anatomy & physiology. 2 main parts lymphatic vessels lymphoid tissues/organs functions: ...
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THE LYMPHATIC SYSTEM
Anatomy & Physiology
LYMPHATIC SYSTEM-GENERAL 2 Main Parts
Lymphatic vessels Lymphoid tissues/organs
FUNCTIONS:Drain excess fluid (edema) and returns it to
bloodPlays essential roles in body defense and
resistance to disease
LYMPHATIC SYSTEM-GENERAL Lymph—excess tissue fluid Properties of lymphatic vessels
One way system toward the heartNo pumpLymph moves toward the heart
Transported through milking action of skeletal muscle
Rhythmic contraction of smooth muscle in vessel walls helps pump the lymph through the system
RELATIONSHIP OF LYMPHATIC VESSELS TO BLOOD VESSELS
LYMPHATIC VESSELS Lymph capillaries
Walls overlap to form flap-like minivalves to allow entrance for lymph Fluid leaks into lymph capillaries
Lymph Capillaries are anchored to connective tissue by filaments
Higher pressure on the inside of the capillary closes minivalves Fluid is forced along the vessel for examination
Examined by cells of immune system for any potential threats
LYMPHATIC VESSELS Lymphatic collecting
vessels Collect lymph from
lymph capillaries Carry lymph to and
away from lymph nodes Return fluid to
circulatory veins near the heart Right lymphatic duct
Drains lymph to right arm/head/thorax
Thoracic duct Drains rest of body that
R.Lymph duct doesn’t
LYMPH Harmful materials that enter lymph
vesselsBacteriaVirusesCancer cellsCell debris
LYMPH NODES Filter lymph before it is returned to the
blood Areas of high concentration?
Inguinal, axillary, and cervical regions Defense cells within lymph nodes
Macrophages—engulf and destroy foreign substances
Lymphocytes—provide immune response to antigens
Nodes swell when fighting infection because nodes have engulfed the foreign substance to prevent it from spreading
LYMPH NODE STRUCTURE Most are kidney-
shaped and less than 1 inch long
Cortex Outer part Contains follicles—
collections of lymphocytes
Medulla Inner part Contains phagocytic
macrophages
OTHER LYMPHOID ORGANS Several other
organs contribute to lymphatic functionSpleenThymusTonsilsPeyer’s patches
SPLEEN Blood filled organ which
filters blood Location: Left side of
abdomen above diaphragm
Functions: Filters/cleanses blood of
foreign substances Destroy worn-out blood
cells Recycles components of
worn out blood cells (i.e. hemoglobin)
Stores platelets Protect body during
hemorrhage
THYMUS GLAND Lymphoid mass
found in throat Function:
Programs lymphocytes with the help of thymosin (hormone)
TONSILS Small, lymphoid
tissue in back of throat
Function: Capture and remove any foreign pathogens(substances)Reason they
become swollen during colds/viruses
PEYER’S PATCHES Location: Wall of
small intestine Function:
Capture and destroy bacteriaPrevent foreign
pathogens from penetrating intestinal wall
BODY DEFENSES The body is constantly in contact with
bacteria, fungi, and viruses The body has two defense systems for
foreign materials Innate (nonspecific) defense system
Attacks ANY foreign pathogenAdaptive (specific) defense system
Attacks SPECIFIC substances
Immunity—specific resistance to disease -Immun=free
IMMUNE SYSTEM
INNATE BODY DEFENSES AKA “non-specific defense system” Innate body defenses are mechanical
barriers to pathogens such asBody surface coverings
Intact skin Mucous membranes
Line all body cavities that are exposed (i.e. digestive, respiratory, urinary, and reproductive tracts)
Specialized human cellsChemicals produced by the body
SURFACE MEMBRANE BARRIERS:FIRST LINE OF DEFENSE Skin and mucous membranes
Physical barrier to foreign materialsAlso provide protective secretions
pH of the skin is acidic to inhibit bacterial growth Sebum is toxic to bacteria Stomach releases hydrochloric acid to kill
pathogens Saliva and lacrimal fluid contain lysozymes
which kill bacteria Mucus traps microorganisms and prevent them
from entering the digestive or respiratory tract
CELLS AND CHEMICALS:SECOND LINE OF DEFENSE Phagocytes
I.e. macrophage or neutrophilSwallows foreign pathogen
Natural killer cellsKill cancer and virus cells Fight off these pathogens by detecting
sugar molecules on pathogen’s surface
CELLS AND CHEMICALS:SECOND LINE OF DEFENSE CONT’D Inflammatory response
Happens when tissue is injured4 signs: Redness, heat, inflammation,
swelling painHistamine & Kinins causes:
Vessels to dilate causing inflammation Activate pain receptors to alert body of problem Attract WBCs and phagocytes to clean cellular
debris from tissue damage
CELLS AND CHEMICALS:SECOND LINE OF DEFENSE CONT’D Antimicrobial proteins
Help fight pathogens by attacking them or inhibiting their progress through the use of? Complement proteins
Bind to sugar receptors on pathogen’s cell and causes holes which allow water to enter the cell and cause it to burst
Interferon: Bind to viruses’ cells and cause proliferation of
interferon molecules which hinder the viruses’ cell replication
CELLS AND CHEMICALS:SECOND LINE OF DEFENSE CONT’D Fever
Effects of fever include: Prohibiting iron or zinc availability which bacteria
require to multiply Increases metabolic rate which in turn increases
the repair process HIGH fevers can denature proteins and enzymes
causing breakdowns within the body
ADAPTIVE DEFENSE SYSTEM: THIRD LINE OF DEFENSE Immune response is the immune
system’s response to a threatProvides protection by the use of antigens
through specificity Immunology is the study of immunity Antibodies are proteins that protect from
pathogens
THIRD LINE OF DEFENSE When the body is exposed to a pathogen
it builds “antibodies”Less likely the body will acquire that same
pathogen again Immune response becomes stronger when
faced with this invading pathogen in the future
3 steps involved in immune response:1. Antigen specific: It attacks particular
pathogens/foreign substances2. Systemic: Immunity is not confined to only
the “initial infection site.” Can work through the circulatory system
3. Memory: Has stronger attacks against previously fought pathogens
THIRD LINE OF DEFENSE Humoral Immunity/Antibody-mediated
immunityAntibodies fight off infection in the blood
stream (humors/fluids)
Cellular Immunity/Cell-mediated immunityFights off viral cells, cancer cells, and
foreign graft cells either directly or indirectly
THIRD LINE OF DEFENSE Antigen:
Any substance responsible for initiating an immune response
Examples of common antigens Foreign proteins (strongest) Nucleic acids Large carbohydrates Some lipids Pollen grains Microorganisms
THIRD LINE OF DEFENSE Self-antigens
Human cells have many surface proteins
Our immune cells do not attack our own proteins because they are recognizable in our bodies
Our cells in another person’s body can trigger an immune response because they are foreign Restricts donors for
transplants Unless…medications are
taken to suppress immune system
Hapten/Incomplete Antigen: A small molecule
antigen that cannot initiate the creation of antibodies
Instead, it binds with our proteins
The body doesn’t not recognize combination and attacks it
Examples: Poison ivy, detergents,
hair dyes, etc
THIRD LINE OF DEFENSE-CELLS B lymphocytes/B-cells
Create antibodies and direct humoral immunity
T lymphocytes/T-cellsThese cells do not produce antibodies Mature T-cells are the most effective in
fighting off foreign antigens
THIRD LINE OF DEFENSE-CELLS Immunocompetent—cell becomes
capable of responding to a specific antigen by binding to it
Cells of the adaptive defense system Lymphocytes
Originate from hemocytoblasts in the red bone marrow
B lymphocytes become immunocompetent in the bone marrow (remember B for Bone marrow)
T lymphocytes become immunocompetent in the thymus (remember T for Thymus)
THIRD LINE OF DEFENSE-CELLS Cells of the adaptive defense system
(continued)Macrophages
Arise from monocytes found in bone marrow Become widely distributed in lymphoid organs Secrete cytokines (proteins important in the
immune response) Tend to remain fixed in the lymphoid organs
Unlike lymphocytes that circulate
HUMORAL (ANTIBODY-MEDIATED) IMMUNE RESPONSE B lymphocytes with specific receptors
bind to a specific antigen The binding event activates the
lymphocyte to undergo clonal selectionLymphocyte grows and multiplies
Most B cells turn into plasma cells The remaining B cells are stored as
memory cells for future encounters with that antigen
HUMORAL (ANTIBODY-MEDIATED) IMMUNE RESPONSE Secondary humoral responses
Memory cells are long-livedA second exposure causes a rapid responseThe secondary response is stronger and
longer lasting
ACTIVE IMMUNITY Occurs when B cells encounter antigens
and produce antibodies Active immunity can be
Naturally acquired during bacterial and viral infections
Artificially acquired from vaccines
PASSIVE IMMUNITY Occurs when antibodies are obtained
from someone elseAcquired naturally from a mother to her
fetus (naturally acquired) when passing through placenta
Conferred artificially from immune serum or gamma globulin (artificially acquired) Shots given after exposure to certain pathogens
Immunological memory does not occur Protection provided by “borrowed
antibodies” Lasts 2-3 weeks
TYPES OF ACQUIRED IMMUNITY
ANTIBODIES (IMMUNOGLOBULINS OR IGS) Secreted by
activated B cells Respond to a
specific antigen
ANTIBODIES (IMMUNOGLOBULINS OR IGS) Antibody classes
Antibodies of each class have slightly different roles
Five major immunoglobulin classes (MADGE) IgM—can fix complement IgA—found mainly in mucus IgD—important in activation of B cell IgG—can cross the placental barrier and fix
complement IgE—involved in allergies
ANTIBODIES Antibody function
Antibodies inactivate antigens in a number of ways Complement fixation
Causes lysis of the cell Neutralization
Bind to bacterial cells to block the release of that cell’s toxic chemicals
AgglutinationClumping of foreign cells
PrecipitationWhen antigen-antibodies combine forming
large complexes that settle out a solution that was agglutinated
ANTIBODY FUNCTION
CELLULAR (CELL-MEDIATED) IMMUNE RESPONSE
Antigens must be presented by macrophages to an immunocompetent T cell
T cells must recognize nonself and self (double recognition)
After antigen binding, clones form as with B cells, but different classes of cells are producedCytotoxic (killer T cells): Attack virus infected,
cancer, or foreign graft cellsHelper T cells: Directors of immune systemRecruit other cells to fight pathogens Regulatory T cells: Stop the immune response
once antigen is destroyed
ORGAN TRANSPLANTS AND REJECTION
Major types of graftsAutografts—tissue transplanted from one
site to another on the same person Isografts—tissue grafts from an identical
person (identical twin)Allografts—tissue taken from an unrelated
personXenografts—tissue taken from a different
animal species
ORGAN TRANSPLANTS AND REJECTION Autografts and isografts are ideal donors Xenografts are never successful Allografts are more successful with a
closer tissue match
DISORDERS OF IMMUNITY: ALLERGIES (HYPERSENSITIVITY) Abnormal, vigorous immune responses Types of allergies
Immediate hypersensitivity Triggered by release of histamine from IgE
binding to mast cellsCauses dilation of small blood vesselsLeads to: itchy, watery, runny nose/eyes
Reactions begin within seconds of contact with allergen
Anaphylactic shock—dangerous, systemic responseThroat closes in response to allergy, blocking
airway
DISORDERS OF IMMUNITY: IMMUNODEFICIENCIES Production or function of immune cells or
complement is abnormal May be congenital or acquired Includes AIDS (Acquired Immune Deficiency
Syndrome) Kills of Helper T-cells
Includes Severe Combined Immunodeficiency Disease (SCID) Congenital condition
The immune system does not distinguish between self and nonself
The body produces antibodies and sensitized T lymphocytes that attack its own tissues