Chapt16 lymphatic and immunity

Brenda Holmes MSN/Ed, RNAssociate Professor

Biology

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South Arkansas Community College

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display

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• The lymphatic system is a vast collection of cells and biochemicals that travel in lymphatic vessels• It is a network of vessels that assist in circulating fluids• It is closely associated with the cardiovascular system• It transports excess fluid away from the interstitial spaces• It transports fluid to the bloodstream• It transports fats to the bloodstream• It helps defend the body against diseases

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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Lymphaticcapillaries

Pulmonarycapillarynetwork

Lymphnode

Lymphaticvessels

Bloodflow

Lymphnode

Lymphflow

Systemiccapillarynetwork

Lymphaticcapillaries

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Tissue cells

ArterioleVenule

Lymphaticcapillary

Capillarybed

Lymphaticvessel


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• The walls are similar but thinner than those of veins• Lymphatic vessels are composed of three layers:

• An endothelial lining (inner)• Smooth muscle (middle)• Connective tissue (outer)

• Larger vessels lead to lymph nodes and then to larger lymphatic trunks


© The McGraw-Hill Companies, Inc./Dennis Strete, photographer

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• The trunks drain lymph from the lymphatic vessels• They are named for the regions they serve such as lumbar, intestinal, intercostal, bronchomediastinal, subclavian, and jugular

Jugular trunk

Right lymphatic duct

Brachiocephalic vein

Bronchomediastinal trunk

Intercostaltrunk

Internal jugular vein

Thoracic duct

Subclavian trunk

Thoracic duct

Intestinaltrunk

Lumbartrunk

Lymphaticvessels


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Lymph nodes Thoracic duct

Thoracic duct

Right lymphatic duct

Right internal jugular vein

(a)

(b)

Area drainedby right lymphatic duct

Right lymphaticduct

Lymphatictrunks

Lymphaticvessels

Left internaljugular vein

Left subclavianvein

Cisternachyli

Right subclavianvein

Axillary lymphnodes

Lymphatics ofmammary gland

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Afferent lymphatic vessel

Collecting duct

Subclavian vein

Efferent lymphatic vessel

Lymphatic capillary

Lymph node

Lymphatic trunk

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• Lymph is essentially tissue fluid that has entered a lymphatic capillary• Lymph formation depends on tissue fluid formation

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• Capillary blood pressure filters water and small molecules from the plasma

• The resulting fluid has:

• Much the same consistency as plasma

• Contains water and dissolved substances

• Contains smaller proteins which create plasma colloid osmotic pressure

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• Filtration from the plasma normally exceeds reabsorption, leading to the net formation of tissue fluid

• This increases the tissue fluid hydrostatic pressure within interstitial spaces forcing fluid into lymphatic capillaries forming lymph

• This process prevents accumulation of excess tissue fluid or edema

• Lymphatic vessels play a role in:• Absorption of dietary fats• Delivering fats to the bloodstream• Collecting of excess interstitial fluids• Delivering excess fluids to the bloodstream• Delivering foreign particles to the lymph nodes


Flow of lymph

Epithelialcell

Filamentsanchored toconnectivetissue

Movement oftissue fluid

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• Hydrostatic pressure of tissue fluid drives the lymph into the lymphatic capillaries• Muscle activity largely influences the movement of lymph through the lymphatic vessels via:

• Action of skeletal muscles• Respiratory movements• Smooth muscle in the larger lymphatic vessels• Valves in the lymphatic vessels

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SinusCapsule

(a)

Nodule HilumArtery

Medulla(macrophages, T cells)

Capsule

Subcapsule(macrophages, B cells)

Efferent lymphatic vessel

Lymph flow

Germinalcenter(B cells)

Vein

Lymph flow

Afferentlymphaticvessel

Germinalcenter

b: © The McGraw-Hill Companies, Inc./Al Telser, photographer

(b)

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Blood vessels

Lymph node

Muscle

Lymphaticvessels

© Dr. Kent M. Van De Graaff

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• Lymph nodes or lymph glands are located along the lymphatic pathways• They contain lymphocytes and macrophages to fight invading pathogens

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Lymph flow

SinusCapsule

(a)

Nodule Hilum

Lymph flowArtery

Vein

Afferentlymphaticvessel

Germinalcenter(B cells)

Subcapsule(macrophages, B cells)

Medulla(macrophages, T cells)

Efferentlymphaticvessel

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• Lymph nodes are found in groups or chains along the paths of the larger lymphatic vessels throughout the body, including the:

• Cervical region• Axillary region• Supratrochlear region• Inguinal region• Pelvic cavity• Abdominal cavity• Thoracic cavity


Thoraciclymphnode

Axillarylymphnode

Cervicallymphnode

Supratrochlearlymph node

Abdominallymph node

Pelvic lymphnode

Inguinallymphnode

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• Lymph nodes have two primary functions:• Filter potentially harmful particles from the lymph• Act with immune surveillance provided by macrophages and lymphocytes

• Along with the red bone marrow, the lymph nodes are centers for lymphocyte production

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• These are two other lymphatic organs with functions similar to those of the lymph nodes

Thymusin fetus

Thymusin adult

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• The thymus is:• Larger in infancy and during puberty• Small in an adult• Replaced by fat and connective tissue in the elderly• Site of T lymphocyte (or T cell) production• Secretes protein hormones called thymosins


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Larynx

Thymus

Lung

Liver

(a)

(b)

Diaphragm

Thyroid gland

Heart

StomachSpleen

Lobule

Trachea

Connectivetissue

b: © The McGraw-Hill Companies, Inc./Dennis Strete, photographer


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• The spleen is:• The largest lymphatic organ• Located in the upper left abdominal quadrant• Has sinuses filled with blood• Contains two tissue types:

• White pulp (lymphocytes)• Red pulp (red blood cells, lymphocytes and macrophages)

Spleen

Artery of pulp

White pulp

Red pulp

(a)

(b)

CapillaryCapsule

CapsuleWhite pulp

Red pulp

Splenicartery

Splenicvein

Connectivetissue

Venous sinus

b: © The McGraw-Hill Companies, Inc./Al Telser, photographer


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• The presence and multiplication of a pathogen in the body may cause an infection• Pathogens are:

• Disease causing agents• Bacteria, viruses, complex microorganisms, and spores of multicellular organisms

• The body can prevent entry of pathogens or destroy them with defense mechanisms such as:

• Innate defenses :• These are general defenses• They protect against many pathogens

• Adaptive defenses:• Known as immunity• More specific and precise targeting specific antigens • Are carried out by lymphocytes

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• Refers to a given type of organism, or species, that develops diseases unique to it

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• The skin and mucous membranes create mechanical barriers• Mechanical barriers are considered the first line of defense (all other non-specific defenses are part of the second line of defense)

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• Enzymes in body fluids provide a chemical barrier to pathogens, and they may include:

• Interferons are horomone-like peptides and stimulate phagocytosis• Defensins are peptides produced by neutrophils and other granulocytes. They cripple microbes.• Collectins are proteins with broad protection against bacteria, yeast and some viruses• Complement is a group of proteins in plasma and other body fluids that stimulate inflammation, attract phagocytes and enhance phagocytosis

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• NK cells are a small population of lymphocytes defending against viruses and cancer by secreting cytolytic substances called perforins that destroy the infected cell• NK may also enhance inflammation

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• Inflammation produces local redness, swelling, heat and pain• Table 16.2 summarizes the process

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• Phagocytosis removes foreign particles from the lymph• Phagocytes are also in the blood vessels and in the tissues of the spleen, liver or bone marrow• The most active phagocytic cells are neutrophils and monocytes• Chemicals attract these phagocytic cells to the injury and this is called chemotaxis

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• A fever begins when a viral or bacterial infection stimulates lymphocytes to proliferate, producing cells that secrete a substance called interleukin-1 (IL-1)

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• This is the third line of defense and known as immunity• It is resistance to particular pathogens or to their toxins or metabolic by-products• It is based on the ability to distinguish molecules that are part of the body (“self” from “non-self”)• Antigens are molecules that can elicit an immune response

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• Antigens may be:• Proteins • Polysaccharides• Glycoproteins• Glycolipids

• The most effective antigens are large and complex• Haptens are small molecules that are not antigenic by themselves, but when they combine with a large molecule can stimulate an immune response

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B cell

Thymus

T cell

T cell

1

2

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B cell

Stem cellsin red bonemarrow giverise tolymphocyteprecursors.

Redbonemarrow

Some lymphocyteprecursors areprocessed withinthe bone marrowto become B cells.

Both T cells and B cells are transported through the blood to lymphatic organs, such as the lymph nodes, lymphatic ducts, and spleen.

Some lymphocyteprecursors areprocessed in thethymus to becomeT cells.

BloodtransportBlood

transport

Lymphocyteprecursors

Bloodtransport

Lymphnode


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• A lymphocyte must be activated before it can respond to an antigen• T cell activation requires antigen-presenting cell (accessory cell) and may include macrophages, B cells and several other types of cells• Requires major histocompatibility complex (MHC) or human leukocyte antigens (HLA) to recognize “non-self”• T cells can synthesize and secrete polypeptides called cytokines• Types of specialized T cells include:

• Helper T cells• Cytotoxic T cells• Memory T cells

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• B cells can be activated when an antigen fits the shape of its receptor• Most of the time B cell activation requires T cells• T cells release cytokines that stimulate B cells• Some B cells may become memory B cells while others differentiate into plasma cells and produce and secrete large globular proteins called antibodies or immunoglobulins

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Cytokines

Antigen

B cells

Activated B cell

Interleukin-2

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3

2

4

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(a)

Macrophage

Helper T cell

(b)

CytotoxicT cell

Cytotoxic T cell contactsDisplayed antigenHelper T cell contacts displayed antigen and proliferates

CytotoxicT cell

HelperT cells

Activated helper T cell interacts with cytotoxic T cell (which has combined with an identical antigen) and releases interleukin-2, which activates the cytotoxic T cell

ProliferationandDifferentiationMemory

T cellCytotoxicT cell

Antigenreceptor

B cell combineswith antigen

Macrophage displays ingestedantigen on its surface

Displayedantigen

b: © Manfred Kage/Peter Arnold


Activated B cell

Proliferation

B cells

Antigen

Cytokines

Activation1

2

3

Antigenreceptor

Stimulation byactivated helper T cell

Clone ofB cells

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Antigen

Proliferation

AntigenReceptor (antibody)

Receptor-antigencombination

ActivatedB cell

Cytokinesfrom helperT cell

Clone ofB cells

Proliferation andDifferentiation

Proliferation andDifferentiation

Endoplasmicreticulum

Releasedantibodies

Plasma cell(antibody-secreting cell)

Memory cell(dormant cell)

Plasma cell(antibody-secreting cell)

Memory cell(dormant cell)

Clone ofB cells


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Immunotherapy

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a a

nti

bo

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co

nc

en

tra

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100 20 30

Primary response

Secondary response

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Days after exposure to antigen


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Type I• Immediate-reaction allergy• Occurs minutes after contact with allergen• Symptoms include hives, hay fever, asthma, eczema, gastric disturbances, and anaphylactic shock

Type II• Antibody-dependent cytotoxic reaction• Takes 1-3 hours to develop• Transfusion reaction

Type III• Immune-complex reaction• Takes 1-3 hours to develop• Antibody complexes cannot be cleared from the body• Damage of body tissues

Type IV• Delayed-reaction allergy• Results from repeated exposure to allergen• Eruptions and inflammation of the skin• Takes about 48 hours to occur

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B cell

Plasma cell

Mast cell

IgE receptor

Granule

(a)

1

2

3

5

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Allergen

Allergen

Allergicreaction

Histamineand otherchemicals

Mast cell releasesallergy mediators

Subsequentcontact withallergen

Antibodiesattach tomast cell

Released IgEantibodies

Initial B cellcontact withallergen

Plasma cellsecretesantibodies

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• Successfully transplanted tissues and organs:• Cornea• Kidney• Liver• Pancreas

• When the donor’s tissues are recognized as foreign there is a tissue rejection reaction• Resembles the cellular immune response against antigens• Important to match MHC antigens• Immunosuppressive drugs used to prevent rejection

• Heart• Bone marrow• Skin

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• The immune system fails to distinguish “self” from “non-self” and the body produces antibodies called autoantibodies, and cytotoxic T cells to attack the body’s tissues and organs

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• The immune system declines early in life as the thymus gland shrinks (only 25% as powerful as it once was)• There is a higher risk of infection• Antibody response to antigens becomes slower• IgA and IgG antibodies increase• IgM and IgE antibodies decrease• Elderly may not be candidates for certain medical treatments that suppresses immunity

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Immunity Breakdown: AIDS

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Important Points in Chapter 16:Outcomes to be Assessed

16.1: Introduction

Describe the general functions of the lymphatic system.

16.2: Lymphatic Pathways

Identify and describe the parts of the major lymphatic pathways.

16.3: Tissue Fluid and Lymph

Describe how tissue fluid and lymph form, and explain the function of lymph.

16.4: Lymph Movement

Explain how lymphatic circulation is maintained, and describe the consequence of lymphatic obstruction.

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16.5: Lymph Nodes

Describe a lymph node and its major functions.

Describe the location of the major chains of lymph nodes.

16.6: Thymus and Spleen

Discuss the locations and functions of the thymus and spleen.

16.7: Body Defenses Against Infection

Distinguish between innate (nonspecific) and adaptive (specific) defenses.

16.8: Innate (Nonspecific) Defenses

List seven innate body defense mechanisms, and describe the action of each mechanism.

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16.9: Adaptive (Specific) Defenses, or Immunity

Explain how two major types of lymphocytes are formed, activated, and how they function in immune mechanisms.

Discuss the origins and actions of the five different types of antibodies.

Distinguish between primary and secondary immune responses.

Distinguish between active and passive immunity.

Explain how allergic reactions, tissue rejection reactions, and autoimmunity arise from immune mechanisms.

16.10: Lifespan Changes

Describe lifespan changes in immunity.

Education

Chapt16 lymphatic and immunity