Lymphatic System Flashcards
What are pathogens?
disease-causing organisms, like viruses, bacteria, fungi, and parasites
What is immunity?
The ability to defend against infection and resist disease
What is the immune system?
All the cells and tissues involved in producing immunity
What does the lymphatic system include?
The lymphatic system (AKA lymphoid system) includes the cells, tissues, and organs responsible for defending the body.
What does the lymphatic system consist of? (4x)
(1) an array of lymphatic tissues and organs scattered throughout the body;
(2) a network of lymphatic vessels, which begin in peripheral tissues and connect to veins;
(3) lymph, a fluid that resembles plasma but contains a much lower concentration of dissolved proteins, flowing in the lymphatic vessels; and
(4) lymphoid cells, including lymphocytes and smaller numbers of phagocytes and other cells.
What are the primary lymphatic tissue/organs?
Primary lymphatic tissues and organs are sites where lymphocytes are formed: red bone marrow and the thymus.
What are the secondary lymphatic tissue/organs?
Secondary lymphatic tissues and organs are where lymphocytes are matured/activated: the tonsils, MALT (mucosa-associated lymphatic tissue), lymph nodes, and spleen.
What is MALT
MALT (mucosa-associated lymphatic tissue),
What are lymphoid tissues?
connective tissues dominated by lymphocytes.
In a lymphoid (or lymphatic) nodule, the lymphocytes are ___________ in an area of ____________ next to the ____________
densely packed; areolar tissue (loose connective tissue); epithelial lining.
What are Peyer’s patches?
clusters of lymphoid nodules along the intestine
Where are large lymphoid nodules located?
tonsils; Peyer’s patches, on the wall of the appendix.
Where are lymphoid nodules located?
within lymphoid organs, i.e., lymph
nodes and the spleen.
What are Lymph nodes?
small lymphoid organs
Where are lymph nodes located? And what do they do?
The greatest number of lymph nodes is located in the neck, axillae, and groin, where they defend us against bacteria and other invaders.
_____ flows through lymph nodes before it reaches the _____
Lymph flows through lymph nodes before it reaches the veins.
What are the functions of lymph nodes? (2x)
1) functions like a kitchen water filter: It purifies lymph before it returns to the veins.
2) an early-warning defense system
How does lymph nodes function as a filter/purifier?
As lymph flows through a lymph node, at least 99% of antigens (i.e., foreign substances) in the lymph are removed by macrophages within the lymph nodes that engulf debris or pathogens in lymph as it flows through.
How does lymph nodes function as an early warning defense system?
Any infection or other abnormality in a peripheral tissue puts antigens into the interstitial fluid, and thus into the lymph. Lymph then carries these antigens to nearby lymph nodes, where macrophages and lymphocytes are activated.
How do lymph nodes function as an early warning defense system?
Any infection or other abnormality in a peripheral tissue puts antigens into the interstitial fluid, and thus into the lymph. Lymph then carries these antigens to nearby lymph nodes, where macrophages and lymphocytes are activated.
What is the function of the Thymus?
primary lymphoid organ. It is necessary in early life for immunity,
Is the Thymus necessary later in life?
later in life atrophies and becomes inactive
Where is the thymus located?
located in the mediastinum, just posterior to the sternum
What is the function of the Spleen in the lymphatic system? (3x)
(1) removing abnormal blood cells and other blood components by phagocytosis, (2) storing iron recycled from old red blood cells, and (3) initiating immune responses by B cells
and T cells in response to antigens in circulating blood
When is the spleen important? Why?
all throughout your life because they help get rid of damaged cells. (Ex: red blood cells, recycle the RBCs to make more RBCs.)
The adult spleen contains the ________ collection of lymphoid tissue in the body.
largest
the spleen performs the same functions for blood that ____________ for the __________
lymph nodes perform for lymph.
What is the function of lymphatic vessels?
carry lymph from peripheral tissues to the venous system.
Where does the lymphatic network begin?
lymphatic capillaries, which branch through peripheral tissues.
How do lymphatic capillaries differ from blood capillaries? (3x)
(1) are closed at one end rather than forming
continuous tubes, (2) have larger luminal diameters, (3) have thinner walls.
Lymph is interstitial fluid that first enters _______ and then drains into ___________
Lymph is interstitial fluid that first enters lymphatic capillaries and then drains into larger major lymph-collecting vessels, known as trunks and ducts.
Lymphatic capillaries (desc)
lined by endothelial cells, but their
the basement membrane is incomplete or absent.
The endothelial cells of a lymphatic capillary are _____________
not bound tightly together, but they do overlap.
How do the unique features of lymphatic capillaries aid in its function?
The endothelial cells of a lymphatic capillary are not bound tightly together, but they do overlap. The region of overlap acts as a one-way valve. It permits fluids and solutes (including proteins) to enter, along with viruses, bacteria, and cell debris, but it prevents them from returning to the intercellular spaces.
From the lymphatic capillaries, lymph flows into _________.
From the lymphatic capillaries, lymph flows into larger lymphatic vessels (trunk) that lead toward the even greater lymphatic vessels (ducts).
How are lymphatic vessels different from blood vessels?
in size, general appearance, and branching patterns.
Most arteries are bright red, veins are dark red (usually illustrated as blue to distinguish them from arteries), and lymphatic vessels
are a
pale golden color.
What do lymphoid cells consist of?
immune system cells found in lymphoid tissues.
Immune cells include
phagocytes and lymphocytes.
What do Phagocytes include? What are their func?
Phagocytes include macrophages and microphages (neutrophils, eosinophils). These cells are the first line of defense against pathogens (bacteria/viruses).
What do lymhocytes respond to? What do they do to them?
specific invading pathogens, as well as to abnormal body cells (such as virus-infected cells or cancer cells). They eliminate these threats through a combination of physical and chemical attacks.
What are the 3 types of lymphocytes?
(1) T (thymus-dependent) cells,
(2) B (bone marrow-derived) cells, and
(3) NK (natural killer) cells.
Circulating lymphocytes are only a small fraction of the total lymphocyte population. (T/F)
True
Where are the majority of lymphocytes?
distributed in tissues throughout the body.
What is one of the functions of the lymphatic system? (involves capillaries)
Capillaries normally deliver more fluid to peripheral tissues than they carry away. The lymphatic vessels return excess tissue fluid (lymph) to the bloodstream (via the venous system) to maintain normal blood volume & tissue fluid level.
What does the continuous circulation of fluid helps with? (3X)
1) transport lymphocytes and white blood cells from one organ to another.
2) distributes hormones, and nutrients to tissue,
3) carries wastes from their tissues of origin to the general circulation.
primary function of the lymphatic system is
to produce, maintain, and distribute lymphocytes and other lymphoid cells that provide defense against infections and foreign substances.
To provide an effective defense, lymphocytes must ________ problems and ____________ site of injury or infection
detect problems; reach the
Lymphocytes are able to enter or leave the capillaries/lymphatic vessels as needed. (T/F)
True
Why do Lymphocytes and other cells circulate within the blood?
Because they must be able to detect problems and reach the site of injury to provide an effective defense
The body’s reaction to these infectious agents and other abnormal substances is known as
immune (immune, protected) response.
What is resistance in relation to immunity?
The closely associated process is resistance, which is the ability of the body to maintain its immunity.
What are the two types of immunity humans have?
innate (natural and “one-size-fits all”) immunity and adaptive (acquired and specific) immunity.
What is the general difference between the two types of immunity?
Each immunity employs specific lymphocytes and mechanisms and both work together to defend us against foreign organisms or substances.
What does innate immunity include?
physical barriers and defense processes that either (a) prevent or slow the entry of infectious organisms or (b) attack them.
What is an example of innate immunity?
The skin (physical barrier, and phagocytes attack invading bacteria.)
Why is skin an example of innate immunity?
It is called innate because you are born with it, and nonspecific because it does not distinguish one pathogen from another. The type of lymphocytes involved is NK cells.
What does adaptive immunity involve?
two classes of lymphocytes, T cells, and B cells, and response to specific antigens.
What does adaptive immunity protect the body from?
protects us against further attacks by the same type of pathogen.
When do we develop our adaptive immunity?
After birth, we develop adaptive immunities as a result of accidental or deliberate exposure to antigens. Our immune system retains the memory and the ability to fight against the same pathogen for long time.
What does Innate immunity include? (More specific) (7x)
- Physical barriers
- Phagocytes
- Immune surveillance
- Interferons
- Complement
- Inflammation
- Fever
Innate Immunity (Physical barriers) (3x) how?
- epithelial covering of the skin has multiple layers, a keratin coating, and a network of desmosomes that tightly lock adjacent cells (skin)
- epithelial cells are tied together by tight junctions, and supported by a dense and fibrous basement membrane. (internal passageways of the respiratory, digestive, urinary, and reproductive tracts,)
- Specialized accessory structures and secretions protect most epithelia.
What are the accessory structures and secretions that protect most epithelia? (in relation to innate immunity) (6x)
The hairs, sebaceous and sweat glands, mucus, and secretions covering epithelium contain protective enzymes (lysozymes) and antibodies.
Innate Immunity: Phagocytes (How?)
Phagocytes serve as janitors and police in peripheral tissues. They remove cellular debris and respond to invasion by foreign substances or pathogens.
What are the two types of phagocytes? (& examples)
- microphages (neutrophils and eosinophils)
- macrophages
What is the function of Microphages?
1) leave the bloodstream and enter peripheral tissues that have been subjected to injury or infection.
How do Neutrophils contribute to the function of Microphages?
Neutrophils are abundant and quick to phagocytize cellular debris or invading bacteria.
How do Eosinophils contribute to the function of Microphages?
Eosinophils are less abundant. They target foreign substances or pathogens that have been coated with antibodies.
What is the function of macrophages?
Macrophages are large, active phagocytes, derived from the monocytes in circulating blood., macrophages are either fixed in position (fixed macrophages) or free macrophages.
Where are macrophages located/ can you find them?
Almost every tissue shelters residents or visiting macrophages.
What is emigration?
When both microphages and macrophages move through capillary walls by squeezing between adjacent endothelial cells.
What do the endothelial cells in an injured area develop? What does it do?
membrane “markers” that signal passing blood cells that something is wrong.
How do phagocytes react to membrane “markers”?
attach to the endothelial lining and migrate into the surrounding tissues.
What is chemotaxis?
When phagocytes are attracted to or repelled by chemicals in the surrounding fluids,
What chemicals are phagocytes sensitive to?
cytokines
Phagocytosis begins with what?
with attachment of the phagocyte to its target.
What happens after the phagocyte attaches to its target?
Adhesion is followed by phagocyte engulfing of the target and the formation of a membrane-bound vesicle containing the target inside the cytoplasm of the phagocyte.
When are the contents of the vesicle are digested?
The contents of the vesicle are digested once the vesicle fuses with lysosomes or peroxisomes within the phagocyte.
_____ can attack bacteria in interstitial fluid, body cells infected with viruses, or cancer cells
A single NK cell
What is the Natural killer cells’ function?
Natural killer (NK) cells are responsible for recognizing and destroying abnormal cells.
What do NK cells do to abnormal cells?
NK cells respond to abnormal antigens on a plasma membrane by initiating attacks.
What is immune surveillance?
Their [NK cells] continuous “policing” of peripheral tissues has been called immune surveillance.
What do abnormal cells have on their plasma membrane?
The plasma membrane of an abnormal cell contains antigens that are not found on the membranes of normal cells.
How can NK cells locate/ recognize abnormal cells?
NK cells recognize an abnormal cell by
detecting those antigens. (antigens that are not found on the membranes of normal cells)
What are the 4 steps on how NK cells kill targets
1) Recognition and adhesion
2) Realignment of Golgi apparatus
3) Secretion of perforin
4) Lysis of abnormal cells
Step 1 of NK cell attack on abnormal cells
(1) NK cell recognizes the antigen on an abnormal cell. NK cell is activated and adheres to the abnormal cell.
Step 2 of NK cell attack on abnormal cells
(2) The Golgi apparatus moves around the nucleus to point directly toward the abnormal cell, like rotating a tank turret to point the cannon toward the enemy. The Golgi apparatus then produces a flood of secretory vesicles containing perforins.
Step 3 of NK cell attack on abnormal cells
(3) Perforins are
released by exocytosis and diffuse toward
the target.
Step 4 of NK cell attack on abnormal cells
(4) Perforin molecules reach the target plasma membrane, forming a network of pores in it. As a result, the target cell quickly disintegrates.
What are interferons and released by what (2x)?
Interferons (IFNs) are small proteins released (1) by activated lymphocytes and macrophages, and (2) by tissue cells infected with viruses.
What is the function of interferons? (2x)
1) Interferon binds to surface receptors on the
membrane of a normal cell (almost all cells in our body express the receptor).
2) Interferon also binds to surface receptors on the membrane of T cells and macrophages.
What does interferon binding trigger?
The binding triggers a series of cellular events in these target cells.
What is the final outcome of interferons?
The final outcome is slowing down the spread of viral infections and clearing out the infected host cells.
What secretes Interferon alpha?
Interferon alfa (IFN-a) is secreted by host cells upon viral infection.
What does interferon do after they bind cell surfaces?
IFN binds to its receptor on the cell surface and initiates IFN signaling events in these target cells.
What are antiviral effects?
Antiviral effects - to clear the virus and infected host cells
1. Signals neighboring uninfected cells to destroy RNA and reduce protein synthesis
2. Signals neighboring infected cells to undergo apoptosis
What are immunomodulatory effects?
Immunomodulatory effects - to boost immune activities to fight off invaders.
1. Activates immune cells
What is the complement system?
Plasma contains over 30 special complement proteins that form the complement system.
What does the term complement refers to in relation to the complement system?
to the fact that this system complements, or enhances, the action of antibodies and phagocytes.
_______ pathways lead to complement activation
three
Three pathways lead to complement
activation and achieve the following effects: (3x) (name which 3 pathways)
killing of the pathogen by cell lysis, enhanced phagocytosis (opsonization), and enhanced inflammation (histamine release).
1. Classical
2. Lectin
3. Alternative
What are tonsils
Large lymphoid nodules in the walls of the pharynx and oral cavity
How does the body repair a tissue injury?
- Chemical change in interstitial fluid
- Release of histamine and heparin from mast cells
3a. Redness, Swelling, Heat, and Pain
3b. Attraction of Phagocytes esp Neutrophils - Tissue Repair
What happens during the Redness, Swelling, Heat, and Pain step?
- Dilation of blood vessels, increased blood flow, and increased vessel permeability
- Clot formation (temp repair)
What happens after the Attraction of Phagocytes?
- Release of cytokines which results in:
2a. Removal of debris by neutrophils and macrophages; stimulation of fibroblasts
2b. Activation of specific defenses
What happens during Tissue Repair step?
- Pathogen removal
- Clot erosion
- Scar tissue formation
Adaptive Immunity results from which lymphocytes?
the coordinated activities of T lymphocytes (T cells) and B lymphocytes (B cells).
Under proper stimulation, T cells can ________________ which attack antigens and help to increase the immune response.
differentiate into several types of cells,
The primary types of T cells are (4x)
1) Cytotoxic T cells
2) Helper T cells
3) Regulatory T cells
4) Memory T cells
What is the function of Cytotoxic T cells
Cytotoxic T cells are involved in direct cellular attack. These cells enter peripheral tissues and attack antigens physically and chemically.
What is the function of Helper T cells
Helper T cells stimulate the responses of both T cells and B cells. Helper T cells are absolutely vital to the immune response because they must activate B cells before the B cells can produce antibodies. The reduction in the helper T cell population that occurs in AIDS is largely responsible for the loss of immunity.
What is the function of Regulatory T cells
Regulatory T cells are a subset of T cells that moderate the immune response.
What is the function of Memory T cells
Memory T cells respond to antigens they have already encountered by cloning (producing identical cellular copies) more lymphocytes to ward off the invader.
Where does the maturation of B cells occur?
The maturation of B lymphocytes occurs in the bone marrow.
B lymphocytes go through _______________ into mature B cells
and further antibody-secreting _________.
B lymphocytes go through a series of steps differentiating into mature B cells and further antibody-secreting plasma cells.
When do B cells differentiate into plasma cells and what do they do as plasma cells?
When stimulated, B cells differentiate into plasma cells that secrete soluble proteins called antibodies.
The binding of an antibody to its target (antigen) leads to what?
the destruction of the target invader.
Cytotoxic T cells provide what type of immunity for adaptive immunity?
cell-mediated immunity, or cellular immunity, which
defends against abnormal cells and pathogens inside cells.
B cells provide what type of immunity for adaptive immunity?
antibody-mediated immunity, which defends against antigens
and pathogens in body fluids. AKA humoral (“body fluid”) immunity because antibodies are found in body fluids.
Why are both kinds of adaptive immunity important?
Both kinds of immunity are important because they come into play under different circumstances.
What are the limitations of T cells?
activated T cells do not respond to antigens in solution
What is the limitation of B cells?
antibodies (produced by activated B cells) cannot cross plasma membranes.
What do both T cells and B cells react to?
Both T and B cells respond to the presence of specific antigens.
How does the Adaptive immunity work?
- Antigens
- Lymphocyte Activation and Clonal selection
Adaptive Immunity (Antigens)
Specific chemical targets called antigens stimulate the immune response. Most antigens are pathogens, parts or products of pathogens, or other foreign substances.
Adaptive Immunity (Lymphocyte Activation and Clonal selection)
A lymphocyte becomes activated when it has contact with an appropriate antigen.
When activated, a lymphocyte begins to divide, producing more lymphocytes with the same specificity (recognizing & binding to the same antigen).
What are antigens made up of?
Antigens are usually proteins, but some lipids, polysaccharides, and nucleic acids are also antigens.
What makes up a clone?
All the identical cells produced by such divisions make up a clone,
All members of that clone share what in common?
all the members of that clone are sensitive (recognizing & binding) to the same specific antigen.
clonal selection is
The process of an antigen selecting particular lymphocytes for clonal expansion
Adaptive Immunity: Properties (4x)
- Specificity
- Versability
- Memory
- Tolerance
What does specificity result from?
Specificity results from the activation of appropriate lymphocytes and the production of antibodies with targeted effects.
Why does Specificity occur?
Specificity occurs because T cells and B cells respond to the molecular structure of an antigen - antigen uniqueness. Each T cell or B cell has receptors that will only bind to the specific antigen, ignoring all others. Activated T cell or B cell will destroy or inactivate that specific antigen without affecting
other antigens or normal tissues.
Versatility results in part from what?
Versatility results in part from the large diversity of lymphocytes in the body, and in part from variability in the diverse structures of antibodies.
During development, lymphoid stems cells differentiate into a huge number of lymphocytes with ____________.
varied antigen sensitivities.
Each population of lymphocytes has ___________ and responds to _________________.
Each population of lymphocytes has unique receptors and responds to a different antigen.
Memory is achieved because of what?
Memory is achieved because two groups of lymphocytes are generated in the cell division process. One group of lymphocytes attacks the invading pathogen immediately. The other group remains dormant/inactive until it meets the same antigen at a later time.
A dormant/inactive group is made up of what?
memory cells that enable your immune system to “remember” an antigen it has previously encountered,
Having memory cells results in what?
to launch a faster, stronger, and longer-lasting counterattack if such an antigen appears again.
The immune system exhibits tolerance toward ____________
The immune system exhibits tolerance toward our own antigens AKA “self-antigens”.
During the development of lymphocytes, in the red bone marrow (B cells) and thymus (T cells), any lymphocytes that react to self-antigens are ________
destroyed
Up to ______ developing T cells are ordered to die (undergo apoptosis, AKA programmed cell death).
98%
