Ch.12: The Lymphatic System and Body Defenses Flashcards
1
Q
The lymphatic system consists of what two semi-independent parts?
A
- Lymphatic vessels
2. Lymphoid tissues and organs
2
Q
What are the functions of the lymphatic system?
A
- Transports escaped fluids from the cardiovascular system back to the blood
- Plays essential roles in body defense and resistance to disease
3
Q
Concept Link 1
A
Recall that the hydrostatic and osmotic pressures operating at capillary beds force fluid out of the blood at the arterial ends of the beds (“upstream”) and cause most of the expelled fluid to be reabsorbed at the venous ends (“downstream”) (Chapter 11, p. 388).
4
Q
Lymph consists of _____ and _____ carried by lymphatic vessels.
A
- Excess tissue fluid
* Plasma proteins
5
Q
If fluids are not picked up, _____ occurs as fluid accumulates in tissues.
A
Edema
6
Q
_____ pick up excess fluid (lymph) and return it to the blood.
A
Lymphatic vessels (lymphatics)
7
Q
What are lymphatic vessels (lymphatics)?
A
- Form a one-way system
* Lymph flows only toward the heart
8
Q
What are lymph capillaries?
A
- Weave between tissue cells and blood capillaries
- Walls overlap to form flaplike minivalves
- Fluid leaks into lymph capillaries
- Capillaries are anchored to connective tissue by filaments
- Higher pressure on the inside closes minivalves
- Fluid is forced along the vessel
9
Q
Concept Link 2
A
This is very similar to the way that valves in veins work to ensure blood returns to the heart, despite being under low pressure (Chapter 11, p. 372).
10
Q
What is the function of lymphatic collecting vessels?
A
• Collect lymph from lymph capillaries
• Carry lymph to and away from lymph nodes
• Return fluid to circulatory veins near the heart
*Right lymphatic duct drains the lymph from the right arm and the right side of the head and thorax
*Thoracic duct drains lymph from rest of body
11
Q
How are lymphatic vessels similar to veins of the cardiovascular system?
A
- Thin-walled
- Larger vessels have valves
- Low-pressure, pumpless system
12
Q
Lymph transport is aided by:
A
- Milking action of skeletal muscles
- Pressure changes in thorax during breathing
- Smooth muscle in walls of lymphatics
13
Q
Lymph nodes filter _____ before it is returned to the blood.
A
Lymph
14
Q
Harmful materials that are filtered include:
A
- Bacteria
- Viruses
- Cancer cells
- Cell debris
15
Q
What are defense cells within lymph nodes?
A
- Macrophages
* Lymphocytes
16
Q
What is the function of macrophages?
A
Engulf and destroy bacteria, viruses, and other foreign substances in lymph
17
Q
What is the function of lymphocytes?
A
Respond to foreign substances in lymph
18
Q
Most lymph nodes are _____-shaped, less than _____ long, and buried in _____.
A
- Kidney
- 1 inch
- Connective tissue
- Surrounded by a capsule
- Divided into compartments by trabeculae
19
Q
What is the cortex (outer part) of a lymph node?
A
- Contains follicles—collections of lymphocytes
* Germinal centers enlarge when antibodies are released by plasma cells
20
Q
What is the medulla (inner part) of a lymph node?
A
Contains phagocytic macrophages
21
Q
What is the flow of lymph through nodes?
A
- Lymph enters the convex side through afferent lymphatic vessels
- Lymph flows through a number of sinuses inside the node
- Lymph exits through efferent lymphatic vessels
- Because there are fewer efferent than afferent vessels, flow is slowed
22
Q
What are other lymphoid organs contribute to lymphatic function (in addition to the lymph nodes)?
A
- Spleen
- Thymus
- Tonsils
- Peyer’s patches
- Appendix
23
Q
What is the function of the spleen?
A
- Located on the left side of the abdomen
- Filters and cleans blood of bacteria, viruses, debris
- Provides a site for lymphocyte proliferation and immune surveillance
- Destroys worn-out blood cells
- Forms blood cells in the fetus
- Acts as a blood reservoir
24
Q
The thymus functions at peak levels only during:
A
Youth
25
Concept Link 3
Remember that the thymus produces hormones, thymosin and others, that function in the programming of T lymphocytes so they can carry out their protective roles in the body (Chapter 9, p. 320).
26
What are tonsils and what are their function?
* Small masses of lymphoid tissue deep to the mucosa surrounding the pharynx (throat)
* Trap and remove bacteria and other foreign pathogens
* Tonsillitis results when the tonsils become congested with bacteria
27
What are Peyer's patches?
* Found in the wall of the small intestine
* Similar lymphoid follicles are found in the appendix
* Macrophages capture and destroy bacteria in the intestine
28
What is mucosa-associated lymphoid tissue (MALT) and what is its function?
```
Includes:
• Peyer’s patches
• Tonsils
• Appendix
• Acts as a sentinel to protect respiratory and digestive tracts
```
29
What are two mechanisms that make up the immune system and defend us from foreign materials?
* Innate (nonspecific) defense system
| * Adaptive (specific) defense system
30
What is immunity?
Specific resistance to disease
31
The immune system is a _____ system rather than an _____ system in an anatomical sense.
* Functional
| * Organ
32
What is the first line of defense?
* Skin
* Mucous membranes
* Secretions of skin and mucous membranes
33
What is the second line of defense?
* Phagocytic cells
* Natural killer cells
* Antimicrobial proteins
* The inflammatory response
* Fever
34
What is the third line of defense?
* Lymphocytes
* Antibodies
* Macrophages and other antigen-presenting cells
35
What is the function of the innate (nonspecific) defense system?
* Mechanisms protect against a variety of invaders
| * Responds immediately to protect body from foreign materials
36
What is the function of the adaptive (specific) defense system?
* Fights invaders that get past the innate system
* Specific defense is required for each type of invader
* The highly specific resistance to disease is immunity
37
Innate body defenses are mechanical barriers to pathogens (harmful or disease-causing microorganisms) and include:
```
• Body surface coverings
*Intact skin
*Mucous membranes
• Specialized human cells
• Chemicals produced by the body
```
38
Surface membrane barriers, such as the skin and mucous membranes, provide the _____ against the invasion of microorganisms.
• First line of defense
• Protective secretions produced by these membranes
*Acidic skin secretions inhibit bacterial growth
*Sebum is toxic to bacteria
*Mucus traps microorganisms
*Gastric juices are acidic and kill pathogens
*Saliva and tears contain lysozyme (enzyme that destroys bacteria)
39
Cells and chemicals provide a second line of defense, such as:
* Natural killer cells and phagocytes
* Inflammatory response
* Chemicals that kill pathogens
* Fever
40
What is the function of natural killer (NK) cells?
* Lyse (burst) and kill cancer cells, virus-infected cells
| * Release chemicals called perforin and granzymes to degrade target cell contents
41
Inflammatory response is triggered when:
Body tissues are injured
42
What are the four most common indicators (cardinal signs) of acute inflammation?
1. Redness
2. Heat
3. Pain
4. Swelling (edema)
43
Damaged cells release inflammatory chemicals, such as:
* Histamine
| * Kinin
44
Inflammatory chemicals cause:
* Blood vessels to dilate
* Capillaries to become leaky
* Phagocytes and white blood cells to move into the area (called positive chemotaxis)
45
What are the functions of the inflammatory response?
* Prevents spread of damaging agents
* Disposes of cell debris and pathogens through phagocytosis
* Sets the stage for repair
46
What is the process of the inflammatory response?
1. Neutrophils migrate to the area of inflammation by rolling along the vessel wall (following the scent of chemicals from inflammation)
2. Neutrophils squeeze through the capillary walls by diapedesis to sites of inflammation
3. Neutrophils gather in the precise site of tissue injury (positive chemotaxis) and consume any foreign material present
47
What is the function of phagocytes?
* Cells such as neutrophils and macrophages engulf foreign material by phagocytosis
* The phagocytic vesicle is fused with a lysosome, and enzymes digest the cell’s contents
48
Antimicrobial proteins enhance innate defenses by:
* Attacking microorganisms directly
| * Hindering reproduction of microorganisms
49
What are the most important types of antimicrobial proteins?
* Complement proteins
| * Interferon
50
What are complement proteins?
* Complement refers to a group of at least 20 plasma proteins that circulate in the plasma
* Complement is activated when these plasma proteins encounter and attach to cells (known as complement fixation)
51
Membrane attack complexes (MACs), one result of complement fixation, produce _____ or _____ in cells.
* Holes
* Pores
* Pores allow water to rush into the cell
* Cell bursts (lyses)
* Activated complement enhances the inflammatory response
52
What are interferons and what are their function?
* Interferons are small proteins secreted by virus-infected cells
* Interferons bind to membrane receptors on healthy cell surfaces to interfere with the ability of viruses to multiply
53
What is a fever?
* Abnormally high body temperature is a systemic response to invasion by microorganisms
* Hypothalamus regulates body temperature at 37°Celsius (98.6°Fahrenheit)
* The hypothalamus thermostat can be reset higher by pyrogens (secreted by white blood cells)
* High temperatures inhibit the release of iron and zinc (needed by bacteria) from the liver and spleen
* Fever also increases the speed of repair processes
54
_____ are the body’s specific defense system, or the third line of defense.
* Adaptive body defenses
* Immune response is the immune system’s response to a threat
* Antigens are targeted and destroyed by antibodies
55
What are the three aspects of adaptive defense?
* Antigen specific—the adaptive defense system recognizes and acts against particular foreign substances
* Systemic—immunity is not restricted to the initial infection site
* Memory—the adaptive defense system recognizes and mounts a stronger attack on previously encountered pathogens
56
What are the two arms of the adaptive defense system?
* Humoral immunity
| * Cellular immunity
57
What is humoral immunity?
* Antibody-mediated immunity
| * Provided by antibodies present in body fluids
58
What is cellular immunity?
* Cell-mediated immunity
| * Targets virus-infected cells, cancer cells, and cells of foreign grafts
59
What are antigens?
Any substance capable of exciting the immune system and provoking an immune response
60
What are examples of common non-self antigens?
* Foreign proteins provoke the strongest response
* Nucleic acids
* Large carbohydrates
* Some lipids
* Pollen grains
* Microorganisms (bacteria, fungi, viruses)
61
What are self-antigens?
• Human cells have many protein and carbohydrate molecules
• Self-antigens do not trigger an immune response in us
• The presence of our cells in another person’s body can trigger an immune response because they are foreign
*Restricts donors for transplants
62
Concept Link 4
Likewise, this explains why only people of compatible blood types can donate blood to one another. Recall our discussion of blood antigens (Chapter 10, p.352). Depending on your individual blood type, one or more blood antigen types may be self to your body, and one or more may be non-self. For example, if you are blood type A, type A antigen is self, but type B antigen is non-self. However, in a person with type A B blood, both A and B antigens are self-antigens.
63
Haptens, or incomplete antigens, are not _____ by themselves.
* Antigenic
* When they link up with our own proteins, the immune system may recognize the combination as foreign and respond with an attack
* Found in poison ivy, animal dander, detergents, hair dyes, cosmetics
64
Lymphocytes respond to:
Specific antigens
65
_____ produce antibodies and oversee humoral immunity
B lymphocytes (B cells)
66
_____ constitute the cell-mediated arm of the adaptive defenses; do not make antibodies
T lymphocytes (T cells)
67
What are antigen-presenting cells (APC)?
Help the lymphocytes but do not respond to specific antigens
68
Lymphocytes arise from _____ of bone marrow.
Hemocytoblasts
69
Whether a lymphocyte matures into a B cell or T cell depends on where it becomes:
Immunocompetent
70
What is immunocompetence?
The capability to respond to a specific antigen by binding to it with antigen-specific receptors that appear on the lymphocyte’s surface
71
T cells develop immunocompetence in the _____ and oversee _____.
* Thymus
* Cell-mediated immunity
* Identify foreign antigens
* Those that bind self-antigens are destroyed
* Self-tolerance is important part of lymphocyte “education”
72
B cells develop immunocompetence in _____ and provide _____.
* Bone marrow
| * Humoral immunity
73
Immunocompetent T and B lymphocytes migrate to the _____ and _____, where encounters with _____ occur.
* Lymph nodes
* Spleen
* Antigens
74
Differentiation from _____ into mature lymphocytes is complete when they bind with recognized _____.
* Naïve cells
| * Antigens
75
Mature lymphocytes (especially T cells) _____ throughout the body.
Circulate continuously
76
Antigen-presenting cells (APCs) engulf _____ and then present fragments of them on their own surfaces, where they can be recognized by _____.
* Antigens
| * T cells
77
What are the major types of cells behaving as APCs?
* Dendritic cells
* Macrophages
* B lymphocytes
78
When antigen-presenting cells present antigens, _____ and _____ activate T cells, which release chemicals.
* Dendritic cells
| * Macrophages
79
B lymphocytes with specific _____ bind to a specific _____.
* Receptors
* Antigen
* The binding event sensitizes, or activates, the lymphocyte to undergo clonal selection
* A large number of clones is produced (primary humoral response)
80
Most of the B cell clone members (descendants) become:
* Plasma cells
* Produce antibodies to destroy antigens
* Activity lasts for 4 or 5 days
* Plasma cells begin to die
81
Some B cells become _____ capable of mounting a rapid attack against the same antigen in subsequent meetings (secondary humoral response)
* Long-lived memory cells
| * These cells provide immunological memory
82
What is active immunity?
Occurs when B cells encounter antigens and produce antibodies
83
Active immunity can be:
* Naturally acquired during bacterial and viral infections
| * Artificially acquired from vaccines
84
What is passive immunity?
• Occurs when antibodies are obtained from someone else
*Naturally acquired from a mother to her fetus or in the breast milk
*Artificially acquired from immune serum or gamma globulin (donated antibodies)
• Immunological memory does not occur
• Protection is short-lived (2–3 weeks)
85
What are monoclonal antibodies?
* Antibodies prepared for clinical testing for diagnostic services
* Produced from descendants of a single cell line
* Exhibit specificity for only one antigen
86
Examples of uses for monoclonal antibodies include:
* Cancer treatment
* Diagnosis of pregnancy
* Treatment after exposure to hepatitis and rabies
87
Antibodies (immunoglobulins, I g s) constitute the _____ part of blood proteins.
* Gamma globulin
* Soluble proteins secreted by activated B cells (plasma cells)
* Formed in response to a huge number of antigens
88
What is the structure of an antibody?
• Four polypeptide chains, two heavy and two light, linked by disulfide bonds to form a T- or Y-shaped molecule
• Each polypeptide chain has a variable (V) region and a constant (C) region
*Variable regions form antigen-binding sites, one on each arm of the T or Y
*Constant regions determine the type of antibody formed (antibody class)
89
What are the five major immunoglobulin classes (MADGE)?
Antibodies of each class have slightly different roles and differ structurally and functionally
1. IgM—can fix complement
2. IgA—found mainly in secretions, such as mucus or tears
3. IgD—important in activation of B cell
4. IgG—can cross the placental barrier and fix complement; most abundant antibody in plasma
5. IgE—involved in allergies
90
Antibodies inactivate antigens in a number of ways, such as:
* Complement fixation: chief antibody ammunition used against cellular antigens
* Neutralization: antibodies bind to specific sites on bacterial exotoxins or on viruses that can cause cell injury
* Agglutination: antibody-antigen reaction that causes clumping of cells
* Precipitation: cross-linking reaction in which antigen-antibody complex settles out of solution
91
What is the main difference between the two arms of the adaptive response?
* B cells secrete antibodies
| * T cells fight antigens directly
92
Like B cells, _____ are activated to form a _____ by binding with a recognized antigen.
* Immunocompetent T cells
| * Clone
93
Unlike B cells, T cells are unable to bind to:
* Free antigens
* Antigens must be presented by a macrophage, and double recognition must occur
* APC engulfs and presents the processed antigen in combination with a protein from the APC
94
What are the different classes of effector T cells?
* Helper T cells
| * Cytotoxic T cells
95
T cells must recognize _____ and _____ through the process of antigen presentation.
* Non-self—the antigen fragment presented by APC
| * Self—coupling with a specific glycoprotein on the APC’s surface at the same time
96
What are cytotoxic (killer) T cells?
* Specialize in killing infected cells
* Insert a toxic chemical (perforin or granzyme)
* The perforin enters the foreign cell’s plasma membrane
* Pores now appear in the target cell’s membrane
* Granzymes (protein-digesting enzymes) enter and kill the foreign cell
* Cytotoxic T cell detaches and seeks other targets
97
What are helper T cells?
* Recruit other cells to fight invaders
* Interact directly with B cells bound to an antigen, prodding the B cells into clone production
* Release cytokines, chemicals that act directly to rid the body of antigens
98
What are regulatory T cells?
* Release chemicals to suppress the activity of T and B cells
* Stop the immune response to prevent uncontrolled activity
* A few members of each clone are memory cells
99
What are major types of transplants, or grafts?
* Autografts
* Isografts
* Allografts
* Xenografts
100
What are autografts?
Tissue transplanted from one site to another on the same person
101
What are isografts?
Tissue grafts from a genetically identical person (identical twin)
102
What are allografts?
Tissue taken from a person other than an identical twin (most common type of graft)
103
What are xenografts?
Tissue taken from a different animal species (never successful)
104
Blood group and tissue matching is done to ensure the best match possible, but a __% match is needed to attempt a graft
75
105
Organ transplant is followed by _____ to prevent rejection.
Immunosuppressive therapy
106
What are the most important disorders of the immune system?
* Allergies
* Autoimmune diseases
* Immunodeficiencies
107
What are allergies?
* Allergies, or hypersensitives, are abnormal, vigorous immune responses
* The immune system overreacts to an otherwise harmless antigen, and tissue damage occurs
108
What are types of allergies?
* Immediate (acute) hypersensitivity
| * Delayed hypersensitivity
109
What is immediate (acute) hypersensitivity?
* Seen in hives and anaphylaxis
* Due to IgE antibodies and histamine
* Anaphylactic shock is systemic, acute allergic response and is rare
110
What is delayed hypersensitivity?
* Reflects activity of T cells, macrophages, and cytokines
* Symptoms usually appear 1–3 days after contact with antigen
* Allergic contact dermatitis (poison ivy, cosmetics)
111
What are autoimmune diseases?
* Occurs when the body’s self-tolerance breaks down
* The body produces auto-antibodies and sensitized T lymphocytes that attack its own tissues
* Most forms of autoimmune disease result from the appearance of formerly hidden self-antigens or changes in the structure of self-antigens, and antibodies formed against foreign antigens that resemble self-antigens
112
What are examples of autoimmune diseases?
* Rheumatoid arthritis—destroys joints
* Myasthenia gravis—impairs communication between nerves and skeletal muscles
* Multiple sclerosis—white matter of brain and spinal cord is destroyed
* Graves’ disease—thyroid gland produces excess thyroxine
113
What are examples of autoimmune diseases?
* Type I diabetes mellitus—destroys pancreatic beta cells, resulting in deficient insulin production
* Systemic lupus erythematosus (SLE)—affects kidney, heart, lung, and skin
* Glomerulonephritis—severe impairment of kidney function due to acute inflammation
114
What are immunodeficiencies?
• May be congenital or acquired
*Severe combined immunodeficiency disease (SCID) is a congenital disease
*AIDS (acquired immune deficiency syndrome) is caused by a virus that attacks and cripples the helper T cells
• Result from abnormalities in any immune element
• Production or function of immune cells or complement is abnormal
115
Lymphatic vessels form by budding off from:
Veins
116
Lymph nodes present by the _____ week of development.
Fifth
117
The _____ and the _____ are the first lymphoid organs to appear in the embryo.
* Thymus
* Spleen
* Other lymphoid organs are poorly developed before birth
118
The immune response develops around the time of:
Birth
119
The ability of immunocompetent cells to recognize foreign antigens is _____ determined.
Genetically
120
_____ appears to interfere with normal immune response.
Stress
121
Efficiency of immune response wanes in _____, and _____, _____, _____, and _____ diseases become more prevalent.
* Old age
* Infections
* Cancer
* Immunodeficiencies
* Autoimmune
