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LYMPHATIC AND
IMMUNE SYSTEMS
Chapter 33
THE LYMPHATIC SYSTEM
The lymphatic system has three main functions• Take up excess tissue fluid and return it to the
bloodstream
• Receive fats called lipoproteins and return them to the
blood stream
• Work with the immune system for defense against disease
The lymphatic system is a one-way system. Lymphatic
capillaries absorb fluid in the blood that has not been
reabsorbed by the blood capillaries.• At this point, the fluid is called lymph
THE LYMPHATIC SYSTEM
The lymphatic capillaries join to lymphatic vessels
that enter either the thoracic duct or the lymphatic
duct.• The thoracic duct serves the lower extremities, abdomen,
and left side of the head, neck and torso
• The lymphatic duct serves the right side of the head, neck,
and torso
Both ducts remove harmful substances from blood
and carry them to lymph nodes where they are isolated
from the rest of the body
LYMPHOID ORGANSLymph nodes
• Lymph nodes are found along the lymphatic
vessels.
• A lymph node contains a cortex and a medulla• Cortex: where lymphocytes congregate when fighting off
a pathogen (hence, the swelling of the lymph nodes if a
patient is sick or fighting a disease)
• Medulla: where macrophages cleanse the lymph as it
passes through
• Lymph nodes are found in the groin, armpits, and
neck and tend to swell when isolating and
containing pathogens
LYMPHOID ORGANS
Tonsils
• Tonsils are located just above the pharynx
• Tonsils behave like lymph nodes for pathogens and
antigens that enter the body through the mouth and
nose
• The function of tonsils was only recently discovered in
the past century, making the 3,000 year old surgery of
tonsillectomy much more rare
LYMPHOID ORGANSSpleen
• The spleen is the primary blood filtering organ
• Located in the upper left abdominal region,
just beneath the diaphragm
• Spleens contain two tissues called white pulp
and red pulp.• The white pulp filters out bacteria and debris from
blood
• The red pulp filters out old red blood cells
LYMPHOID ORGANS
Thymus gland• Located along the trachea behind the sternum
• T lymphocytes mature in the thymus
• Immunity hormones, such as thymosin, are produced
here
Bone Marrow• Contains the stem cells for all types of blood cells
• The bone marrow is connected to sinuses, where
matured and differentiated blood cells enter the
blood stream
IMMUNE SYSTEM:
INNATE DEFENSE
Immunity is the body’s ability to defend itself against
infectious agents, foreign cells, and even abnormal body
cells such as cancer.
Innate defense systems recognize most common
microbe invaders automatically whether or not the
immune system has encountered this particular microbe
before.
They lack any “memory” system. Even if they
encounter the same microbe 1000’s of times the response
doesn’t change.
INNATE IMMUNITY:P HYSICAL & CHEM ICAL BARRIERS
Skin and mucus membranes limit where pathogens can
enter the body to only a few locations (mouth, nose, ears,
genitals)
Oil secretions contain additional chemicals that weaken
or kill some bacteria that make contact with the skin
Respiratory tracts are lined with cilia. Mucus surrounds
and collects pathogens, then cilia sweep the pathogen to the
throat where it can be swallowed or expectorated (coughed
out)
Symbiotic bacteria in our bodies also fight off invaders
INNATE IMMUNITY:
INFLAMMATORY RESPONSEDamaged tissues initiate an inflammatory response which
makes both the organism and the immune system aware of a
problem.
Inflamed areas show redness, heat, swelling and pain.
Histamines trigger the capillaries of the tissues to dilate and
allow a higher volume of blood cells to enter.
White blood cells enter the area to cleanse any foreign
microbes
Clotting occurs to prevent any bacteria from entering while
the tissue is repaired and allow the internal homeostatic
environment to continue.
PHAGOCYTES AND NKC’SNatural Killer Cells
• NK cells kill virus-infected cells and tumor cells. They
are triggered only by chance cell-to-cell encounters
• They know if a cell is foreign because the cell doesn’t
know how to build the specific antigens for that cell
Neutrophils
• These immune cells can leave bloodstreams and enter
tissues to fight infections
Eosinophils
• These cells are designed to attack larger parasitic
infections like roundworm or tapeworm that are too
big for individual phagocytizing cells.
INNATE IMMUNITY:
PROTECTIVE PROTEINS Protective Proteins are produced in a domino effect called the complement system. One protein activation triggers production of all othersThese proteins are only activated by pathogens and work in one of three ways:
• 1: They increase the inflammation response if large microbes are involved
• 2: They increase phagocytosis by binding to pathogens and giving neutrophils and macrophages something to latch on to.
• 3: They poke holes in pathogens to force water and salts to enter until the molecule bursts.
Interferon is a protective protein produced by virus-infected cells. Interferon binds to non-infected cells causing them to go into hibernation mode and limiting the number of cells the virus could spread to.
IMMUNE SYSTEM: ADAPTIVE
DEFENSE
Adaptive defenses are designed to respond to specific diseases
with higher frequency after each encounter
Adaptive defense relies on B cells (which are made in marrow)
and T cells (which are made in the thymus)• Both B and T cells recognize your personal antigens and distinguish
them from other microbial antigens
• B and T cells have millions of different antigen receptors on their
plasma membranes for recognizing foreign invaders.
The simplest difference between B cells and T cells is that B
cells attack pathogens from the outside and T cells attack from
the inside.
https://goo.gl/Hq6YGg
B CELLS & ANTIBODY-MEDIATED
(HUMORAL) IMMUNITY
Antibodies help to prevent an infection BEFORE it
occurs• Antibodies match with antigens and act as beacons for the
immune system to respond to.
• They also cover the invading microbes to the point that it
has difficulty binding to a new victim cell
Microbes are delivered to the spleen and lymph
nodes thanks to the lymphatic system, where B cells are
waiting for them.
B CELLS & ANTIBODY-MEDIATED
(HUMORAL) IMMUNITY
When the B cell finds the antigen on a microbe it
divides over and over again creating…• Plasma Cells: Cells filled with Rough ER for producing antibodies
that match with this specific antigen
• Memory B Cells: Seek out this specific antigen for increased
immune response.
The most common antibody is IgG, a Y-shaped
protein.• The Y-shape is altered in the presence of specific antigens
• Leukocytes recognize the shape of this antigen and begin
phagocytosis.
T CELLS & CELL-MEDIATED
IMMUNITYT cells come in two categories: helper and cytotoxic.
Helper T cells cannot recognize foreign antigens on their own.
• Antigen presenting cells seek out and respond to foreign antigens.
• When they find an antigen, they “cap” it with an MHC protein.
• The MHC protein then attracts a helper T cell which binds to the microbe.
Helper T cells attract B cells to the microbe
Helper T cells also clone themselves upon binding to a microbe to
create memory T cells, which look for the same microbe in the future
to attract T cells.
At this point, B cells would normally have completed their task. But
T cells go one step further.
T CELLS & CELL-MEDIATED
IMMUNITY
Cytotoxic T cells contain vacuoles filled with a chemical
called perforins and granzymes
The cytotoxic T cell is incredibly deadly, so it can only be
activated with the presence of specific MHC proteins and
helper T cells
When the cell locates its target, perforins create a pore in
the plasma membrane of the microbe or cancerous cell
Granzymes then enter the cell through the pore and force
apoptosis
ACTIVE INDUCED IMMUNITYActive immunity is your body’s direct response to a specific threat.
We can artificially preempt an active immune response thanks to
immunizations
• A vaccine is a substance that contains the antigen to which the
immune system responds (not the whole cell, just the antigen)
and produces antibodies
• Antibodies are destroyed every time they fight off an infection.
Unless your body makes new antibodies, you’ll eventually run
out.
• Over the course of the year or lifetime the titer will eventually
dwindle as the antibodies are used up or broken down while
fighting off disease
• Some vaccines are good for life; other’s require periodic “booster”
shot
PASSIVE INDUCED IMMUNITY
Passive immunity is when an individual is given
prepared antibodies through natural means to
combat a disease.
• Infants are given antibodies from their mother
through blood that passes the placenta or
through transfer within breast milk
IMMUNITY DISORDERS
Allergies are hypersensitivities to substances that ordinarily would do no harm to the body.The response to these antigens, called allergens, is either: Immediate Allergic Response
• An IAR can occur within seconds. Coldlike symptoms are common, but the worst-case scenario is anaphylactic shock, a sudden drop in blood pressure.
• IgE Antibodies attached to the plasma membrane of tissue and blood release histamines as if a dangerous pathogen just invaded them, triggering these cold or anaphylactic symptoms
Delayed Allergic Response• Memory T cells are initiated at the site of the allergen.• These trigger cytokines, which trigger the immune response.
IMMUNITY DISORDERS
Autoimmune disease is when cytotoxic T cells or
antibodies accidentally attack the body’s own cells.
These are sometimes the result of overactive T cells
still functioning after a foreign-pathogen-initiated
infection has occurred.
Lupus, rheumatoid arthritis, and muscular disorders
are believed to be triggered by an autoimmune disease.