Lymphatic System and Disorders
Download
Report
Transcript Lymphatic System and Disorders
Lymphatic System and
Disorders
BIO 238
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
• Functions of the
Lymphatic System
▫ Return excess
interstitial fluid to the
blood
Helps maintain water
balance in the body
▫ Involved in the
absorption of fats from
digestive tract through
lacteals
▫ Works with white
blood cells to protect
the body against
pathogens
Lymph
• Lymph is the fluid flowing inside lymphatic
vessels
▫ Derived from blood plasma
• Formation of lymph
▫ Capillary leakage causes blood proteins to enter
interstitial fluid (IF); increases osmotic pressure
▫ Excess fluid accumulates in the interstitial space
▫ Lymphatic vessels pick up and return the accumulated
fluid to blood
▫ This process prevents edema from occurring in body
tissues
Lymphatic Capillaries and Vessels
• Lymphatic trunks drain into lymphatic collecting ducts
▫ Right lymphatic duct
R side of head and neck , R arm and shoulder, R thorax
▫ Thoracic duct
Remainder of body
• Collecting ducts empty into the R or L subclavian veins
Lymphatic Organs
• All lymphatic organs are site of lymphocyte
production
• Lymphocytes may remain in the lymphatic
organs or migrate in blood to other sites
Lymph Nodes
• Widely distributed
throughout body
• Filters and cleanses
lymph
▫ Trapped substances are
destroyed by lymphocytes
and macrophages
Tonsils
▫ Lymphatic tissue underneath mucus membranes
of nasal and oral cavities
▫ Intercept and destroy pathogens that enter
through nose and mouth
▫ Three groups of tonsils
Palatine tonsils
Pharyngeal tonsil
Lingual tonsils
• Thymus
▫ Located in the
mediastinum
▫ Large in infants and
decreases in size
with age
▫ Produces thymosin,
which promotes T
lymphocytes (T cells)
differentiation and
division
Spleen
▫ Cleanses and filters blood
and lymph
▫ Store reserve supply of red
blood cells
▫ Major site of red blood cell
destruction and removal
▫ Major site of lymphocyte
production
Nonspecific Resistance Against
Disease
• Protection against all pathogens and foreign
substances
Not directed against a specific pathogen
• Mechanisms include
▫
▫
▫
▫
▫
Mechanical barriers
Chemical actions
Phagocytosis
Inflammation
Fever
Mechanical and Chemical Barriers
• Mechanical Barriers
▫ Skin
Packed epidermal cells
Acid pH
▫ Mucus membranes
Trap foreign substances
▫ Tears
▫ Saliva
▫ Urine flow
• Chemical Actions
▫ Lysozyme: destroys bacteria
▫ Mucus: traps pathogens
▫ Gastric juice: low pH and
enzyme pepsin
▫ Interferon: causes
uninfected cells to make antiviral replication proteins
Phagocytosis
▫ The engulfing and destruction of
microorganisms
▫ Carried out by neutrophils and
monocytes
Monocytes entering the infected tissues are
called macrophages
Inflammation
▫ Localized response to infection or injury
Promotes pathogen destruction and the healing
process
▫ Characterized by redness, pain, heat, and swelling
▫ Process of inflammation
Cells release chemicals that dilate arterioles and
increase capillary permeability
Increased blood flow causes redness and heat
Increased fluid movement out of capillaries causes
swelling
Irritations of nerve endings causes pain
Pus
Accumulated mass of living and dead leukocytes,
tissue cells, and bacteria at the infection site
Fibrinogen and fibroblasts work to seal off the
infected area and prevent pathogen spread
Dead pathogens are cleaned up by
phagocytes
New cells are formed to repair area of damage
Fever
▫ Abnormally high body temperature
▫ Functions
Inhibits growth of certain pathogens
Increases rates of body processes, including
those that fight infections
Immunity
• Specific resistance directed at specific
pathogens and foreign cells
▫ Production of specific cells and substances
that attack a specific invader
• It has a “memory”
▫ Allows a quicker and stronger response to
subsequent infections
• Involves lymphocytes and macrophages
▫ Separated into cell-mediated immunity and
antibody-mediated immunity
Specialization of Lymphocytes
▫ Lymphocytes are born in red bone marrow
▫ Lymphocyte specialization
In the thymus become T lymphocytes (T cells)
In bone marrow, spleen, or liver become B
lymphocytes (B cells)
▫ T and B cells flow through the blood to lymphatic
organs where they form large populations
▫ 75% of circulating lymphocytes are T cells
▫ 25% of circulating lymphocytes are B cells
Recognizing Pathogens
▫ Cells of each person has a unique set of surface
recognizing molecules called antigens
▫ Lymphocytes learn how to distinguish self from
non-self
Allows them to recognize foreign cells and
pathogens
Each B and T cell has receptors that can bind with a
specific antigen
Only those cells that can bind the antigen are involved
in the immune response
• Cell-Mediated Immunity
▫ First step is to recognize the foreign
antigen
Antigen-presenting cell engulfs the
pathogen
Expresses part of the antigen on its plasma
membrane
Helper T cell that can bind to the antigen
is activated and begins the immune
response
T Cells
▫ Helper T cells
Start and intensify an immune response
Release cytokines when activated
Stimulate T and B cell clone formation
Stimulate Cytotoxic T cells
▫ Cytotoxic T cells
Attack and destroy specific abnormal body cells
Release a cytotoxin that ruptures the cell
membrane of the target cell
Release cytokines that attract other lymphocytes
and macrophages
T Cells
▫ Memory T cells
Remain to launch a strong response should the
same antigen ever enter the body again
▫ Supressor T cells
Suppresses the immune response
Antibody-Mediated Immunity
▫ A B cell becomes activated when it
Binds a specific antigen
Is stimulated by cytokines by an activated Helper T cell
▫ Activated B cell forms a clone of B cells that all have
the same antigen receptor
▫ Clone contains
Plasma cells that produce antibodies against the specific
antigen
Memory B cells that allow for a stronger response with
another encounter later on
Antibodies (Immunoglobulins)
Form antigen-antibody complexes that mark the
pathogen for destruction
Allows for complement fixation
Binding of complement to the antigen
Complement punches holes in the cell and it
bursts
Debris is cleaned up by phagocytes
Antibodies bind bacterial toxins, blocking their action
on body cells
Complexes are destroyed by phagocytes
• The six basic ways antibodies function:
▫
▫
▫
▫
▫
▫
Promote inflammation
Promote phagocytosis
Activate the immune complement
Stimulate apoptosis
Agglutination
Inactivate a pathogen or toxin
Immune Responses
• Primary immune response
▫ Occurs with the first encounter of a pathogen
▫ T and B cells make clones to destroy the antigen
▫ Produces memory cells that recognize the same
antigen if it ever reenters the body
• Secondary immune response
▫ Occurs with another invasion of the same antigen
▫ Memory T and B cells launch a more rapid and
intense response then the primary immune
response
• Types of Immunity
▫ Mechanisms are grouped into two
broad categories
Active immunity
Person is directly involved in the development
of immunity
Longer lasting then passive immunity
Passive immunity
Person is not directly involved in the
development of immunity
Types of Immunity
▫ Naturally acquired active immunity
Person gets the disease and recovers
Leaves memory T and B cells to fight later infections
▫ Artificially acquired active immunity
Person receives a vaccine of dead or weakened
pathogens
Triggers a response that forms memory cells
Booster shots cause a secondary response to
boost antibodies levels
Types of Immunity
▫ Naturally acquired passive immunity
Infants receive mother’s antibodies through placenta
and breast milk
▫ Artificially acquired passive immunity
Receiving injections of antibodies produced by
another person or animal
Rejection of Organ Transplants
• Major challenge after a transplant is organ rejection
▫ Body recognizes the new organ as non-self and attacks it
• Compatibility of donor and recipient are determined
before transplant
• Immunosuppressive therapy is administered to
prevent rejection
▫ B cells are still able to provide antibody-mediated immunity
against pathogens
• Bacterial and viral infections are primary causes of
death
▫ 75% match is considered minimal for a transplant
Disorders of the Lymphatic and
Immune Systems
• Disorders can be grouped according to
▫ Infectious disorders
▫ Noninfectious disorders
Infectious Disorders
• Acquired immune deficiency syndrome
(AIDS)
▫ Caused by the human immunodeficiency virus
(HIV)
▫ Attacks and kills Helper T cells
▫ Invade macrophages that serve as a reservoir
for the virus
AIDS
▫ Transmission occurs by
Sexual intercourse
Exchanges of blood
Childbirth
▫ Immune defenses in the individual decrease
▫ Leads to development of secondary diseases
Pneumocystis carinii
Kaposi’s sarcoma
▫ No cure
• Elephantiasis
▫ Tropical disease
▫ Characterized by greatly swollen legs or other
body parts
Lymphatic vessels are blocked by round worms
▫ Transmitted by some mosquito species
• Tonsillitis
▫ Inflammation of the tonsils due to bacterial
infections
Noninfectious Disorders
• Allergy or hypersensitivity
▫ Abnormally intense immune response to an
antigen harmless to most people
▫ Allergens
▫ Sensitization to an allergen results in reactions
whenever exposure occurs
▫ Reactions can be
Immediate
Delayed
▫ Immediate reactions
Occur when allergens bind with IgE antibodies
on basophil and mast cell surfaces
Cells release histamine, which stimulate an
inflammatory responses
Localized reactions are unpleasant but not life
threatening
Example: hay fever, hives
Systemic reactions (anaphylaxis) are life
threatening
Impair breathing and cause circulatory failure
Example: bee stings and penicillin
▫ Delayed allergic reactions
Appear 1-3 days after antigen exposure
Due to cytokines from t cells
Example: poison ivy
• Autoimmune Diseases
▫ T and B cells recognize body tissues as nonself
Produces an immune response
▫ Due possibly to change in body molecules
▫ Example: rheumatoid arthritis, multiple sclerosis
• Lymphoma
▫ Any tumor of lymphatic tissue
▫ Hodgkin’s disease
Malignant lymphoma
Enlarged and painless lymph nodes, fatigue,
fever, night sweats
Chemotherapy and radiation can yield a high
cure rate early