The Lymphatic System and Immunity
Chapter 22; Tortora
Terms in this set (67)
List the components and major functions of the lymphatic system
the lymphatic system includes lymph nodes, lymphatic vessels, lymph, lymphatic tissue, and red bone marrow. it assists in circulating body fluids, drains excess interstitial fluid, transports dietary lipid, and helps defend the body against disease-causing agents
Describe the organization of lymphatic vessels.
begin as lymphatic capillaries located between cells and closed at one end; they unite to form the vessels with thin walls and fluid moving valves that push interstitial fluid through lymph nodes that consist of masses of B cells, T cells
Explain the formation of lymph
excess filtered fluid (3L/day) drains into the lymphatic vessels and becomes lymph, contains small amount of protein
Explain the flow of lymph
Blood capillaries (blood) >> interstitial spaces (interstitial fluid) >> lymphatic capillaries (lymph) >> lymphatic vessels (lymph) >> lymphatic ducts (lymph) >> junction of the internal jugular and subclavian veins (blood); skeletal muscle pump, respiratory pump propel lymph
Compare the structure and functions of the primary and secondary lymphatic organs and tissues
primary lymphatic organs are the sites where stem cells divide and become immunocompetent (capable of mounting an immune response); the organs include: red bone marrow, and the thymus; secondary lymphatic organs and tissues are the sites where most immune responses occur; they include lymph nodes, spleen, lymphatic nodules
What tissue contains stem cells that develop into lymphocytes?
Red bone marrow.
Is lymph more similar to blood plasma or to interstitial fluid? Why?
lymph is more similar to interstitial fluid because the protein content is so low
Which lymphatic vessels empty into the cisterna chyli?
the right and left lumbar trunks and the intestinal trunk empty into the cisterna chyli, which then drains into the thoracic duct
Does inhalation promote or hinder the flow of lymph?
Inhalation promotes the flow of lymph as it maintained by the respiratory pump as well as the skeletal muscle pump
Which type of lymphocytes mature in the thymus?
What happens to foreign substances in lymph that enter a lymph node?
Foregin substances in lymph that enter a lymph node may be phagocytized by macrophages or attacked by lymphocytes that mount immune responses
After birth, what are the main functions of the spleen?
White pulp of the spleen functions in immunity; red pulp of the spleen performs functions related to blood cells
How do interstitial fluid and lymph differ?
Lymph differs from interstitial fluid (tissue fluid) in that lymph is a clear, watery fluid found in the lymphatic vessels (nodes) while interstitial fluid is the fluid that fills the gaps between body cells. Lymph works by capturing and returning water and proteins back to the blood stream while the interstitial fluid's main function is to feed the cells, removal of waste materials and also intercellular communication. The lymphatic system helps in the transport of tissue fluid.
How are interstitial fluid and lymph similar?
Lymph is considered a part of the interstitial fluid. The lymphatic system returns protein and excess interstitial fluid to the circulation. The ionic composition of the interstitial fluid and blood plasma vary due to the Gibbs-Donnan effect.
How do lymphatic vessels differ in structure from veins?
Have thinner walls and more valves
What is the role of the thymus in immunity?
The thymus produces hormones that regulate T-cell maturation and serves as the incubator against infections. It forms part of the immune system and it is positioned in the upper part of the chest known as the breastbone.
What functions do lymph nodes serve?
The main function of lymph nodes is to act as a drainage system by absorbing and expelling proteins, dead cells, bacteria and other waste products from the body. Basically they clean and filter the lymph before it is returned to the blood.
What function does the spleen serve?
The spleen is a lymphatic organ adjacent to the stomach. It breaks down old red blood cells and is also involved in the body's immune system; The spleen is a lymphatic organ adjacent to the stomach. It breaks down old red blood cells and is also involved in the body's immune system.
What function do the tonsils serve?
Tonsils are part of the lymphatic system. They are located in the back of the throat. They function to guard against inhaled and ingested pathogens. They have deep pits that catch bacteria and food debris. This is then circulated by the circulatory system and eaten by macrophages.
Describe the components of innate (nonspecific) immunity.
includes the external physical and chemical barriers provided by the skin and mucous membranes; internal defenses like antimicrobial substances, natural killer cells, pagocytes, inflammation and fever
Describe the first line of defense in immunity.
the skin, mucous membranes, hairs, cilia, lacrimal apparatus, lysozyme, saliva, urine, vaginal secretions, defecation, vomiting, sebum, gastric juice, perspiration
Describe the second line of defense in immunity
antimicrobial substances (interferons, complement, iron-binding proteins, antimicrobial proteins) produced by lymphocytes, macrophages, and fibroblasts; compliment system (normally inactivated proteins in blood plasma that enhance immune reaction); iron-binding proteins (bind to iron that bacteria needs to survive); antimicrobial proteins (broad spectrum of activity)
What are natural killer cells?
NK cells have the ability to kill a wide variety of infected body cells and certain tumor cels; attack any body cell that displays abnormal or unusual plasma membrane proteins
What are phagocytes?
specialized cells that perform phagocytosis, the ingestion of microbes or other particles; two major types neutrophils and macrophages
Describe the process of phagocytosis.
1. Chemotaxis: chemically stimulated movement of phagocytes to site of damage
2. Adherence: attachment of phagocyte to defective cell; binding of compliment proteins,
3. Ingestion: phagocyte extends and engulfs the microbe then fuse surrounding microbe with a sac
4. Digestion: phagocyte enters cell, merges with lysozyme, breaks down microbial walls, forms lethal oxidants
5. Killing: chemical onslaught kills many types of microbes, any remaining material is termed residual bodies
What chemicals are responsible for killing ingested microbes?
Lysozyme, digestive enzymes, and oxidants
What are the three stages of inflammation?
1. vasodilation and increased permeability of blood
2. phagocyte emigration
3. tissue repair
What causes the following signs and symptoms of inflammation: redness, pain, heat, swelling?
heat and redness result from the large amount of blood that accumulates in the damaged area; edema results from increased permeability of blood vessels; pain results injury to neurons and from toxic chemicals released by microbes
What is a histamine?
a compound that is released by cells in response to injury and in allergic and inflammatory reactions, causing contraction of smooth muscle and dilation of capillaries.
What are kinins?
any of a group of substances formed in body tissue in response to injury. They are polypeptides and cause vasodilation and smooth muscle contraction.
What are prostaglandins?
Lipids; released by damaged cells and intensify the effects of histamine and kinins; may also stimulate emigration of phagocytes
What are leukotrienes?
produced by basophils and mast cells; cause increased permeability; function in adherence and chemotaxis
What is a compliment?
components that stimulate a heistamine release; attract neutrophils; promote phagocytosis; destroy bacteria
What physical and chemical factors provide protection from disease in the skin and mucous membranes?
The physical and chemical factors that provide protection from disease in the skin and mucous membranes are the many layers of closely packed, keratinized cells, in the epidermis that provides a formidable physical barrier to the entrance of microbes. The epithelial layer of mucous membranes secret a fluid called mucus that is sticky and traps microbes and foreign substances. The lacrimal apparatus produces and drains away tears in response to irritants, diluting microbes and keep them from setting on the surface of the eyes. Sebaceous glands of the skin secrete an oil substance called sebum that forms a protective film over the surface of the skin. Perspiration helps flush microbes from the surface of the skin and contains lysozyme, an enzyme capable of breaking down the cell walls of certain bacteria.
What internal defenses provide protection against microbes that penetrate the skin and mucous membranes?
Interferons, complement system, transferrins, antimicrobial peptides, natural killer cells, phagocytes, inflammation and fever.
How are the activities of natural killer cells and phagocytes similar and different?
Natural killer (NK) cells are lymphocytes (a subclass of white blood cells) that recognize infected or tumorogenic cells and kill them; phagocytic cells clean up behind them.
What are the main signs, symptoms, and stages of inflammation?
symptoms of inflammation and fever; the redness, heat and swelling due to increased blood pressure, congestion and the accumulation of exudates; the pain due to irritation and to pressure on the nerves.
What is adaptive immunity?
the ability of the body to defend itself agents such as bacteria, toxins, viruses, and foreign substances
How do T cells and B cells arise?
They both originate in bone marrow. B cells mature in bone marrow and T cells in the thymus
What is the relationship between an antigen and an antibody?
An antibody is generated by an antigen. Antigen literally means ANTIbody GENerator
What is the function of cell-mediated immunity?
cytotoxic T cells directly attack invading antigens; CD4 cells or helper T cells provide protection against different pathogens. Cytotoxic T cells cause death by apoptosis without using cytokines, therefore in cell mediated immunity cytokines are not always present.
What is the function of antibody-mediated immunity?
antibody production and the accessory processes that accompany it, including: Th2 activation and cytokine production, germinal center formation and isotype switching, affinity maturation and memory cell generation. It also refers to the effector functions of antibodies, which include pathogen and toxin neutralization, classical complement activation, and opsonin promotion of phagocytosis and pathogen elimination
Which type of T cell participates in both cell-mediated and antibody-mediated immune responses?
active helper T cells
What is the difference between an epitope and a hapten?
An epitope, is the part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, or T cells; A hapten is a small molecule that can elicit an immune response only when attached to a large carrier such as a protein; the carrier may be one that also does not elicit an immune response by itself.
What types of cells are APCs, and where in the body are they found?
Dendritic cells, B cells, and macrophages play a major role in the innate response, and also act as dedicated antigen-presenting cells (APC). These dedicated APCs are equipped with special immunostimulatory receptors that allow for enhanced activation of T cells.
What are some examples of endogenous antigens?
Endogenous antigens include xenogenic (heterologous), autologous and idiotypic or allogenic (homologous) antigens.
What is immunocompetence, and which body cells display it?
Immunocompetence is the ability of the body to produce a normal immune response following exposure to an antigen; In reference to lymphocytes, immunocompetence means that a B cell or T cell is mature and can recognize antigens and allow a person to mount an immune response.
How do major histocompatibility complex class I and class II self-antigens function?
their normal function is to help T cells recognize that an antigen is foreign, not self. Class I built into plasma membranes; class II appear on surface of APCs
How do antigens arrive at lymphatic tissue?
via the blood stream; directly enter lymphatic vessels; or by penetrating the mucous membranes and are entrapped by mucosa-associated lymphatic tissue
How do antigen-presenting cells process exogenous antigens?
ingestion of antigen; digestion into peptide fragments; synthesis of MHC-II molecules; packaging of MHC-II molecules; Fusion of vesicles; binding of peptide fragments to MHC-II; instertion of antigen-MCH-II complexes into the plasma membrane
What are cytokines, where do they arise, how do they function?
Cytokines are small protein hormones that stimulate or inhibit many normal cell functions. Lymphocytes, fibroblasts, endothelial cells, monocytes, hepatocytes, kidney cells and APCs secrete cytokines; some stimulate proliferation blood cells is RBM, others regulate activites of cells involved in innate defenses or adaptive immune responses
How are T cells activated?
Helper T cells become activated when they are presented with peptide antigens by MHC class II molecules, which are expressed on the surface of antigen-presenting cells (APCs). Once activated, they divide rapidly and secrete small proteins called cytokines that regulate or assist in the active immune response.
What are the steps in a cell-mediated immune response?
1. Antigen is engulfed and presented by macrophage
2. T cells with specific receptors recognize the antigen
3. Several cycles of mitosis occur
4. T cells differentiate into cytotoxic T cells or T memory cells
5. Cytotoxic T cells migrate to focus of infection
6. Cytotoxic T cells release perforin and/or lymphotoxin
Distinguish between the action of natural killer cells and cytotxic T cells.
Natural killer cells a lymphocyte able to bind to certain tumor cells and virus-infected cells without the stimulation of antigens, and kill them by the insertion of granules containing perforin.
A cytotoxic T cell is a T lymphocyte (a type of white blood cell) that kills cancer cells, cells that are infected (particularly with viruses), or cells that are damaged in other ways.
Define immunological surveillance.
A theory that the immune system continually recognizes and removes malignant cells that arise during one's life
What is the function of the CD8 protein of a cytotoxic T cell?
Most T cells that display CD8 develop into cytotoxic T cells
In addition to cells infected by microbes, what other types of target cells are attacked by cytotoxic T cells?
body cells infected by microbes; some tumor cells; cells of tissue transplant
What are the functions of helper T cells?
helper T cells functions to empower macrophages so that they can destroy intravesicular pathogens (bacteria)
What are the functions of memory T cells?
Memory cells are made at this point for future protection and FasR & CTLA-4 is released from the helper T cells to disable the cytotoxic T cells.
What are the functions of cytotoxic T cells?
Cytotoxic T (or CD8) cells are activated in your lymph nodes by dendritic cells. Once activated they are sent out to the site of infection and they bind to the cells that express the MHC class I that are presenting the foreign antigen. They will then release perforin (punch holes in the infected cell) and granzymes (induces apoptosis). The infected cells are now destroyed.
Describe the steps in antibody-mediated immune response
immunity conferred to an individual through the activity of B cells and their progeny, which produce circulating antibodies in response to the presence of a foreign substance and recognize the substance upon renewed exposure.
What are the chemical characteristics and actions of antibodies?
four polypeptide chains (2H, 2L); disulfide bonds; they neutralize antigens, immobilize bacteria, clump together antigens, activate complement, enhance phagocytosis
Explain how the compliment system operates
1. splits into activated Ca and Cb
2. enhances phagocytosis; opsonization
4. inflammation (cytolosis)
5. lysis, apoptosis
Distinguish between a primary and secondary response to an infection.
Primary response: no antibodies present, slow rise in ab's, the gradual decline
Secondary response: new encounter with same antigen, rapid proliferation of memory cells, successful in warding off antigen
Immunoglobulin G; most abundant 80%; against bacteria and viruses; calls of antibody to cross placenta from mother to fetus
Immunoglogulin A; found in sweat, tears, saliva, mucus, breast milk, GI secretions; localized protection of mucous membranes against bacteria and viruses.
How are cell-mediated and antibody-mediated immune responses similar and different?
CM = killer T cells, immune responses; ABM = B cells, plasma cells, immunoglobins
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