By:Michelle RondillaValeria PulgarGenesis VillacampaDaniel Poveda

THE LYMPHATIC SYSTEM

Lymphatic System

• The Lymphatic System is made up of lymphatic vessels and various lymphatic organs. • This body system is closely linked to the cardiovascular system, and performs 3 main functions that contribute to the maintenance of the body’s homeostasis.

Functions of the Lymphatic System• Balance of fluid – takes up excess tissue fluid and returns in to the bloodstream. • Lymphatic cavities lie near blood capillaries, and serve as additional help to return fluid that has left the blood capillaries.

• Absorption of fat – absorbs fats from the digestive tract, transports them into the bloodstream.• Special lymphatic capillaries called lacteals are located in the intestinal villi, providing the absorption of dietary lipids and lipid-soluble vitamins into the blood.

Functions of the Lymphatic System• Defense against diseases – helps defend the body against diseases through white blood cells in lymphatic vessels and lymphatic organs, as well as in the blood and between tissue cells. • Other than fighting off diseases, white blood cells play an important role in the destruction of dead and dying tissue cells, and in defending the body against cells that have mutated and become cancerous.

Lymphatic Vessels• Form a one-way traveling systems for fluids, that begins in lymphatic capillaries found in most areas of the body. • These capillaries are small, close-ended vessels made up of simple squamous epithelium, and take up excess tissue fluid. • These fluids are mostly water, but can also contain solutes such as nutrients, electrolytes, and oxygen. • These solutes come from plasma and cellular products like hormones, enzymes, and wastes that are secreted by cells.• All these fluids become lymph, the fluid inside lymphatic vessels. • Lymphatic capillaries join together and form lymphatic vessels that come together before entering either the thoracic duct or the right lymphatic duct.

Lymphatic Vessels• Thoracic duct - The larger duct, returns lymph collected from below the thorax, left arm, left side of the head and neck and returns it into the left subclavian vein.• The lymphatic vessels of the thoracic duct are made up very

similar to cardiovascular veins with valves. • The movement of lymph within these vessels depends on the

contraction of skeletal muscle —when the muscles contract, lymph is squeezed past a valve that closes, preventing lymph from flowing backward.

•Right lymphatic duct – Smaller duct, returns lymph from the right arm and right side of the head and neck into the right subclavian vein.

Organs, Tissues, and Cells of the Immune System• The immune system plays and important role in protecting the body from illnesses and keeping it healthy through a system of networks of lymphatic organs, tissues, and cells; and the products from these cells such as antibodies and regulatory agents.• Immunity – the ability to react to antigens and fight off foreign bodies so that the body can remain free of disease.• Diseases are a result of a failure of the body to keep homeostasis, can be caused by the infection by foreign microbes, as well as the failure of the immune system to properly function

Primary Lymphatic Organs

• Lymphatic (lymphoid) organs have large amounts of lymphocytes, a type of white blood cell that plays an important role in the body’s immunity. • The primary lymphatic organs are the red bone marrow and the thymus gland. Lymphocytes originate and mature in these organs.

Red Bone Marrow• Red Bone Marrow - stem cells divide and produce blood cells. • Some of these cells become white blood cells: neutrophils,

eosinophils, basophils, lymphocytes, and monocytes.

• In a child - most of the body’s bones have red bone marrow, but as you age into • Adulthood - this red bone marrow sternum, vertebrae, ribs, the skull, part of the pelvic girdle, humerus and femur.• Lymphocytes are classified into the B lymphocytes and the T lymphocytes. • B lymphocytes grow and mature in the bone marrow• T lymphocytes mature in the thymus.

Thymus Gland• Thymus - a soft, bilobed gland in the thoracic cavity between the trachea and the sternum, above the heart. • Varies in size, being its biggest in children and shrinking as the body ages.• The thymus gland produces thymic hormones, such as thymosin, that are thought to • aid in the maturing of T lymphocytes; • immunity.

• The thymus gland is very important in the role of the body’s immunity• without the thymus, body will allow all foreign tissues to enter,

• blood lymphocyte levels are drastically reduced, and the

• body’s response to most antigens becomes poor if there is any at all.

Secondary Lymphatic Organs

• The secondary lymphatic organs are the spleen, lymph nodes, and other organs such as the tonsils, Peyer patches, and the appendix. All the secondary organs are places where lymphocytes encounter and bind with antigens, where they begin to multiply and become active cells.

Spleen• Largest lymphatic organ• Located in the upper left region of the abdominal cavity, posterior to the stomach. • Divided into various compartments by connective tissue, all of which contain:• White pulp - contains a large concentration of lymphocytes.• Red pulp - filters the blood surrounding venous sinuses

• Lymphocytes and macrophages react to pathogens, and macrophages eat up debris and remove old and worn out red blood cells.• Outer layer is thin, an infection or hit can cause the spleen to burst.• If the spleen is damaged, other organs of the body can take on its functions, but a person without a spleen is slightly more sensitive to infections, and may have to receive antibiotic therapy.

Lymph Nodes• Small, egg-shaped structures• Located along the lymphatic vessels• Connective tissue forms the outer covering of a lymph node and divides the organ into compartments• Each compartment has a nodule packed with B lymphocytes and a sinus that grows toward the center of the node. • T lymphocytes are also found in sinuses and fight off infections and attack cancer cells.• Each compartment of the anterior cavity has superficial and deep lymph nodes named by their location. • Inguinal nodes are located in the groin• axillary nodes are in the armpits.

• Swollen or tender lymph nodes are a sign of the body fighting off an infection.

Lymphatic Nodules • Lymphatic Nodules are concentrations of lymphatic tissue that are not surrounded by a covering or capsule. • The tonsils are lymphatic nodules in the posterior pharynx.

• These tonsils have the same functions as lymph nodes, but because of their locations around the mouth and nose, they are the first to encounter pathogens and antigens entering through these cavities.

Nonspecific and Specific Defenses• In the lymphatic system, there are nonspecific and specific defenses. • There are five types of nonspecific defenses

1. Barriers to entry

2. The inflammatory reaction

3. Nonspecific phagocytic white blood cells

4. Natural Killer Cells

5. Protective Proteins• Specific defenses are effective against a particular

infectious agent.

Nonspecific Defenses• Barriers to Entry• The body has built-in barriers to help prevent infection. • An example of a built-in barrier is our skin, which prevents infection.• Mucous membranes line the respiratory, digestive, reproductive, and urinary tracts, which protect from pathogens. • Sebaceous (oil) glands secrete from the skin, which contains chemicals to kill certain bacteria.• Perspiration, saliva, and tears contain an antibacterial enzyme called lysozyme.• A significant chemical barrier is normal flora.• normal flora – microbes that normally reside in the mouth,

intestines and other areas to prevent pathogens from taking up residence.

Nonspecific Defenses• Inflammatory Reaction• Whenever tissue is damaged by physical or chemical agents or pathogens, a series of events occurs that is known as inflammatory reaction.• Mast cells – one of the types of white cells found in the blood.• The inflamed area will exhibit four signs: redness, heat, swelling & pain. • Histamine – released by damaged tissues and mast cells, which cause the capillaries to dilate and become more permeable. • Excess blood flow due to growth of capillaries will cause the skin to redden and become warm.• Swelling occurs to “wall off” the area from the rest of the body.

Nonspecific Defenses

•Natural Killer (NK) Cells• NK cells kill virus-infected cells and tumor cells by cell-to-cell contact. • They are large, granular leukocytes.

Specific Defenses• Specific defenses respond to antigens, which are molecules the immune system recognizes to be foreign.• Immunity is the primarily the result of the action of the B lymphocytes and the T lymphocytes. • T lymphocytes mature in the thymus gland.• B lymphocytes mature in the bone marrow and give rise to plasma cells, which produce antibodies.• Antibodies – proteins shaped like the antigen receptor and are capable of combining and neutralizing a specific antigen.

B Cells and Antibody-Mediated Immunity•When a cell encounters a specific antigen, it is activated to divide many times. Most of the resulting cells are plasma cells.• Plasma cell – a mature B cell that mass-produces antibodies against a specific antigen• The clonal selection theory states that the antigen selects one particular lymphocyte to reproduce multiple copies of itself. The resulting group of identical cells is called a clone.• The majority of these clones will mature to form plasma cells. • Once the threat of infection has passed, these plasma cells undergo apoptosis.• Apoptosis – programmed cell death• It is important these cells are destroyed because they could mistakenly destroy body cells.

Structure and Function of Antibodies • The basic unit that composes of an antibody molecules is a Y-shaped protein molecule with two arms. • Each arm has a “heavy”(long) polypeptide chain and a “light”(short) polypeptide chain. • Also known as immunoglobulins.

Classes of Antibodies

Types of T Cells1. Cytotoxic T Cells – also called CD8 leukocytes; can bring about the destruction of antigen-bearing cells.• Cytotoxic cells have storage vacuoles containing perforin molecules.• Perforin – molecules that punch holes into a plasma membrane forming a pore that allows water and salts to enter.

2. Helper T Cells – also called CD4 leukocytes; regulate immunity by secreting cytokines, the chemicals that enhance the response of other immune cells

Cytokines in Cancer Chemotherapy•Whenever cancer develops, it is possible that cytotoxic T cells have not been activated. •With this in mind, cytokines have been used as immunotherapeutic drugs to enhance the ability of T cells to fight cancer.

Induced Immunity

• Active Immunity:

Individual produces antibodies against an antigen. Long-lasting.

• Passive Immunity:

Individual receives prepared antibodies from another person. Temporary.

Active Immunity

• Develops naturally after infection, once recovered the person will have a natural active immunity from the antibodies used to fight the infection.• Artificial active immunity is provided by immunization, because the individual produces their own antibodies to fight the given antigen.• Immunization: Involves the use of Vaccines, substances that contain an antigen to which the Immune system responds.• Antibody titer: The amount of antibody present in a sample of plasma. Used to follow the immune response.• Active Immunity relies on Memory B cells and Memory T cells, because they are capable of responding to low doses of antigen.

Passive Immunity

• Patient receives a gamma globulin injection (possibly taken from someone who recovered from the illness).

- This imparts an artificial passive immunity, and the person will also develop their own antibodies which creates an artificial active immunity.

Monoclonal Antibodies

• Antibodies that are secreted from the same B cell, and fight one specific antigen. Used for quick diagnosis of certain conditions.

Ex. A monoclonal antibody can detect a specific hormone found in a pregnant woman’s urine.

Hypersensitivity Reactions

• Allergies: hypersensitivities to substances such as animal hair or pollen that ordinarily would do no harm to the body

- Allergens: Response to these antigens, usually includes some tissue damage

• There are 4 type of allergic responses, the two most important are IgE-mediated Allergic Response, and T-cell-Mediated Allergic Response• Tissue Rejection• Autoimmune Disease• Immune Deficency

IgE-Mediated Allergic Response

• Referred to as immediate allergic response • Caused by antibodies known as IgE • IgE antibodies are attached to plasma

membranes of most cells in tissues and to basophils in the blood.

• When allergens attach to the IgE antibodies mast cells release histamine and other substances that bring about allergic reactions

• Anaphylactic Shock: IgE mediated allergic response that occurs when an allergen enters the bloodstream. Sudden drop in blood pressure due to increased blood vessel dilation.

T-cell-Mediated Allergic Response

• Initiated by memory T-cells at the site of allergen contact in the body• Sometimes called delayed response because it develops slowly• The allergic response is regulated by cytokines secreted by memory T-cells and macrophages

Ex. Contact Dermatitis that occurs when someone is allergic to poison ivy, jewelry, cosmetics and other substances that touch the skin.

Tissue Rejection

• Results because the recipient’s immune system recognizes the transplanted tissue is not “self”• Cytotoxic T-cells (antibodies) respond by causing disintegration of the transplanted tissue• Rejection can be controlled by selecting organs with the same type of HLA antigens as the recipient and administering immunosuppressive drugs.

Autoimmune Disease

• Occurs when cytotoxic T-cells (antibodies) mistakenly attack the body’s own cells as if they had foreign antigens.

Examples:• Multiple Sclerosis: the myelin sheath or nerve fiber is attacked• Rheumatoid Arthritis: the joints are affected• Systematic Lupus Erythematosus: antibodies attack multiple self antigens, including their own DNA molecules.

Immune Deficiency

• The immune system is unable to protect the body against disease• There are acquired immune deficiencies like AIDS, Genetic immune deficiencies acquired from parents, and Congenital immune deficiencies which are due to failure of lymphatic tissue to develop. • Severe Combined Immunodeficiency Disease (SCID): a genetic disorder, both antibody and cell-mediated immunity are lacking or inadequate.

13.5 Effects of Aging • Skin is more vulnerable to all types of infections and diseases because the immune system becomes slower and “worn out”• Skin is more vulnerable due to the thymus gland degenerating. • The thymus gland • Childhood: reaches its maximum size • After puberty: it shrinks • Old age: virtually disappears

Effects of Aging

• Thymus gland decreases in size, number of T cells also decreases • The number of remaining T cells do not respond to foreign antigens• Chance of having cancer increases. • B cells sometimes fail to form clones. If they do form clones, the antibodies released may not function well. • This causes infections to be more common among the elderly. • Antibodies are more likely to attack the body’s own tissues,

increasing occurrence of autoimmune diseases.

• Response to vaccines is decreased.

13.6 Homeostasis• Fluid balance, fat absorption, & defense assist homeostasis. • Helps the digestive system by absorbing fats. • Lacteals absorb fat-soluble vitamins.

• Assists the cardiovascular system by absorbing excess tissue fluid. • Return excess tissue fluid as lymph to cardiovascular veins in

the thorax.

• Lymphatic organs protect people from infectious diseases. • The skin & the mucous membranes of the respiratory tract, the digestive tract, & the reproductive & urinary system all resist invasion by viruses & bacteria.

Homeostasis• Phagocytic white blood cells try to engulf as many pathogens as possible. • Macrophages devour viruses & bacteria by phagocytosis. • Complement: is a series of proteins that work in diverse ways to keep the blood free of disease-causing organisms & their toxins.

B & T Cells • Specific defenses are dependent upon blood cells. • B & T cells have antigen receptors & can distinguish self from nonself. • Binding of the antigen selects which specific B or T cells will undergo clonal expansion. • B cells are capable or recognizing an antigen directly• T cells must have the antigen displayed by an APC in the grove of an HLA antigen. • Plasma cells (mature B cells) produce antibodies• T cells kill virus-infected & cancer cells outright.

Lymphatic System and Immunity• In the red bone marrow:• White blood cells are made• B cells mature

• T cells mature in the thymus. • Spleen filters the blood directly.• Clonal expansion of lymphocytes occurs in the lymph nodes• Lymphocytes have receptor proteins for a wide variety of hormones.

Lymphatic System and Immunity• Thymus gland produces hormones that influence the immune response. • Cytokines produced by T lymphocytes help the body recover from disease • Cytokines symptoms:• Sluggishness• Sleepiness• Loss of appetite.

• These behaviors tend to make people take care of themselves until they feel better.• Cortisone has to ability to decrease the inflammatory reaction in the joints.

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