Module 3 Flashcards
Lymphatic system actually consists of two semi-independent parts:
1) a meandering network of lymphatic vessels
2) various lymphoid tissues and organs scattered throughout the body
What do the lymphatic vessels do?
The lymphatic vessels transport fluids that have escaped from the blood vascular system back to the blood.
The lymphoid organs house ______ ______ and ________, which play essential roles in _____ ____ and ________ __ ________.
Phagocytic cells and lymphocytes, body defence and resistance to disease.
The function of the lymphatic vessels is to:
Pick up this excess tissue fluid, now called lymph (lymph = clear water), and return it to the blood stream.
Harmful materials that enter lymph vessels:
Bacteria, viruses, cancer cells, cell debris
How does lymph move?
It has no pumping system, its a milking action of skeletal muscle. Rhythmic contractions of smooth muscle in vessel walls and breathing.
Medial iliac lymph nodes:
These are located at the point where the aorta splits in the pelvic region. They drain the pelvic viscera and pelvic limbs
Lateral iliac lymph nodes:
Not always present, located at the bifurcation of the deep circumflex iliac artery
Internal iliac lymph nodes:
Located adjacent to the internal iliac artery, drain adjacent regions
Sacral lymph nodes:
Located ventral to the sacrum, drains the adjacent region
Anorectal lymph nodes:
Located lateral to the rectum, drains the adjacent region
Iliofemoral lymph centre
Located along the course of the femoral continuation of the external iliac artery.
Ischial lymph centre
Located on the lateral aspect of the sacrosciatic ligament, adjacent to the ischial tuberosity
Popliteal lymph center
Located caudal to the stifle and drains the distal limb
Elastin makes up 40% of equine lymphatic vessel walls, assisting them to stretch and contract while on the other hand having fewer smooth muscle cells than those of people. True or False
True
All lymph vessels follow the pattern of the main veins, eventually discharging into a venous vessel - the lumbar duct. True or False
False. Thoracic duct
More closely related to the immune system, what do the lymph nodes do?
They help protect the body by removing foreign material such as bacteria and tumor cells from the lymphatic stream and by producing lymphocytes that function in the immune response.
Explain macrophages.
They engulf and destroy bacteria, viruses, and other foreign substances in the lymph before it is returned to the blood.
Why is the flow of lymph through the node very slow?
Allows time for the lymphocytes and macrophages to perform their protective function.
What happens to a lymph node once it is destroyed?
Nothing since they do not come back.
What are lymphoid organs?
Tonsils, thymus, spleen, peyer’s patches and bone marrow
Spleen:
Located on the left side of the abdomen, filters blood, destroys worn out cells, forms blood cells in the fetus, acts as a blood resevoir
Thymus:
Located low in throat, overlying the heart, functions at peak levels only during childhood, produces hormones to program lymphocytes
Tonsils:
Small masses of lymphoid tissue around the pharynx, trap and remove bacteria and other foreign materials, tonsillitis is caused by congestion of bacteria
Peyers Patches:
Found in the wall of the small intestine, resemble tonsils in structure, capture and destroy bacteria in the intestine, appendix is an offshoot from the large intestine
The thymus is comprised of lobes what are they?
Capsule, Cortex, Medulla
The thymus provides the environment in which stem cells that migrated from the postnatal bone marrow proliferate and differentiate into T-lymphocyte. True or False
True
What is the thymus is referred to?
Primary Lymphatic Organ
What does the thymus do during puberty?
It reaches its maximum size at puberty and then begins to involute. Involution is characterized by gradual depletion of lymphocytes especially of the cortex.
What are more resistant to involution than lymphocytes?
Epithelial reticular cells and thymic corpuscles.
What is the thymus sensitive too?
Radiation and Infection
Bone Marrow:
soft material in the cavities of bones, produces both red and white cells including lymphocytes. T cells and B cells are also produced
What do T cells and B cells do during maturation?
T cells move to the thymus for final development, and B cells remain in the bone marrow. Once B cells are fully developed in the bone marrow, they are also released into circulation and most of them take up residence in the secondary lymphatic organs.
There are two systems that defend our bodies:
1) non specific defence system
2) specific defence system
How does the non specific system work?
Responds immediately to protect the body from all foreign substances.
The non specific defences are provided by:
Intact skin and mucous membranes, the inflammatory response and a number of proteins produced by body cells.
How does the non specific system reduce the workload of the second protective arm?
By preventing entry and spread of microorganisms throughout the body.
What is the specific defence system?
More commonly called the immune system, mounts the attack against particular foreign substances.
The immune system is an organ system rather than a functional system in an anatomical sense. True or False
False. Is a functional system
What are the specific defences structure like?
Its structures are a variety of molecules and trillions of immune cells, which inhabit lymphatic tissues and circulate in body fluids.
What are the more important immune cells?
Lymphocytes and macrophages.
Whats the main difference between nonspecific defences and the immune system?
The immune system must first “meet” or be primed by an exposure to a foreign substance (antigen) before it can protect the body against it.
The acid pH of skin secretions inhibits bacterial growth, and _________ contains chemicals that are toxic to bacteria. Vaginal secretions of adult females are also very ______.
Sebum and acidic.
The stomach ______ secrets hydrochloric acid and protein-digesting enzymes. Both _____ pathogens.
Mucosa, kill
Saliva and lacrimal fluid contain _________. and enzyme that destroys bacteria.
Lysozyme
Sticky mucus traps many microorganisms that enter ________ and _________ passageways.
Digestive and respiratory
The body uses enormous number of cells and chemicals to protect itself. These defences rely on what?
The destructive powers of phagocytes and natural killer cells, the inflammatory response, and variety of chemical substances that kill pathogens and help repair tissue.
Fever is not considered to be a nonspecific response. True or False
False it is considered
When pathogens make it through the mechanical barriers are confronted by?
Phagocytes
Where are phagocytes?
They are nearly in every body organ.
What does a phagocyte do?
Such as macrophages or neutrophils, they engulf a foreign particle much the way amoeba ingests food particles.
Flowing cytoplasmic extensions bind to the particle and then pull it inside, enclosed in a vacuole. Once this happens what does the vacuole do?
The vacuole is then fused with lysosome and it’s contents are broken down or digested.
Why are natural killer cells an unique group?
They are an unique group of defensive cells that can lyse and kill cancer cells and virus-infected body cells well before the immune system is enlisted in the fight.
Unlike lymphocytes of the immune system, which can recognize and react only against specific virus-infected or tumor cells, natural killer cells can act ___________ against any such target by recognizing certain _____ on the intruders surface.
Spontaneously, sugars
Natural Killer cells are not phagocytic. True or False
True
Why do Natural Killer Cells serve to contain viral infections?
So when this is happening the adaptive immune response is generating antigen-specific cytotoxic T cells that can clear the infection.
What are the four cardinal signs and major symptoms of an acute inflammation is:
Redness, heat, swelling, and pain
When cells are injured they release inflammatory chemicals such as?
Histamine and kinnis
What do histamine and kinnis do?
Cause blood vessels in the involved area to dilate and capillaries to become leaky, activate pain receptors and attract phagocytes and WHB cells to the area.
What are chemotaxis?
Cells are following a chemical gradient.
Dilation of the blood vessels increases the blood flow to the area, accounting for the _____ and ____ observed, increased permeability of the capillaries allows plasma to leak from the bloodstream into the tissue spaces, causing local ______ that also activates pain receptors in the are.
Redness, heat, edema.
What is the fifth cardinal sign of inflammation?
Limitation of joint movement.
Why is the inflammatory response important?
Prevents the spread of damaging agents to nearby tissues, disposes of cell debris and pathogens and sets the stage for repair.
Within an hour or so after the inflammatory process has began, _________ are squeezing through the capillary walls to enter the area and begin the cleanup detail by ________ damaged or dead tissue cells and or pathogens.
Neutrophils, engulfing
Monocytes are fairly poor phagocytes but within 8 to 12 hours after entering the tissues they become _______.
Macrophages.
Why are the macrophages the central actors?
They are the central actors in the final disposal of cell debris as the inflammation subsides.
Besides phagocytosis, other protective events are also occurring at the inflamed site, what are they?
Clotting proteins, leaked into the area from the blood, are activated and begin to wall off the damaged area with fibrin to prevent the spread of pathogens or harmful agents to neighbouring tissues the fibrin mesh also forms a scaffolding for permanent repair, the local heat increases the metabolic rate of the tissues, speeding up their defensive actions and repairs processes.
Why does pus form?
It forms when there is a severely infected area, the battle takes a considerable toll on both sides and thats when pus may be formed in the wound.
What is pus?
Pus is a mixture of dead or dying neutrophils, broken down tissue cells and living and dead pathogens.
Surgical drainage of abscesses is often necessary before healing can occur. True or False
True
What are the body’s most important antimicrobial chemicals are?
Complement proteins and interferon.
The term complement refers to a group of at least __________________ that circulate in the blood in a inactive state.
20 plasma proteins
When complement becomes attached, or fixed to foreign cells such as bacteria, fungi, or mismatched red blood cells, what happens?
It is activated and becomes a major factor in the fight against the foreign cells.
When does the complement fixation occur?
When complement proteins bind to certain sugars or proteins, such as antibodies, on the foreign cell’s surface, a result of complement fixation is that lesions, complete with holes, form in the foreign cell’s surface. These allow water to rush into the cell. Causing it to burst.
Besides having the ability to rupture, or lyse, invading microorganisms and other foreign cells, activated complement also:
Amplifies the inflammatory response, some to the molecules released during the activation process are vasodilators and some are chemotaxis chemical that attract neutrophils and macrophages into the region.
What is the effect opsonisation?
Others cause the cell membranes of the foreign cells to become sticky so they are easier to phagocytize.
The compliment itself is a ________ ________ ________ that “compliments” or enhances the effectiveness of both nonspecific and specific defences.
Nonspecific Defensive Mechanism
Viruses lack the cellular machinery required to generate ATP or make proteins, they do their dirty work or damage the body by:
Entering tissue cells and taking over the cellular machinery needed to reproduce themselves.
When a tissue cell is infected with a virus, they can do little to save themselves, but what do they do to help defend others?
They help defend cells that have not yet been infected by secreting small proteins called interferons.
What do interferons do?
The interferon molecules diffuse to nearby cells and bind to their membrane receptors. Somehow this binding hinders the ability of viruses to multiply within these cells.
What is the body temperature regulated by?
By a part of the hypothalamus.
What is the normal temperature of a horse?
37.5 C
What makes the temperature of a horse go up?
In response to pyrogens, chemicals secreted by WBC and macrophages exposed to foreign cells or substances in the body.
Although high fevers are dangerous because excess heat scrambles enzymes and other body proteins, mild or moderate fever seems to benefit the body how?
Bacteria require large amounts of iron and zinc to multiply, but during a fever the liver and spleen gather up these nutrients, making them less available. Fever also increases the metabolic rate of tissue cells in general, speeding up the repair processes.
The immune system is a functional system that recognizes foreign molecules (antigens) and acts to inactivate or destroy them. True or False
True
What happens when the third line of defence, the immune system, fails?
Some of the most devastating diseases such as cancer may result.
What are three important aspects to the immune response?
1) it is antigen specific: it recognizes and acts against particular pathogens or foreign substances
2) it is systemic: immunity is not restricted to the initial infection site
3) it has memory: it recognized and mounts even stronger attacks on previously encountered pathogens
What is humoral immunity also called antibody-mediated immunity?
Provided by antibodies present in the body’s “humors” or fluids. When lymphocytes themselves defend the body, the immunity is called cell-mediated immunity because the protective factor is living cells.
How do lymphocytes act against targets such as, virus-infected cells, cancer cells and cells with foreign grafts?
Directly by tying the foreign cells or indirectly by releasing chemicals that enhance the inflammatory response or activate other immune cells.
What is an antigen?
An antigen is any substance capable of exciting our immune system and provoking an immune response, most antigens are large, complex molecules that are not normally present in our bodies.
What does our immune system think of our antigens?
They are foreign intruders or nonself.
What are examples of antigens and what is the strongest?
Foreign proteins, nucleic acids, many large carbohydrates and some lipids. Proteins are the strongest.
The troublesome small molecule that can cause reactions is called?
Hapten (haptein = to grasp)
The crucial cells of the immune system are _______ and ________.
Lymphocytes and macrophages.
Lymphocytes exist in two major “flavors”. What are they and what do they do?
B cells produce antibodies and oversee humoral immunity.
T cells statute the cell-mediated arm of immunity.
What makes macrophages differ from lymphocytes?
Unlike the two types of lymphocytes, macrophages do not respond to specific antigens but instead play an essential role in helping the lymphocytes that do.
Where do lymphocytes originate from?
From hemocytoblasts in the red bone marrow
The immature lymphocytes released from marrow are essentially identical. Whether a given lymphocyte matures into a B cell or T cell depends on where in the body it becomes __________, that is, capable of responding to specific antigen by binding to it.
Immunocompetant.
Where do T cells migrate to?
Thymus, where they undergo a maturation process of 2 to 3 days directed by thymic hormones.
Within the thymus, the immature lymphocytes divide rapidly and their numbers increase enormously, but which ones survive?
Only those maturing T cells with the sharpest ability to identify foreign antigens survive.
The T cells capable to binding strongly with self-antigens and of acting against body cells are _______ _____ ___ and ________, thus, the development of tolerance for self-antigens is an essential part of the lymphocytes “education”
Vigorously weeded out and destroyed
Do B cells get weeded out and destroyed as well?
Yes
Where do B cells develop?
They immunocompetence in bone marrow, but little is known about the factor that regulate B cell maturation.
Once a lymphocyte is immunocompetent, it will be able to react to all antigens because all the antigen receptors on its external surface can change. True or False
False. It will be able to react to one distinct antigen and only one, because all the antigen receptors on its external surface are the same.
Although the details of maturation process of lymphocytes are still beyond our grasp, we know that lymphocytes become immunocompetent ________ meeting the antigens they may later attack.
Before
After becoming immunocompetant, both T cells and B cells migrate to ____ ____ and _____ ______ (___ ______ ______ ______), where their encounters with antigens will occur.
Lymph nodes and the spleen (and loose connective tissue)
When the lymphocytes bind with recognized antigens, what do they do?
They complete their differentiation into fully mature T cells and B cells.
Where do macrophages arise from?
Monocytes formed in the bone marrow.
What is the major role of macrophages?
To engulf foreign particles and present fragments of these antigens, like signal flags, on their own surfaces, where they can be recognized by immunocompetent T cells. Thus, they act as antigen presenters.
What kind of protein do macrophages secrete?
Monokines, that are important to the immune system.
Activated T cells release chemicals that cause macrophages to become insatiable phagocytes or killer macrophages. True or False
True
Macrophages tend to remain fixed in the lymphoid organs while T cells _______ _________ through the body.
Circulate continously
The immune systems ability to respond to such threats depends on the ability of its cells how?
1) to recognize foreign substances (antigens) in the body by binding to them
2) to communicate with one another so that the system as a whole mounts a response specific to those antigens
An immature B cells is stimulated to complete its development into a fully mature B cell when?
When an antigen binds to its surface receptors.
When a B cell is fully matured and binds to a surface receptor, this binding event sensitizes or activates the lymphocyte to “switch on” and undergo _____ _____.
Clonal selection.
When undergoing clonal selection, the lymphocyte begins to grow and then multiplies rapidly to form an army of cells all exactly like itself and bearing the same antigen-specific receptors. True or False
True
Clone formation is the primary _____ _______ to that antigen.
Humoral response
What do most of the B cell clone members become?
Plasma cells
What happens to B cell clone members that do not become plasma cells?
They become long-lived memory cells capable of responding to the same antigen at later meetings with it.
Memory cells are responsible for the immunological “memory”. True or False
True
What is a secondary response?
When the body can react much faster, more prolonged and more effective because all the preparations for this attack to the “old enemy” antigen have already been made.
Active immunity occurs when we?
1) naturally acquired during bacterial and viral infections
2) artificially acquired when we receive vaccines.
Passive immunity is quite different from active immunity, both in the antibody source and in the degree of protection it provides. True or False
True
What is the difference between passive and active immunity?
Passive immunity is when the antibodies are obtained from the serum of an immune human or animal donor, as a result your B cells are not challenged by the antigen, immunologic memory does not occur and the temporary protection provided by the “borrowed antibodies” ends when they naturally degrade in the body.
_________ immunity is conferred naturally on a fetus when the mother’s antibodies cross the placenta and enter the fetal circulation.
Passive
What is gamma globulin?
Commonly administered after exposure to hepatitis.
________ immunity is artificially conferred when one receives immune serum or gamma globulin.
Passive
________ ____________ used for such purposes are produced by descendants of a single cells and are pure antibody preparations that exhibit specificity for one and only one antigen.
Monoclonal antibodies.
What is the basic structure monomer of each type of antibody?
They are formed by four amino acid (polypeptide) chains that are joined by disulfide bonds. Two of the chains are short, light chairs; the other two are long, heavy chains.
What does each chain have?
A variable (V) region (different in different antibodies), and a constant (C) region (essentially identical in different antibodies of the same class)
The variable regions are the antigen-binding sites of the antibody hence, each antibody monomer has two antigen-binding sites. True or False
True
What are antibodies also referred as?
Immunoglobulin or Igs.
Antibodies constitute the _____ _____ part of the blood proteins
Gamma globulin.
Antibodies are ____ _____, secreted by activated B cells or by their plasma-cell offspring in response to an antigen, and they are capable of _____ _____ with that antigen.
Soluble proteins, binding specifically
Despite antibodies variety, they all have a similar basic anatomy that allows them to be grouped into six Ig classes, each slightly different in structure and function. True or False.
False five
Two of the four chains are identical and contain approximately _____ amino acids each; these are the ______ chains.
400, heavy
The other two chains, the light chains are so identical to each other but are only about _____ as long.
half
When both chains are combined, the molecule as a whole is __ or __ shaped.
T or Y
Antibodies responding to different antigens had very different variable regions but their constant region were the same or nearly so. True or False
True
What are the five major immunoglobulin classes?
IgM, IgA, IgD, IgG, IgE (MADGE)
IgD, IgG, IgE antibodies have the same basic __ shaped structure, and are referred to as ______.
Y, monomers
IgA antibodies occur in both monomer and dimer (two linked monomers) forms. True or False
True
Compared to other antibodies, IgM antibodies are _____, because they are constructed of _____ linked monomers. IgM antibodies are called ______.
Huge, five, pentamers (penta=five)
The antibodies of each class have slightly different biological roles and locations in the body. True or False
True
Antibodies inactivate antigens in a number of ways like?
By complement fixation, neutralization, agglutination and precipitation.
Which is the most importance important complement fixation to body protection?
Neutralization
Complement is the chief _____ ______ used against cellular antigens, such as bacterial or mismatched red blood cells.
Antibody Animation
Complement is fixed (activated) during ______ _____ ______.
Nonspecific body defenses
How is a complement also activated?
It is also activated very efficiently when it binds to antibodies attached to cellular targets, this triggers events that result in lysis of the foreign cell and release of molecules that tremendously enhance the inflammatory process.
When does neutralization occur?
It occurs when antibodies bind to specific sites on bacterial exotoxins or on viruses that can cause cell injury
What is agglutination?
When the cross-linking involves cell-bound antigens, the process causes clumping of the foreign cells.
What is precipitation?
When the cross-linking process involves soluble antigenic molecules, the resulting antigen-antibody complexes are so large that they become insoluble and settle out of solution.
After macrophages have ingested an antigen what do they do next?
They display parts of it on their surface membranes, where it can be recognized by a helper cell bearing receptors for the same antigen.
During the binding process, the T cell binds simultaneously to the antigen and to the macrophage (self) receptor, which leads to?
T cell activation and cloning, in addition, the macrophages releases monokines, which enhance T cell activation.
Activated helper T cells release lymphocytes, which stimulate proliferation and activity of the helper T cells and help activate cytotoxic T cells and B Cells. True or False
True
