Flashcards in A&P Chapter 21 Lymphatics and Immune Deck (46):
What are the Lymphatic System functions?
1. To provide an alternative pathway for extracellular fluids to return to circulation.
2. Provide pathways for waste materials to be removed from tissues/organs and to be destroyed.
3. Provide a protective lining along internal organs which are exposed to the environment such as the organs of the respiratory, digestive and reproductive systems.
4. To provide places for surveillance, proliferation and maturation of lymphocytes and other immune cells.
What are the two interrelated components of the lymphatic system?
1. The network of lymphatic capillaries, ducts and vessels.
2. The lymphatic organs such as the spleen and lymph nodes. Lymphatic tissues such as the tonsils and the Lymphatic cells dispersed through the walls of organs.
What are the major cells of the lymphatic system? Where are they found?
Macrophages and Lymphocytes, they are found everywhere except the CNS, the brain and spinal cord.
Describe the flow of lymph:
Tissues-->Lymphatic Capillaries -->Lymphatic ducts --> Lymphatic Vessels
Tissue fluid flows into lymphatic capillaries embedded in the capillary beds of the cardiovascular system.
The lymphatic capillaries carry lymph to lymphatic ducts then to lymphatic vessels. Along the way the lymph flows through many lymph nodes.
Where are lymph nodes concentrated?
The Inguinal, Axillary and Cervical Regions
Describe the ANATOMY of a Lymph Node:
Small and bean shaped. It has as many as 30-40 AFFERENT lymphatic vessels draining into the node. The node is surrounded by a cortex, just inside the cortex are lymphatic nodules where lymphocytes and macrophages are rapidly reproducing. The center of the lymphatic nodule is called the GERMINAL CENTER. The space between nodules is called the CORTICAL SINUS. The center of a lymph node is called the MEDULLA. There is a single EFFERENT lymphatic vessel through which lymph travels after it has passed through the medulla.
Where does lymph flow back into the blood supply?
The majority of lymph returns via the Thoracic duct draining into the left subclavian vein. The thoracic duct drains the lower half of the body and the left upper half of the body.
The right lymphatic duct drains the right arm, thorax and head. It flows into the right subclavian vein.
What are the lymphatic organs?
The Spleen and Thymus.
Describe the Spleen:
It is located in the left upper quadrant of the abdomen, it's inferior to the diaphragm. It has a large blood supply fed by the splenic artery.
The spleen filters damaged RBC's.
It is made of two types of tissue: Red Pulp and White pulp. The Red Pulp is a reservoir for erythrocytes not in use by the body. In newborns and infants the red pulp is a site of Erythropoiesis.
The white pulp is comprised of lymphocytes and macrophages. These remove bacteria, viruses, debris from the blood as well as old damaged erythrocytes.
Describe the Thymus:
It sits anterior to the aorta, superior to the heart and posterior to the sternum. It is Large in children and shrinks in adults.
The thymus secrets a hormone that causes undifferentiated lymphocytes to mature into T Lymphocytes which stands for Thymic-derived lymphocytes.
Many lymphocytes that leave the bone marrow and goto the thymus are killed by macrophages instead of differentiating into T cells.
Describe Lymphoid tissues:
Lymphoid tissues line hollow organs exposed to the external environment, the digestive tract, the respiratory tract and the reproductive organs.
All of the different kinds of leukocytes can be found in lymphoid tissues but the lymphocytes and macrophages make up the majority.
The tissues contain clusters of closely packed, rapidly proliferating lymphocytes and macrophages called LYMPHATIC NODULES. The nodules lie just deep to the epithelia that lines the hollow organ. This allows them easy access to incoming antigens they also secrete antibodies into and across the epithelia into the lumen.
Describe the location of Lymphatic Nodules:
They are located in the connective tissue just deep to the basement membrane of the epithelia that lines hollow organs.
Connective Tissue--> Lymphatic nodules in the connective tissue.
What are examples of named Lymphoid tissues?
Tonsils located in the pharynx and Peyer's patches in the small intestines. The Peyer's patches are much larger than nodules by 5-9x's.
What are the two forms of body defenses?
Nonspecific Defenses which are a generalized defense, they are the first line of defense and Specific Defenses which are targeted against a specific threat.
What are the Nonspecific Body Defenses?
First line:Epithelial Barriers, Phagocytes and Antimicrobial chemicals.
Second line: Fever and Inflammation
Describe the Epithelia barriers of Nonspecific Body Defenses
The epithelial barriers are the skin, cornea, mucous membranes, etc. They do 90% of the work of the defense system and they are indiscriminant. They try to prevent stuff from getting into the body.
What are the Phagocytes of the Nonspecific Body Defenses?
The Macrophages, Neutrophils, and Eosinophils.
Describe the Antimicrobial chemicals of the Nonspecific Body Defenses
Acids: found in the stomach, vagina and urethra.
Lyozyme: A polysaccharide that binds to and destroys cell walls.
Compliment: proteins that bind to bacteria and parasites. These directly lyse them, they also mark them for phagocytes. They attach together and become more effective punching a hold in an individual cell wall.
Inferons: Proteins that are active against viruses. They prevent viruses from entering a cell, they tag viruses and mark them (like a red flashing light saying come eat me).
Describe a Fever and how it is a defense against invaders.
Normal body temp is 37degrees C. Bacteria/viruses/parasites have adapted to thrive in this temp. The body runs a fever and goes up a couple degrees C to slow down/inactivate foreign invaders. It also slows down the bodies ability to do what it's supposed to do as well.
Temperatures of 41+degrees C can do permanent damage to the body.
Inflammatory chemicals are released from damaged tissues. They cause several things to happen: Vasodilation, Pain, Increased capillary permeability, Swelling, Increased O2 and the attraction of Leukocytes.
A foreign material enters tissues causing inflammatory chemicals to be released which causes Basophils diapedese out into tissues becoming MAST cells and release Heparin (a blood thinner) and Histamine (helps makes the vessel dilate and leaky) resulting in vasodilation and increased capillary permeability which allows more Leukocytes to diapedese out of the blood vessels into the tissue.
You CAN HAVE INFLAMMATION WITHOUT INFECTION. Such as Rheumatoid Arthritis (autoimmune disease)
What are the characteristics of a SPECIFIC Immune Defense?
Specific: Provides a defense against a SPECIFIC antigen recognized as NON-SELF.
Adaptive: Defenses can be targeted against NEW antigens.
Systematic: Defenses are distributed throughout the entire body.
Memory: The body mounts a stronger/faster defense against PREVIOUSLY encountered antigens.
What is Self-Tolerance? Why do we need this?
It is the body's ability to recognize itself and distinguish it from foreign invaders. The body must have self-tolerance so that the immune defense won't attack ones own body.
Define a Pathogen:
Any LIVING organism (bacteria, virus, parasite) against which the immune system RESPONDS.
Define an Antigen:
Any molecule against which the immune system responds, it may be an isolated molecule floating around or it maybe part of a larger structure such as a protein molecule on the surface of a cell membrane.
A specific protein, AKA an IMMUNOGLOBIN, which binds to an antigen. ALL ANTIBODIES ARE PRODUCED BY LYMPHOCYTES.
Define Antigenic Determinant:
The SPECIFIC PART of an antigen which an antibody recognizes and binds to.
How many binding sites does an antibody have?
What does having 2 binding sites allow an antibody to do?
1. It allows it to clump antigens together. By attaching to an Antigenic determinant on one antigen and an Antigenic Determinant on another the antibody can clump antigens together. AGGLUTINATION.
2. It allows it to bind to an Antigenic determinant with one binding site and to signal attacker cells with the other.
What are the interrelated components of Specific Immune Defenses?
Cell Mediated Immunity and Humoral Immunity
Describe Cell Mediated Immunity
Where Macrophages and T-Lymphocytes DIRECTLY ATTACK invading or damaged cells.
The lymphocytes will have antibodies on their cell membranes.
Describe Humoral Immunity
Antibodies produced by PLASMA CELLS (B-Lymphocytes) float free in the extracellular matrix and attach to invading cells or isolated antigens.
Outline the Development of Immunity
It can be EITHER Naturally Acquired or Artificially Acquired.
Within each it can be actively or passively acquired.
Describe the ACTIVE Naturally Acquired Immunity
Where you get an infection, come in direct contact with a pathogen and actually have a disease, survive and gain an immunity to it afterwards.
Describe PASSIVE Naturally Acquired Immunity
Where antibodies pass from mother to fetus via the placenta or to infant via mothers milk.
Describe ACTIVE Artificially Acquired Immunity
This is a vaccination with a dead or damaged pathogen resulting in an immune response which prepares the body for future encounters.
Describe PASSIVE Artificially Acquired Immunity
The injection of antibodies or immune serum into a person. This is seen mainly in the elderly who lack the ability to make antibodies. The antibodies from one person are isolated and put directly into someone else.
What are the cells of the immune system?
T Lymphocytes: Cytotoxic T Cells (Killer T Cells), Helper T-Cells, Suppressor T-Cells, Memory Cells
B Lymphocytes: Plasma Cells, Memory Cells
Describe the Role Macrophages play in the immune system.
Macrophages: Engulf and destroy pathogens, damaged cells, etc. They PRESENT antigens to lymphocytes. They SECRETE ACTIVATION FACTORS which tells other leukocytes that the macrophage ate something.
Describe the process a Macrophage goes through to PRESENT AN ANTIGEN FRAGMENT
1. The Antigen is Phagocytosed.
2. Lysosomes fuse with the Phagocytosed Antigen
3. The Antigen and Enzymes Mix.
4. The Antigen is degraded
5. ANTIGEN FRAGMENTS ARE DISPLAYED ON THE CELL MEMBRANE on a protein called the MAJOR HISTOCOMPATIBILITY COMPLEX.
6. The degraded antigen residue is voided (exocytosis) by the macrophage.
What is the MAJOR HISTOCOMPATIBILITY COMPLEX? What does it do/help with?
It is a protein that allows a Macrophage to display a degraded antigen fragment to lymphocytes. This will SPEED UP an immune response, this presentation activated lymphocytes.
Where do T-Lymphocytes become Immunocompetent?
In the THYMUS
Explain Humoral Immune Response and how B Lymphocytes Cap and Endocytose antigens.
Humoral immunity is effective against both isolated antigens AND cells.
It begins when an immunocompetent B-Lymphocyte recognizes and binds to an antigen becoming activated. Multiple receptors on the plasma membrane of the B Cell bind to the antigen, they cluster around it and take it into the cell by endocytosis.
If the B Cell cannot bind to the antigen AND take it inside it will NEVER make needed antibodies.
Explain the steps required for producing antibodies by plasma cells:
1. The B-Lymphocyte uses its receptors to bind to a specific antigen.
2. The B-Lymphocyte DISPLAYS processed (brokendown) antigen fragments. Helper T-Cells bind to the B Cell and secretes the helper factor.
3. The helper factor stimulates the B Cell to DIVIDE rapidly and form clones.
4. Some of the Clones become PLASMA CELLS and some become MEMORY B CELLS.
5. The PLASMA CELLS synthesize and secrete lots of antibodies.
Explain Cell-Mediated Immune Response
It is effective against INVADING CELLS or damaged cells.
It begins when a macrophage or INFECTED cells (of the body) PRESENT antigen fragments to immunocompetent T-Lymphocytes, this ACTIVATES THE T-CELLS.
When a HELPER T-Cell is activated (by a MACROPHAGE PRESENTING THE DEGRADED ANTIGEN FRAGMENT) it secrets chemicals which activates other macrophages and stimulates the reproduction of both B Cells and Cytotoxic T-Cells.
When Cytotoxic (Killer) T-Cells are activated they bind to a target cell and release molecules which directly damage the cell. They can be perforin, lymphtoxins, tumor necrosis factors or oxygen free radicals.
What do Suppressor T-Lymphocytes do?
They secrete chemicals which suppress the activites of both T and B Cells. It also tells plasma cells to STOP producing antibodies.
They are nessecary to wind down the immune response after antigens or invading cells are destroyed.
Minimizes the risk of CROSS REACTIVITY and damaging "Self" cells. (Autoimmune diseases).
They help convert activated T and B cells to MEMORY CELLS.