Lymphatic system

Humoral immunity:

(1) antigen presentation and Thelper cell recognition, (2) cloning and differentiation, (3) antibody production for the attack.

Cellular immunity:

(1) antigen recognition, (2) costimulation to verify the epitope is foreign, (3) cloning and differentiation, (4) lethal hit or interleukin secretion to initiate other outcomes.

Tcytotoxic cell attacking a cancer cell.

(a) Tcytotoxic cell docks to a cancer cell. (b) Tcytotoxic cell delivers a lethal hit to the cancer cell.

Lymph drainage to the subclavian veins:

(a) in the thoracic region, (b) of the whole body.

Lymphatic capillaries

(a) interspersed with a blood capillary bed, (b) lymph entering a lymph capillary.

Lymph node

(a) lymph node showing direction of lymph flow, (b) micrograph of a lymph node, (c) dissection of lymph node and lymph vessels.

Valves in lymphatic vessels

(a) micrograph, (b) diagram showing one-way direction of flow.

The steps in the inflammatory process are as follows (in order of occurrence):

1) Inflammatory Chemicals (vasodilators) are released by damaged tissues and basophils. The chemicals diffuse across the surrounding tissues and affect any blood vessels in the area. The dilation of these vessels causes increased blood flow to the area and increased vessel permeability. The increased blood flow accounts for the signs of redness and heat (blood from the core transports heat), while the increased permeability accounts for the swelling and pain (more fluid to tissues causes the swelling, which puts pressure on nerve endings, causing the pain). The heat increases the local metabolic rate to increase cell division and healing. The increased blood flow dilutes possible toxins produced by pathogens, provides cells with more oxygen and nutrients, and removes more wastes. The increased permeability facilitates the movement of leukocytes to the tissues. 2) WBCs stick to the walls of the dilated vessels in the inflamed area (margination). Neutrophils will be the first on the scene. 3) WBCs crawl through the vessel walls (diapedesis). 4) WBCs move to where the concentration of chemicals from damaged tissues is the greatest (chemotaxis). Since the chemicals move by diffusion, the greatest concentration will be at the source of the damage. 5)WBCs phagocytize foreign material, debris, and pathogens along the way (phagocytosis). The accumulation of WBCs, debris, bacteria, and interstitial fluid is called pus.

White blood cell (WBC) count

A blood test that determines the number of leukocytes. The normal number of all the leukocytes is 3,540-9,060/mm3 of blood.

White blood cell (WBC) differential: Neutrophils Basophils Eosinophils Lymphocytes Monocytes

A blood test that gives the percentage of each type of leukocyte in the total number of leukocytes. Normal values: Neutrophils: 40%-70% Basophils: 0%-2% Eosinophils: 0%-6% Lymphocytes: 20%-50% Monocytes: 4%-8%

Bone marrow aspiration and biopsy

A procedure used to collect and examine bone marrow for the presence of abnormal cells.

Lymph node biopsy

A procedure used to collect and examine part of a lymph node for the presence of abnormal cells.

Lumbar puncture

A procedure used to collect and look at cerebrospinal fluid (CSF) surrounding the brain and spinal cord for the presence of abnormal WBCs.

How does APC work?

APC in the process of presenting an antigen. In this case, the APC is a macrophage, but the process is the same for B cells and other APCs. Imagine that the APC is in an axillary lymph node. Its job is to sample antigens in the surrounding environment by phagocytosis (1). It may sample a foreign antigen or a self-antigen. Next, a lysosome fuses with the vesicle carrying the phagocytized antigen (2). The antigens and the enzymes of the lysosome mix (3). The antigen is broken down to fragments, or degraded (4). Most of the antigen residue is expelled from the cell by exocytosis (5). Some of the antigen fragments (epitopes) are displayed on an MHC protein on the surface of the APC (6). An MHC protein is like a billboard posting what the APC has sampled. MHC stands for major histocompatibility complex. Other cells in the body have MHC proteins too. Unlike APC cells that sample their surrounding environment and post what they find, these other body cells present what is inside themselves on their MHC protein. In that case, the MHC protein is posting, "This is me." Therefore, an MHC protein displays what is self and what is foreign. Specific immunity hinges on being able to tell the difference. If the MHC protein displays self-antigens, nothing happens. However, if the epitope in the MHC is foreign, a specific immune response is initiated. humoral immunity form of specific immunity that involves B cells making antibodies to attack a foreign antigen. Also called antibody-mediated immunity. one form of specific immunity.

Effects of Aging on the Lymphatic System

Ability to move fluid between his cardiovascular system and the lymphatic system does not decrease with age. Lymph will continue to leave the blood vessels to nourish cells far from the blood capillaries and remove their wastes. Lymph will also continue to carry the products of lipid digestion in old age. The number of B cells in lymphoid tissues will remain relatively stable. What is affected is the number of new T cells because the thymus will have shrunk and much of the tissue will have been replaced with connective tissue. T cells in other lymphoid tissues will still be able to clone themselves, but not as many will be made with each clone. The decrease in Thelper cells could mean that his recognition of pathogens will be slower. This slowdown may be a reason that cancer is more prevalent in elderly people. Vaccinations might not offer as much protection as they did when younger. The age-related changes to the immune system may have a positive effect if the elderly individual has allergies because this hyperimmune response may be slowed as well

Computed tomography (CT)

An imaging technique used to visualize internal structures. The scan produces images in "slices" of areas throughout the body. In regard to lymphatic system disorders, CT can be used to determine changes in lymphatic organs.

Magnetic resonance imaging (MRI) or nuclear magnetic resonance imaging (NMRI)

An imaging technique used to visualize internal structures. This test provides great contrast between various soft tissues in the body. In regard to disorders of the lymphatic system, MRI can be used to detect changes in lymphatic organs.

Fluid exchange between the cardiovascular and lymphatic systems.

Arrows within the blood vessels show the path of blood. Arrows outside the blood vessels show the path of lymph leaving the blood capillaries and rejoining the circulatory system at the subclavian veins.

With the second exposure of a pathogen, the response time for antibody production is much shorter. This is due to the work of which lymphocyte?

Bmemory Cells

Multiple Myeloma

Cancer of the plasma cells in the bone marrow. B cells differentiate into two types of cells, memory cells and plasma cells. Plasma cells are responsible for secreting antibodies to fight infections. In multiple myeloma, plasma cell growth is accelerated and eventually forms tumors in bone tissue. Symptoms include abnormal bleeding and infection resulting from anemia, fatigue, fever, and bone fractures. Multiple myeloma is diagnosed using a variety of blood tests, including CBC, bone X-rays, bone density testing, and bone marrow biopsy. Treatment involves a combination of therapies such as chemotherapy, radiation, bone marrow transplant, and medications used to reduce pain and prevent fractures.

The human body contains two systems of circulating fluids

Cardiovascular and lymphatic

One branch of immune system uses antibodies to fight pathogens, while the other branch called ________ immunity, uses cells

Cell-mediated

X-ray

Electromagnetic radiation that sends photons through the body, allowing the visualization of dense structures. In regard to lymphatic system disorders, X-rays can be used to view the spleen for diagnosis of splenomegaly.

Antigen fragments that are displayed on MHC proteins are?

Epitopes

The three basic lines of defense against pathogens are the following:

External barriers-Nonspecific Inflammation, antimicrobial proteins, fever, and other active attacks-Nonspecific Specific immunity The lines of defense are not mutually exclusive more than one line of defense is likely to be at work at the same time to eliminate the same pathogen.

Functions of the Lymphatic System

Fluid balance. Every minute of every day, people lose fluid (lymph) from the cardiovascular system. In order to maintain homeostasis, the interstitial fluid washes over his tissues, delivering nutrients and removing wastes. It is collected by open-ended lymph vessels, which return it back to the bloodstream at the subclavian veins as lymph. Lipid absorption. The lymph drained from digestive system organs carries the products of lipid digestion. Defense against disease. Although the skin as an external barrier has been broken with the scrape on aknee, other nonspecific defenses are at work to destroy any pathogens that may have entered the damaged tissue. Dendritic cells in the skin are serving as APCs to present foreign antigens to Thelper cells so that macrophages can be activated. These Thelper cells may also activate the complement system. The inflammatory process has started, too, and will bring neutrophils to the area. The neutrophils will crawl out of the dilated blood vessels and move to the damaged tissue, consuming bacteria along the way. Immunity. At a young age the thymus gland is still growing and maturing the T cells that detect foreign antigens and destroying those that react to your own cells. T cells will be vital for the lymphatic system to accomplish the third line of defense, whether it be humoral or cellular immunity. The immune system is capable of making at least 10 billion different antibodies, each specific to a particular pathogen.

The pressure from the buildup of interstitial fluid in the tissues causes?

Fluid to enter lymph capillaries as lymph. Once lymph is in the capillaries, the skeletal muscle pump moves lymph through the lymph vessels to the collecting ducts and back into blood circulation at the subclavian veins. This is the same skeletal muscle pump that is partially responsible for venous return in the cardiovascular system. The cardiovascular and lymphatic systems are interconnected by this shared fluid—called plasma while in blood, interstitial fluid when it leaves the capillaries with fewer proteins to go to the tissues, and lymph when it is drained into lymph capillaries. It must be returned to the bloodstream to make up for the lost volume at the blood capillaries.

Cellular (Cell-Mediated) Immunity

Form of specific immunity it works on the principles of recognize, react, and remember. Like humoral immunity, cellular immunity starts with an antigen-presenting cell, or any other cell presenting something on an MHC molecule. The epitope can be an antigen the cell sampled from its external environment (such as an APC) or a fragment of something in the cytoplasm of the cell itself (such as other body cells). The epitope may even be a part of an unusual (foreign) protein formed inside a cancer cell. In this form of immunity, a Thelper or Tcytotoxic cell reacts by binding to the APC because it recognizes the epitope as being foreign. It verifies that the epitope is foreign by binding to a costimulation protein on the APC, if there is one. Then either T cell releases interleukin-1 to cause the T cell to clone itself to become many Tcytotoxic cells (TC), Thelper cells (TH), and Tmemory cells (TM) that all recognize this antigen as foreign (recognize stage). An activated Tcytotoxic cell then travels throughout the body seeking cells with this specific foreign antigen. If it finds the foreign antigen, it docks to the cell and delivers a lethal hit to the cell. Unlike the antibodies released from B cells safe and secure in lymphoid tissue, Tcytotoxic cells mount a direct cell-to-cell attack. The Thelper cells of the clone secrete interleukins to attract neutrophils and NK cells to the area, attract and activate macrophages to clean up any debris, and further activate more Tcytotoxic and B cells. Of the T cells, only Tcytotoxic cells directly attack a pathogen or cancer cell (react stage) in this form of specific immunity. Cellular immunity is effective against virally infected cells. Viruses are basically pieces of nucleic acids surrounded by a protein coat. They penetrate a cell of choice (specific to each virus) and insert their viral (foreign) nucleic acid into the DNA of the cell. The cell then drops its normal function to become a viral factory, producing more and more virus until the cell bursts with all of the virus it has produced. The free virus (enclosed in its protein coat) then seeks out other cells to invade. Tcytotoxic cells destroy the self cell that has been turned into a viral factory. Tmemory cells stand by until the pathogen reoccurs in the body. If it does reoccur, these cells mount a cellular immunity response that is faster and stronger than the initial response (remember stage).

There are two types of lymphoma:

Hodgkin lymphoma and non-Hodgkin lymphoma. Both types of lymphoma are characterized by abnormal B-cell or T-cell lymphocytes. Hodgkin lymphoma is characterized by the presence of abnormal B cells called Reed-Sternberg cells. These cells are large, multinucleated macrophages that do not function as normal lymphocytes. They also proliferate and grow into tumors. Similar to Hodgkin lymphoma, non-Hodgkin lymphoma is characterized by abnormal B cells and T cells; however, these abnormal cells are not considered to be the Reed-Sternberg cells distinctive of Hodgkin lymphoma. Hodgkin lymphoma is less common than non-Hodgkin lymphoma. The symptoms of both Hodgkin and non-Hodgkin lymphomas are similar. Individuals may suffer from lymph node swelling, fever, weight loss, fatigue, and night sweats. Diagnosis is accomplished by physical examination, blood tests to determine the presence of abnormal WBCs or the presence of Reed-Sternberg cells (in the case of Hodgkin lymphoma), and bone marrow and lymph node biopsies. Treatment options for these cancers are also similar and include chemotherapy, radiation, medications, and bone marrow transplants.

Trauma to the spleen can be dangerous because it is such a highly vascular organ.

In cases of trauma, surgical removal of the spleen is often easier than trying to deal with a repair and possible fatal hemorrhaging. It is possible to live a normal life without a spleen. Without a spleen, there is no reservoir for blood. However, the other functions of the spleen can be accomplished by the liver (breakdown of erythrocytes) and other lymphoid tissues (storage of lymphocytes and site to fight pathogens).

The inflammatory response, illustrating margination, diapedesis, chemotaxis, and phagocytosis.

Inflammation works this way for all sorts of pathogens to limit their spread, to remove debris and damaged tissue, and to initiate tissue repair. If another splinter damages tissue a week from Tuesday, the response will be the same because this is a nonspecific line of defense.

Fever-Non specific

Initiated by the production of chemicals (pyrogens) from activated macrophages. These pyrogens travel to the hypothalamus, which then raises the set point for body temperature. The body responds by shivering to produce more heat, while the blood vessels in the skin constrict to preserve the heat being generated. Once the new set point is reached (a stage called stadium), the liver and spleen hoard zinc and iron, which are necessary for bacteria growth. This gives time for other defenses to work to defeat the pathogen and increase cellular metabolism needed to heal damaged tissue. Once the pathogen is defeated, the hypothalamus resets the temperature to normal and the brain may initiate sweating to cool the body to homeostasis (defervescence).

Elephantiasis

Is a tropical disease caused by a roundworm that blocks lymphatic drainage. The roundworm gets into the system through a mosquito bite and infects a lymph node (to be discussed shortly), which blocks the flow of lymph, causing edema in the area before the blockage. Typical areas include the legs, arms, breasts, or scrotum.

Circulation of lymph

It is forced out of capillaries due to blood pressure and washes over tissues to deliver nutrients and remove wastes. The pressure of the lymph in the tissues forces lymph back into lymph capillaries so that the lymph vessels can return it to the bloodstream at the subclavian veins.

Specific immunity differs from nonspecific resistance because?

It requires a prior exposure to a pathogen in order to work. During the first exposure, the immune system recognizes the specific pathogen as being foreign, reacts to it, and then remembers it. The process starts with an antigen-presenting cell

Specific immunity

It requires a prior exposure to a pathogen so that the system can recognize the pathogen, react to the pathogen to fight it off, and then remember the specific pathogen so that it can be fought off faster and stronger if it ever occurs in the body again.

Inflammation, Antimicrobial Proteins, Fever, and Other Active Attacks

Like external barriers, each of these nonspecific defenses works against a variety of pathogens in the same way regardless of the number of exposures to the pathogen.

Tonsils

Like lymph nodes, tonsils are lymphoid tissue with high concentrations of lymphocytes. (a) location of tonsils, (b) histology of a pharyngeal tonsil showing crypts.

Anatomy of the Lymphatic System

Lymph Lymphatic vessels Lymphatic tissue Lymphatic nodules Lymph nodes Tonsils Spleen Thymus

Mucous membranes-External barrier

Mucous membranes (lining all the tracts through the body for the respiratory, digestive, urinary, and reproductive systems) also serve as an external barrier for the following reasons: Mucus traps microbes. Mucus, tears, and saliva contain lysozymes to destroy pathogens. Deep to the mucous membranes is loose areolar connective tissue with fibers to hamper the progress of pathogens.

These terms are used to classify the four types of acquired immunity:

Natural active immunity is an example of humoral and cellular immunity. A pathogen invades the body through everyday activities; the body responds by recognizing the specific pathogen as foreign and reacting to it by producing antibodies or activating Tcytotoxic cells to destroy the pathogen. The body then remembers the specific pathogen so that it can fight the pathogen faster and stronger if it reappears. An example of this is catching a cold from someone in your class. Your body recognizes the cold virus as foreign, activates Tcytotoxic cells to destroy your virally infected cells, and then remembers that specific cold virus so you do not get that cold again. The fact that you may get a cold every year does not mean your immune system is faulty. It just means that there are many different cold viruses. Specific immunity is specific to each cold virus. Natural passive immunity means that the body has acquired specific immunity through natural means from someone else. Some antibodies can pass from mother to child through breast milk. The child has specific immunity to some pathogens because the child has acquired its mother's antibodies. This is one of many reasons some mothers choose to nurse their infants. Artificial active immunity occurs when the body acquires a pathogen in an artificial way and then develops its own humoral or cellular immunity. Artificial passive immunity is acquired when an individual receives an injection of serum containing antibodies from another person or an animal such as a horse or pig. Antibodies can also be synthetically made or produced by bacteria. The effect is temporary because the body has not actively developed the mechanism to replace the injected antibodies that will eventually be used up. This type of immunity is used for the emergency treatment of tetanus, rabies, and snakebites.

The cells of the Lymphatic System fall into 5 categories.

Natural killer cells (NK cells). T lymphocytes (T cells). B lymphocytes (B cells). Macrophages. Dendritic cells.

External barriers, inflammation, antimicrobial proteins, and fever are parts of?

Nonspecific defenses

Graph of fever

Normal body temperature approximates the temperature set by the hypothalamus. (1) The onset of a fever begins when the hypothalamus raises the set point. (2) The body temperature then approximates the new set point; this is called stadium. (3) Once the infection ends, the hypothalamus resets the body temperature to normal. (4) The body temperature decreases in a process called defervescence.

The four terms that are relevant in acquired immunity are explained in the following list:

Passive is used to indicate that the immunity was acquired through someone or something else (an animal like a horse or a pig). Active is used to indicate that the body actively created its own immunity. Natural is used to indicate that the immunity was accomplished through naturally occurring means. Artificial is used to indicate that the immunity was not acquired through naturally occurring means.

Immun/o

Protection

The build up of leukocytes, baceria, lymph, and debris, which forms a thick whitish fluid, is called?

Pus

Spleen

Role in the life cycle of a red blood cell and as a reservoir for blood, but it also has functions in the lymphatic system. The spleen is located in the upper left quadrant (ULQ), posterior and lateral to the stomach. Tissues in the spleen consist of two types—red pulp and white pulp. Red pulp serves as a reservoir for RBCs and destroys old, worn-out red blood cells. White pulp is a reservoir for lymphocytes and macrophages, and it functions similarly to lymph nodes as a site of battle between lymphatic cells and pathogens. The spleen also maintains homeostasis by regulating blood volume by transferring excess fluid in the blood to the lymphatic system as lymph. (a) spleen in a cadaver with the stomach removed, (b) medial surface of the spleen, (c) white and red pulp.

Skin-External barrier

Skin acts as an external barrier to pathogens for several reasons: Keratin is a tough protein that bacteria cannot easily break through. Skin is dry, with few nutrients for bacteria and other pathogens. The skin has an acid mantle, which makes it inhospitable for bacteria and other pathogens.

Two mechanical barriers that prevent pathogen entry into the body?

Skin; Mucous membranes

If the barrier defenses and other nonspecific defenses are penetrated by a pathogen, the third line of defense, _______, will try to eliminate it.

Specific Immunity

The thoracic and right lymphatic ducts deliver lymph to the

Subclavian veins, where it rejoins the circulating blood. The right lymphatic duct drains lymph from the right side of the head, the right arm, and the right side of the thorax to the right subclavian vein. The thoracic duct delivers lymph from the rest of the body to the left subclavian vein.

Cell-mediated (cellular) immunity is a specific defense mediated by ___________ lymphocytes, which interact directly with antigen-presenting cells

T

The type of T cell that binds to the surface of an antigen-bearing cell and attacks it is a?

T cytotoxic cell.

What is produced in the bone marrow, and mature in the thymus?

T lymphocytes

Name all the responses that occur because of cell-mediated immunity

T-cells activated an phagocytosis stimulated Destruction of intercellular pathogens, foreign and diseased cells Attack against foreign antigens by chemical and physical means

Inflammation-Nonspecific

The functions of inflammation are threefold. See if you can picture how the steps in the inflammatory process meet the following functions of inflammation: To limit the spread of pathogens To remove debris and damaged tissue To initiate tissue repair The signs of inflammation are redness, heat, pain, and swelling.

The locations of the tonsils are as follows

The pharyngeal tonsil (adenoids) is located on the roof of the nasopharynx (section of throat at the back of the nasal cavity). The palatine tonsils, located laterally in the oropharynx (section of the throat at the back of the mouth) are commonly recognized as the tonsils. These tonsils often swell and become inflamed during a throat infection and can be seen by looking in the mouth. The lingual tonsils have many nodules filled with lymphocytes at the root of the tongue.

Importance of Thelper Cells in Nonspecific Resistance and Specific Immunity

Thelper cells provide a vital role in nonspecific defense and specific immunity. Thelper cells activate macrophages for nonspecific defenses such as inflammation and fever. Thelper cells are also important for both forms of specific immunity. In humoral immunity, these cells first recognize what is foreign and then release interleukin-2 to have B cells react by cloning themselves and producing antibodies. In cellular immunity, Thelper cells recognize what is foreign and release interleukin-1 to get Tcytotoxic cells to clone themselves and attack.

Antimicrobial proteins-Non specific

There are two types of antimicrobial proteins that provide the body with nonspecific resistance to pathogens. These antimicrobial proteins interferons and the 20 inactive proteins that make up the complement system—are explained as follows: Interferons are chemicals released by virally infected cells. They do not help the cell that produced them. Interferons encourage surrounding healthy cells to make antiviral proteins so that the virus will not invade them. Interferons also activate macrophages and NK cells to fight cancer cells. The complement system includes 20 inactive proteins (always present in the blood) that may be activated by the presence of a pathogen. Once activated, the proteins initiate one of several different pathways to ensure pathogen destruction through increased inflammation, breaking apart of the pathogen (cytolysis), or coating a pathogenic cell to make it easier for a macrophage to phagocytize it (opsonization).

Dendritic cells.

These are immune system cells of the epidermis that stand guard to alert the body of pathogens entering through the skin. They also function as APCs.

Macrophages.

These cells are not lymphocytes. They are monocytes that were produced in the red bone marrow and have migrated to the tissues to become macrophages. Their purpose, in the nonspecific defense of the body, is to phagocytize bacteria, debris, and dead neutrophils. Like B cells, macrophages are APCs.

Natural killer cells (NK cells)

These large lymphocytes are important in nonspecific defense. NK cells destroy bacteria, fight against transplanted tissues, attack cells infected by viruses, and destroy cancer cells.

Lymph Nodes

These lymphatic structures act as filters along lymph vessels. Remove anything that may be potentially harmful in lymph, much like a water-purification filter may remove impurities in the drinking water arriving at your kitchen faucet. Each lymph node has many nodules packed with lymphocytes and macrophages. Several lymph vessels direct lymph flow into the lymph node. There, fibers trap debris, cells, and bacteria picked up by the lymph in the tissues. Macrophages phagocytize the debris, while lymphocytes mount an attack on the pathogens. If an infection is present, germinal centers (sites for cloning lymphocytes) in the lymph nodes produce more B lymphocytes. The lymph circulates through the lymph node on its way to larger lymph vessels. When a pathogen is under attack by the lymph node's lymphocytes, the lymph node may become swollen and painful to the touch. This condition is called lymphadenitis.

B lymphocytes (B cells).

These lymphocytes migrate from the red bone marrow to lymphoid tissues, such as lymph nodes, tonsils, and the spleen (covered in the next section). B cells also function as antigen-presenting cells (APCs) by constantly sampling material from their environment, processing it, and then displaying it for other cells to see. There are two basic types of B cells: 1) Bplasma cells are important in specific immunity because they produce antibodies, which are dissolved proteins in plasma that seek out specific foreign antigens for their destruction. 2) Bmemory cells, like Tmemory cells, remember pathogens that have been introduced to the body so that repeat exposure can be fought more swiftly.

T lymphocytes (T cells)

These lymphocytes migrate from the red bone marrow to the thymus gland, where they mature. Several classes of T cells, based on their function, include the following: 1) Thelper cells are important for nonspecific defense and specific immunity by recognizing foreign pathogens and activating the cells to fight them. 2) Tcytotoxic cells directly kill cells infected by viruses and cancer cells in specific immunity. 3) Tmemory cells are also used in specific immunity. They remember pathogens that have been introduced to the body so that repeat exposure can be fought more swiftly. 4) Tregulatory cells suppress an immune response by inhibiting multiplication and chemical secretions from other T cells. 5)Tregulatory cells are important in limiting and preventing autoimmune responses.

Peyer's Patches

These patches of lymphatic tissue are located at the distal end of the small intestine, just before the opening to the large intestine. Peyer's patches are an example of more densely packed pockets of lymphocytes called nodules. These particular nodules fight any bacteria moving into the small intestine from the colon, where they naturally reside.

External Barriers

This first line of defense protects body tissues from pathogens in the outside environment.

Humoral (Antibody-Mediated) Immunity

This form of specific immunity involves B cells making antibodies to attack a foreign antigen. It begins when a B cell (APC) in lymphoid tissue displays an epitope from its environment on an MHC protein. A Thelper cell passing by either does nothing because the epitope is self or reacts to it by binding to the B cell because it recognizes the epitope as foreign. All T cells that react to self are destroyed in the thymus. The Thelper cell then communicates to the B cell by releasing a chemical (interleukin-2) that tells the B cell that the epitope is foreign and that the B cell should clone itself. The steps up to this point have been the recognize stage of specific immunity. Under the direction of the Thelper cell, the B cell (still in the lymphoid tissue) begins to clone itself in the germinal centers in the lymphatic nodules. This clone develops (differentiates) into two types of B cells: plasma B cells that start to produce specific antibodies (to attack the specific antigen that was displayed previously) and memory B cells (that do nothing now). The antibodies produced by the plasma B cells leave the lymphoid tissue with the lymph and enter the blood at the subclavian veins. From there, they travel throughout the body seeking out the specific antigen from the specific pathogen wherever it may be. The antibodies may cover up the binding sites of the foreign invader (rendering the invader harmless), activate the complement system, or agglutinate the antigen so that macrophages can phagocytize it. The B cell does not need to be present at the attack site because antibodies, which act as guided missiles, are sent from bunkers in the lymphoid tissues where the B cells reside. This describes the react stage of humoral immunity. It takes 3 to 6 days for humoral immunity to accomplish antibody production in the first exposure to the pathogen. It will take another 10 days before the amount of antibody production reaches its peak. Once the pathogen is defeated, the amount of antibody in the system decreases, but it never totally drops to zero. If the pathogen enters the body again, Bmemory cells will recognize it immediately. The Bmemory cells will then increase antibody production to reach a peak in approximately 2 to 5 days, instead of 13 to 16. The pathogen will likely be defeated before any signs of its presence are even noticed. With a repeated exposure like this, antibody production will stay high because the immune system has learned that this pathogen reoccurs. Specific immunity does not prevent a pathogen from entering the body. Instead, it fights it so much faster and stronger with repeated exposure that the pathogen is defeated before it can make you sick. This describes the remember stage of specific immunity.

Other active attacks-Non specific

This line of defense refers to the functions of leukocytes other than lymphocytes. As a means of nonspecific resistance, these cells make their attacks with the same speed and strength each time any pathogen enters the body. Here is how each of these cell types works: Neutrophils fight bacteria. Basophils release histamine to promote inflammation. Eosinophils attack worm parasites. Monocytes become macrophages to phagocytize bacteria.

The disease AIDS is an acronym that stands for?

acquired immune deficiency syndrome

Splenomegaly

an enlargement of the spleen that can be caused by any number of pathological conditions, including anemia, cancers, and certain infections. Symptoms include tenderness or pain in the upper left abdomen or back, hiccups, and the inability to eat a large meal. Doctors can diagnose splenomegaly by physical examination, X-ray, CT scan, or MRI. The danger of an enlarged spleen is its effect on circulating blood cells. The enlarged spleen will trap blood cells, therefore reducing the number of circulating blood cells in the body. Trapped red blood cells are eventually destroyed in the spleen along with abnormal red blood cells. The excess cells can clog the organ, preventing it from functioning properly. Treatment of splenomegaly involves treating the cause of the condition. A splenectomy (surgical removal of the spleen) may also be performed.

Allergies

are hypersensitivities to a foreign antigen (allergen). The process in an allergy is the same as an immune response—the immune system recognizes the foreign antigen, reacts to it, and then remembers it so that it can mount a faster and stronger attack if it should ever occur in the body again. The difference between an allergic reaction and a normal immune response is that the allergic response produces undesirable side effects such as increased inflammation. The effect may even be lethal. Asthma is an example of an immediate hypersensitivity in which the allergen is inhaled. The allergen triggers the release of histamines in the bronchioles of the lungs, and this causes the bronchioles to constrict, making breathing difficult.

Vaccines

are preparations of pathogenic particles that have been killed or weakened so that they do not cause disease. These harmless particles provide cells of the lymphatic system a first exposure to a specific, potentially lethal pathogen. As a result of the clinical administration of a vaccine, APCs present epitopes of the killed or weakened pathogen and Thelper cells respond by starting the recognize, react, and remember steps of humoral and cellular immunity to that particular pathogen. The body develops specific immunity to mount a faster and stronger attack on a live, stronger version of the pathogen in future exposures.

Pelvic lymph nodes

deep in the pelvic region and surround the iliac arteries and veins. They also filter lymph from the urinary and reproductive systems.

Nonspecific resistance

defenses are widespread, meaning they work to fight many pathogens without prior exposure. These defenses work to fend off any pathogen in the same way every time the pathogen comes along in the body.

Lymph is a?

fluid derived from plasma, but it has fewer dissolved proteins. This fluid from plasma leaves the capillaries to become interstitial fluid (extracellular fluid out in the tissues), which washes over the tissues delivering nutrients to the cells and washing away wastes, cellular debris, viruses, bacteria, and loose (possibly cancerous) cells. Lymph reaches cells that are not immediately adjacent to blood capillaries, so it helps these cells meet their nutrient and waste-removal needs. Unlike the circulation of blood through a closed system of blood vessels, this fluid leaves the system of blood vessels through the capillaries due to blood pressure and must then return to the cardiovascular system through a network of open lymph capillaries and vessels that drain the tissues of what is now called lymph. Gaps between the endothelial cells of the lymph capillaries allow lymph, bacteria, and even loose cells to enter the vessel. Valves inside the lymph vessels direct the flow of lymph to larger and larger lymph vessels. These vessels eventually drain into one of two collecting ducts—the thoracic duct and the right lymphatic duct.

Mucosa-associated lymphatic tissue (MALT)

is a scattering of lymphocytes located throughout the mucous membranes lining tracts to the outside environment, such as the tracts for the digestive, respiratory, urinary, and reproductive systems. The purpose of MALT is to stand guard against and fight any pathogens trying to enter the body.

Anaphylaxis

is an example of an immediate allergic reaction that can be life-threatening. An immune response to penicillin or bee stings is the most common cause. In anaphylaxis, systemic vasodilation (systemwide dilation of blood vessels) within a few minutes of exposure to the allergen can cause a drop in blood pressure and even cardiac failure.

The primary cells of the lymphatic system are?

leukocytes—particularly, lymphocytes. all of the formed elements are produced in the red bone marrow.

Cervical lymph nodes

located in groups in the neck. They filter lymph from the head and neck.

Axillary lymph nodes

located in the axillary region and the lateral margin of the breast. They filter lymph from the breasts and arms.

Thoracic lymph nodes

located in the mediastinum surrounding the trachea and bronchi. They filter lymph from organs in the thoracic cavity.

Intestinal and mesenteric lymph nodes

located in the mesenteries and surround the mesenteric arteries and veins. They filter lymph from the digestive organs. Lymph from the digestive system appears milky because it carries the products of lipid digestion.

Popliteal lymph nodes

located in the popliteal region (behind the knee). They filter lymph from the leg.

Abdominal lymph nodes

located in the posterior wall of the abdominopelvic cavity. They filter lymph from the urinary and reproductive systems.

Thymus Gland

located in the superior mediastinum between the sternum and the aortic arch. It is well developed at birth and continues to develop during childhood, but it starts to shrink around the age of 14. (a) of a fetus, (b) of an adult. T cells migrate from the red bone marrow to the thymus gland, where they mature. In the maturation process, the thymus introduces self-antigens to the developing T cells. If the T cell reacts to the self-antigen, the T cell is destroyed. Only those T cells that do not react to self-antigens are stimulated to further develop by chemicals secreted by the thymus. These T cells are an important part of the immune system because they react only to foreign (not self-) antigens.

lymph/o

lymph

lymphaden/o

lymph node

Lymphoid tissues and organs

may be as small as a scattering of lymphocytes in mucous membranes or may be full-size organs, such as the spleen.

delayed hypersensitivities

may take hours or even days to develop side effects. Examples of these allergies include contact hypersensitivities to poison ivy, poison oak, soaps, or cosmetics. The allergen in this type of allergy comes in contact with epithelial cells (skin, mucous membranes). Next, T cells initiate inflammation, which causes excessive itching. Scratching the affected area further damages tissue. Allergies are hypersensitivities to foreign antigens, but some disorders of the lymphatic system do not involve foreign antigens at all. These disorders are autoimmune disorders, in which the body's immune system attacks the body's own tissues.

Three types of tonsils

one pharyngeal, two palatine, and numerous lingual tonsils—ring the pharynx (throat) to guard against pathogens entering the body through the nose or mouth. Each tonsil has pits (crypts) to give the lymph nodules (small, localized collections of lymphoid tissue) more exposure to whatever may be passing by.

splen/o

spleen

Inguinal lymph nodes

superficial in the groin. They filter lymph from the lower limbs.

thym/o

thymus gland

Lymphoma

type of cancer that affects white blood cells and can develop in the organs of the lymphatic system.