Essentials Lymphatic System Immunity

Essentials of Anatomy and Physiology, Seventh Edition
Valerie C. Scanlon and Tina Sanders
Copyright © F.A. Davis Company 2015
Chapter 14
The Lymphatic System and Immunity

Functions of the Lymphatic System
1. To return tissue fluid to the blood to maintain blood volume
2. To protect the body against pathogens and other foreign
material
This protection may be short-term or long-term.
Question: Can you give an example of short-term protection and long-term
protection?

Answer
An example of short-term protection is recovery from a cold
virus.
An example of long-term protection is the immunity provided
by many of our available vaccines.

Parts of the Lymphatic System
Lymph and the system of lymphatic vessels
Lymphatic tissue—consists mainly of lymphocytes and
monocytes (macrophages) in a supportive network of
connective tissue; has stem cells for lymphocytes;
lymphocytes mature and become active.
Locations: lymph nodes and nodules, spleen, thymus gland

Lymph—the tissue fluid that enters lymph capillaries
Lymph is similar to plasma but contains more WBCs
and has less protein.
Lymph must be returned to the blood—
Questions: Where does the tissue fluid that becomes lymph come from?
By what process is tissue fluid formed, and where?

Answers
Tissue fluid comes from blood plasma.
Tissue fluid is formed by the process of filtration in capillaries.

System of Lymph Vessels
Dead-end lymph capillaries in most tissue spaces—
Larger lymph vessels are structurally similar to veins—
Lymph is kept moving in lymph vessels by:
Constriction of the vessels
The skeletal muscle pump
The respiratory pump

System of Lymph Vessels (continued)
Lymph from lower body  cisterna chyli
Thoracic duct—lymph from cisterna chyli and upper left
quadrant; empties into left subclavian vein
Right lymphatic duct—returns lymph from upper right
quadrant to the right subclavian vein

Lymph Nodes—encapsulated masses of lymphatic tissue
Lymph nodes are located in groups along the pathways of
lymph vessels.
As lymph flows through nodes:
Foreign material is phagocytized—
Antibodies are produced—
The major paired groups of lymph nodes:
Cervical
Axillary
Inguinal

Lymph Nodules—unencapsulated masses of lymphatic
tissue
Lymph nodules are located beneath the epithelium of all
mucous membrane tracts:
Contain macrophages and plasma cells—
Tonsils—
Peyer’s patches—

Spleen—the largest lymphatic organ
The fetal spleen produces red blood cells.
After birth:
Contains lymphocytes and fixed plasma cells—
Contains monocytes and fixed macrophages—
Forms bilirubin—
Is a reservoir for platelets and destroys damaged platelets
Question: Describe the location of the spleen.

Answer
The spleen is located in the upper left abdominal quadrant
behind the stomach.

Spleen (continued)
If the spleen is damaged and must be removed, other organs
will compensate:
Liver and red bone marrow:
Lymph nodes and nodules:

Thymus Gland—below the thyroid gland, largest in
the fetus and young child
Produces T lymphocytes:
Produces thymic hormones that enable T cells to become
immunologically competent:
Immunological competence consists of:
Self-recognition—
Self-tolerance—

Immunity—the ability to destroy foreign antigens and
prevent future cases of certain infectious diseases
Antigens – chemical markers that identify cells
Human cells have “self” antigens, the HLA types.
Foreign antigens stimulate antibody production and other
immune mechanisms.
Question: Name the different kinds of foreign antigens a person may encounter.

Answer
Foreign antigens include bacteria; viruses; fungi, such as
yeasts; protozoa, such as malaria; and malignant cells that
arise from mutations.

Innate Immunity
Characteristics:
Is nonspecific
Responses are always the same
Does not create memory
Does not become more efficient with repeated exposure
Parts: Barriers
Defensive cells
Chemical defenses

Innate Immunity (continued)
Barriers:
Unbroken stratum corneum—
Subcutaneous tissue with WBCs—
Mucous membranes with areolar connective tissue and
WBCs—
Respiratory epithelium—
Gastric epithelium—
Lysozyme—

Defensive cells:
Phagocytes: macrophages, neutrophils—
Langerhans cells and other dendritic cells—
Natural killer cells—
Basophils and mast cells—produce histamine and leukotrienes

Chemical defenses:
Interferon—
Complement proteins—
Inflammation: the body’s response to damage
Vasodilation and increased capillary permeability—
Purpose:
Signs:

Adaptive Immunity
Characteristics:
Is very specific
May involve antibody production
Does create memory
Often becomes more efficient with repeated exposure
Parts: T cells, B cells, macrophages
Two mechanisms: cell-mediated (cellular) immunity
and antibody-mediated (humoral) immunity

Adaptive Immunity (continued)
Cell-mediated immunity—does not involve antibodies; is
effective against intracellular pathogens and malignant cells:
Helper T cells and macrophages—
Memory T cells—
Cytotoxic (killer) T cells—
Regulatory T cells—

Adaptive Immunity (continued)
Antibody-mediated immunity—does involve antibody
production; is effective against pathogens and foreign cells
Helper T cells and macrophages, B cells—
Memory B cells—
B cells become plasma cells—
Antigen–antibody complex: opsonization—
Complement fixation—

Antibodies (immune globulins or gamma globulins)
(see Table 14–1)
Proteins produced by plasma cells; each is specific—
The five classes of antibodies:
IgG
IgA
IgM
IgD
IgE

Antibody Responses
On a first exposure to a pathogen—
On a second exposure to the pathogen—
Antibodies inactivate foreign antigens by:
Agglutination—bacteria
Neutralization—viruses, bacterial toxins

Types of Immunity (see Table 14–2)
Genetic immunity—in DNA
Acquired immunity—involves antibodies
Passive:
Natural:
Artificial:
Active:
Natural:
Artificial:

Wrap-Up Question
For each, state if it is part of innate immunity (I), adaptive
immunity (A), or both.
1. Helper T cells
2. Plasma cells
3. Macrophages
4. Langerhans cells
5. Ciliated epithelium
6. Basophils
7. Memory B cells
8. Interferon
9. Natural killer cells
10. Cytotoxic T cells
11. Lysozyme
12. Complement
13. Leukotrienes
14. Histamine
15. Opsonization
16. Defensins

Answers
1. Helper T cells—A
2. Plasma cells—A
3. Macrophages—both
4. Langerhans cells —I
5. Ciliated epithelium—I
6. Basophils—I
7. Memory B cells—A
8. Interferon—I
9. Natural killer cells—I
10. Cytotoxic T cells—A
11. Lysozyme—I
12. Complement—both
13. Leukotrienes—I
14. Histamine—I
15. Opsonization—A
16. Defensins—I

Essentials Lymphatic System Immunity

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