The Body Defenses - Chapter 12
Immunity is the body’s ability to resist or eliminate potentially harmful foreign materials or abnormal cells.
The immune system plays a key role in this. It:
defends against invading pathogens,
removes "worn-out" cells
identifies and destroys abnormal or mutant cells.
leads to allergies or autoimmune responses in the face of foreign antigens.
The primary pathogens are bacteria and viruses.
A. The lymphatic system is comprised of a network of:
1. Vessels that transport body fluids that closely follow the circulatory system
2. The cells and chemicals in those vessels
3. The organs and glands that produce them.
Three functions of the lymphatic system are:
1. Defense against disease.
2. Collection and transport of excess fluid from interstitial spaces
3. Transport of fats to the circulatory system through vessels called lacteals.
Lymph Formation and Function
Increasing pressure forces blood plasma into the interstitial space, and some of the fluid into lymphatic capillaries.
The same forces that move blood in veins (skeletal muscle contraction, breathing movements, and contraction of smooth muscle in the walls of lymphatic trunks) are the forces that propel lymph through lymphatic vessels.
The lymphatic system also has one-way valves that keep back-flow from occurring
A condition that interferes with the flow in lymph will result in edema.
¬ Lymphatic Pathways
Lymphatic pathways start as lymphatic capillaries that merge to form larger vessels that empty into the circulatory system.
¬ Lymph Nodes
A. Lymph nodes, which contain lymphocytes and macrophages, are located along lymphatic pathways.
B. Functions of a Lymph Node
1. These contain both lymphocytes and macrophages which remove bacteria and clean the lymph as it flows through the node.
Concentrations of lymphatic tissue not surrounded by a capsule scattered throughout connective tissue of mucous membranes
Peyer’s patches in the ileum of the small intestine
Tonsils form ring at top of throat
adenoids (pharyngeal tonsil)
palatine tonsils (on each side wall)
lingual tonsil in the back of the tongue
CANCER AND METASTASIS THROUGH THE LYMPHATIC SYSTEM
Caused by mutation or abnormal activation of cellular genes that control cell growth and cells mitosis.
Most mutations eliminated by immune system
Characteristic of malignant tumors
Spread of disease from one organ to another
cancer cells travel via blood or lymphatic system
cells establish new tumors where lodge
Secondary tumor sites can be predicted by direction of lymphatic flow from primary site
Cancerous lymph nodes are firm, enlarged and nontender -- infected lymph nodes are not firm and are very tender
Cancers of lymphatic organs, especially lymph nodes
No known cause
Good survival rate with treatment
Chemotherapy, radiation therapy, bone marrow transplant
¬ Other Lymphatic Organs: Thymus and Spleen
A. The functions of the thymus and spleen are similar to those of lymph nodes.
1. Contains lymphocytes, some of which mature into T lymphocytes (T cells) that leave the thymus to provide immunity.
1. The spleen lies in the upper left abdominal cavity and is the body’s largest lymphatic organ.
2. The spleen resembles a large lymph node except that it contains blood instead of lymph.
3. The spleen filters the blood and removes damaged blood cells and bacteria.
¬ PART II: Body Defenses Against Infection
A. Diseases-causing agents, also called pathogens, can produce infections within the body.
B. The body has two lines of defense against pathogens: nonspecific defenses (innate or inborn) that guard against any pathogen, and specific defenses (acquired immunity) that mount a response against a very specific target.
¬ Nonspecific Defenses
A. Present at Birth
1. Immediate protection wide variety of pathogens
2. Come in three forms.-
-External mechanical (skin, mucous)
- Chemical (sebum, gastric juices, perspiration)
NK cells, phagocytes
Inflammation and fever
B. External Mechanisms (Mechanical and Chemical)
Skin – keratinized
(i) is a barrier – sheds easily
Tears (i) wash away pathogens
Urine (i) washes away pathogens
Vaginal lining: (i) mucous membranes
Saliva (i) digestive enzymes
Stomach (i) has a low pH
C. Internal, Non-specific
NK cells, Macrophages and phagocytes
1. Inflammation, a tissue response to a pathogen, is characterized by
2. Major actions that occur during an inflammatory response include:
a. dilation of blood vessels;
b. increase of blood volume in affected areas;
c. invasion of white blood cells into the affected area;
d. appearance of fibroblasts and their production of a sac around the area.
Abnormally high body temperature that occurs because the hypothalamic thermostat is reset
Occurs during infection & inflammation
bacterial toxins trigger release of fever-causing agents
intensifies effects of interferons, inhibits bacterial growth, speeds up tissue repair
5 Stages of Inflammatory Response
1. Localized Vasodilation
Histamine increases capillary permeability. antibodies and clotting factors escape into tissue fluid
2. Localized Edema
3. Isolation of Invader
4. Phagocyte migration
F. Tissue Repair. Finally, the inflammatory process repairs tissues
Salicylates (aspirin) and glucocorticoid drugs suppress the inflammatory response.
Salicylates also reduce fever by inhibiting the production of prostaglandins.
Glucocorticoids suppress most aspects of the inflammatory response.
Specific Resistance: Acquired Immunity
A. Immunity is body’s ability to defend itself against specific foreign material or organisms
- bacteria, toxins, viruses, cat dander, etc.
Differs from nonspecific defense mechanisms
-specificity----recognize own cells & non-self cells
-memory----2nd encounter produces even more vigorous response
C. Lymphocyte Functions
T cells attack foreign, antigen-bearing cells, such as bacteria, by direct cell-to-cell contact, providing "cell-mediated immunity."
B cells are the main warriors of immunity in body fluids
They secretes antibodies
Antibodies mark antigens for elimination
Like T cells, some of the B cells become memory cells to respond to future encounters with the antigen
D. Acquired Active Immune Responses
1. When B or T cells become activated the first time, their actions constitute a primary immune response, after which some cells remain as memory cells.
2. If the same antigen is encountered again, more numerous memory cells can mount a more rapid response, known as the secondary immune response. The ability to produce a secondary immune response may be long-lasting.
Two Types of Acquired Active Immune Response:
E. Immunological Memory
F. Transplantation and Tissue Rejection
Rheumatoid Arthritis: An Auto-Immune Disease
3. AIDS leaves the body defenseless