the lymphatic system and body defenses chapter 12

The Lymphatic System The Lymphatic System and Body Defensesand Body Defenses

Chapter 12Chapter 12

The Lymphatic SystemThe Lymphatic System Consists of two semi-independent partsConsists of two semi-independent parts

Lymphatic vesselsLymphatic vessels Lymphoid tissues and organsLymphoid tissues and organs

Lymphatic system functionsLymphatic system functions

Transport fluids back to the bloodTransport fluids back to the blood Approx. 30 L of fluid pass from blood Approx. 30 L of fluid pass from blood

capillaries to interstitial fluid, but only 27 L capillaries to interstitial fluid, but only 27 L fluid come back to blood capillariesfluid come back to blood capillaries

Extra 3 L fluid stays in interstitial fluidExtra 3 L fluid stays in interstitial fluid Returns back to blood capillaries by Returns back to blood capillaries by

lymphatic systemlymphatic system

Play essential roles in body defense and Play essential roles in body defense and resistance to diseaseresistance to disease

Lymphatic VesselsLymphatic Vessels

Properties of Properties of lymphatic vesselslymphatic vesselsOne way system One way system

toward the hearttoward the heartBegins in tissues and Begins in tissues and

deposit in superior deposit in superior vena cavavena cava

No pumpNo pump

Mechanism for movement of lymph through L. vessel:Mechanism for movement of lymph through L. vessel:

Contraction of lymphatic vessels:Contraction of lymphatic vessels: - Lymph moves into chambers formed by unidirectional - Lymph moves into chambers formed by unidirectional valve by smooth muscle contractionvalve by smooth muscle contraction

Contraction of Skeletal muscles:Contraction of Skeletal muscles: - Lymphatic vessels get compressed when surrounding- Lymphatic vessels get compressed when surrounding muscle contracts, cause lymph movementmuscle contracts, cause lymph movement

Thoracic Pressure changes:Thoracic Pressure changes: - During inspiration, pressure decreases, vessels expand, lymph- During inspiration, pressure decreases, vessels expand, lymph flows inflows in - During expiration, pressure increases, vessels compressed, - During expiration, pressure increases, vessels compressed, cause lymph movementcause lymph movement

LymphLymph Lymph –Lymph – excess tissue fluid carried by lymphatic excess tissue fluid carried by lymphatic

vesselsvessels Materials returned to the bloodMaterials returned to the blood

WaterWater hormones, enzymes, waste productshormones, enzymes, waste products from blood cells from blood cells Some proteins from plasmaSome proteins from plasma

Harmful materials that enter lymph vesselsHarmful materials that enter lymph vessels BacteriaBacteria VirusesViruses Cancer cellsCancer cells Cell debrisCell debris

Lymph vessels include:Lymph vessels include: Lymphatic capillariesLymphatic capillaries Lymphatic collecting vesselsLymphatic collecting vessels Trunks and ductsTrunks and ducts

Microscopic, permeable, dead-ended capillariesMicroscopic, permeable, dead-ended capillaries

Found between the tissue cells and blood capillariesFound between the tissue cells and blood capillaries Found in all parts of the body except nervous system, Found in all parts of the body except nervous system,

bone marrow, and tissues without blood vessels bone marrow, and tissues without blood vessels (cartilage, cornea, epidermis) (cartilage, cornea, epidermis)

Similar to blood capillaries, with modifications:Similar to blood capillaries, with modifications: Very permeableVery permeable endothelium lack basement membraneendothelium lack basement membrane And adjacent cells overlap, forms minivalvesAnd adjacent cells overlap, forms minivalves

Function of mini – valve :Function of mini – valve : Act as one-way gate Act as one-way gate Allow interstitial fluid to enter lymph capillariesAllow interstitial fluid to enter lymph capillaries Do not allow lymph to go back to interstitial spaceDo not allow lymph to go back to interstitial space

Lymphatic VesselsLymphatic Vessels Lymphatic collecting Lymphatic collecting

vesselsvessels Collects lymph from Collects lymph from

lymph capillarieslymph capillaries

Carries lymph to and Carries lymph to and away from lymph nodesaway from lymph nodes

Deposit into venous Deposit into venous system by two major system by two major vesselsvessels

Right lymphatic duct:Right lymphatic duct: right arm and right side right arm and right side of head and thoraxof head and thorax

Thoracic duct :Thoracic duct : rest of rest of the bodythe body

Lymphatic OrgansLymphatic Organs Lymph NodesLymph Nodes Principal lymphoid organs of the bodyPrincipal lymphoid organs of the body Distributed along the lymphatic Distributed along the lymphatic

vesselsvessels Approx. 450 lymph nodes found Approx. 450 lymph nodes found

throughout bodythroughout body Filter lymph before it is returned to the Filter lymph before it is returned to the

bloodblood Functions:Functions:

Filtration –Filtration – Macrophages present Macrophages present within lymph nodes engulf and within lymph nodes engulf and destroy microorganisms and destroy microorganisms and debris that enter the lymphdebris that enter the lymph

Provide Immune Response –Provide Immune Response – Lymphocytes monitor for antigens Lymphocytes monitor for antigens and attack on themand attack on them

Structure of a Lymph NodeStructure of a Lymph Node Lymph nodes are small, Lymph nodes are small,

round or round or kidney-shaped, less kidney-shaped, less than 1 inch long than 1 inch long & surrounded & surrounded by a fibrous capsuleby a fibrous capsule

Strands from fibrous capsule Strands from fibrous capsule called called trabeculaetrabeculae extend extend inward and divide the node inward and divide the node into no. of compartmentsinto no. of compartments

Lymph nodes have two Lymph nodes have two distinct regions: distinct regions:

cortex cortex medullamedulla

Lymph Node StructureLymph Node Structure

CortexCortex Outer partOuter part Contains follicles – Contains follicles –

collections of collections of lymphocyteslymphocytes

MedullaMedulla Inner partInner part Contains phagocytic Contains phagocytic

macrophagesmacrophages

Lymph Node StructureLymph Node Structure Lymph enters the convex side Lymph enters the convex side

through through afferent lymphatic vesselsafferent lymphatic vessels

Lymph flows through a number of Lymph flows through a number of sinuses inside the nodesinuses inside the node

Lymph exits through Lymph exits through efferent efferent lymphatic vesselslymphatic vessels

Because there are fewer efferent Because there are fewer efferent vessels than afferent vessels, the vessels than afferent vessels, the flow of lymph is very slow in the nodeflow of lymph is very slow in the node

This allows time for lymphocytes and This allows time for lymphocytes and macrophages to carry out protective macrophages to carry out protective functionsfunctions

Other Lymphoid OrgansOther Lymphoid Organs

Several other Several other organs contribute to organs contribute to lymphatic functionlymphatic functionSpleenSpleenThymusThymusTonsilsTonsilsPeyer’s patchesPeyer’s patches

Largest lymphoid organ, Largest lymphoid organ, located on the left side of the located on the left side of the abdominal cavity beneath the abdominal cavity beneath the diaphragm, curves around left diaphragm, curves around left side of stomachside of stomach

Filters bloodFilters blood

Destroys worn out blood cellsDestroys worn out blood cells

Acts as a blood reservoirActs as a blood reservoir

SpleenSpleen

Located low in the throat, Located low in the throat, overlying the heartoverlying the heart

Functions at peak levels Functions at peak levels only during childhoodonly during childhood

Produces hormones (like Produces hormones (like thymosin) to program thymosin) to program lymphocyteslymphocytes

ThymusThymus

Tonsils:Tonsils:Small masses of lymphoid Small masses of lymphoid tissue around the pharynxtissue around the pharynx

Trap and remove bacteria Trap and remove bacteria and other foreign materialsand other foreign materials

Tonsillitis Tonsillitis is caused by is caused by congestion with bacteriacongestion with bacteria

Peyer’s patches: Peyer’s patches: Found in the wall of the Found in the wall of the

small intestinesmall intestine

Resemble tonsils in Resemble tonsils in structurestructure

Capture and destroy Capture and destroy bacteria in the intestinebacteria in the intestine

Mucosa-Associated Lymphatic Tissue (MALT)Mucosa-Associated Lymphatic Tissue (MALT)

Includes:Includes: Peyer’s patchesPeyer’s patches TonsilsTonsils Other small accumulations Other small accumulations

of lymphoid tissueof lymphoid tissue

Protect respiratory and Protect respiratory and digestive tractsdigestive tracts

Found in mucous membrane Found in mucous membrane linings of digestive, linings of digestive, respiratory tractsrespiratory tracts

Body DefensesBody Defenses

The body is constantly in contact with The body is constantly in contact with bacteria, fungi, and virusesbacteria, fungi, and viruses

The body has two defense systems for The body has two defense systems for foreign materialsforeign materials

Innate (Nonspecific) defense systemInnate (Nonspecific) defense systemAdaptive (Specific) defense systemAdaptive (Specific) defense system

Body DefensesBody Defenses

Nonspecific defense systemNonspecific defense systemMechanisms protect against a variety of Mechanisms protect against a variety of

invaders (harmful microorganisms)invaders (harmful microorganisms)Responds immediately to protect body from Responds immediately to protect body from

foreign materialsforeign materialsSpecific defense systemSpecific defense system

Specific defense is required for each type of Specific defense is required for each type of invaderinvader

Also known as the immune systemAlso known as the immune system

Nonspecific Body DefensesNonspecific Body Defenses Body surface coveringsBody surface coverings

Intact skinIntact skin Mucous membranesMucous membranes

Specialized CellsSpecialized Cells Chemicals produced by the bodyChemicals produced by the body

Surface Membrane Barriers – First Line of Surface Membrane Barriers – First Line of DefenseDefense

The skin and Mucous membranesThe skin and Mucous membranesSkin is physical barrier to foreign materialsSkin is physical barrier to foreign materialsMucous membranes provide protective Mucous membranes provide protective

secretionssecretions pH of the skin is acidic to inhibit bacterial growthpH of the skin is acidic to inhibit bacterial growth Sebum is toxic to bacteriaSebum is toxic to bacteria Vaginal secretions are very acidicVaginal secretions are very acidic

Surface Membrane Barriers – First Line Surface Membrane Barriers – First Line of Defenseof Defense

Stomach mucosaStomach mucosa Secretes hydrochloric acidSecretes hydrochloric acid Has protein-digesting enzymesHas protein-digesting enzymes Both kill pathogensBoth kill pathogens

Saliva and lacrimal fluid contain lysozymeSaliva and lacrimal fluid contain lysozyme An enzyme that destroys bacteriaAn enzyme that destroys bacteria

Mucus traps microogranisms in digestive and Mucus traps microogranisms in digestive and respiratory pathwaysrespiratory pathways

PhagocytesPhagocytesNatural killer cellsNatural killer cells Inflammatory responseInflammatory responseAntimicrobial proteinsAntimicrobial proteinsFeverFever

Cells and Chemicals:Cells and Chemicals:Second Line of DefenseSecond Line of Defense

Phagocytes Phagocytes (neutrophils and (neutrophils and macrophages)macrophages)

Engulfs foreign Engulfs foreign material into a vacuolematerial into a vacuole

Enzymes from Enzymes from lysosomes digest the lysosomes digest the materialmaterial


Events of PhagocytosisEvents of Phagocytosis

Microbe attaches to the Microbe attaches to the phagocytephagocyte

Microbe is engulfed by the Microbe is engulfed by the phagocytephagocyte

Lysosome is fused with Lysosome is fused with phagocytic vesiclephagocytic vesicle

Microbe is killed and digested Microbe is killed and digested by lysosomal enzymeby lysosomal enzyme

Undigested material is Undigested material is removed by exocytosisremoved by exocytosis

Natural killer (NK) cellsNatural killer (NK) cellsCan lyse and kill cancer cellsCan lyse and kill cancer cellsCan destroy virus- infected cellsCan destroy virus- infected cells


Inflammatory responseInflammatory response Triggered when body tissues are injuredTriggered when body tissues are injured Produces four cardinal signsProduces four cardinal signs

RednessRedness HeatHeat SwellingSwelling PainPain

Results in a chain of events leading to protection Results in a chain of events leading to protection and healingand healing

Cells and Chemicals: Second Line of DefenseCells and Chemicals: Second Line of Defense

Steps in the Inflammatory ResponseSteps in the Inflammatory Response

Functions of the inflammatory response Functions of the inflammatory response Prevents spread of damaging agentsPrevents spread of damaging agentsDisposes of cell debris and pathogens Disposes of cell debris and pathogens

through phagocytosisthrough phagocytosisSets the stage for repairSets the stage for repair

Cells and Chemicals: Second Line Cells and Chemicals: Second Line of Defenseof Defense

FeverFever Abnormally high body temperatureAbnormally high body temperature

Hypothalmus heat regulation can be reset by pyrogens Hypothalmus heat regulation can be reset by pyrogens (secreted by white blood cells)(secreted by white blood cells)

High temperatures inhibit the release of iron and zinc High temperatures inhibit the release of iron and zinc from liver and spleen needed by bacteria to multiplyfrom liver and spleen needed by bacteria to multiply

Fever also increases the speed of tissue repair by Fever also increases the speed of tissue repair by increasing metabolic rate of cellsincreasing metabolic rate of cells

Cells and Chemicals: Second Line of Cells and Chemicals: Second Line of DefenseDefense

Antimicrobial proteinsAntimicrobial proteinsAttack microorganismsAttack microorganismsHinder reproduction of microorganismsHinder reproduction of microorganisms

Most important antimicrobial proteins are:Most important antimicrobial proteins are:Complement proteinsComplement proteins InterferonInterferon


Complement ProteinsComplement Proteins A group of at least 20 A group of at least 20

plasma proteinsplasma proteins

Activated when they Activated when they encounter and attach to encounter and attach to foreign cells (complement foreign cells (complement fixation)fixation)

Damage foreign cell Damage foreign cell surfacessurfaces


InterferonInterferonProteins secreted by virus-infected cellsProteins secreted by virus-infected cells

Bind to healthy cell surfaces to inhibit viruses Bind to healthy cell surfaces to inhibit viruses bindingbinding


Three aspects of adaptive defense:Three aspects of adaptive defense:

Antigen specific–Antigen specific– recognizes and acts against particular recognizes and acts against particular foreign substances foreign substances

Systemic –Systemic – not restricted to the initial infection site not restricted to the initial infection site

Has memory –Has memory – recognizes and mounts even stronger recognizes and mounts even stronger attack on previously encountered pathogensattack on previously encountered pathogens

Adaptive Body Defenses: Third Line of Adaptive Body Defenses: Third Line of DefenseDefense

Antigens (Nonself)Antigens (Nonself)

Any substance capable of exciting the immune Any substance capable of exciting the immune system and provoking an immune responsesystem and provoking an immune response

Examples of common antigensExamples of common antigens Foreign proteinsForeign proteins Nucleic acidsNucleic acids Large carbohydratesLarge carbohydrates Some lipidsSome lipids Pollen grainsPollen grains MicroorganismsMicroorganisms

Self-AntigensSelf-Antigens

Human cells have many surface proteinsHuman cells have many surface proteins

Our immune cells do not attack our own proteinsOur immune cells do not attack our own proteins

Our cells in another person’s body can trigger an Our cells in another person’s body can trigger an immune response because they are foreignimmune response because they are foreign

Restricts donors for transplantsRestricts donors for transplants

AllergiesAllergies Many small molecules (called Many small molecules (called haptenshaptens or incomplete or incomplete

antigens) are not antigenic, but link up with our own proteinsantigens) are not antigenic, but link up with our own proteins

The immune system may recognize the combination as The immune system may recognize the combination as foreign and attackforeign and attack

The immune response is harmful rather than protective The immune response is harmful rather than protective because it attacks our own cellsbecause it attacks our own cells

Chemicals that act as Chemicals that act as haptenshaptens are found in some drugs, are found in some drugs, detergents, hair dyes, cosmeticsdetergents, hair dyes, cosmetics

Types of ImmunityTypes of ImmunityHumoral immunityHumoral immunity

Antibody-mediated immunityAntibody-mediated immunityProvided by antibodies present in body fluidsProvided by antibodies present in body fluids

Cellular immunityCellular immunityCell-mediated immunityCell-mediated immunityTargets virus-infected cells, cancer cells, and Targets virus-infected cells, cancer cells, and

cells of foreign graftscells of foreign grafts

Adaptive Defense System: Third Line of Adaptive Defense System: Third Line of DefenseDefense

Cells of the Immune SystemCells of the Immune System

LymphocytesLymphocytes Originate from hemocytoblasts in the red bone marrowOriginate from hemocytoblasts in the red bone marrow B lymphocytesB lymphocytes become immunocompetent (capable of become immunocompetent (capable of

responding to specific antigen) in the bone marrowresponding to specific antigen) in the bone marrow T lymphocytesT lymphocytes become immunocompetent in the become immunocompetent in the

thymusthymus

MacrophagesMacrophages Arise from monocytesArise from monocytes Become widely distributed in lymphoid organsBecome widely distributed in lymphoid organs Promote phagocytosisPromote phagocytosis

Humoral (Antibody-Mediated) Immune Humoral (Antibody-Mediated) Immune ResponseResponse

B lymphocytesB lymphocytes with with specific receptors bind to specific receptors bind to a specific antigena specific antigen

The binding event The binding event activates the lymphocyte activates the lymphocyte to undergo to undergo clonal clonal selectionselection

A large number of clones A large number of clones are produced are produced (primary (primary humoral response)humoral response)

Most B cells become Most B cells become plasma cellsplasma cells

Produce antibodies to Produce antibodies to destroy antigensdestroy antigens

Activity lasts for four or Activity lasts for four or five daysfive days

Some B cells become Some B cells become long-lived long-lived memory memory cellscells (secondary (secondary humoral response)humoral response)

Humoral (Antibody-Mediated) Immune Humoral (Antibody-Mediated) Immune ResponseResponse

Primary and Secondary ResponsePrimary and Secondary Response

Primary response:Primary response: exposure to exposure to antigen stimulating the B cells antigen stimulating the B cells

Generates memory cellsGenerates memory cells

Secondary response:Secondary response: when body is when body is exposed to the same antigen the exposed to the same antigen the second timesecond time

Stimulate B memory cellsStimulate B memory cells Memory cells are long-livedMemory cells are long-lived

A second exposure causes a rapid A second exposure causes a rapid responseresponse

The secondary response is stronger The secondary response is stronger and longer lastingand longer lasting

Active ImmunityActive Immunity

Occurs when B cells Occurs when B cells encounter antigens and encounter antigens and produce antibodiesproduce antibodies

Active immunity can be Active immunity can be Naturally acquiredNaturally acquired during during

bacterial and viral bacterial and viral infectionsinfections

Artificially acquiredArtificially acquired from from vaccinesvaccines

Passive ImmunityPassive Immunity Occurs when antibodies are obtained from someone elseOccurs when antibodies are obtained from someone else

As a result Immunological memory does not occurAs a result Immunological memory does not occur

Protection provided by Protection provided by “borrowed antibodies”“borrowed antibodies”

Conferred naturally from a mother to her fetusConferred naturally from a mother to her fetus

Conferred artificially when one receives Conferred artificially when one receives immune serumimmune serum ( eg. Antivenom, antitoxin)( eg. Antivenom, antitoxin)

Or Or gamma globulin,gamma globulin, administered after exposure to administered after exposure to

hepatitishepatitis

Antibodies (Immunoglobulins) (Igs)Antibodies (Immunoglobulins) (Igs)

Soluble proteins Soluble proteins secreted by B cells secreted by B cells (plasma cells)(plasma cells)

Carried in blood plasmaCarried in blood plasma

Capable of binding Capable of binding specifically to an antigenspecifically to an antigen

Antibody StructureAntibody Structure Four amino acid chains linked Four amino acid chains linked

by disulfide bondsby disulfide bonds

Two identical amino acid Two identical amino acid chains are linked to form a chains are linked to form a heavy chainheavy chain

The other two identical chains The other two identical chains are light chainsare light chains

Have variable (V) and Have variable (V) and constant (C) regionconstant (C) region

V: V: variable region that helps variable region that helps in binding to antigenin binding to antigen

Forms specific antigen-Forms specific antigen-binding sitesbinding sites

Antibody ClassesAntibody Classes

Antibodies of each class have slightly Antibodies of each class have slightly different rolesdifferent roles

Five major immunoglobulin classesFive major immunoglobulin classes IgM – can fix complementIgM – can fix complement IgA – found mainly in mucusIgA – found mainly in mucus IgD – important in activation of B cellIgD – important in activation of B cell IgG – can cross the placental barrierIgG – can cross the placental barrier IgE – involved in allergiesIgE – involved in allergies

Immunoglobin ClassesImmunoglobin Classes

Antibody FunctionAntibody Function

Antibodies inactivate antigens in a number Antibodies inactivate antigens in a number of waysof waysComplement fixationComplement fixationNeutralizationNeutralizationAgglutinationAgglutinationPrecipitationPrecipitation

Antibody FunctionAntibody Function

Cellular (Cell-Mediated) Immune ResponseCellular (Cell-Mediated) Immune Response Antigens must be presented by macrophages to Antigens must be presented by macrophages to

an immuno-competent T cell (antigen an immuno-competent T cell (antigen presentation)presentation)

– Antigen-presenting cell self protein binds with antigen Antigen-presenting cell self protein binds with antigen nonself molecules and displays them on the cell surface nonself molecules and displays them on the cell surface

– Helper T cells recognize and bind to the self-nonself complexHelper T cells recognize and bind to the self-nonself complex– Binding activates helper T cellsBinding activates helper T cells

T cells Activated helperT cells Activated helper promote the immune promote the immune response, particularly response, particularly secretion of stimulatory secretion of stimulatory proteinsproteins

Make helper T cells grow Make helper T cells grow and divide, producing and divide, producing memory cells and memory cells and additional helper T cellsadditional helper T cells

Help activate B cells, Help activate B cells, stimulating humoral stimulating humoral immunityimmunity

Stimulate activity of Stimulate activity of cytotoxic T cellscytotoxic T cells

(cell-mediated immunity)(cell-mediated immunity)

Cellular (Cell-Mediated) Immune Cellular (Cell-Mediated) Immune ResponseResponse


Cytotoxic T cells:Cytotoxic T cells: destroy infected destroy infected body cellsbody cells

Like helper T cells, cytotoxic T Like helper T cells, cytotoxic T cells recognize and bind with cells recognize and bind with self-nonself complexes on self-nonself complexes on infected cellsinfected cells

Mechanism of cytotoxic T cell Mechanism of cytotoxic T cell actionaction Binding to infected cell Binding to infected cell

stimulates cytotoxic T cell stimulates cytotoxic T cell to synthesize the protein - to synthesize the protein - perforinperforin

Perforin makes holes in Perforin makes holes in infected cell's membrane, infected cell's membrane, and T cell enzymes enterand T cell enzymes enter

Infected cell is destroyedInfected cell is destroyed

Suppressor T cellsSuppressor T cells Release chemicals to suppress Release chemicals to suppress

the activity of T and B cellsthe activity of T and B cells

Stop the immune response to Stop the immune response to prevent uncontrolled activityprevent uncontrolled activity

A few members of each clone are A few members of each clone are memory cellsmemory cells


Disorders of Immunity: Disorders of Immunity: ImmunodeficienciesImmunodeficiencies

Production or function of immune cells or complement is Production or function of immune cells or complement is abnormalabnormal

May be congenitalMay be congenital Eg. Severe combined immunodeficiency disease (SCID): Eg. Severe combined immunodeficiency disease (SCID):

Deficit of both B and T cellsDeficit of both B and T cells

or acquiredor acquired

Eg. AIDS – Acquired Immune Deficiency Syndrome, by Eg. AIDS – Acquired Immune Deficiency Syndrome, by interfering with the activity of helper T cellsinterfering with the activity of helper T cells

Disorders of Immunity: Autoimmune Disorders of Immunity: Autoimmune DiseasesDiseases

The immune system does not distinguish The immune system does not distinguish between self and nonselfbetween self and nonself

The body produces antibodies and The body produces antibodies and sensitized T lymphocytes that attack its sensitized T lymphocytes that attack its own tissuesown tissues

Autoimmune DiseasesAutoimmune Diseases Multiple sclerosisMultiple sclerosis – white matter of brain and spinal – white matter of brain and spinal

cord are destroyedcord are destroyed

Myasthenia gravis –Myasthenia gravis – impairs communication between impairs communication between nerves and skeletal musclesnerves and skeletal muscles

Juvenile diabetes –Juvenile diabetes – destroys pancreatic beta cells destroys pancreatic beta cells that produce insulinthat produce insulin

Rheumatoid arthritis –Rheumatoid arthritis – destroys joints destroys joints

Systemic lupus erythematosus (SLE) –Systemic lupus erythematosus (SLE) – affects affects kidney, heart, lung and skinkidney, heart, lung and skin

the lymphatic system and body defenses chapter 12

Documents

lymphatic vessels materials

blood capillaries

movement of lymph

vessels trunks

unidirectional lymph

lymph flows

blood materials

interstitial fluid