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ELAINE N. MARIEB
EIGHTH EDITION
12
ESSENTIALSOF HUMANANATOMY
& PHYSIOLOGY
The Lymphatic System and Body Defenses
Lymphatic System & Body Defenses
Objective 1
Describe the structure and function of the structures composing
the lymphatic system.
Objective 2
Describe the composition of lymph, and explain its formation and transport
The Lymphatic System Lymphatic system functions
Transport fluids back to the blood
House the cells/chemicals involved with immunity
Lymph Lymph –fluid that leaks from other
cells/blood. Carried by lymphatic vessels
Properties of lymphatic system
One way system toward the heart
No pump
Lymphatic Vessels
Figure 12.2
Lymph capillaries collect fluid from around blood vessels
Lymph Materials returned to the blood
Water
Red/White Blood cells
Proteins
Lymph Harmful materials that can enter lymph
vessels
Bacteria
Viruses
Cancer cells
Cell debris
Lymph Nodes offer protection 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
Lymph Nodes
Figure 12.3
Other Lymphoid Organs Several other organs
contribute to lymphatic function
Spleen
Thymus
Tonsils
Peyer’s patches
Figure 12.5
The Spleen Located on the left side of the abdomen
Filters blood
Destroys worn out blood cells
Acts as a blood reservoir
The Thymus Located low in the throat, overlying the heart
Produces hormones (like thymosin) to program lymphocytes during childhood
Tonsils Small masses of lymphoid tissue around the
pharynx
Trap and remove bacteria and other foreign materials
Peyer’s Patches Found in the wall of the small intestine
Resemble tonsils in structure
Capture and destroy bacteria in the intestine
Body Defenses The body is constantly in contact with
bacteria, fungi, and viruses
The body has two defense systems for foreign materials
Nonspecific defense system
Specific defense system
Body Defenses Nonspecific defense system
protect against a variety of invaders
Responds immediately
Specific defense system
Specific defense is required for each type of invader
Also known as the immune system
Body Defenses
Figure 12.6
Lymphatic System & Body Defenses
Objective 3
Describe the protective functions of skin and mucous membranes
Surface Membrane Barriers – First 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 – First Line of Defense Stomach mucosa
Secretes hydrochloric acid
Has protein-digesting enzymes
Saliva and lacrimal fluid (tears) contain lysozyme
Mucus traps microogranisms in digestive and respiratory pathways
Lymphatic System & Body Defenses
Objective 4Explain the importance of phagocytes and natural killer cells
Defensive Cells – 2nd Line of Defense Phagocytes
(neutrophils and macrophages)
Engulfs foreign material into a vacuole
Enzymes from lysosomes digest the material
Figure 12.7a
Events of Phagocytosis
Figure 12.7b
Defensive Cells Natural killer cells
(yes…that is really their name…)
Can lyse and kill cancer cells
Can destroy virus- infected cells
Lymphatic System & Body Defenses
Objective 5
Describe the inflammatory process
Inflammatory Response - Second Line of Defense Triggered when body tissues are injured
Produces four cardinal signs
Redness Heat
Swelling Pain
chain of events leads to protection and healing
Prevents spread of damaging agents
Disposes of cell debris and pathogens
Sets the stage for repair
Steps in the Inflammatory Response
Figure 12.8
Lymphatic System & Body Defenses
Objective 6
Name antimicrobial substances produced in the body
Antimicrobial Chemicals Complement
A group of at least 20 plasma proteins
Activated when they encounter and attach to cells (complement fixation)
Damage foreign cell surfaces Figure 12.10
Antimicrobial Chemicals Interferon
Secreted proteins of virus-infected cells
Bind to healthy cell surfaces to inhibit viruses binding
Pyrogens Cause abnormally high body temperature =
Fever
Resets hypothalmus’ heat regulation system
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 System – Third Line of Defense1. Antigen specific – recognizes and acts
against particular foreign substances
2. Systemic – not restricted to the initial infection site
3. Has memory – recognizes and mounts a stronger attack on previously encountered pathogens
Lymphatic System & Body Defenses
Objective 7
Define antigen and hapten, and name substances that act as complete antigens
Antigens (Nonself) Any substance capable of exciting the
immune system and provoking an immune response
Examples of common antigens
Foreign proteins
Pollen grains
Microorganisms
Self-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
Activation of Lymphocytes
Figure 12.11
Lymphatic System & Body Defenses
Objective 8
Name the two arms of the immune response and relate each to a specific lymphocyte type.
Types of Immunity Humoral immunity
Cells produce chemicals for defense
Antibody immunity
Cellular immunity
Cell-mediated immunity
Cells target virus infected cells
Humoral (Antibody-Mediated) Immune 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) Immune 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 Response
Figure 12.12
Secondary Response Memory cells are
long-lived
A second exposure causes a rapid response
The secondary response is stronger and longer lasting
Figure 12.13
Lymphatic System & Body Defenses
Objective 11
List the 5 antibody classes and describe their specific roles
Antibodies (Immunoglobulins) (Igs) Soluble proteins secreted by B cells (plasma
cells)
Carried in blood plasma
Capable of binding specifically to an antigen
Figure 12.15a
Antibody Structure Four amino acid chains
Two identical amino acid chains are linked to form a heavy chain
The other two identical chains are light chains
Specific antigen-binding sites are present
Figure 12.15b
Antibody Classes Antibodies of each class have slightly
different roles
Five major immunoglobulin classes
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
Antibody Function Antibodies inactivate antigens in a number of
ways
Complement fixation – lyse cell (bacteria)
Neutralization – block/mask harmful effects (viruses)
Agglutination – clump together
Precipitation – settle out of solution, easier for body to break it down
Antibody Function
Figure 12.16
Back to Cell Mediated Immunity…
Cells of the Immune System Lymphocytes
Originate from 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 lymph organs
Cellular (Cell-Mediated) Immune Response Antigens must be presented by macrophages
to an activated 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 Response
Figure 12.17
T Cell Clone Classes 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 Clones Suppressor T cells
Release chemicals to stop 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 Response
Figure 12.19
Organ Transplants and Rejection Major types of grafts
Autografts – tissue transplanted from one site to another on the same person - “skin graft”
Isografts – tissue grafts from an identical person (identical twin) – hence very rare
Allografts – tissue taken from an unrelated person (most connon)
Xenografts – tissue taken from a different animal species (pig heart valves)
Organ Transplants and Rejection Autografts and isografts are ideal donors
Xenografts are never successful for long
Allografts are more successful with a closer tissue match
Lymphatic System & Body Defenses
Objective 12
Distinguish between active and passive immunity
Active Immunity Your B cells
encounter antigens and produce antibodies
Active immunity can be natural (from an infection) or artificial (vaccine/dead pathogen) acquired
Figure 12.14
Passive Immunity Antibodies are obtained from someone else
Conferred naturally from a mother to her fetus
Conferred artificially from immune serum or gamma globulin
Immunological memory does not occur
Protection provided by “borrowed antibodies”
Lymphatic System & Body Defenses
Objective 13
Distinguish between types of immunodeficiencies, allergies, and autoimmune diseases.
Disorders of Immunity: Allergies (Hypersensitivity) Abnormal, vigorous immune responses
Types of allergies
Immediate hypersensitivity
Triggered by release of histamine from IgE binding to mast cells
Reactions begin within seconds of contact with allergen
Anaphylactic shock – dangerous, systemic response
Disorders of Immunity: Allergies (Hypersensitivity) Types of allergies (continued)
Delayed hypersensitivity
Triggered by the release of lymphokines from activated helper T cells
Symptoms usually appear 1–3 days after contact with antigen
Allergy Mechanisms
Figure 12.20
Disorders of Immunity: Immunodeficiencies Production or function of immune cells or
complement is abnormal
May be congenital (at birth) or acquired
Includes AIDS – Acquired Immune Deficiency Syndrome
Disorders of Immunity: Autoimmune Diseases The immune system does not distinguish
between self and nonself
The body produces antibodies and sensitized T lymphocytes that attack its own tissues
Disorders of Immunity: Autoimmune Diseases 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
