lymphatic system
Post on 02-Nov-2014
11 Views
Preview:
DESCRIPTION
TRANSCRIPT
LECTURER: Lorraine Veraces-Pilapil, OTRP, OTR
Fluid balanceFat absorptionDefense
FLUID BALANCE30 L of fluid blood capillaries to interstitial
spaces each day27 L of fluid interstitial spaces into blood3 L of fluid enters the lymphatic capillaries
(lymph) and passes through the lymphatic vessels to return to the blood.
Lymph contains solutes derived from two sources:Substances in plasma, such as ions, nutrients,
gases, and some proteinsSubstances such as hormones, enzymes, and waste
products derived from cells within the tissues.
FAT ABSORPTIONFrom the digestive tractLacteals (special lymphatic vessels)
located in the lining of the small intestine fat enters lymphatic vessels venous circulationChyle is lymph that is milky in appearance
due to the fat content.
DEFENSE
Microorganisms and other foreign substances filtered from lymph by lymph nodes and from blood by the spleen.
Lymphatic system does not circulate blood to and from tissues.Carries fluid in one direction from tissues to the circulatory system.
LYMPHATIC CAPILLARIESTiny closed-ended vessels consisting of simple
squamous epithelium.More permeable than blood capillaries because they
lack a basement membrane, and fluid moves easily into the lymphatic capillaries
Overlapping squamous cells of the lymphatic capillary walls act as valves that prevent the back-flow of fluid.
Are located in most tissues of the body except the CNS, bone marrow, and tissues without blood vessels such as epidermis and cartilages
Superficial group drains the dermis and hypodermis
Deep group drains muscles, viscera, and other deep structures
LYMPHATIC VESSELSResemble small veinsBeaded appearance because of one way valvesThree factors that cause compression of the
lymphatic vessels:Contraction of surrounding skeletal muscle during
activityPeriodic contraction of smooth muscle in the lymphatic
vessel wallPressure changes in the thorax during respiration
Lymphatic vessels converge and eventually empty into:Right lymphatic duct upper right limb and the
right half of the head, neck, and chest and empties into the right subclavian vein.
Thoracic duct rest of the body and empties into the left subclavian vein.
Tonsils Lymph Nodes SpleenThymus Gland
LYMPHATIC TISSUESConsists of many lymphocytes and macrophagesFound within lymphatic organsOriginate from the red bone marrow and are
carried by the blood to lymphatic organsThey divide and increase in number when the
body is exposed to microorganisms or foreign substances
Has very fine reticular fibers that form an interlaced network that holds the lymphocytes and other cells in place as well as traps microorganisms and other items in the lymph.
TONSILSThey form a protective ring of lymphatic
tissue around the openings between the nasal and oral cavities and the pharynx.
Provide protection against pathogens and other potentially harmful material entering from the nose and mouth.
In adults, the tonsils decrease in size and may eventually disappear.
Three group of tonsils:Palatine tonsils (“the tonsils”) – located on
each side of the posterior opening of the oral cavity.
Pharyngeal tonsils – located near the internal opening of the nasal cavity and when enlarged is commonly referred as “adenoid”
Lingual tonsils – posterior surface of the tongue.
LYMPH NODESRounded structures that vary in size.Distributed along the various lymphatic vessels
and most lymph passes through at least one lymph node before entering the blood.
Three superficial aggregations:Inguinal nodesAxillary nodesCervical nodes
Capsule – dense connective tissue that surrounds each lymph node
Trabeculae – extensions of the capsule and subdivides lymph nodes into compartments containing lymphatic tissue and lymphatic sinuses.
LYMPH NODESLymphatic nodules – are dense
aggregations of lymphatic tissue containing lymphocytes and other cells
Lymphatic sinuses – spaces between lymphatic tissue which contain macrophages on a network of fibers.
Germinal centers – lymph nodules containing rapidly dividing lymphocytes
Lymph enters the lymph node through afferent vessels, passes through the lymphatic tissue and sinuses, and exits through efferent vessels.
2 functions:Activation of the immune systemRemoval of microorganisms and foreign substances
from the lymph by macrophages
SPLEENRoughly the size of a clenched fist located
in the left, superior corner of the abdominal cavity.
Outer capsule – dense connective tissue and a small amount of smooth muscle
Trabeculae – divide the spleen into small, interconnected compartments containing two specialized types of lymphatic tissue:White pulp – lymphatic tissue surrounding the
arteries within the spleenRed pulp – associated with veins and consists of
a fibrous network filled with macrophages and red blood cells, and enlarged capillaries that connect to the veins.
SPLEENSpleen filters blood instead of lymph.Cells within the spleen detect and respond to
foreign substances in the blood and destroy worn-out red blood cells.
Also function as a blood reservoir holding a small volume of blood.
THYMUSBilobed gland roughly triangular in shapeLocated in the superior mediastinumThe thymus increase in size until the first
year of life, after which it remains approximately the same size even though the size of the individual increases
After 60 years of age, it decreases in sizeBy 40 years of age much of the thymus has
been replaced with adipose tissue.Capsule – thin connective tissue that
surrounds each lobe of the thymusTrabeculae – divide each lobe into lobules
THYMUSCortex – an area near the capsule and trabeculae
where lymphocytes are numerous and form a dark-staining area
Medulla – lighter staining central portion of the lobule and has fewer lymphocytes
Thymus functions as a site for production and maturation of lymphocytes
Large numbers of lymphocytes are produced in the thymus, but for unknown reasons, most degenerate.
While in the thymus, lymphocytes do not respond to foreign substances
Matured lymphocytes enter the blood and travel to other lymphatic tissues help protect against microorganisms and other foreign substances
IMMUNITYIs the ability to resist damage from foreign substances,
such as microorganisms, and harmful chemicals, such as toxins released by microorganisms
Innate immunity – body recognizes and destroys certain foreign substances, but the response to them is the same each time the body is exposed to them
Adaptive immunity – body recognizes and destroys foreign substances, but the response to them improves each time the foreign substance is encountered.Specificity and memory are characteristics of adaptive immunity
which results in a faster, stronger and longer response.Specificity – the ability of adaptive immunity to recognize a
particular substanceMemory – the ability of adaptive immunity to “remember”
previous encounters with a particular substance
Mechanical mechanism Chemical mediators Cells Inflammatory response
MECHANICAL MECHANISMSPrevent the entry of microorganisms and
chemicals in 2 ways:Skin and mucous membranes form barriers
that prevent their entryTears, saliva, and urine act to wash them from
the surfaces of the body
CHEMICAL MEDIATORSMolecules responsible for many aspects of
innate immunity.Lysozyme in tears and saliva are surface
chemicals that kill microorganisms or prevent their entry.
Histamine, complement, prostaglandins, leukotrines, promote inflammation by causing vasodilation, increasing vascular permeability, and stimulating phagocytosis
Interferons protect cells against viral infections.
A. ComplementA group of approximately 20 proteins found
in plasmaNormally circulate in blood in an inactive
form activated by combining with foreign substances or by combining with antibodies each complement protein activates the next promote inflammation and phagocytosis and directly lyse bacterial cells
B. InterferonsProteins that protect the body against viral
infectionsViruses stimulate infected cells to produce
interferons bind to the surface of neighboring cells and stimulate them to produce antiviral proteins inhibit viral reproduction by preventing the production of new viral nucleic acids and proteins.
Some play a role in the activation of immune cells such as macrophages and natural killer cells
CELLSWhite blood cells are the most important
cellular components of immunityWBC are produces in the bone marrow and
lymphatic tissue.Chemotaxis – is the movement of WBC
toward chemicals (complement, leukotrines, kinins, and histamine).
A. Phagocytic CellsPhagocytes – most important are neutrophils,
and macrophagesPhagocytosis – is the ingestion and
destruction of particles by phagocytesNeutrophils
Small phagocytic cells that are usually the first to enter infected tissues
Often die after phagocytizing a single microorganism
Pus – is an accumulation of fluid, dead neutrophils, and other cells at site of infection.
A. Phagocytic CellsMacrophages
Monocytes that enlarge fivefold after entering the tissues.
Form the mononuclear phagocytic system because they are phagocytes with a single, unlobed nucleus.
Kupffer cells – liverMicroglia – CNSIngest more and larger items than neutrophils
and they appear in the later stages of infectionFound in uninfected tissues
B. Cells of InflammationBasophils – derived from red bone marrow are
motile WBC that can leave the blood and enter infected tissues.
Mast cells Derived from red bone marrow are nonmotile cells in
connective tissues near capillariesLocated at potential points of entry for microorganisms
such as the skin, lungs, GI tract, urogenital tract.
Basophils and mast cells can be activated in innate and adaptive immunity. They release chemicals such as histamine and leukotrines that produce an inflammatory response or activate other mechanisms such as smooth muscle contraction in the lungs.
B. Cells of InflammationEosinophils
Produces in red bone marrowEnzymes break down chemicals released by
basophils and mast cells that contain and reduce the inflammatory response
Too much inflammation is harmful, resulting in unnecessary destruction of healthy tissues as well as the destruction of the microorganisms.
C. Natural Killer CellsType of lymphocyte produced in the red bone
marrow15% of lymphocytesRecognize classes of cells such as tumor cells
or virus-infected cells in general do not exhibit memory response
Release chemicals that damage cell membranes, causing the cell to lyse.
Most are very similar, although some details can vary depending on the intensity of the response and the type of injury. Fibrinogen is converted to fibrin which isolates the infection by walling off the infected area.
A. Local InflammationConfined to a specific area of the bodySymptoms – redness, heat, swelling, pain,
and loss of function.Redness, heat, swelling – result of increased
blood flow and increased vascular permeability
Pain – caused by swelling and by chemical mediators acting on pain receptors
Loss of function – tissue destruction, swelling, and pain.
B. Systemic InflammationDistributed throughout the bodyThree features
Red bone marrow produces and releases large numbers of neutrophils
Pyrogens released by microorganisms, neutrophils, and other cells stimulate fever production Affect the temperature-regulating mechanisms in the
hypothalamus of the brain Fever promotes the activities of the immune system,
such as phagocytosis, and inhibits the growth of some microorganisms
In sever cases, vascular permeability can increase can cause shock and death
ADAPTIVE IMMUNITYExhibits specificity and memoryAntigens are substances that stimulate
adaptive response. Two groups of antigens:
Foreign antigenSelf-antigens
FOREIGN ANTIGENSIntroduced from outside the bodyBacteria and viruses, components of
microorganisms are examples of antigensPollen, animal hairs, foods, and drugs –
allergic reactionsTransplanted tissues and organs contain
foreign antigens
SELF-ANTIGENSMolecules produced by the person’s body
that stimulate an immune system response.Beneficial – recognition of tumor antigens
can result in destruction of the tumor.Harmful – autoimmune diseases
Divisions of Adaptive Immunity
Humoral immunity or antibody-mediated immunity
Cell-mediated immunity
LYMPHOCYTES2 TYPES:
B cellsGive rise to cells that produce proteins called
antibodies which are found in the plasma.Responsible for antibody-mediated immunity.
T cells Responsible for cell-mediated immunitySubpopulations
Cytotoxic T cells produce the effects of cell-mediated immunity
Helper T cells can promote or inhibit the activities of both antibody-mediated immunity and cell-mediated immunity.
ORIGIN AND DEVELOPMENT OF LYMPHOCYTESThere are about 5 T cells for every B cell
in the blood.Clones
Are small groups of identical B or T cells formed during embryonic development.
Each clone is derived from a single, unique B or T cell
Each can respond only to a particular antigen.
Antigen Recognition Lymphocyte proliferation
A NTIGEN RECOGNITIONLymphocytes have antigen receptors in their surface
(B-cell receptors, T-cell receptors)Each receptor binds with only a specific antigenB and T cells typically recognize antigens after large
molecules have been processed or broken down into smaller fragments
Major histocompatibility complex (MHC) moleculesGlycoproteins that have binding sites for antigensSpecific “serving trays” that hold and present a processed antigen
on the outer surface of the cell membrane.
ANTIGEN RECOGNITIONCostimulation is a second signal required
to produce a response from a B or T cell.Achieved by cytokins (ex. Interleukin I) which
are proteins or peptides secreted by one cell as a regulator of neighboring cells.
CD4 of helper T cells and CD8 of cytotoxic T cells helps connect the T cells to the macrophage by binding to MHC molecules.
LYMPHOCYTE PROLIFERATION
Helper T cells produce interleukin 2 receptors and interleukin 2.
Interleukin 2 binds to the receptors and stimulates the helper T cell to divide
Are proteins produced in response to an antigen
Y-shaped molecules consisting of four polypeptide chains: two identical heavy chains and two identical light chains.
Variable Region End of each arm of the antibodyPart of the antibody that combines with the antigenCan only join a particular antigen
Constant regionRest of the antibodySeveral functions: activate complement, or attach
the antibody to cells such as macrophages, basophils, and mast cells.
ANTIBODIES
ANTIBODIESAntibodies make up a large portion of the
proteins in plasmaMost plasma proteins can b separated into
albumin and alpha, beta, and gamma globulin portions.
Called gamma globulins because they are found mostly in the gamma globulin part of plasma
Called immunoglobulins (Ig) because they are globulin proteins involved in immunity.
Five general classes of immunoglobulins : IgG, IgM, IgA, IgE, and IgD
EFFECTS OF ANTIBODIES
Directly or indirectly
ANTIBODY PRODUCTIONPrimary response results from the first
exposure of a B cell to an antigenB cells divide and form memory cells and plasma
cells.Plasma cells – produce antibodiesNormally takes 3-14 days to produce enough
antibodies to be effective against the antigen
Secondary or memory responseMemory B cellsOccurs when the immune system is exposed to an
antigen against which it has already produced a primary response.
When exposed to the antigen, the B memory cells quickly divide to form plasma cells.
ANTIBODY PRODUCTIONSecondary or memory response
Provides better protection than primary response for two reasons:The time required to produce antibodies is lessMore plasma cells and antibodies are
producedAlso includes the formation of new memory
cells, which provides protection against additional exposures to a specific antigen
Plasma cells die after the destruction of antigen
Memory cells persists for many years
CELL-MEDIATED IMMUNITYFunction of cytotoxic cellsMost effective against microorganisms that
live inside the cells of the bodyInvolved with some allergic reactions, control
of tumors, and graft rejections.Essential for fighting viral infections.
top related