Week 5 Flashcards
(110 cards)
1
Q
What is the Lymphatic System?
A
System that returns fluids that have leaked from blood vessels back to the blood. Pathogens travel throughout body via lymphatics
2
Q
What does the lymphatic system consist of?
A
Consists of three parts:
1. Network of lymphatic vessels (lymphatics)
2. Lymph – fluid in vessels
3. Lymph nodes – cleanse lymph
3
Q
Function of lymphatic vessels (lymphatics)
A
Return interstitial fluid and leaked plasma proteins back to blood
~3L/day
4
Q
What is lymph?
A
It is the interstitial fluid that enters
lymphatics
5
Q
Where do lymphatic vessels flow towards?
A
One-way system; lymph flows
toward heart
6
Q
What do Lymphatic vessels include:
A
Lymphatic vessels include:
– Lymphatic capillaries
– Collecting lymphatic vessels – Lymphatic trunks and ducts
7
Q
Lymphatic vessels diagram
A
8
Q
What are lymphatic capillaries?
A
Similar to blood capillaries, except:
• Very permeable (take up proteins, cell debris, pathogens, and cancer cells)
– Endothelial cells overlap loosely to form
one-way minivalves
– Anchored by collagen filaments,
preventing collapse of capillaries; increased ECF volume opens the minivalves
9
Q
Lymphatic capillaries are absent from:
A
bones, teeth, bone marrow, and CNS
10
Q
What are lacteals?
A
Lacteals: specialized lymph capillaries present in intestinal mucosa
11
Q
Lacteals function
A
Absorb fat and deliver fatty lymph (chyle) to the blood
12
Q
What are Lymphatic Collecting Vessels ?
A
Similar to veins, except:
• Have thinner walls, with more internal valves
• Anastomose more frequently
– Collecting vessels in skin
travel with superficial veins
– Deep vessels travel with arteries
13
Q
What do the lymphatic collecting vessels travel with?
A
Collecting vessels in skin
travel with superficial veins
14
Q
What do the deep lymphatic collecting vessels travel with?
A
Deep vessels travel with arteries
15
Q
Lymphatic Collecting Vessels diagram
A
16
Q
What do lymphatic vessels include:
A
Lymphatic Capillaries, Lymphatic Collecting Vessels, Lymphatic Trunks and Lymphatic Ducts
17
Q
What are lymphatic trunks formed by?
A
Formed by union of largest collecting ducts • 2x lumbar
• 2x bronchomediastinal • 2x subclavian
• 2x jugular
• 1x intestinal
18
Q
Diagram of major lymphatic trunks and ducts.
A
19
Q
What ducts are the lymph delivered into?
A
– Lymph delivered into one of two large ducts
• Right lymphatic duct drains rightupperarmandrightside of head and thorax
• Thoracic duct arises as cisterna chyli; drains rest of body
20
Q
Where do the 2 large lymphatic ducts empty unto?
A
Each empties lymph into venous circulation at junction of internal jugular and subclavian veins on its own side of body
21
Q
Diagram of lymphatic trunks?
A
22
Q
What is the Lymph fluid propelled by?
A
Lymph fluid is propelled by:
– Milking action of skeletal muscle
– Pressure changes in thorax during breathing
– Valves to prevent backflow
– Pulsations of nearby arteries
– Contractions of smooth muscle in walls of lymphatics
23
Q
What are the lymph fluids?
A
Interstitial fluid, leukocytes, and reticular cells
24
Q
What is interstitial fluid?
A
Interstitial Fluid; water, carbohydrates, fats & proteins
25
What do Leukocytes consist of?
– Lymphocytes
• Arise in red bone marrow
• Protect against foreign antigens
– Bacteria and bacterial toxins, viruses, mismatched RBCs, cancer cells
• Mature into one of two main varieties:
– T cells (T lymphocytes)
» Manage immune response
» Attack and destroy infected cells
– B cells (B lymphocytes)
» Produce plasma cells, which secrete antibodies
(antibodies mark antigens for destruction by phagocytosis or other means)
– Macrophages
• phagocytize foreign substances; help activate T cells
– Dendritic cells
• capture antigens and deliver them to lymph nodes; activate T cells
26
What do reticular cells produce ?
produce reticular fibre stroma that supports other cells in lymphoid organs
27
Function of Lymphoid Organs and Tissues
• Provide structural basis of immune system
• House phagocytic cells and lymphocytes
28
What structures do Lymphoid Organs and Tissues include?
Structures include spleen, thymus, tonsils, lymph nodes, other lymphoid tissues
29
What does Lymphoid Tissue house?
Houses, and provides proliferation site for lymphocytes
30
Lymphoid tissue is known as the surveillance…
Surveillance vantage point for lymphocytes and macrophages
31
What does lymphoid tissue consist of?
Surveillance vantage point for lymphocytes and macrophages
32
What is largely reticular connective tissue?
- Largely reticular connective tissue – type of loose connective tissue
33
What are the 2 main types of Largely reticular connective tissue?
Two main types:
– Diffuse lymphoid tissue of lymphoid cells and reticular fibres in almost
every body organ
•Larger collections in lamina propria of mucous membranes
– Lymphoid follicles/nodules are solid, spherical bodies of tightly packed lymphoid cells and reticular fibres
• Germinal centres of proliferating B cells
• Mayformpartoflargerlymphoidorgans
• Isolated aggregations,e.g.palatinetonsils,Peyer'spatches(SI)
•Similar to lymph nodes except that they are not surrounded by a connective
tissue capsule
34
What are lymph nodes?
Principal lymphoid organs of body
35
Where are lymph nodes found?
• Embedded in connective tissue, in clusters along lymphatic vessels
• Near body surface in inguinal, axillary, and cervical regions of body
36
Functions of lymph nodes:
1. Filter lymph—macrophages destroy microorganisms and debris
2. Immune system activation—lymphocytes activated and mount attack against antigens
37
What is the largest lymphoid organ?
Spleen
38
Where is the spleen found?
Found in the left upper quadrant of the abdomen
39
What artery and vein is the spleen served by?
Served by splenic artery and vein, which enter and exit at the hilum
40
Functions of the spleen?
• Functions:
– Site of lymphocyte proliferation, and immune surveillance and response – Cleanses blood of aged cells and platelets; macrophages remove debris – Stores breakdown products of RBCs (e.g., iron) for later use
– Stores blood platelets, and the precursors of macrophages and dendritic
cells
41
Picture of spleen location
42
Where is the thymus found?
Found in inferior neck; extends into mediastinum; partially overlies heart
43
Does thymus continuously grow?
Stops growing during adolescence, then gradually atrophies
44
What are most thymic cells?
Most thymic cells are lymphocytes
45
What does the cortex contain?
Cortex contains rapidly dividing lymphocytes and scattered macrophages
46
Medulla contains….
Medulla contains fewer lymphocytes and thymic corpuscles involved in regulatory T cell development (prevent autoimmunity)
47
How does the thymus function differently to other lymphoid organs?
Differs from other lymphoid organs in important ways:
– Has no B cells
– Does not directly fight antigens
• Functions strictly in T lymphocyte maturation-(trains the T cells)
48
What is MALT?
Mucosa-associated Lymphoid Tissue (MALT)
49
What is Mucosa-associated Lymphoid Tissue (MALT)?
Lymphoid tissues in mucous membranes throughout body
50
Mucosa-associated Lymphoid Tissue (MALT) function
Protects from pathogens trying to enter body
51
Where is Mucosa-associated Lymphoid Tissue (MALT) found?
Largest collections of MALT in tonsils, Peyer's patches, appendix
• Also, in mucosa of respiratory and genitourinary organs; rest of digestive tract
52
What is Mucosa-associated Lymphoid Tissue (MALT) tonsils
- Simplest lymphoid organs
Malt Forms ring of lymphatic tissue around
pharynx (Waldeyer’s Ring):
– Palatine tonsils: at posterior end of oral cavity
– Lingual tonsil: grouped at base of tongue
– Pharyngeal tonsil: in posterior wall of
nasopharynx
– Tubal tonsils: surrounding openings of
pharyngotympanic tubes into pharynx
53
MALT TONSILS FUNCTION:
Gather and remove pathogens in food or air
54
WHAT DO MALT TONSILS CONTAIN?
• Contain follicles with germinal centers
• Are not fully encapsulated
• Overlying epithelium invaginates forming tonsillar crypts
– Trap and destroy bacteria and particulate matter
– Allow immune cells to build memory for pathogens
55
WHAT IS Peyer's patches?
– Clusters of lymphoid follicles/nodules (egg-shaped)
– In wall of distal portion of small intestine (ileum)
– Monitor intestinal bacteria populations and
preventing the growth of pathogenic bacteria in the
intestines
– Generate "memory" lymphocytes
56
WHERE IS Appendix LOCATED?
sits at the junction of the small intestine and large
intestine (off the caecum)
57
WHAT IS THE FUNCTION OF APPENDIX?
Function is still under debate
– Theorised to be a “safe house” for commensal
bacteria, providing support for bacterial growth and potentially facilitating re-inoculation of the colon if the contents of the intestinal tract are evacuated following exposure to a pathogen
58
WHAT IS THE IMMUNE SYSTEM?
Functional system rather
than an organ system.
59
IMMUNE SYSTEM FUNCTION
• Provides lines of defence against foreign material, bacteria, viruses, cancers, etc.
THERE ARE TWO SYSTEMS Innate (~born with) and adaptive (~develops over time/exposure) defences intertwined
– Innate responses release proteins that alert cells of adaptive system to foreign molecules
60
WHAT IS IMMUNITY
Resistance to disease
INVOLVES THE Immune system;Two intrinsic systems:
• Innate (non-specific) defence system
– First line of defence - external body membranes (skin and mucosae)
– Second line of defence - antimicrobial proteins, phagocytes, and other cells
» Inhibit spread of invaders
» Inflammation most important
mechanism
• Adaptive (specific) defence system
– Third line of defence attacks particular foreign substances via cell-mediated response and humoral response
– Takes longer to react than innate system
61
IMMUNE SYSTEM DIAGRAM
62
WHAT ARE INNATE DEFENCES
SURFACE BARRIERS
63
WHAT ARE SURFACE BARRIERS?
– provide the first line of defence
– ward off invading pathogens
Follicles of a Peyer’s patch (aggregated lymphoid nodules)
• Skin, mucous membranes, and their secretions
– Physical barrier to
most microorganisms
– Keratin resistant to
weak acids and bases, bacterial enzymes, and toxins
– Mucosae provide similar mechanical barriers
64
WHAT DO SURFACE BARRIERS PRODUCE?
- produce protective chemicals to inhibit or destroy microorganisms
– Acidity of skin and secretions
• inhibitsmicroorganismgrowth(immunomodulatory)
- Enzymes e.g., lysozyme of saliva, respiratory mucus, and lacrimal fluid
• breakdown/killmanymicroorganisms(immunomodulatory) -Defensins: antimicrobial peptides
• inhibitsmicroorganismgrowth(immunomodulatory)
• immunesignallingactivities(chemotactic)
-Other chemicals: lipids in sebum, dermcidin (antibiotic peptide) in sweat
• toxictomicroorganisms(immunomodulatory) -Respiratory system modifications
• Mucus-coatedhairsinnose
• Ciliaofupperrespiratorytractsweepdust-andbacteria-ladenmucustoward mouth
65
WHAT HAPPENS IF SURFACE BARRIERS ARE BREACHED?
If surface barriers are breached by scratches or cuts - second line of defence (internal defences) must protect deeper tissues
66
WHAT DO INTERNAL DEFENCES PROVIDE?
provide the second line of defence (necessary if microorganisms invade deeper tissues)
67
WHAT DO INNATE DEFENCES INVOLVE?
involve cells and chemicals
• Phagocytes
• Natural killer (NK) cells
• Inflammatory response (leukocytes and inflammatory chemicals)
• Antimicrobial proteins (interferons and complement proteins)
• Fever
68
WHAT DO PHAGOCYTES CONSIST OF:
– Neutrophils most Phagosome (phagocytic vesicle) abundant but die fighting
• Become phagocytic on exposure to infectious material
– Macrophages are the chief phagocytic cells which are very robust
• Free macrophages wander through tissue spaces, e.g., alveolar macrophages
• Fixed macrophages permanent residents of some organs; e.g., stellate macrophages (liver) and microglia (brain)
69
EVENTS OF PHAGOCYTOSIS
1 Phagocyte adheres to pathogens or debris.
2 Phagocyte forms pseudopods that eventually engulf the particles, forming a phagosome.
3 Lysosome fuses with the phagocytic vesicle, forming a phagolysosome.
4 Lysosomal enzymes digest the particles, leaving a residual body.
5 Exocytosis of the vesicle removes indigestible and residual material.
70
WHAT ARE Internal Defences: Natural Killer (NK) Cells
– Non-phagocytic large granular
lymphocytes
71
Internal Defences: Natural Killer (NK) Cells FUNCTIONS
– Attack altered self-cells
• Induce apoptosis in cancer cells and virus-infected cells by releasing cytotoxic proteins into the cells
– Secrete potent chemicals that enhance inflammatory response
72
WHAT IS THE INTERNAL DEFENCE: INFLAMMATION
– Triggered whenever body tissues injured – Prevents spread of damaging agents
– Disposes of cell debris and pathogens
– Alerts adaptive immune system
– Sets the stage for repair
– Cardinal signs of acute inflammation:
1. Redness
2. Heat
3. Swelling
4. Pain
(Sometimes 5. Impairment of function)
73
INFLAMMATORY RESPONSE CAN BE EITHER
local or systemic (throughout the body)
74
WHAT DOES THE IMFLAMMATORY RESPONSE BEGIN WITH?
BeginswithchemicalsreleasedintoECFbyinjured tissues, immune cells, blood proteins, etc.
75
HOW ARE THE INFLAMMATORY MEDIATORS RELEASED?
Inflammatory mediators are released
– Mast cells release histamine • Dilatelocalarterioles
– Causes redness and heat of inflamed region • Makecapillariesleaky
– Macrophages and epithelial cells of boundary tissues bear specialised receptors which recognise specific
classes of infecting microbes
• oncethesespecialisedreceptorsare
activated, they release cytokines, signaling molecule that modulate the immune response and promote blood flow to the area
76
EFFECTS OF IMFLAMMATORY RESPONSE ON CAPILLARIES
•INCREASED Capillarypermeability LEADS TO exudate to tissues
– Fluid containing clotting factors and antibodies – Causes local swelling (oedema)
– Swelling pushes on nerve endings =pain
• Pain also from bacterial toxins, prostaglandins, and kinins
– Moves foreign material into lymphatic vessels
– Delivers clotting proteins and complement
• Clotting factors form fibrin mesh
– Scaffold for repair
– Isolates injured area so invaders cannot spread
77
OUTLINE THE PROCESS OF PHAGOCYTE MOBILISATION?
1. Leukocytosis: release of neutrophils from bone marrow in response to leukocytosis-inducing factors from injured cells 2. Margination: neutrophils cling to walls of capillaries in inflamed area in response to cell adhesion molecules
3. Diapedesis: neutrophils flatten and squeeze out of capillary
4. Chemotaxis:
inflammatory chemicals (chemotactic agent) promote positive chemotaxis of neutrophils
78
WHAT DOES Internal Defences: Antimicrobial Proteins CONSIST OF
– Interferons (IFNs)
• Family of immune modulating proteins (many types)
– Viral-infected cells secrete IFNs (e.g., IFN alpha and beta) to "warn" neighbouring cells
» IFNs enter neighbouring cells produce proteins that block viral reproduction and activate NK cells
– IFN gamma (immune interferon)
» Secreted by lymphocytes
» Widespread immune mobilizing effects which activates macrophages
– Complement proteins
• Proteins that circulate in the blood (many types)
• Unleashes inflammatory chemicals that amplify all aspects of
inflammatory response
• Kills bacteria and certain other cell types by cell lysis • Enhances both innate and adaptive defences
79
WHAT IS Internal Defences: Fever
– Abnormally high body temperature
– Systemic response to invading microorganisms
– Leukocytes and macrophages exposed to foreign substances secrete pyrogens
– Pyrogens act on body's thermostat in hypothalamus, raising body temperature
80
BENEFITS OF MODERATE FEVER
– Benefits of moderate fever
• Causes liver and spleen to sequester iron and zinc (needed by microorganisms)
• Increases metabolic rate = faster repair
81
Adaptive immune (specific defence) system function:
– Protects against infectious agents and abnormal body cells
– Amplifies inflammatory response
– Has memory – stronger attacks to "known" antigens
82
What do Adaptive immune (specific defence) system cells use to destroy foreign substances?
Uses lymphocytes, Antigen-Presenting Cells (APCs), and specific molecules to identify and destroy non-self substances
83
For the adaptive immune system it Depends upon ability of its cells to:
• Recognise antigens by binding to them
• Communicate with one another so that whole system mounts
specific response
84
Adaptive defences include 2 separate…
• Two separate, overlapping arms:
• Humoral (antibody-mediated) immunity • Cellular (cell-mediated) immunity
85
What are antigens?
• Surface proteins found on all cells
• Substances that can mobilise adaptive defenses and provoke an immune response
• Targets of all adaptive immune responses (antibodies [blue] created by B lymphocytes)
86
What size are most antigens?
Most are large, complex molecules not normally found in body (non-self)
87
Are antigens immunogenic?
Only certain parts of the entire antigen are immunogenic
88
What are antibodies made by and for what?
Made by B lymphocytes for specific targets
89
Antibodies Varying functions include:
– directly neutralizing a threat (e.g. aggregation, immobilisation, destabilisation)
– preventing a pathogen from attaching or entering a cell
– preventing intruders from leaving cells (if they made it in)
– tag invaders for phagocytosis
90
Explain the 3 different types of cells in adaptive defences.
– Antigen-presenting cells (APCs)
• Do not respond to specific antigens
• Play essential support roles in immunity – Two types of lymphocytes
• B lymphocytes (B cells) - humoral immunity
– Involved in attacking intruders outside of cells via antibodies
• T lymphocytes (T cells) - cellular immunity
– Lymphocytes can only connect to virus antigens on the outside of infected cells
91
Antigen-presenting Cells (APCs) function
Engulf antigens and present fragments of antigens to T lymphocytes for recognition
92
What are the 3 major types of Antigen-presenting Cells (APCs)
• Major types:
– Dendritic cells in connective tissues and epidermis • phagocytize pathogens, enter lymphatics to present
antigens to T lymphocytes in lymph node – Most effective antigen presenter known
– Key link between innate and adaptive immunity
– Macrophages in connective tissues and lymphoid organs
• present antigens to T lymphocytes to activate themselves into phagocytes that secrete bactericidal chemicals
– B Lymphocytes (B cells)
93
The difference between humoral and cellular immunity
94
B cell types diagram
95
T cell types diagram
96
Adaptive Defences Lymphocyte Development, Maturation and Activation diagram
97
Table comparing B lymphocytes and T lymphocytes
98
What are the three main Antigen Presenting Cells (APC)?
Dendritic cells, Macrophages and B cells
99
Lymph fluid is propelled by:
a. Milking action of skeletal muscle
b.
Pressure changes in thorax during breathing
c.
Valves to prevent backflow
d.
Pulsations of nearby arteries
e.
Contractions of smooth muscle in walls of lymphatics
100
what is are located in the spleens white pulp?
lymphocytes
101
.... are the first line of defense and include the skin and mucous membranes
surface barriers
102
Adaptive immunity involves ...
humoral (B cell) and cellular (T cell) immunity.
103
Aggregates of lymphoid nodules located in the wall of the ileum of the small intestine are _________
Peyer's patches
104
A "non-self" substance that can provoke an immune response is called a(n) __________
Antigens are surface proteins that provoke an immune repsonse.
105
the four steps involved in phagocyte mobilisation
1. Leukocytosis
2. Margination
3. Diapedesis
4. Chemotaxis
106
What lymphatic structure absorbs lipids in the intestine?
Lacteals are lymph capillaries in the intestinal mucosa which absorb and deliver fatty lymph to the blood.
107
Lymphocytes that develop immunocompetence in the thymus are __________
.
T lymphocytes
108
Which of the following best describes the arrangement of lymphatic vessels?
The lymphatic system is best described as a one-way system of vessels beginning with blind-ended lymphatic capillaries, which functions to return leaked interstitial fluid back to the circulation.
109
Fever is a part of the ....
second line of defense
110
