Structural and Functional Organization of the Lymphatic and Immune Systems Flashcards
What type of tissue is lymphatic tissue?
A specialized form of reticular connective tissue that contains large numbers of lymphocytes.
What is the main difference of interstitial fluid and lymph compared to blood plasma?
They contain less protein than blood plasma because most plasma protein molecules are too large to filter through capillary walls.
How many liters of fluid filter from blood into tissue spaces each day?
20 liters.
How many liters of fluid is filtered from the arterial end of blood capillaries?
17 liters of the initial 20. This fluid returns to the blood directly by reabsorption at the venous end of capillaries.
How many liters per day passes into the lymphatic vessels to be returned to the blood?
3 liters out of the original 20.
What are the three primary functions of the lymphatic system?
1) Drains excess interstitial fluid.
- This helps to maintain fluid balance in the body and prevents the depletion of plasma.
2) Transports dietary lipids.
- Lymphatic vessels transport lipids and lipid-soluble vitamins (ADEK) absorbed by the GI tract into the blood.
3) Carries out immune response.
- Lymphatic tissue initiates highly specific responses against particular microbes or abnormal cells.
How are lymphatic capillaries different to blood capillaries?
They are slightly larger and are structured to let interstitial fluid to flow into them, but not back out.
Describe how interstitial fluid enters the lymphatic capillaries.
When pressure is greater in interstitial fluid (outside) than in lymph, the cells separate slightly and interstitial fluid enters the lymphatic capillary (via the one-way valve).
When pressure is greater in the lymphatic capillary, the cells adhere more closely and lymph cannot escape back into the interstitial fluid.
What are located at intervals along lymphatic vessels?
Lymph nodes, which are masses of B and T cells surrounded by a capsule.
What two main channels does lymph pass into?
The thoracic duct and the right lymphatic duct.
The thoracic duct is the main duct.
What areas of the body does the thoracic duct receive lymph from?
Left side of the head, neck, and chest
Left upper limb
Entire body below the ribs
What areas of the body does the right lymphatic duct receive lymph from?
Upper right side of the body
Where do the thoracic and right lymphatic ducts ultimately drain into?
Thoracic:
Junction of the left internal jugular and left subclavian veins
Right lymphatic:
Junction of the right internal jugular and right subclavian veins
What two pumps maintain the flow of lymph?
Skeletal muscle pump
-“Milking action” of skeletal muscle contractions compresses lymphatic vessels and forces lymph toward the subclavians.
Respiratory pump
- During inhalation, lymph flows from the abdominal region (higher pressure), toward the thoracic region (lower pressure).
- When the pressure reverses during exhalation, the valves prevent back flow of lymph.
What are the two primary lymphatic organs where stem cells divide and develop into mature B and T cells?
Red bone marrow - flat bones and the ends of long bones of adults.
*Stem cells create mature B cells and immature T cells.
Thymus - two lobed organ located posterior to the sternum.
*Immature T cells migrate to the thymus where they mature into functional T cells.
What are the secondary lymphatic organs?
Lymph nodes
Spleen
Lymphatic nodules
Describe lymph nodes
“Bouncers”
Heavily concentrated near the mammary glands, axillae, and groin.
Contain mature B cells, plasma cells, T cells, dendritic cells, and macrophages.
They filter lymph and trap foreign substances.
Describe the spleen
It is the largest single mass of lymphatic tissue in the body.
It is located between the stomach and diaphragm and covered by a capsule of dense connective tissue.
It contains two types of tissue:
-White pulp, which is lymphatic tissue where B and T cells carry out immune responses.
-Red pulp, which are blood filled sinuses where worn out blood cells and platelets are removed (like the graveyard).
Describe lymphatic nodules
Egg shaped masses of lymphatic tissue not surrounded by a capsule.
They are plentiful in the connective tissue of mucous membranes lining the GI, urinary, and reproductive tracts as well as the respiratory airways.
Which type of immunity is non-specific?
Innate Immunity
This includes barriers provided by the skin and mucous membranes (First Line Defense) as well as various internal defenses (Second Line Defense) such as:
Antimicrobial substances NKCs Phagocytes Inflammation Fever
What type of immunity involves lymphocytes?
Adaptive Immunity
It involves lymphocytes called B and T cells.
There are two types of adaptive immunity:
- Cell-Mediated Immunity
- Antibody-Mediated Immunity
What type of immunity are we born with?
Innate Immunity
These cells are present in the spleen, nodes and red bone marrow, and have the ability to kill a wide variety of microbes and tumor cells.
Natural Killer Cells.
They make up 5-10% of lymphocytes.
They cause cellular destruction by releasing proteins that destroy the target cell’s membrane.
What second line defense intensifies the effects of interferons?
Fever.
It inhibits microbial growth and speeds up reactions that aid in repair.
What are the four main types of antimicrobial substances contained within various body fluids?
Lymphocytes
Macrophages
Fibroblasts infected with viruses produce interferons
What cells diffuse to uninfected cells to stimulate the synthesis of proteins that interfere with viral replication?
Interferons
What are the components of the Complement System?
A group of normally inactive proteins in blood plasma and on plasma membranes.
When activated, they “complement” or enhance certain immune, allergic or inflammatory reactions.
What happens when the complement system creates holes in the plasma membrane of an invading microbe?
1) Cytolysis: extracellular fluid moves into the holes, causing the microbe to burst.
2) Chemotaxis: the chemical attraction of phagocytes to a site (signaling the phagocytes what/where to eat).
3) Opsonization: complement proteins bind to the surface of a microbe and promote phagocytosis (they hold the microbe down so the phagocytes can eat it).
What are examples of iron-binding proteins?
Transferrin
-Blood and tissue fluids
Lactoferrin
-Milk, saliva and mucus
Ferritin
-Liver, spleen and red bone marrow
Hemoglobin
-Red blood cells
These inhibit the growth of bacteria by reducing the amount of available iron.
What are short peptides that have a broad spectrum of antimicrobial activity?
Antimicrobial Proteins (AMPs)
They kill a wide range of microbes and can attract dendritic cells and mast cells to participate in immune response.
Examples:
Dermicidin
-Produced by sweat glands
Defensins and Cathelicidins
-Produced by neutrophils, macrophages, and epithelia
Thrombocidin
-Produced by platelets
What non-specific defense responds when microbes penetrate the skin and mucus membranes, or bypass the antimicrobial substances in the blood?
Phagocytes and NKCs
What action disposes of microbes, toxins, or foreign material, prevents their spread to other tissues, and prepares the site for tissue repair?
Inflammation
This helps to restore true homeostasis.
What are the four signs of inflammation?
Redness, pain, heat and swelling
Why does fever occur?
Due to the hypothalamic thermometer being reset.
What does bacteria trigger that causes toxins to elevate body temperature?
Fever causing substances such as Interleukin-1 from macrophages.
What is an antigen?
Any substance, such as microbes, foods, drugs, pollen, or tissue, that the immune system recognizes as foreign.
What is self-tolerance?
The ability of the adaptive immune system cells to recognize and not attack its own tissues and chemicals.
What are the two types of mature T cells that exit the thymus?
Helper T cells
Cytotoxic T cells
What happens in cell-mediated immunity?
Cytotoxic T cells directly attack invading antigens.
What happens in antibody-mediated immunity?
B cells transform into plasma cells, which synthesize and secrete specific proteins called antibodies.
A given antibody can bind to and inactivate a specific antigen.
What is special about Helper T cells?
They can aid in the immune responses of both cell-mediated and antibody-mediated immunity.
What is cell-mediated immunity effective against?
1) Intracellular pathogens such as viruses, bacteria or fungi that are inside cells.
2) Cancer cells
3) Foreign tissue transplants
What type of immunity always involves cells attacking cells?
Cell-mediated
What immunity works mainly against extracellular pathogens?
Antibody-mediated.
It works against viruses, bacteria or fungi that are in body fluids outside of the cells.
It is also referred to as humoral immunity because it involves antibodies that bind to antigens in body humors or fluids.
What is Clonal Selection?
The process by which a lymphocyte proliferates (divides) and differentiates (forms a more highly specialized cell) in response to a specific antigen.
The result is the formation of many identical cells called clones that can recognize the specific antigen in the original lymphocyte that was cloned.
What is an important benefit of clonal selection?
When a new antigen enters the body, only a few lymphocytes can recognize and respond to it. After clonal selection occurs, there are thousands of lymphocytes that can respond.
Where does clonal selection occur?
Secondary lymphatic organs and tissues
What types of cells does a lymphocyte undergoing clonal selection create?
Effector cells
- These carry out immune response tat end in the destruction or inactivation of the antigen. Most eventually die after the response has been completed.
- These include active Helper T cells, active Cytotoxic cells, and plasma cells (part of the B cell clone).
Memory cells
- These do not participate in the initial immune response. They remember the antigen, and if that antigen reenters the body in the future the thousands of memory cells from the original lymphocyte clone initiate a very quick reaction (immune response). They have a long life span that can last for decades, and do not die at the end of an immune response.
- These include:
Memory Helper T cells (part of the Helper T clone)
Memory Cytotoxic T cells cells (part of the Cytotoxic T cell clone)
Memory B cells (part of the B cell clone)
What causes the body to produce specific antibodies and/or T cells that react with it?
Antigens.
Examples of antigens include:
Chemical components of bacterial structures such as flagella, capsules, cell walls, bacterial toxins, and viral proteins.
Pollen, egg white, incompatible blood cells, transplanted tissues and organs.
What are known as “self antigens”?
Major Histocompatibility Complex proteins (MHC).
They are located on the plasma membrane surface of most body cells (except RBCs). Their function is to help T cells recognize whether an antigen is self or foreign, and are the reason most transplanted tissues may be rejected.
What shapes can antibodies assume, and why?
T or Y, because antibody “arms” can move somewhat in order to enhance the ability of the antibody to bind to two identical antigens at the same time.
What are the five classes of Immunoglobulins?
IgG IgA IgM IgD IgE
What Ig appears first and indicate recent invasion?
IgM. They are also short lived.
What can help to identify the cause of an illness in a sick patient?
High level of IgM against a particular pathogen.
What Ig causes resistance of a fetus and newborn to infection?
Maternal IgG antibodies that cross the placenta before birth, and IgA antibodies in breast milk after birth.
What is “Antigen Presentation”?
When the antigen-MHC complex is inserted into the plasma membrane of a body cell.
