Lymphatic 101021070045-phpapp01

Essentials of Human Anatomy & Physiology

Seventh EditionElaine N. Marieb

Chapter 12The Lymphatic System

and Body Defenses

Lymph NodesLymph Nodes

Figure 12.3

The Lymphatic SystemThe Lymphatic System

Two parts

Lymphatic vessels

Lymphoid tissues and organs

Lymphatic system functions

Transport fluids back to the blood

Play essential roles in body defense and resistance to disease

Absorb digested fat at the intestinal villi

Lymphatic CharacteristicsLymphatic Characteristics

Lymph – excess tissue fluid carried by lymphatic vessels

Properties of lymphatic vessels One way system toward the heart

No pump

Lymph moves toward the heart

Milking action of skeletal muscle

Rhythmic contraction of smooth muscle in vessel walls

Lymphatic VesselsLymphatic Vessels

Figure 12.1

Lymphatic collecting vessels

Collects lymph from lymph capillaries

Carries lymph to and away from lymph nodes

Figure 12.2

Lymphatic collecting vessels (continued)

Returns fluid to circulatory veins near the heart

Right lymphatic duct

Thoracic ductFigure 12.2

LymphLymph

Materials returned to the blood Water Blood cells Proteins

LymphLymph

Harmful materials that enter lymph vessels Bacteria

Viruses

Cancer cells

Cell debris

Filter lymph before it is returned to the blood

Defense cells within lymph nodes

Macrophages – engulf and destroy foreign substances

Lymphocytes – provide immune response to antigens

Figure 12.3

Lymph Node StructureLymph Node Structure

Figure 12.4

Other Lymphoid OrgansOther Lymphoid Organs

Several other organs contribute to lymphatic function

Spleen

Thymus

Tonsils

Peyer’s patchesFigure 12.5

The SpleenThe Spleen

Located on the left side of the abdomen

Filters blood

Destroys worn out blood cells

Forms blood cells in the fetus

Acts as a blood reservoir

The ThymusThe Thymus

Located low in the throat, overlying the heart

Functions at peak levels only during childhood

Produces hormones (like thymosin) to program lymphocytes

TonsilsTonsils

Small masses of lymphoid tissue around the pharynx

Trap and remove bacteria and other foreign materials

Tonsillitis is caused by congestion with bacteria

Peyer’s PatchesPeyer’s Patches

Found in the wall of the small intestine

Resemble tonsils in structure

Capture and destroy bacteria in the intestine

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

Includes:

Peyer’s patches

Tonsils

Other small accumulations of lymphoid tissue

Acts as a guard to protect respiratory and digestive tracts

Body DefensesBody Defenses

The body is constantly in contact with bacteria, fungi, and viruses (pathogens)

The body has two defense systems for foreign materials

Nonspecific defense system

Mechanisms protect against a variety of invaders

Responds immediately to protect body from foreign materials

Body DefensesBody Defenses

Specific defense system

Specific defense is required for each type of invader

Also known as the immune system

Nonspecific Body DefensesNonspecific Body Defenses

Body surface coverings

Intact skin

Mucous membranes

Specialized human cells

Chemicals produced by the body

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

The skin

Physical barrier to foreign materials

pH of the skin is acidic to inhibit bacterial growth

Sebum is toxic to bacteria

Vaginal secretions are very acidic

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

Stomach mucosa

Secretes hydrochloric acid

Has protein-digesting enzymes

Saliva and lacrimal fluid contain lysozyme

Mucus traps microogranisms in digestive and respiratory pathways

Defensive CellsDefensive Cells

Phagocytes (neutrophils and macrophages)

Engulfs foreign material into a vacuole

Enzymes from lysosomes digest the material

Figure 12.6b

Macrophage attacking e-coli.

Defensive CellsDefensive Cells

Natural killer cells

Can lyse and kill cancer cells

Can destroy virus- infected cells

Figure 12.6b

Inflammatory Response - Inflammatory Response - Second Line of DefenseSecond Line of Defense

Triggered when body tissues are injured

Produces four cardinal signs Redness

Swelling

Results in a chain of events leading to protection and healing

Functions of the Inflammatory Functions of the Inflammatory ResponseResponse

Prevents spread of damaging agents

Disposes of cell debris and pathogens

Sets the stage for repair

Steps in the Inflammatory ResponseSteps in the Inflammatory Response

Figure 12.7

Antimicrobial ChemicalsAntimicrobial Chemicals

Complement A group of at

least 20 plasma proteins

Activated when they encounter and attach to cells (complement fixation) Figure 12.8

Complement (continued)

Damage foreign cell surfaces

Will rupture or lyse the foreign cell membrane

Figure 12.8

Interferon

Secreted proteins of virus-infected cells

Bind to healthy cell surfaces to inhibit viruses binding

Interferons are a family species-specific proteins synthesized by eukaryotic cells in response to viruses and a variety of natural and synthetic stimuli. There are several different interferons commonly used as therapeutics, termed alpha, beta, and gamma. These peptides are used to treat hairy cell leukemia, AIDS-related Kaposi's sarcoma, laryngeal papillomatosis, genital warts, and chronic granulomatous disease. Side effects include black tarry stools, blood in the urine, confusion, and loss of balance.

FeverFever

Abnormally high body temperature

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

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

Fever also increases the speed of tissue repair

Specific Defense: The Immune Specific Defense: The Immune System – Third Line of DefenseSystem – Third Line of Defense

Antigen specific – recognizes and acts against particular foreign substances

Systemic – not restricted to the initial infection site

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

Types of ImmunityTypes of Immunity

Humoral immunity

Antibody-mediated immunity

Cells produce chemicals for defense

Cellular immunity

Cell-mediated immunity

Cells target virus infected cells

Antigens (Nonself)Antigens (Nonself)

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

Examples of common antigens Foreign proteins

Nucleic acids

Large carbohydrates

Some lipids

Pollen grains

Microorganisms

Self-AntigensSelf-Antigens

Human cells have many surface proteins

Our immune cells do not attack our own proteins

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

Restricts donors for transplants

AllergiesAllergies

Many small molecules (called haptens or incomplete antigens) are not antigenic, but link up with our own proteins

The immune system may recognize and respond to a protein-hapten combination

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

Cells of the Immune SystemCells of the Immune System

Lymphocytes Originate from hemocytoblasts in the red bone

marrow

B lymphocytes become immunocompetent in the bone marrow

T lymphocytes become immunocompetent in the thymus

Macrophages Arise from monocytes

Become widely distributed in lymphoid organs

Activation of LymphocytesActivation of Lymphocytes

Figure 12.9

Humoral (Antibody-Mediated) Humoral (Antibody-Mediated) Immune ResponseImmune Response

B lymphocytes with specific receptors bind to a specific antigen

The binding event activates the lymphocyte to undergo clonal selection

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

Humoral (Antibody Mediated) Humoral (Antibody Mediated) Immune ResponseImmune Response

Most B cells become plasma cells

Produce antibodies to destroy antigens

Activity lasts for four or five days

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

Humoral Immune ResponseHumoral Immune Response

Figure 12.10

Active ImmunityActive Immunity

Your B cells encounter antigens and produce antibodies

Active immunity can be naturally or artificially acquired

Figure 12.12

Passive ImmunityPassive Immunity

Antibodies are obtained from someone else Conferred naturally from a mother to her

Conferred artificially from immune serum or gamma globulin

Immunological memory does not occur

Protection provided by “borrowed antibodies”

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

Soluble proteins secreted by B cells (plasma cells)

Carried in blood plasma

Capable of binding specifically to an antigen

Antibody ClassesAntibody Classes

Antibodies of each class have slightly different roles

Five major immunoglobulin classes – (Do Not Need to know!) IgM – can fix complement

IgA – found mainly in mucus

IgD – important in activation of B cell

IgG – can cross the placental barrier

IgE – involved in allergies

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

Antigens must be presented by macrophages to an immunocompetent T cell (antigen presentation)

T cells must recognize nonself and self (double recognition)

After antigen binding, clones form as with B cells, but different classes of cells are produced

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

Figure 12.15

T Cell ClonesT Cell Clones

Cytotoxic T cells

Specialize in killing infected cells

Insert a toxic chemical (perforin)

Helper T cells

Recruit other cells to fight the invaders

Interact directly with B cells

T Cell ClonesT Cell Clones

Suppressor T cells

Release chemicals to suppress the activity of T and B cells

Stop the immune response to prevent uncontrolled activity

A few members of each clone are memory cells

Summary of the Immune ResponseSummary of the Immune Response

Figure 12.16

Organ Transplants and RejectionOrgan Transplants and Rejection

Major types of grafts

Autografts – 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 person

Xenografts – tissue taken from a different animal species

Organ Transplants and RejectionOrgan 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: Disorders of Immunity: ImmunodeficienciesImmunodeficiencies

Production or function of immune cells or complement is abnormal

May be congenital or acquired

Includes AIDS – Acquired Immune Deficiency Syndrome

Disorders of Immunity: Disorders of Immunity: Autoimmune DiseasesAutoimmune Diseases

The immune system does not distinguish between self and nonself

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

Examples of autoimmune diseases Multiple sclerosis – white matter of brain

and spinal cord are destroyed

Myasthenia gravis – impairs communication between nerves and skeletal muscles

Juvenile diabetes – destroys pancreatic beta cells that produce insulin

Rheumatoid arthritis – destroys joints

Examples of autoimmune diseases (continued)

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

Glomerulonephritis – impairment of renal function

• HIV targets cells

• Retrovirus attaches to CD4 receptors of T helper cells

– Transmission: Body fluids, i.e., blood, semen, breast milk, vaginal secretions

Immune Deficiency: AIDS

The Structure of HIV

Figure 9.19

Time Course of the Progression of AIDS after HIV Infection

Figure 9.21

•AIDS progression:

–Phase I: few weeks to a few years; flu like symptoms, swollen lymph nodes, chills, fever, fatigue, body aches. Virus is

multiplying, antibodies are made but ineffective for complete virus removal

–Phase II: within six months to 10 years; opportunistic infections present, Helper T cells affected, 5% may not

progress to next phase

–Phase III: Helper T cells fall below 200 per cubic millimeter of blood AND the person has an opportunistic infection or type

of cancer. Person is now termed as having “AIDS” May include pneumonia, meningitis, tuberculosis, encephalitis,

Kaposi’s sarcoma, and non-Hodgkin’s lumphoma….

• More than 36 million infected with HIV worldwide

• Most infections in sub-Sahara of Africa

• Increasing spread in Asia and India

• Most often spread by heterosexual contact outside U.S.

AIDS Pandemic

Lymphatic 101021070045-phpapp01

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