for allergic reactions

Antigen (Ag)- Large complex molecules (usually proteins) that are capable of provoking an immune response

A molecule is antigenic when it carries antigens on their surfaces (bacteria and viruses)
Originate from hemocytoblasts in red bone marrow
Two types:
1. B Lymphocytes (B Cells) - create antibodies and oversee humoral immunity
2. T Lymphocytes (T Cells) - don’t produce antibody but constitute the cell-mediated arm of the defense system

B Lymphocytes stay in the Bone marrow, T Lymphocytes go to the Thymus gland
After maturation, T Cells and B Cells go into the lymph nodes and spleen to encounter antigens

Created from monocytes in bone marrow
Engulf foreign particles and secrete cytokines
Macrophages also have antigens to be recognized by T Cells
Wait in lymphoid organs until T cells signal the presence of antigens
B Cells are the main tool of Primary Humoral Response
When activated by an antigen, they split into plasma cells and memory cells
Humoral Immunity
Plasma cells will unleash thousands of antibodies for a few days before dying,
Memory cells that will remember the antigen and be responsible for a larger, faster, and more effective secondary humoral response
This second response will quickly make more plasma cells, that will create thousands more antibodies that will last longer than last time

Active immunity is when B Cells create antibodies themselves either
(1) when an actual pathogen enters our body and our body responds to it through antibody creation
(2) when vaccines of dead or weakened pathogens trigger antibody production

Therefore when the same pathogen hits, our body can quickly respond because it’s not the first encounter

Active vs. Passive Immunity
Passive immunity is when the body receives antibodies from an outside source, not created from the B Cells
Immunological memory does not occur
Active Immunity
Passive Immunity
When mother gives her child antibodies through her fetal circulation and breast feeding
Immune serums (such as gamma globulin) are artificially created and administered to treat illnesses immediately such as hepatitis or rabies or snakebites.
This is because the disease will likely kill the person before active immunity takes over.

Immunoglobulins (Igs),
They are the main force for identifying and binding with antigens

two are shorter (the light chains) than the other (heavy chains)
Y or T shape
a variable region - different for each antibody because that end is responsible for the antigen-binding site
a constant region- responsible for the type of antibody and how it performs its job,

There are five classes, IgM, IgA, IgD, IgG,IgE
IgD - surface receptor of B Cell, always attached
IgM - antigen receptor first released from plasma as an agglutinating agent
IgG - Responsible for passive immunity in fetus
IgA - Battles pathogens in body’s mucus
IgE - Triggers the release of histamine
Antibodies deactivate antigens in many ways
*Complement Fixation -
binds to antibodies attached to cellular targets that trigger lysis of the foreign cell
*neutralization -
bind to specific sites on bacteria or viruses that inhibit their lethality
agglutination -
clumping of foreign cells, occurs in mismatched blood transfusions
precipitation -
When the antigen-antibody complexes (clumps) become so large that they are insoluble and settle out of solution
The System
consists of two semi-independent parts
lymphatic vessels
lymphoid tissues and organs
lymphatic vessels transport back fluids to the blood that have escaped from the blood vascular system
lymphoid tissues and organs house phagocytic cells and lymphocytes (body defense and resistance to disease)

Lymphatic Vessels
fluid forced out of blood must be carried back to the bood for sufficient blood volume
lymphatic vessels form an elaborate drainage system that picks up excess fluid (lymph) and returns it to the blood
lymphatic vessels form a one-way system; lymph flows only towards the heart
lymph capillaries absorb leaked fluid
edges of endothelial cells in lymph capillaries loosely overlap one another, forming "minivalves"
Lymphatic Vessels cont.
lymph is transported from the lymph capillaries through successively larger lymphatic collecting vessels
lymph is returned to venous system through one of two large ducts in thoracic region
right lymphatic duct — drains lymph from right arm and right side of head and thorax
thoracic duct — receives lymph from the rest of the body
both ducts empty lymph into the subclavian vein on their own side of the body
lymphatic vessels are most similar to veins
Lymph Nodes
lymph nodes help protect the body by removing foreign material from the lymphatic stream and by producing lymphocytes
large clusters of lymph nodes are found in the inguinal, axillary, and cervical regions of the body
most are kidney-shaped, less than 1 inch long, and "buried" in connective tissue that surrounds them
the outer part of the node (cortex) contains a collection of lymphocytes (follicles) which have dark-stained centers (germinal centers)
these centers enlarge when B-cells generate daughter cells (plasma) that release antibodies
the rest of the cortical cells are T-cells that circulate continuously between the blood, lymph nodes, and lymphatic stream to perform surveillance
lymph enters node through afferent lymphatic vessels, then flows through sinuses, finally exists from hilum via efferent lymphatic vessels
Lymphoid Organs
common feature of all of these organs is a predominance of reticular connective tissue and lymphocytes
spleen — located beneath diaphragm and curls around anterior aspect of stomach; filters and cleanses blood of bacteria, viruses, and other debris; destroys worn-out red blood cells and returns products to the liver
thymus gland — found in throat overlying heart; produces hormones that function in the programming of lymphocytes; functions at peak levels only during youth
tonsils — ring the pharynx and found in mucosa; trap and remove bacteria or other foreign pathogens that enter the throat
Peyer's patches — found in wall of small intestine; macrophages capture and destroy bacteria, thereby preventing penetration of intestinal wall
tonsils and Peyer's patches make up mucosa-associated lymphatic tissue (MALT) that protect upper respiratory and digestive tracts
Cellular (Cell-Mediated) Immune Reponse
Body Defenses
The immune system consists of 2 systems
- Innate Defense System
- Adaptive Defense System
Innate system is always prepared to protect body from foreign substances
Adaptive system must be initially exposed to foreign substance before it starts attacking
When the immune system is operating effectively, it protects us from most bacteria, viruses, transplanted organs, and cells that turn against us
Zimmermann, By Kim Ann. "Lymphatic System: Facts, Functions & Diseases." LiveScience. TechMedia Network, 08 Feb. 2013. Web. 23 June 2015.
"Google Images." Google Images. N.p., n.d. Web. 23 June 2015.
Surface Membrane Barriers
The body's first line of defense against disease-causing microorganisms is skin and mucous membranes
Serve as physical barriers against microorganisms
These membranes produce protective secretions:
- 1) acidic pH of skin secretions inhibits bacterial growth
- 2) stomach mucosa secretes hydrochloric acid and protein-digesting enzymes
- 3) Lysozyme destroys bacteria
- 4)Sticky mucus traps many microorganisms that enter digestive & respiratory passages
Internal Defenses: Cells and Chemicals
Body's second line of defense uses cells and chemicals to protect itself
These defenses rely on phagocytes and natural killer cells, inflammatory response, and chemicals that kill pathogens and help repair tissue
Fevers are also considered an innate protective response
T Cells are also activated with a special kind of antigen recognition or "Antigen Presentation"
1. Macrophages first engulf foreign antigens
2.Macrophage then presents the self-antigen and foreign antigen to the T Cells to activate them
Internal Defenses (Cont.)
phagocytes engulf foreign particles when it makes it through the mechanical barriers
Natural killer cells are a group of lymphocytes that lyse and kill cancer cells and virus-infected cells
inflammatory response is triggered whenever body tissues are injured
-4 Common Signs: Heat, redness, swelling, pain
When cells are injured they release inflammatory chemicals which cause
1) blood vessels to dilate and capillaries to become leaky
2) activate pain receptors
3) attract phagocytes and white blood cells
3. T Cells undergo clonal replication into different classes of T Cells
Fever is a systemic response to invading microorganisms
Mild/moderate fevers are considered beneficial to the body
During a fever, the liver and spleen take up nutrients, making them less available for bacteria in order to multiply
Fever also increases the metabolic rate of tissue cells, speeding up repair processes
cytotoxic (killer) T Cell - kills foreign particles by binding to it and releasing chemicals into the particles’ membranes
Helper T Cells - are the “managers” of the immune system, directing other cells to fight invaders by increasing their effectiveness
Regulatory T cells - suppresses the activity of B and T Cells to slow down and stop the immune response after the antigen has been destroyed
Memory T Cells - memorizes each antigen encountered so that the body can respond quickly to subsequent invasions

Different Types of T Cells
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